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Sample records for switch mode dc-dc

  1. Novel bidirectional DC-DC converters based on the three-state switching cell

    NASA Astrophysics Data System (ADS)

    da Silva Júnior, José Carlos; Robles Balestero, Juan Paulo; Lessa Tofoli, Fernando

    2016-05-01

    It is well known that there is an increasing demand for bidirectional DC-DC converters for applications that range from renewable energy sources to electric vehicles. Within this context, this work proposes novel DC-DC converter topologies that use the three-state switching cell (3SSC), whose well-known advantages over conventional existing structures are ability to operate at high current levels, while current sharing is maintained by a high frequency transformer; reduction of cost and dimensions of magnetics; improved distribution of losses, with consequent increase of global efficiency and reduction of cost associated to the need of semiconductors with lower current ratings. Three distinct topologies can be derived from the 3SSC: one DC-DC converter with reversible current characteristic able to operate in the first and second quadrants; one DC-DC converter with reversible voltage characteristic able to operate in the first and third quadrants and one DC-DC converter with reversible current and voltage characteristics able to operate in four quadrants. Only the topology with bidirectional current characteristic is analysed in detail in terms of the operating stages in both nonoverlapping and overlapping modes, while the design procedure of the power stage elements is obtained. In order to validate the theoretical assumptions, an experimental prototype is also implemented, so that relevant issues can be properly discussed.

  2. Improvement of burst-mode control of piezoelectric transformer based DC/DC converter

    NASA Astrophysics Data System (ADS)

    Vasic, Dejan; Liu, Yuan-Ping; Schwander, Denis; Costa, François; Wu, Wen-Jong

    2013-05-01

    Burst-mode operation is adopted sometimes in piezoelectric transformer based converters for two major purposes: (1) to achieve voltage regulation in DC/DC converters and (2) to achieve dimming control in backlight inverters. Burst-mode control enables the converter to operate at a constant switching frequency as well as to maintain good efficiency at light load conditions. However, in practice, the piezoelectric transformer cannot instantly stop vibrating in the burst-mode due to its high quality factor. The delay in the output voltage change resulting from this behavior influences the accuracy of the regulation. This paper proposes a control strategy to make the piezoelectric transformer stop more quickly so as to enhance the accuracy of burst-mode control. The proposed method only modifies the control signal of the burst-mode driving circuit. The proposed control strategy is verified by experiments in a step-down 9 W DC/DC converter.

  3. Switching coordination of distributed dc-dc converters for highly efficient photovoltaic power plants

    DOEpatents

    Agamy, Mohammed; Elasser, Ahmed; Sabate, Juan Antonio; Galbraith, Anthony William; Harfman Todorovic, Maja

    2014-09-09

    A distributed photovoltaic (PV) power plant includes a plurality of distributed dc-dc converters. The dc-dc converters are configured to switch in coordination with one another such that at least one dc-dc converter transfers power to a common dc-bus based upon the total system power available from one or more corresponding strings of PV modules. Due to the coordinated switching of the dc-dc converters, each dc-dc converter transferring power to the common dc-bus continues to operate within its optimal efficiency range as well as to optimize the maximum power point tracking in order to increase the energy yield of the PV power plant.

  4. Multiple output zero-current switching switched-capacitor bidirectional dc-dc converter

    NASA Astrophysics Data System (ADS)

    Lee, Yuang-Shung; Ko, Yi-Pin; Chi, Chien-An

    2010-08-01

    The proposed circuit is a multiple output quasi-resonant (QR) zero-current switching (ZCS) switched-capacitor (SC) converter with a bidirectional power flow control conversion scheme. The principles of the proposed multiple output QR ZCS SC bidirectional dc-dc converter are described using a detailed circuit model for analysis. Simulation and experimental results are carried out to verify the validity and the soft switching performance of the proposed converter. The maximum efficiency achievable is about 94 and 92% for the forward and reverse power flow control schemes, respectively. The output voltage can be regulated by changing the switching frequency for the designed compensated closed-loop controller.

  5. Computer-aided analysis and simulation of switched dc-dc converters

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Yu, Y.

    1978-01-01

    State space techniques are employed to derive an equivalent nonlinear recurrent time-domain model that describes the switched dc-dc converter behavior exactly. This model is employed effectively to analyze both large signal behavior by propagating the recurrence equation and matching boundary conditions through digital computation and small signal behavior by linearizing it about the equilibrium state.

  6. A digitally controlled PWM/PSM dual-mode DC/DC converter

    NASA Astrophysics Data System (ADS)

    Shaowei, Zhen; Bo, Zhang; Ping, Luo; Sijian, Hou; Jingxin, Ye; Xiao, Ma

    2011-11-01

    A digitally controlled pulse width modulation/pulse skip modulation (PWM/PSM) dual-mode buck DC/DC converter is proposed. Its operation mode can be automatically chosen as continuous conduction mode (CCM) or discontinuous conduction mode (DCM). The converter works in PSM at DCM and in 2 MHz PWM at CCM. Switching loss is reduced at a light load by skipping cycles. Thus high conversion efficiency is realized in a wide load current. The implementations of PWM control blocks, such as the ADC, the digital pulse width modulator (DPWM) and the loop compensator, and PSM control blocks are described in detail. The parameters of the loop compensator can be programmed for different external component values and switching frequencies, which is much more flexible than its analog rivals. The chip is manufactured in 0.13 μm CMOS technology and the chip area is 1.21 mm2. Experimental results show that the conversion efficiency is high, being 90% at 200 mA and 67% at 20 mA. Meanwhile, the measured load step response shows that the proposed dual-mode converter has good stability.

  7. Wide-range 7-switch flying capacitor based dc-dc converter for point-of-load applications

    NASA Astrophysics Data System (ADS)

    Jain, Parth

    In this thesis a dc-dc converter referred to as the 7-switch flying capacitor (7SFC) based multi-level buck converter intended for point-of-load applications is presented. The 7SFC operates with the principle of "transformability" which allows it to run in several switching modes when paired with a digital controller. The mode is selected based on input and output conditions by estimating the highest efficiency mode. The 7SFC converter utilizes a flying capacitor, which for certain modes allows for a large reduction in switching losses, especially when the converter is operated with high-input voltages. Compared to the conventional 2-phase interleaved buck converter, the 7SFC is able to reduce the size of the output inductors and capacitor by 33%. The 7SFC discrete prototype is able to achieve efficiencies greater than 90% over the majority of the operating range.

  8. A Compact, Soft-Switching DC-DC Converter for Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Button, Robert; Redilla, Jack; Ayyanar, Raja

    2003-01-01

    A hybrid, soft-switching, DC-DC converter has been developed with superior soft switching characteristics, high efficiency, and low electro-magnetic interference. This hybrid topology is comprised of an uncontrolled bridge operating at full pulse-width, and a controlled section operating as a conventional phase modulated converter. The unique topology is able to maintain zero voltage switching down to no load operating conditions. A breadboard prototype was developed and tested to demonstrate the benefits of the topology. Improvements were then made to reduce the size of passive components and increase efficiency in preparation for packaging. A packaged prototype was then designed and built, and several innovative packaging techniques are presented. Performance test data is presented that reveals deficiencies in the design of the power transformer. A simple redesign of the transformer windings eliminated the deficiency. Future plans to improve the converter and packaging design are presented along with several conclusions.

  9. A novel PWM control for a bi-directional full-bridge DC-DC converter with smooth conversion mode transitions

    NASA Astrophysics Data System (ADS)

    Lorentz, V. R. H.; Schwarzmann, H.; März, M.; Bauer, A. J.; Ryssel, H.; Frey, L.; Poure, P.; Braun, F.

    2011-08-01

    A novel CMOS integrated pulse-width modulation (PWM) control circuit allowing smooth transitions between conversion modes in full-bridge based bi-directional DC-DC converters operating at high switching frequencies is presented. The novel PWM control circuit is able to drive full-bridge based DC-DC converters performing step-down (i.e. buck) and step-up (i.e. boost) voltage conversion in both directions, thus allowing charging and discharging of the batteries in mobile systems. It provides smooth transitions between buck, buck-boost and boost modes. Additionally, the novel PWM control loop circuit uses a symmetrical triangular carrier, which overcomes the necessity of using an output phasing circuit previously required in PWM controllers based on sawtooth oscillators. The novel PWM control also enables to build bi-directional DC-DC converters operating at high switching frequencies (i.e. up to 10 MHz and above). Finally, the proposed PWM control circuit also allows the use of an average lossless inductor-current sensor for sensing the average load current even at very high switching frequencies. In this article, the proposed PWM control circuit is modelled and the integrated CMOS schematic is given. The corresponding theory is analysed and presented in detail. The circuit simulations realised in the Cadence Spectre software with a commercially available 0.18 µm mixed-signal CMOS technology from UMC are shown. The PWM control circuit was implemented in a monolithic integrated bi-directional CMOS DC-DC converter ASIC prototype. The fabricated prototype was tested experimentally and has shown performances in accordance with the theory.

  10. Integrated on-chip 0.35 μm BiCMOS current-mode DC-DC buck converter

    NASA Astrophysics Data System (ADS)

    Lee, Chan-Soo; Kim, Nam-Soo; Gendensuren, Munkhsuld; Choi, Jae-Ho; Choi, Joong-Ho

    2012-12-01

    A current-mode DC-DC buck converter with a fully integrated power module is presented in this article. The converter is implemented using BiCMOS technology in amplifier and power MOSFET in a current sensor. The current sensor is realised by the power lateral double-diffused MOSFET with the aspect ratio much larger than that of a matched p-MOSFET. In addition, BiCMOS technology is applied in the error amplifier for an accurate current sensing and a fast transient response. The DC-DC converter is fabricated with 0.35 µm BiCMOS process. Experimental results show that the fully integrated converter operates at 1.3 MHz switching frequency with a supply voltage of 5 V. The output DC voltage is obtained as expected and the output ripple is controlled to be within 2% with a 30 µH off-chip inductor and 100 µF off-chip capacitor.

  11. Critical conditions of saddle-node bifurcations in switching DC-DC converters

    NASA Astrophysics Data System (ADS)

    Fang, Chung-Chieh

    2013-08-01

    Although existence of multiple periodic orbits in some DC-DC converters have been known for decades, linking the multiple periodic orbits with the saddle-node bifurcation (SNB) is rarely reported. The SNB occurs in popular DC-DC converters, but it is generally reported as a strange instability. Recently, design-oriented instability critical conditions are of great interest. In this article, average, sampled-data and harmonic balance analyses are applied and they lead to equivalent results. Many new critical conditions are derived. They facilitate future research on the instability associated with multiple periodic orbits, sudden voltage jumps or disappearances of periodic orbits observed in DC-DC converters. The effects of various converter parameters on the instability can be readily seen from the derived critical conditions. New Nyquist-like plots are also proposed to predict or prevent the occurrence of the instability.

  12. Multiphase soft switched DC/DC converter and active control technique for fuel cell ripple current elimination

    DOEpatents

    Lai, Jih-Sheng; Liu, Changrong; Ridenour, Amy

    2009-04-14

    DC/DC converter has a transformer having primary coils connected to an input side and secondary coils connected to an output side. Each primary coil connects a full-bridge circuit comprising two switches on two legs, the primary coil being connected between the switches on each leg, each full-bridge circuit being connected in parallel wherein each leg is disposed parallel to one another, and the secondary coils connected to a rectifying circuit. An outer loop control circuit that reduces ripple in a voltage reference has a first resistor connected in series with a second resistor connected in series with a first capacitor which are connected in parallel with a second capacitor. An inner loop control circuit that reduces ripple in a current reference has a third resistor connected in series with a fourth resistor connected in series with a third capacitor which are connected in parallel with a fourth capacitor.

  13. Complete bifurcation analysis of DC-DC converters under current mode control

    NASA Astrophysics Data System (ADS)

    Pikulin, D.

    2014-03-01

    The purpose of this research is to investigate to what extend application of novel method of complete bifurcation groups to the analysis of global dynamics of piecewise-smooth hybrid systems enables one to highlight new nonlinear effects before periodic and chaotic regimes. Results include the construction of complete one and two-parameter bifurcation diagrams, detection of various types of bifurcation groups and investigation of their interactions, localization of rare attractors, and the investigation of different principles of birth of chaotic attractors. Effectiveness of the approach is illustrated in respect to one of the most widely used switching systems-boost converter under current mode control operating in continuous current mode.

  14. Cascaded transformerless DC-DC voltage amplifier with optically isolated switching devices

    NASA Technical Reports Server (NTRS)

    Sridharan, Govind (Inventor)

    1993-01-01

    A very high voltage amplifier is provided in which plural cascaded banks of capacitors are switched by optically isolated control switches so as to be charged in parallel from the preceding stage or capacitor bank and to discharge in series to the succeeding stage or capacitor bank in alternating control cycles. The optically isolated control switches are controlled by a logic controller whose power supply is virtually immune to interference from the very high voltage output of the amplifier by the optical isolation provided by the switches, so that a very high voltage amplification ratio may be attained using many capacitor banks in cascade.

  15. Milliwatt dc/dc Inverter

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W.

    1983-01-01

    Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

  16. Early Oscillation Detection Technique for Hybrid DC/DC Converters

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2011-01-01

    Oscillation or instability is a situation that must be avoided for reliable hybrid DC/DC converters. A real-time electronics measurement technique was developed to detect catastrophic oscillations at early stages for hybrid DC/DC converters. It is capable of identifying low-level oscillation and determining the degree of the oscillation at a unique frequency for every individual model of the converters without disturbing their normal operations. This technique is specially developed for space-used hybrid DC/DC converters, but it is also suitable for most of commercial and military switching-mode power supplies. This is a weak-electronic-signal detection technique to detect hybrid DC/DC converter oscillation presented as a specific noise signal at power input pins. It is based on principles of feedback control loop oscillation and RF signal modulations, and is realized by using signal power spectral analysis. On the power spectrum, a channel power amplitude at characteristic frequency (CPcf) and a channel power amplitude at switching frequency (CPsw) are chosen as oscillation level indicators. If the converter is stable, the CPcf is a very small pulse and the CPsw is a larger, clear, single pulse. At early stage of oscillation, the CPcf increases to a certain level and the CPsw shows a small pair of sideband pulses around it. If the converter oscillates, the CPcf reaches to a higher level and the CPsw shows more high-level sideband pulses. A comprehensive stability index (CSI) is adopted as a quantitative measure to accurately assign a degree of stability to a specific DC/DC converter. The CSI is a ratio of normal and abnormal power spectral density, and can be calculated using specified and measured CPcf and CPsw data. The novel and unique feature of this technique is the use of power channel amplitudes at characteristic frequency and switching frequency to evaluate stability and identify oscillations at an early stage without interfering with a DC/DC converter s

  17. A fully on-chip three-terminal switched-capacitor DC-DC converter for low-voltage CMOS LSIs

    NASA Astrophysics Data System (ADS)

    Kojima, Yuta; Hirose, Tetsuya; Tsubaki, Keishi; Ozaki, Toshihiro; Asano, Hiroki; Kuroki, Nobutaka; Numa, Masahiro

    2016-04-01

    In this paper, we present a fully on-chip switched-capacitor DC-DC converter for low-voltage CMOS LSIs. The converter has three terminals of input, ground, and output, by developing control circuits with fully on-chip configuration. We employ an ultra low-power nanoampere bias current and voltage reference circuit to achieve ultra low-power dissipation of control circuits. It enables us to realize a highly efficient power conversion circuit at light-load-current applications. The converter achieves highly efficient and robust voltage conversion using a pulse frequency modulation control circuit and a start-up/fail-safe circuit. Measurement results demonstrated that the converter can convert a 3.0 V input into 1.2 V output successfully. The start-up and fail-safe operations were confirmed through the measurement. The efficiency was more than 50% in the range of 2-6 µA load current.

  18. High power density dc/dc converter: Selection of converter topology

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1990-01-01

    The work involved in the identification and selection of a suitable converter topology is described. Three new dc/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC/DC Converter; Single Phase Dual Active Bridges DC/DC Converter; and Three Phase Dual Active Bridges DC/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each consists of an input and output bridge, input and output filter and a transformer, all components essential for a high power dc/dc conversion process; (2) All devices of both the bridges can operate under near zero-voltage conditions, making possible a reduction of device switching losses and hence, an increase in switching frequency; (3) All circuits operate at a constant frequency, thus simplifying the task of the magnetic and filter elements; (4) Since, the leakage inductance of the transformer is used as the main current transfer element, problems associated with the diode reverse recovery are eliminated. Also, this mode of operation allows easy paralleling of multiple modules for extending the power capacity of the system; (5) All circuits are least sensitive to parasitic impedances, infact the parasitics are efficently utilized; and (6) The soft switching transitions, result in low electromagnetic interference. A detailed analysis of each topology was carried out. Based on the analysis, the various device and component ratings for each topology operating at an optimum point, and under the given specifications, are tabulated and discussed.

  19. A unified analysis and design procedure for a standardized control module for dc-dc switching regulators

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Yu, Y.; Mahmoud, M. F.

    1980-01-01

    Three basic switching regulators: buck, boost, and buck/boost, employing a multi-loop control module (SCM) were characterized by a common small signal block diagram. Employing the unified model, regulator performances such as stability, audiosusceptibility, output impedance and step load transient are analyzed and key performance indexes are expressed in simple analytical forms. More importantly, the performance characteristics of all three regulators are shown to enjoy common properties due to the unique SCM control scheme which nullifies the positive zero and provides adaptive compensation to the moving poles of the boost and buck/boost converters. This allows a simple unified design procedure to be devised for selecting the key SCM control parameters for an arbitrarily given power stage configuration and parameter values, such that all regulator performance specifications can be met and optimized concurrently in a single design attempt.

  20. Nonlinear Phenomena and Resonant Parametric Perturbation Control in QR-ZCS Buck DC-DC Converters

    NASA Astrophysics Data System (ADS)

    Hsieh, Fei-Hu; Liu, Feng-Shao; Hsieh, Hui-Chang

    The purpose of this study is to investigate the chaotic phenomena and to control in current-mode controlled quasi-resonant zero-current-switching (QR-ZCS) DC-DC buck converters, and to present control of chaos by resonant parametric perturbation control methods. First of all, MATLAB/SIMULINK is used to derive a mathematical model for QR-ZCS DC-DC buck converters, and to simulate the converters to observe the waveform of output voltages, inductance currents and phase-plane portraits from the period-doubling bifurcation to chaos by changing the load resistances. Secondly, using resonant parametric perturbation control in QR-ZCS buck DC-DC converters, the simulation results of the chaotic converter form chaos state turn into stable state period 1, and improve ripple amplitudes of converters under the chaos, to verify the validity of the proposes method.

  1. Radiation effects on DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Zhang, Dexin; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2000-01-01

    DC-DC switching converters are circuits that can be used to convert a DC voltage of one value to another by switching action. They are increasing being used in space systems. Most of the popular DC-DC switching converters utilize power MOSFETs. However power MOSFETs, when subjected to radiation, are susceptible to degradation of device characteristics or catastrophic failure. This work focuses on the effects of total ionizing dose on converter performance. Four fundamental switching converters (buck converter, buck-boost converter, cuk converter, and flyback converter) were built using Harris IRF250 power MOSFETs. These converters were designed for converting an input of 60 volts to an output of about 12 volts with a switching frequency of 100 kHz. The four converters were irradiated with a Co-60 gamma source at dose rate of 217 rad/min. The performances of the four converters were examined during the exposure to the radiation. The experimental results show that the output voltage of the converters increases as total dose increases. However, the increases of the output voltage were different for the four different converters, with the buck converter and cuk converter the highest and the flyback converter the lowest. We observed significant increases in output voltage for cuk converter at a total dose of 24 krad (si).

  2. Chaos, bifurcation and intermittent phenomena in DC-DC converters under resonant parametric perturbation

    NASA Astrophysics Data System (ADS)

    Deivasundari, P.; Geetha, R.; Uma, G.; Murali, K.

    2013-07-01

    DC-DC converters act as a black box to study various bifurcations. In the present study, the influence of external periodic interference signal in the input of DC-DC voltage-mode controlled buck converter has been considered. It is found that the presence of sinusoidal or saw-tooth interference signal whose frequency is comparable with the switching frequency of the converter or its rational multiples manifests as remerging chaotic band attractors (or Feigenbaum trees) and intermittent chaos. However, the presence of sinusoidal interference signal having irrational frequency ratios with the switching frequency of the converter leads to quasi-periodic route to chaos. The study was carried out both theoretically and experimentally.

  3. Radiation Effects on DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Zhang, De-Xin; AbdulMazid, M. D.; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2001-01-01

    In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25

  4. A Switching-Mode Power Supply Design Tool to Improve Learning in a Power Electronics Course

    ERIC Educational Resources Information Center

    Miaja, P. F.; Lamar, D. G.; de Azpeitia, M.; Rodriguez, A.; Rodriguez, M.; Hernando, M. M.

    2011-01-01

    The static design of ac/dc and dc/dc switching-mode power supplies (SMPS) relies on a simple but repetitive process. Although specific spreadsheets, available in various computer-aided design (CAD) programs, are widely used, they are difficult to use in educational applications. In this paper, a graphic tool programmed in MATLAB is presented,…

  5. High performance dc-dc conversion with voltage multipliers

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T.; Myers, I. T.

    1974-01-01

    The voltage multipliers using capacitors and diodes first developed by Cockcroft and Walton in 1932 were reexamined in terms of state of the art fast switching transistors and diodes, and high energy density capacitors. Because of component improvements, the voltage multiplier, used without a transformer, now appears superior in weight to systems now in use for dc-dc conversion. An experimental 100-watt 1000-volt dc-dc converter operating at 100 kHz was built, with a component weight of about 1 kg/kW. Calculated and measured values of output voltage and efficiency agreed within experimental error.

  6. Experiences in the Application of Project-Based Learning in a Switching-Mode Power Supplies Course

    ERIC Educational Resources Information Center

    Lamar, D. G.; Miaja, P. F.; Arias, M.; Rodriguez, A.; Rodriguez, M.; Vazquez, A.; Hernando, M. M.; Sebastian, J.

    2012-01-01

    This paper presents the introduction of problem-based learning (PBL) in a power electronics course at the University of Oviedo, Gijon, Spain, by means of two practical projects: the design and construction of a switching-mode power supply (SMPS) prototype and the static study of a dc-dc converter topology. The goal of this innovation was for…

  7. New topology for DC/DC bidirectional converter for hybrid systems in renewable energy

    NASA Astrophysics Data System (ADS)

    Lopez, Juan Carlos; Ortega, Manuel; Jurado, Francisco

    2015-03-01

    This article presents a new isolated DC/DC bidirectional converter with soft switching, using a transformer with two voltage taps and two full bridges with insulated-gate bipolar transistors (IGBTs), one on each side of the transformer to be integrated in hybrid systems of renewable energy. A large voltage conversion ratio can be achieved using this converter, in buck and booster modes. Also medium and high DC power can be converted with a good efficiency. Analysis and switching techniques have been reported. To verify the principle of operation, a laboratory prototype of 10 kW has been performed. Experimental results are presented, operating in boost mode. The switching algorithm used has been modelled in MATLAB-Simulink to generate C code. This code has been implemented in a DSP F2812, which has been used to build the prototype.

  8. Fast response double series resonant high-voltage DC-DC converter

    NASA Astrophysics Data System (ADS)

    Lee, S. S.; Iqbal, S.; Kamarol, M.

    2012-10-01

    In this paper, a novel double series resonant high-voltage dc-dc converter with dual-mode pulse frequency modulation (PFM) control scheme is proposed. The proposed topology consists of two series resonant tanks and hence two resonant currents flow in each switching period. Moreover, it consists of two high-voltage transformer with the leakage inductances are absorbed as resonant inductor in the series resonant tanks. The secondary output of both transformers are rectified and mixed before supplying to load. In the resonant mode operation, the series resonant tanks are energized alternately by controlling two Insulated Gate Bipolar Transistor (IGBT) switches with pulse frequency modulation (PFM). This topology operates in discontinuous conduction mode (DCM) with all IGBT switches operating in zero current switching (ZCS) condition and hence no switching loss occurs. To achieve fast rise in output voltage, a dual-mode PFM control during start-up of the converter is proposed. In this operation, the inverter is started at a high switching frequency and as the output voltage reaches 90% of the target value, the switching frequency is reduced to a value which corresponds to the target output voltage. This can effectively reduce the rise time of the output voltage and prevent overshoot. Experimental results collected from a 100-W laboratory prototype are presented to verify the effectiveness of the proposed system.

  9. Efficient, lightweight dc/dc switching converter

    NASA Technical Reports Server (NTRS)

    Cuk, S.; Middlebrook, R. D.

    1981-01-01

    Converters have input properties of boost power stage and output properties of buck power stage, yet they perform general conversion function with high efficiency. Other features include non-pulsating input/output currents, use of capacitive energy transfer, low output voltage ripple, reduced EMI, and small size.

  10. Optimum Design of CMOS DC-DC Converter for Mobile Applications

    NASA Astrophysics Data System (ADS)

    Katayama, Yasushi; Edo, Masaharu; Denta, Toshio; Kawashima, Tetsuya; Ninomiya, Tamotsu

    In recent years, low output power CMOS DC-DC converters which integrate power stage MOSFETs and a PWM controller using CMOS process have been used in many mobile applications. In this paper, we propose the calculation method of CMOS DC-DC converter efficiency and report optimum design of CMOS DC-DC converter based on this method. By this method, converter efficiencies are directly calculated from converter specifications, dimensions of power stage MOSFET and device parameters. Therefore, this method can be used for optimization of CMOS DC-DC converter design, such as dimensions of power stage MOSFET and switching frequency. The efficiency calculated by the proposed method agrees well with the experimental results.

  11. DC/DC Converter Stability Testing Study

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2008-01-01

    This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

  12. High-Efficiency dc/dc Converter

    NASA Technical Reports Server (NTRS)

    Sturman, J.

    1982-01-01

    High-efficiency dc/dc converter has been developed that provides commonly used voltages of plus or minus 12 Volts from an unregulated dc source of from 14 to 40 Volts. Unique features of converter are its high efficiency at low power level and ability to provide output either larger or smaller than input voltage.

  13. Bi-Directional DC-DC Converter for PHEV Applications

    SciTech Connect

    Abas Goodarzi

    2011-01-31

    Plug-In Hybrid Electric Vehicles (PHEV) require high power density energy storage system (ESS) for hybrid operation and high energy density ESS for Electric Vehicle (EV) mode range. However, ESS technologies to maximize power density and energy density simultaneously are not commercially feasible. The use of bi-directional DC-DC converter allows use of multiple energy storage, and the flexible DC-link voltages can enhance the system efficiency and reduce component sizing. This will improve fuel consumption, increase the EV mode range, reduce the total weight, reduce battery initial and life cycle cost, and provide flexibility in system design.

  14. Step-by-Step Design of an FPGA-Based Digital Compensator for DC/DC Converters Oriented to an Introductory Course

    ERIC Educational Resources Information Center

    Zumel, P.; Fernandez, C.; Sanz, M.; Lazaro, A.; Barrado, A.

    2011-01-01

    In this paper, a short introductory course to introduce field-programmable gate array (FPGA)-based digital control of dc/dc switching power converters is presented. Digital control based on specific hardware has been at the leading edge of low-medium power dc/dc switching converters in recent years. Besides industry's interest in this topic, from…

  15. High power density dc/dc converter: Component selection and design

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1989-01-01

    Further work pertaining to design considerations for the new high power, high frequency dc/dc converters is discussed. The goal of the project is the development of high power, high power density dc/dc converters at power levels in the multi-kilowatt to megawatt range for aerospace applications. The prototype converter is rated for 50 kW at a switching frequency of 50 kHz, with an input voltage of 200 Vdc and an output of 2000 Vdc. The overall power density must be in the vicinity of 0.2 to 0.3 kg/kW.

  16. A Low-Power Asynchronous Step-Down DC-DC Converter for Implantable Devices.

    PubMed

    Al-Terkawi Hasib, Omar; Sawan, M; Savaria, Y

    2011-06-01

    In this paper, we present a fully integrated asynchronous step-down switched capacitor dc-dc conversion structure suitable for supporting ultra-low-power circuits commonly found in biomedical implants. The proposed converter uses a fully digital asynchronous state machine as the heart of the control circuitry to generate the drive signals. To minimize the switching losses, the asynchronous controller scales the switching frequency of the drive signals according to the loading conditions. It also turns on additional parallel switches when needed and has a backup synchronous drive mode. This circuit regulates load voltages from 300 mV to 1.1 V derived from a 1.2-V input voltage. A total of 350 pF on-chip capacitance was implemented to support a maximum of 230-μ W load power, while providing efficiency up to 80%. The circuit validating the proposed concepts was fabricated in 0.13- μm complementary metal-oxide semiconductor technology. Experimental test results confirm the expected functionality and performance of the proposed circuit. PMID:23851480

  17. A 10 kW dc-dc converter using IGBTs with active snubbers. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Masserant, Brian J.; Shriver, Jeffrey L.; Stuart, Thomas A.

    1993-01-01

    This full bridge dc-dc converter employs zero voltage switching (ZVS) on one leg and zero current switching (ZCS) on the other. This technique produces exceptionally low IGBT switching losses through the use of an active snubber that recycles energy back to the source. Experimental results are presented for a 10 kW, 20 kHz converter.

  18. Radiation-Tolerant DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

    2012-01-01

    A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

  19. A Three-Phase Bidirectional DC-DC Converter for Automotive Applications

    SciTech Connect

    Su, Gui-Jia; Tang, Lixin

    2008-01-01

    This paper presents a three-phase soft-switching, bidirectional dc-dc converter for high-power automotive applications. The converter employs dual three-phase active bridges and operates with a novel asymmetrical but fixed duty cycle for the top and bottom switches of each phase leg. Simulation and experimental data on a 6-kW prototype are included to verify the novel operating and power flow control principles.

  20. A high-power switch-mode dc power supply for dynamic loads

    SciTech Connect

    Shimer, D.W.; Lange, A.C.; Bombay, J.N.

    1994-06-23

    High-voltage dc power supplies are often required to operate with highly dynamic loads, such as arcs. A switch-mode dc power supply can offer significant advantages over conventional thyristor-based dc power supplies under such conditions. It can quickly turn off the supply to extinguish the arc, and it can quickly recover after the arc. It has a relatively small output filter capacitance, which results in small stored energy available to the arc. A 400-kW, 50-kV switch-mode dc power supply for an electron-beam gun that exploits these advantages was designed and tested. It uses four 100-kW, current-source-type dc-dc converters with inputs in parallel and outputs in series. The dc-dc converters operate at 20 kHz in the voltage regulator part and 10 kHz in the inverter, transformer, and output rectifier part of the circuit. Insulated gate bipolar transistors (IGBTs) are used as the power switches. Special techniques are used to protect the power supply and load against arcs and hard shorts. The power supply has an efficiency of 93%, an output voltage ripple of 1%, and fast dynamic response. In addition, it is nearly one-third the size of conventional power supplies.

  1. Intelligent dc-dc Converter Technology Developed and Tested

    NASA Technical Reports Server (NTRS)

    Button, Robert M.

    2001-01-01

    The NASA Glenn Research Center and the Cleveland State University have developed a digitally controlled dc-dc converter to research the benefits of flexible, digital control on power electronics and systems. Initial research and testing has shown that conventional dc-dc converters can benefit from improved performance by using digital-signal processors and nonlinear control algorithms.

  2. Bifurcation boundary conditions for current programmed PWM DC-DC converters at light loading

    NASA Astrophysics Data System (ADS)

    Fang, Chung-Chieh

    2012-10-01

    Three types of bifurcations (instabilities) in the PWM DC-DC converter at light loading under current mode control in continuous-conduction mode (CCM) or discontinuous-conduction mode (DCM) are analysed: saddle-node bifurcation (SNB) in CCM or DCM, border-collision bifurcation during the CCM-DCM transition, and period-doubling bifurcation in CCM. Different bifurcations occur in some particular loading ranges. Bifurcation boundary conditions separating stable regions from unstable regions in the parametric space are derived. A new methodology to analyse the SNB in the buck converter based on the peak inductor current is proposed. The same methodology is applied to analyse the other types of bifurcations and converters. In the buck converter, multiple stable/unstable CCM/DCM steady-state solutions may coexist. Possibility of multiple solutions deserves careful study, because an ignored solution may merge with a desired stable solution and make both disappear. Understanding of SNB can explain some sudden disappearances or jumps of steady-state solutions observed in switching converters.

  3. Model predictive control of bidirectional isolated DC-DC converter for energy conversion system

    NASA Astrophysics Data System (ADS)

    Akter, Parvez; Uddin, Muslem; Mekhilef, Saad; Tan, Nadia Mei Lin; Akagi, Hirofumi

    2015-08-01

    Model predictive control (MPC) is a powerful and emerging control algorithm in the field of power converters and energy conversion systems. This paper proposes a model predictive algorithm to control the power flow between the high-voltage and low-voltage DC buses of a bidirectional isolated full-bridge DC-DC converter. The predictive control algorithm utilises the discrete nature of the power converters and predicts the future nature of the system, which are compared with the references to calculate the cost function. The switching state that minimises the cost function is selected for firing the converter in the next sampling time period. The proposed MPC bidirectional DC-DC converter is simulated with MATLAB/Simulink and further verified with a 2.5 kW experimental configuration. Both the simulation and experimental results confirm that the proposed MPC algorithm of the DC-DC converter reduces reactive power by avoiding the phase shift between primary and secondary sides of the high-frequency transformer and allow power transfer with unity power factor. Finally, an efficiency comparison is performed between the MPC and dual-phase-shift-based pulse-width modulation controlled DC-DC converter which ensures the effectiveness of the MPC controller.

  4. Programmed pulsewidth modulated waveforms for electromagnetic interference mitigation in dc-dc converters

    SciTech Connect

    Wang, A.C.; Sanders, S.R.

    1993-10-01

    The regular switching action of a pulsewidth modulated (PWM) circuit generates conducted and radiated electro-magnetic interference (EMI), and may also generate acoustical disturbances. Programmed pulsewidth modulation techniques have been applied suing various methods to control harmonics inherent in switched power circuits. In this paper, a method to generate an optimal programmed switching waveform for a dc-dc converter is presented. This switching waveform is optimized to reduce the amplitude of harmonic peaks in the EMI generated by the converter. Experimental results, a brief discussion of sensitivity, and a practical implementation of a circuit to generate the PWM waveform are given.

  5. A Nonlinear Digital Control Solution for a DC/DC Power Converter

    NASA Technical Reports Server (NTRS)

    Zhu, Minshao

    2002-01-01

    A digital Nonlinear Proportional-Integral-Derivative (NPID) control algorithm was proposed to control a 1-kW, PWM, DC/DC, switching power converter. The NPID methodology is introduced and a practical hardware control solution is obtained. The design of the controller was completed using Matlab (trademark) Simulink, while the hardware-in-the-loop testing was performed using both the dSPACE (trademark) rapid prototyping system, and a stand-alone Texas Instruments (trademark) Digital Signal Processor (DSP)-based system. The final Nonlinear digital control algorithm was implemented and tested using the ED408043-1 Westinghouse DC-DC switching power converter. The NPID test results are discussed and compared to the results of a standard Proportional-Integral (PI) controller.

  6. Efficiency and weight of voltage multiplier type ultra lightweight dc-dc converters

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1975-01-01

    An analytical and experimental study was made of a capacitor-diode voltage multiplier without a transformer which offers the possibility of high efficiency with light weight. The dc-dc conversion efficiencies of about 94 percent were achieved at output powers of 150 watts at 1000 volts using 8x multiplication. A detailed identification of losses was made, including forward drop losses in component, switching losses, reverse junction capacitance charging losses, and charging losses in the main ladder capacitors.

  7. Linearized stability analysis and design of a flyback dc-dc boost regulator.

    NASA Technical Reports Server (NTRS)

    Wester, G. W.

    1973-01-01

    Analytic expressions for the small-signal power-stage describing functions of a switched dc-dc boost regulator are derived from an approximate continuous circuit model which is developed by a time-averaging technique. Closed-loop stability is attained through the design of frequency compensation of the loop gain. Open- and closed-loop regulator output impedances are derived from the linearized models for the given configuration. The analysis and design are compared with and confirmed by breadboard measurements.

  8. DC-DC powering for the CMS pixel upgrade

    NASA Astrophysics Data System (ADS)

    Feld, Lutz; Fleck, Martin; Friedrichs, Marcel; Hensch, Richard; Karpinski, Waclaw; Klein, Katja; Rittich, David; Sammet, Jan; Wlochal, Michael

    2013-12-01

    The CMS experiment plans to replace its silicon pixel detector with a new one with improved rate capability and an additional detection layer at the end of 2016. In order to cope with the increased number of detector modules the new pixel detector will be powered via DC-DC converters close to the sensitive detector volume. This paper reviews the DC-DC powering scheme and reports on the ongoing R&D program to develop converters for the pixel upgrade. Design choices are discussed and results from the electrical and thermal characterisation of converter prototypes are shown. An emphasis is put on system tests with up to 24 converters. The performance of pixel modules powered by DC-DC converters is compared to conventional powering. The integration of the DC-DC powering scheme into the pixel detector is described and system design issues are reviewed.

  9. Early Oscillation Detection for DC/DC Converter Fault Diagnosis

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2011-01-01

    The electrical power system of a spacecraft plays a very critical role for space mission success. Such a modern power system may contain numerous hybrid DC/DC converters both inside the power system electronics (PSE) units and onboard most of the flight electronics modules. One of the faulty conditions for DC/DC converter that poses serious threats to mission safety is the random occurrence of oscillation related to inherent instability characteristics of the DC/DC converters and design deficiency of the power systems. To ensure the highest reliability of the power system, oscillations in any form shall be promptly detected during part level testing, system integration tests, flight health monitoring, and on-board fault diagnosis. The popular gain/phase margin analysis method is capable of predicting stability levels of DC/DC converters, but it is limited only to verification of designs and to part-level testing on some of the models. This method has to inject noise signals into the control loop circuitry as required, thus, interrupts the DC/DC converter's normal operation and increases risks of degrading and damaging the flight unit. A novel technique to detect oscillations at early stage for flight hybrid DC/DC converters was developed.

  10. Bifurcation Analysis of a DC-DC Bidirectional Power Converter Operating with Constant Power Loads

    NASA Astrophysics Data System (ADS)

    Cristiano, Rony; Pagano, Daniel J.; Benadero, Luis; Ponce, Enrique

    Direct current (DC) microgrids (MGs) are an emergent option to satisfy new demands for power quality and integration of renewable resources in electrical distribution systems. This work addresses the large-signal stability analysis of a DC-DC bidirectional converter (DBC) connected to a storage device in an islanding MG. This converter is responsible for controlling the balance of power (load demand and generation) under constant power loads (CPLs). In order to control the DC bus voltage through a DBC, we propose a robust sliding mode control (SMC) based on a washout filter. Dynamical systems techniques are exploited to assess the quality of this switching control strategy. In this sense, a bifurcation analysis is performed to study the nonlinear stability of a reduced model of this system. The appearance of different bifurcations when load parameters and control gains are changed is studied in detail. In the specific case of Teixeira Singularity (TS) bifurcation, some experimental results are provided, confirming the mathematical predictions. Both a deeper insight in the dynamic behavior of the controlled system and valuable design criteria are obtained.

  11. High efficiency and low electromagnetic interference boost DC-DC converter

    NASA Astrophysics Data System (ADS)

    Yajun, Li; Xinquan, Lai; Qiang, Ye; Bing, Yuan

    2014-04-01

    A synchronous boost DC-DC converter with an adaptive dead time control (DTC) circuit and anti-ringing circuit is presented. The DTC circuit is used to provide adjustable dead time and zero inductor current detection for power transistors and therefore, a high efficiency is achieved by minimizing power losses, such as the shoot-through current loss, the body diode conduction loss, the charge-sharing loss and the reverse inductor current loss. Simultaneously, a novel anti-ringing circuit controlled by the switching sequence of power transistors is developed to suppress the ringing when the converter enters the discontinuous conduction mode (DCM) for low electromagnetic interference (EMI) and additional power savings. The proposed converter has been fabricated in a 0.6 μm CDMOS technology. Simulation and experimental results show that the power efficiency of the boost converter is above 81% under different load currents from 10 to 250 mA and a peak efficiency of 90% is achieved at about 100 mA. Moreover, the ringing is easily suppressed by the anti-ringing circuit and therefore the EMI noise is attenuated.

  12. A High Voltage Ratio and Low Ripple Interleaved DC-DC Converter for Fuel Cell Applications

    PubMed Central

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters. PMID:23365536

  13. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    PubMed

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters. PMID:23365536

  14. SUBCONTRACT REPORT: DC-DC Converter for Fuel Cell and Hybrid Vehicles

    SciTech Connect

    Marlino, Laura D; Zhu, Lizhi

    2007-07-01

    The goal of this project is to develop and fabricate a 5kW dc-dc converter with a baseline 14V output capability for fuel cell and hybrid vehicles. The major objectives for this dc-dc converter technology are to meet: Higher efficiency (92%); High coolant temperature,e capability (105 C); High reliability (15 Years/150,000miles); Smaller volume (5L); Lower weight (6kg); and Lower cost ($75/kW). The key technical challenge for these converters is the 105 C coolant temperatures. The power switches and magnetics must be designed to sustain these operating temperatures reliably, without a large cost/mass/volume penalty.

  15. ASIC and FPGA based DPWM architectures for single-phase and single-output DC-DC converter: a review

    NASA Astrophysics Data System (ADS)

    Chander, Subhash; Agarwal, Pramod; Gupta, Indra

    2013-12-01

    Pulse width modulation (PWM) has been widely used in power converter control. This paper presents a review of architectures of the Digital Pulse Width Modulators (DPWM) targeting digital control of switching DC-DC converters. An attempt is made to review the reported architectures with emphasis on the ASIC and FPGA implementations in single phase and single-output DC-DC converters. Recent architectures using FPGA's advanced resources for achieving the resolution higher than classical methods have also been discussed. The merits and demerits of different architectures, and their relative comparative performance, are also presented. The Authors intention is to uncover the groundwork and the related references through this review for the benefit of readers and researchers targeting different DPWM architectures for the DC-DC converters.

  16. A Plasma-Based DC-DC Electrical Transformer

    NASA Astrophysics Data System (ADS)

    Nebel, Richard; Finn, John

    2013-10-01

    Previous work has indicated that it may be possible to make DC-DC electrical transformers using plasmas. The mechanism is an MHD electromagnetic relaxation process induced by helical electrodes. This process is now being tested on the Bismark device at Tibbar Technologies.

  17. A 1.6-kW, 110-kHz dc-dc converter optimized for IGBT's

    NASA Technical Reports Server (NTRS)

    Chen, Keming; Stuart, Thomas A.

    1993-01-01

    A full bridge dc-dc converter using a zero-current and zero-voltage switching technique is described. This circuit utilizes the characteristics of the IGBT to achieve power and frequency combinations that are much higher than previously reported for this device. Experimental results are included for a 1.6-kW, 110-kHz converter with 95 percent efficiency.

  18. Digital Control Technologies for Modular DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Button, Robert M.; Kascak, Peter E.; Lebron-Velilla, Ramon

    2002-01-01

    Recent trends in aerospace Power Management and Distribution (PMAD) systems focus on using commercial off-the-shelf (COTS) components as standard building blocks. This move to more modular designs has been driven by a desire to reduce costs and development times, but is also due to the impressive power density and efficiency numbers achieved by today's commercial DC-DC converters. However, the PMAD designer quickly learns of the hidden "costs" of using COTS converters. The most significant cost is the required addition of external input filters to meet strict electromagnetic interference (MIAMI) requirements for space systems. In fact, the high power density numbers achieved by the commercial manufacturers are greatly due to the lack of necessary input filters included in the COTS module. The NASA Glenn Research Center is currently pursuing a digital control technology that addresses this problem with modular DC-DC converters. This paper presents the digital control technologies that have been developed to greatly reduce the input filter requirements for paralleled, modular DC-DC converters. Initial test result show that the input filter's inductor size was reduced by 75 percent, and the capacitor size was reduced by 94 percent while maintaining the same power quality specifications.

  19. SSP Technology Investigation of a High-Voltage DC-DC Converter

    NASA Technical Reports Server (NTRS)

    Pappas, J. A.; Grady, W. M.; George, Patrick J. (Technical Monitor)

    2002-01-01

    The goal of this project was to establish the feasibility of a high-voltage DC-DC converter based on a rod-array triggered vacuum switch (RATVS) for the Space Solar Power system. The RATVS has many advantages over silicon and silicon-carbide devices. The RATVS is attractive for this application because it is a high-voltage device that has already been demonstrated at currents in excess of the requirement for an SSP device and at much higher per-device voltages than existing or near-term solid state switching devices. The RATVS packs a much higher specific power rating than any solid-state device and it is likely to be more tolerant of its surroundings in space. In addition, pursuit of an RATVS-based system would provide NASA with a nearer-term and less expensive power converter option for the SSP.

  20. Light weight, high power, high voltage dc/dc converter technologies

    NASA Technical Reports Server (NTRS)

    Kraus, Robert; Myers, Ira; Baumann, Eric

    1990-01-01

    Power-conditioning weight reductions by orders of magnitude will be required to enable the megawatt-power-level space systems envisioned by the Strategic Defense Initiative, the Air Force, and NASA. An interagency program has been initiated to develop an 0.1-kg/kW dc/dc converter technology base for these future space applications. Three contractors are in the first phase of a competitive program to develop a megawatt dc/dc converter. Researchers at NASA Lewis Research Center are investigating innovative converter topology control. Three different converter subsystems based on square wave, resonant, and super-resonant topologies are being designed. The components required for the converter designs cover a wide array of technologies. Two different switches, one semiconductor and the other gas, are under development. Issues related to thermal management and material reliability for inductors, transformers, and capacitors are being investigated in order to maximize power density. A brief description of each of the concepts proposed to meet the goals of this program is presented.

  1. Commercial Of-The Shelf DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Denzinger, W.; Baumel, S.

    2011-10-01

    A commercial of-the-shelf (COTS) DC/DC converter for the supply of digital electronics on board of spacecraft has been developed with special emphasis on: *Low cost Readily available *Easy manufacturing *No use of ITAR listed EEE parts like rad-hard mosfets *Minimum number of rad-hard digital and analog IC's *Design tolerance against SEE by appropriate filtering The study was supported by the European Space Agency (ESA) under the contract number 21729/08/NL7LvH.

  2. Low dose failures of hardened DC-DC power converters

    NASA Technical Reports Server (NTRS)

    Lehman, J.; Yui, C.; Rax, B. G.; Miyahira, T. F.; Weideman, M.; Schrick, P.; Swift, G. M.; Johnston, A. H.

    2002-01-01

    Box-level total dose testing of the FOG (Fiber Optic Gyro) by IXSEA at ESA's GammabeamFacility were abruptly terminated at 8krad (Si) due to catastrophic failure (complete shutdown). This was unexpected because all components within the gyro were supposedly radiation tolerant. Further testing showed that the components responsible for the failure were two DC-DC converters, manufactured by Interpoint, that stopped regulating shortly before shutdown. This paper summarizes diagnostic test results for the converters to determine the underlying cause of the unexpected failure at low levels of radiation.

  3. Performance of a spacecraft DC-DC converter breadboard modified for low temperature operation

    NASA Technical Reports Server (NTRS)

    Gerber, Scott S.; Stell, Chris; Patterson, Richard; Ray, Biswajit

    1996-01-01

    A 1OW 3OV/5.OV push-pull dc-dc converter breadboard, designed by the Jet Propulsion Laboratory (JPL) with a +50 C to +5 C operating range for the Cassini space probe, was characterized for lower operating temperatures. The breadboard converter which failed to operate for temperatures below -125 C was then modified to operate at temperatures approaching that of liquid nitrogen (LN2). Associated with this low operating temperature range (greater than -196 C) was a variety of performance problems such as significant change in output voltage, converter switching instability, and failure to restart at temperatures below -154 C. An investigation into these problems yielded additional modifications to the converter which improved low temperature performance even further.

  4. High efficiency interleaved bi-directional ZVS DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zafarullah Khan, M.; Mohsin Naveed, M.; Akbar Hussain, D. M.

    2013-06-01

    A high efficiency interleaved bi-directional ZVS DC-DC converter is presented in this paper. This converter can be operated in both buck and boost mode. CoolMOS is used as a power device to achieve low conduction losses and fast turn off. The value of inductance is selected such that the CoolMOS drain-to-source voltage always falls to zero before it turns on and ZVS is achieved. Multiphase interleaved inductors are used to achieve high power and low ripple currents. Converter is operated at 50kHz and MATLAB Simulink simulation is performed. 6kW prototype converter is implemented in buck mode and simulation results are verified.

  5. Bi-Directional Isolated DC-DC Converter for Next-Generation Power Distribution—Comparison of Converters Using Si and SiC Devices

    NASA Astrophysics Data System (ADS)

    Biela, Juergen; Aggeler, Daniel; Inoue, Shigenori; Akagi, Hirofumi; Kolar, Johann W.

    In this paper two bi-directional DC-DC converters for a 1MW next-generation BTB system of a distribution system, as it is applied in Japan, are presented and compared with respect to design, efficiency and power density. One DC-DC converter applies commercially available Si-devices and the other one high voltage SiC switch, which consists of a SiC JFET cascode (MOSFET+1 JFET) in series with five SiC JFETs. In the comparison also the high frequency, high voltage transformer, which ensures galvanic isolation and which is a core element of the DC-DC converter, is examined in detail by analytic calculations and FEM simulations. For validating the analytical considerations a 20kW SiC DC-DC converter has been designed in detail. Measurement results for the switching and conduction losses have been acquired from the SiC and also for a Si system for calculating the losses of the scaled 1MW system.

  6. Analysis of Discontinuity Induced Bifurcations in a Dual Input DC-DC Converter

    NASA Astrophysics Data System (ADS)

    Giaouris, Damian; Banerjee, Soumitro; Mandal, Kuntal; Al-Hindawi, Mohammed M.; Abusorrah, Abdullah; Al-Turki, Yusuf; El Aroudi, Abdelali

    DC-DC power converters with multiple inputs and a single output are used in numerous applications where multiple sources, e.g. two or more renewable energy sources and/or a battery, feed a single load. In this work, a classical boost converter topology with two input branches connected to two different sources is chosen, with each branch independently being controlled by a separate peak current mode controller. We demonstrate for the first time that even though this converter is similar to other well known topologies that have been studied before, it exhibits many complex nonlinear behaviors that are not found in any other standard PWM controlled power converter. The system undergoes period incrementing cascade as a parameter is varied, with discontinuous hard transitions between consecutive periodicities. We show that the system can be described by a discontinuous map, which explains the observed bifurcation phenomena. The results have been experimentally validated.

  7. Advanced DC/DC Converters towards higher Volumetric Efficiencies for Space Applications

    NASA Technical Reports Server (NTRS)

    Plante, Jeannette; Shue, Jack; Liu, David; Wang, Bright; Shaw, Harry

    2005-01-01

    Contents include the following: 1. NASA mission outlook. 2. Issues with DC/DC converter for space. 3. Statement of newly initiated engineering activities for DC/DC converter. 4. Overview of prototyping work with novel materials. 5. Results of cryogenic testing.

  8. Path planning during combustion mode switch

    SciTech Connect

    Jiang, Li; Ravi, Nikhil

    2015-12-29

    Systems and methods are provided for transitioning between a first combustion mode and a second combustion mode in an internal combustion engine. A current operating point of the engine is identified and a target operating point for the internal combustion engine in the second combustion mode is also determined. A predefined optimized transition operating point is selected from memory. While operating in the first combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion engine to approach the selected optimized transition operating point. When the engine is operating at the selected optimized transition operating point, the combustion mode is switched from the first combustion mode to the second combustion mode. While operating in the second combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion to approach the target operating point.

  9. Mode Switching and Filtering in Nanowire Lasers.

    PubMed

    Röder, Robert; Sidiropoulos, Themistoklis P H; Buschlinger, Robert; Riediger, Max; Peschel, Ulf; Oulton, Rupert F; Ronning, Carsten

    2016-04-13

    Coherent light sources confining the light below the vacuum wavelength barrier will drive future concepts of nanosensing, nanospectroscopy, and photonic circuits. Here, we directly image the angular emission of such a light source based on single semiconductor nanowire lasers. It is confirmed that the lasing switches from the fundamental mode in a thin ZnO nanowire to an admixture of several transverse modes in thicker nanowires approximately at the multimode cutoff. The mode competition with higher order modes substantially slows down the laser dynamics. We show that efficient photonic mode filtering in tapered nanowires selects the desired fundamental mode for lasing with improved performance including power, efficiency, and directionality important for an optimal coupling between adjacent nanophotonic waveguides. PMID:27007261

  10. ZVS Full-Bridge Based DC-DC Converter with Linear Voltage Gain According to Duty Cycle

    NASA Astrophysics Data System (ADS)

    Do, Hyun-Lark

    2013-09-01

    This paper presents a zero-voltage-switching (ZVS) full-bridge based DC-DC converter with linear voltage gain according to duty cycle. The proposed converter is based on an asymmetrical pulse-width-modulation (APWM) full-bridge converter which has various advantages over other converters. However, it has some drawbacks such as limited maximum duty cycle to 0.5 and narrow input range. The proposed converter overcomes these problems. The duty cycle is not limited and input voltage range is wide. Also, the ZVS operation of all power switches is achieved. Therefore, switching losses are significantly reduced and high-efficiency is obtained. Steady-state analysis and experimental results for the proposed converter are presented to validate the feasibility and the performance of the proposed converter.

  11. Achievement of Bevalac rapid mode switching

    SciTech Connect

    Lothrop, F.; Stevenson, R.; Miller, R.; Alonso, J.

    1985-05-01

    Rapid changes of ion, intensity, beam line, and output energy between two modes have been achieved. The techniques for switching among the Bevalac's several injectors are described. Energy level limits at the output (for q/A = 1/2) are 470 to 2100 MeV/n (high power) or 50 to 1050 MeV/n (low power). Depending on specific field value differences, the total time required for a mode change is less than one minute. This mode of operation greatly improves program efficiency in interleaving medical and nuclear science programs at the Bevalac.

  12. Automatic Mode Switch (AMS) Causes Less Synchronization

    PubMed Central

    Jorat, Mohammadvahid; Nikoo, Mohammadhossein

    2016-01-01

    Introduction: Cardiac resynchronization devices are part of modern heart failure management. After implantation, we analyze and program devices in an attempt to ensure their success. Biventricular pacing should be 98% or more for the lowest mortality and best symptom improvement. Case Presentation: In this case series, we present a combination of far field sensing and automatic mode switching (AMS) in six patients. It is found that this combination causes ventricular sensing (VS) episodes with wide QRS and no synchronization. We turn off the AMS and alleviate the problem. Conclusions: Switching AMS off may increase biventricular pacing in some patients. PMID:26949695

  13. Recovery Act: Integrated DC-DC Conversion for Energy-Efficient Multicore Processors

    SciTech Connect

    Shepard, Kenneth L

    2013-03-31

    In this project, we have developed the use of thin-film magnetic materials to improve in energy efficiency of digital computing applications by enabling integrated dc-dc power conversion and management with on-chip power inductors. Integrated voltage regulators also enables fine-grained power management, by providing dynamic scaling of the supply voltage in concert with the clock frequency of synchronous logic to throttle power consumption at periods of low computational demand. The voltage converter generates lower output voltages during periods of low computational performance requirements and higher output voltages during periods of high computational performance requirements. Implementation of integrated power conversion requires high-capacity energy storage devices, which are generally not available in traditional semiconductor processes. We achieve this with integration of thin-film magnetic materials into a conventional complementary metal-oxide-semiconductor (CMOS) process for high-quality on-chip power inductors. This project includes a body of work conducted to develop integrated switch-mode voltage regulators with thin-film magnetic power inductors. Soft-magnetic materials and inductor topologies are selected and optimized, with intent to maximize efficiency and current density of the integrated regulators. A custom integrated circuit (IC) is designed and fabricated in 45-nm CMOS silicon-on-insulator (SOI) to provide the control system and power-train necessary to drive the power inductors, in addition to providing a digital load for the converter. A silicon interposer is designed and fabricated in collaboration with IBM Research to integrate custom power inductors by chip stacking with the 45-nm CMOS integrated circuit, enabling power conversion with current density greater than 10A/mm2. The concepts and designs developed from this work enable significant improvements in performance-per-watt of future microprocessors in servers, desktops, and mobile

  14. Discrete time domain modelling and analysis of dc-dc converters with continuous and discontinuous inductor current

    NASA Technical Reports Server (NTRS)

    Iwens, R. P.; Lee, F. C.; Triner, J. E.

    1977-01-01

    Using discrete time state variable representation, a generalized computer-aided modeling and analysis of dc-dc converters is presented. The methodology provides exact modeling and is applicable to all types of power stages and duty-cycle control, including continuous and discontinuous inductor current operation. Converter stability, transient behavior and audio susceptibility can be analytically evaluated and predicted. The generalized theory of the proposed approach to converter modeling and analysis is presented first, followed by a demonstrative example applying the theory to a constant frequency buck converter operating in continuous and discontinuous inductor current mode. Excellent agreement with laboratory test data has been observed.

  15. Fuzzy logic mode switching in helicopters

    NASA Technical Reports Server (NTRS)

    Sherman, Porter D.; Warburton, Frank W.

    1993-01-01

    The application of fuzzy logic to a wide range of control problems has been gaining momentum internationally, fueled by a concentrated Japanese effort. Advanced Research & Development within the Engineering Department at Sikorsky Aircraft undertook a fuzzy logic research effort designed to evaluate how effective fuzzy logic control might be in relation to helicopter operations. The mode switching module in the advanced flight control portion of Sikorsky's motion based simulator was identified as a good candidate problem because it was simple to understand and contained imprecise (fuzzy) decision criteria. The purpose of the switching module is to aid a helicopter pilot in entering and leaving coordinated turns while in flight. The criteria that determine the transitions between modes are imprecise and depend on the varied ranges of three flight conditions (i.e., simulated parameters): Commanded Rate, Duration, and Roll Attitude. The parameters were given fuzzy ranges and used as input variables to a fuzzy rulebase containing the knowledge of mode switching. The fuzzy control program was integrated into a real time interactive helicopter simulation tool. Optimization of the heading hold and turn coordination was accomplished by interactive pilot simulation testing of the handling quality performance of the helicopter dynamic model. The fuzzy logic code satisfied all the requirements of this candidate control problem.

  16. Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    NASA Astrophysics Data System (ADS)

    Feld, L.; Fimmers, C.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Rittich, D.; Sammet, J.; Wlochal, M.

    2014-01-01

    A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

  17. High reliability DC/DC converter module for electronic boards equipped with FPGAs

    NASA Astrophysics Data System (ADS)

    Viganò, W.; Boccardi, A.; Zamantzas, C.

    2015-01-01

    The Beam Instrumentation Group at CERN is designing a new general-purpose VME carrier module utilising several PTH04T230W DC/DC converters. These off-the-shelf converters are built with unshielded inductors and need to be mounted on the printed circuit board as stand-alone components. Thus, reducing the global manageability and increasing the total cost of the carrier module. The new design aims to develop a module with better power dissipation, efficiency and reliability. In the future, it should be also possible to be directly integrated on the mainboard. For this reason, a Buck DC/DC converter has been implemented with the following main characteristics: input range from 3.0 V to 5.5 V; output range from 0.6 V to 3.3 V, settable by means of an external resistor; output current protection at 6 A; maximum output ripple ± 50 mVpp; switching frequency of 300KHz; short circuit protection; On/Off function; EMI reduction with frequency spread spectrum; soft-start function and thermal shutdown, in a 16 × 19 mm compact size. The selected buck controller is the TPS40303 integrated circuit and drives the CSD16321 power MOSFET, both from Texas Instruments. All selected components have been used at a minimum derating of 50% to reduce component stress and increase the reliability of this module. The selected inductors, i.e. Bourns SRP1055, are the main contributor for the high efficiency (95%), due to their very low equivalent series resistance. On the 4-layer PCB comprising all the components of this module, a snubber circuit, for further reduction of the output ripple due to the MOSFET ringing, can be mounted optionally. It is left as an option due to its effect on the total efficiency. The board layout has been optimized for maximum heat transfer and it can be used without active cooling. The board can maintain the maximum temperature on its surface, while at maximum current output, below 55°C at 25°C ambient temperature. An example of the electrical performance

  18. Electrodeposited Nanolaminated CoNiFe Cores for Ultracompact DC-DC Power Conversion

    SciTech Connect

    Kim, J; Kim, M; Herrault, F; Park, JY; Allen, MG

    2015-09-01

    Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni-80 Fe-20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300-500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g., higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc-dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W.

  19. An Optimal Current Observer for Predictive Current Controlled Buck DC-DC Converters

    PubMed Central

    Min, Run; Chen, Chen; Zhang, Xiaodong; Zou, Xuecheng; Tong, Qiaoling; Zhang, Qiao

    2014-01-01

    In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally. PMID:24854061

  20. An optimal current observer for predictive current controlled buck DC-DC converters.

    PubMed

    Min, Run; Chen, Chen; Zhang, Xiaodong; Zou, Xuecheng; Tong, Qiaoling; Zhang, Qiao

    2014-01-01

    In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally. PMID:24854061

  1. Comparative analysis between overlapping and non-overlapping operation modes for the PWM buck converter using the three-state switching cell

    NASA Astrophysics Data System (ADS)

    Robles Balestero, Juan Paulo; Lessa Tofoli, Fernando; Mendes de Seixas, Claudiner; Torrico Bascopé, Grover Victor; José Mendes de Seixas, Falcondes

    2014-04-01

    This article presents a comparative study involving a buck converter derived from the three-state switching cell in both operation modes, i.e. non-overlapping and overlapping modes, since it is well known in literature that several advantages can be addressed to topologies based on this approach. In the case of the mentioned converter, only part of the load delivered to the load flows through the controlled switches, so that operation at high-current high-power levels is possible. Besides, the design of reactive elements such as very autotransformer and filter inductor is performed for twice the switching frequency, with consequent reduction of size, weight and volume. Another clear advantage is that the area for which the converter operates in continuous conduction mode is wider than that for the discontinuous conduction mode in comparison with the so-called classical non-isolated buck converter. The operation of the converter, which was previously proposed in literature, is analysed considering the aforementioned modes in terms of the efficiency, and similar approaches for the non-isolated dc-dc conversion are also investigated.

  2. Robust DC/DC converter control for polymer electrolyte membrane fuel cell application

    NASA Astrophysics Data System (ADS)

    Wang, Ya-Xiong; Yu, Duck-Hyun; Chen, Shi-An; Kim, Young-Bae

    2014-09-01

    This study investigates a robust controller in regulating the pulse width modulation (PWM) of a DC/DC converter for a polymer electrolyte membrane fuel cell (PEMFC) application. A significant variation in the output voltage of a PEMFC depends on the power requirement and prevents a PEMFC from directly connecting to a subsequent power bus. DC/DC converters are utilized to step-up or step-down voltage to match the subsequent power bus voltage. In this study, a full dynamic model, which includes a PEMFC and boost and buck DC/DC converters, is developed under MATLAB/Simulink environment for control. A robust PWM duty ratio control for the converters is designed using time delay control (TDC). This control enables state variables to accurately follow the dynamics of a reference model using time-delayed information of plant input and output information within a few sampling periods. To prove the superiority of the TDC performance, traditional proportional-integral control (PIC) and model predictive control (MPC) are designed and implemented, and the simulation results are compared. The efficacies of TDC for the PEMFC-fed PWM DC/DC converters are validated through experimental test results using a 100 W PEMFC as well as boost and buck DC/DC converters.

  3. High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

    DOEpatents

    Shimer, D.W.; Lange, A.C.

    1995-05-23

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

  4. High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

    DOEpatents

    Shimer, Daniel W.; Lange, Arnold C.

    1995-01-01

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

  5. Low-to-Medium Power Single Chip Digital Controlled DC-DC Regulator for Point-of-Load Applications

    NASA Technical Reports Server (NTRS)

    Adell, Philippe C. (Inventor); Bakkaloglu, Bertan (Inventor); Vermeire, Bert (Inventor); Liu, Tao (Inventor)

    2015-01-01

    A DC-DC converter for generating a DC output voltage includes: a digitally controlled pulse width modulator (DPWM) for controlling a switching power stage to supply a varying voltage to an inductor; and a digital voltage feedback circuit for controlling the DPWM in accordance with a feedback voltage corresponding to the DC output voltage, the digital voltage feedback circuit including: a first voltage controlled oscillator for converting the feedback voltage into a first frequency signal and to supply the first frequency signal to a first frequency discriminator; a second voltage controlled oscillator for converting a reference voltage into a second frequency signal and to supply the second frequency signal to a second frequency discriminator; a digital comparator for comparing digital outputs of the first and second frequency discriminators and for outputting a digital feedback signal; and a controller for controlling the DPWM in accordance with the digital feedback signal.

  6. Asynchronous Transfer Mode (ATM) Switch Technology and Vendor Survey

    NASA Technical Reports Server (NTRS)

    Berry, Noemi

    1995-01-01

    Asynchronous Transfer Mode (ATM) switch and software features are described and compared in order to make switch comparisons meaningful. An ATM switch's performance cannot be measured solely based on its claimed switching capacity; traffic management and congestion control are emerging as the determining factors in an ATM network's ultimate throughput. Non-switch ATM products and experiences with actual installations of ATM networks are described. A compilation of select vendor offerings as of October 1994 is provided in chart form.

  7. Experimental study of a bidirectional DC-DC converter for the DC link voltage control and the regenerative braking in PM motor drives devoted to electrical vehicles

    SciTech Connect

    Caricchi, F.; Crescimbini, F.; Noia, G.; Pirolo, D.

    1994-12-31

    The use of a bidirectional DC-DC converter operating in the DC link of CRPWM-inverter-fed motor drives devoted to electric vehicles (EVs) application allows a suitable control of both motoring and regenerative braking operations, and it can contribute to a significant increase of the motor drive overall efficiency. This paper deals with the experimental study of a bidirectional DC-DC converter prototype which has been designed for application in small-size EVs propelled by axial-flux PM motor drives. The paper discusses the converter modes of operation and reports the experimental results taken from a converter prototype which has been constructed using an IGBTs power module rated 600 V, 50 A. 2 refs.

  8. Development of a fuzzy logic controller for dc/dc converters: Design, computer simulation, and experimental evaluation

    SciTech Connect

    So, W.C.; Tse, C.K.; Lee, Y.S.

    1996-01-01

    The design of a fuzzy logic controller for dc/dc converters is described in this paper. A brief review of fuzzy logic and its application to control is first given. Then, the derivation of a fuzzy control algorithm for regulating dc/dc converters is described in detail. The proposed fuzzy control is evaluated by computer simulations as well as experimental measurements of the closed-loop performance of simple dc/dc converters in respect of load regulation and line regulation.

  9. Modelling and Simulation of Digital Compensation Technique for dc-dc Converter by Pole Placement

    NASA Astrophysics Data System (ADS)

    Shenbagalakshmi, R.; Sree Renga Raja, T.

    2015-09-01

    A thorough and effective analysis of the dc-dc converters is carried out in order to achieve the system stability and to improve the dynamic performance. A small signal modelling based on state space averaging technique for dc-dc converters is carried out. A digital state feedback gain matrix is derived by pole placement technique in order to achieve the stability of a completely controllable system. A prediction observer for the dc-dc converters is designed and a dynamic compensation (observer plus control law) is provided using separation principle. The output is very much improved with zero output voltage ripples, zero peak overshoot, and much lesser settling time in the range of ms and with higher overall efficiency (>90 %).

  10. DC/DC Power Converter for Super-Capacitor Supplied by Electric Power Splitter

    NASA Astrophysics Data System (ADS)

    Haubert, T.; Mindl, P.

    The aim of the article is design of DC/DC converter and discussing of problematic supply using electric power splitter. The electric power splitter with AC/DC converter is source for the DC/DC converter, which is dedicated for charging and discharging of hybrid car drive super-capacitor energy storage. The electric power splitter is synchronous machine with two rotating parts. First rotor contains permanent magnet and the second rotor contains three-phase windings. The amplitude of output voltage depends on difference between first and second rotor speed. The main role of the DC/DC converter is to optimize energy content in super-capacitor storage used to acceleration and deceleration driving period of the passenger car with hybrid electric vehicle (HEV) drive system using electric power splitter.

  11. The DC-DC conversion power system of the CMS Phase-1 pixel upgrade

    NASA Astrophysics Data System (ADS)

    Feld, L.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Schmitz, St.; Wlochal, M.

    2015-01-01

    The pixel detector of the CMS experiment will be exchanged during the year-end technical stop in 2016/2017, as part of the experiment's Phase-1 upgrade. The new device will feature approximately twice the number of readout channels, and consequently the power consumption will be doubled. By moving to a DC-DC conversion powering scheme, it is possible to power the new pixel detector with the existing power supplies and cable plant. The power system of the Phase-1 pixel detector is described and the performance of the new components, including DC-DC converters, DC-DC converter motherboards and various power distribution boards, is detailed. The outcome of system tests in terms of electrical behaviour, thermal management and pixel module performance is discussed.

  12. Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

    NASA Technical Reports Server (NTRS)

    Patterson, Richard; Hammoud, Ahmad

    2010-01-01

    DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

  13. Application handbook for a Standardized Control Module (SCM) for DC-DC converters, volume 1

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Mahmoud, M. F.; Yu, Y.

    1980-01-01

    The standardized control module (SCM) was developed for application in the buck, boost and buck/boost DC-DC converters. The SCM used multiple feedback loops to provide improved input line and output load regulation, stable feedback control system, good dynamic transient response and adaptive compensation of the control loop for changes in open loop gain and output filter time constraints. The necessary modeling and analysis tools to aid the design engineer in the application of the SCM to DC-DC Converters were developed. The SCM functional block diagram and the different analysis techniques were examined. The average time domain analysis technique was chosen as the basic analytical tool. The power stage transfer functions were developed for the buck, boost and buck/boost converters. The analog signal and digital signal processor transfer functions were developed for the three DC-DC Converter types using the constant on time, constant off time and constant frequency control laws.

  14. Advanced DC/DC Converters Towards Higher Volumetric Efficiencies For Space Applications

    NASA Technical Reports Server (NTRS)

    Shaw, Harry; Shue, Jack; Liu, David; Wang, Bright; Plante, Jeanette

    2005-01-01

    A new emphasis on planetary exploration by NASA drives the need for small, high power DC/DC converters which are functionally modular. NASA GSFC and other government space organizations are supporting technology development in the DC/DC converter area to both meet new needs and to promote more sources of supply. New technologies which enable miniaturization such as embedded passive technologies and thermal management using high thermal conductivity materials are features of the new designs. Construction of some simple DC/DC converter core circuits using embedded components was found to be successful for increasing volumetric efficiency to 37 W/inch. The embedded passives were also able to perform satisfactorily in this application in cryogenic temperatures.

  15. Analysis of high voltage step-up nonisolated DC-DC boost converters

    NASA Astrophysics Data System (ADS)

    Alisson Alencar Freitas, Antônio; Lessa Tofoli, Fernando; Junior, Edilson Mineiro Sá; Daher, Sergio; Antunes, Fernando Luiz Marcelo

    2016-05-01

    A high voltage step-up nonisolated DC-DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC-DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.

  16. Efficiency and Regulation of Commercial Low Power DC/DC Converter Modules at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

    2000-01-01

    DC/DC converters that are capable of operating at cryogenic temperatures are anticipated to play an important role in the power systems of future NASA deep space missions. Design of these converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. At the NASA Glenn Research Center Low Temperature Electronics Laboratory, several commercial off-the-shelf dc/dc converter modules were evaluated for their low temperature performance. Various parameters were investigated as a function of temperature, in the range of 20 C to -190 C. Data pertaining to the efficiency and voltage regulation of the tested converters is presented and discussed.

  17. Single Event Burnout in DC-DC Converters for the LHC Experiments

    SciTech Connect

    Claudio H. Rivetta et al.

    2001-09-24

    High voltage transistors in DC-DC converters are prone to catastrophic Single Event Burnout in the LHC radiation environment. This paper presents a systematic methodology to analyze single event effects sensitivity in converters and proposes solutions based on de-rating input voltage and output current or voltage.

  18. Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System

    ERIC Educational Resources Information Center

    Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

    2012-01-01

    We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

  19. Regulation of a lightweight high efficiency capacitator diode voltage multiplier dc-dc converter

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  20. A DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    NASA Astrophysics Data System (ADS)

    Feld, L.; Fleck, M.; Friedrichs, M.; Hensch, R.; Karpinski, W.; Klein, K.; Sammet, J.; Wlochal, M.

    2013-02-01

    The CMS pixel detector was designed for a nominal instantaneous LHC luminosity of 1ṡ1034 cm-2s-1. During Phase-1 of the LHC upgrade, the instantaneous luminosity will be increased to about twice this value. To preserve the excellent performance of the pixel detector despite the increase in particle rates and track densities, the CMS Collaboration foresees the exchange of its pixel detector in the shutdown 2016/2017. The new pixel detector will be improved in many respects, and will comprise twice the number of readout channels. A powering scheme based on DC-DC conversion will be adopted, which will enable the provision of the required power with the present cable plant. The powering scheme of the CMS pixel detector will be described, and the performance of prototype DC-DC buck converters will be presented, including power efficiency, system tests with DC-DC converters and pixel modules, thermal management, reliability at low temperature, and studies of potential frequency locking between DC-DC converters.

  1. Regulation of a lightweight high efficiency capacitor diode voltage multiplier dc-dc converter

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  2. Electrically controlled optical-mode switch for fundamental mode and first order mode

    NASA Astrophysics Data System (ADS)

    Imansyah, Ryan; Tanaka, Tatsushi; Himbele, Luke; Jiang, Haisong; Hamamoto, Kiichi

    2016-08-01

    We have proposed an optical mode switch, the principle of which is based on the partial phase shift of injected light; therefore, one important issue is to clarify the proper design criteria for the mode combiner section. We focused on the bending radius of the S-bend waveguide issue that is connected to the multi mode waveguide in the Y-junction section that acts as mode combiner. Long radius leads to undesired mode coupling before the Y-junction section, whereas a short radius causes radiation loss. Thus, we simulated this mode combiner by the beam-propagation method to obtain the proper radius. In addition, we used a trench pin structure to simplify the fabrication process into a single-step dry-etching process. As a result, we successfully fabricated an optical-mode switch with the bending radius R = 610 µm. It showed the successful electrical mode switching and the achieved mode crosstalk was approximately ‑10 dB for 1550 nm wavelength with the injection current of 60 mA (5.7 V).

  3. Switching of Swimming Modes in Magnetospirillium gryphiswaldense

    PubMed Central

    Reufer, M.; Besseling, R.; Schwarz-Linek, J.; Martinez, V.A.; Morozov, A.N.; Arlt, J.; Trubitsyn, D.; Ward, F.B.; Poon, W.C.K.

    2014-01-01

    The microaerophilic magnetotactic bacterium Magnetospirillum gryphiswaldense swims along magnetic field lines using a single flagellum at each cell pole. It is believed that this magnetotactic behavior enables cells to seek optimal oxygen concentration with maximal efficiency. We analyze the trajectories of swimming M. gryphiswaldense cells in external magnetic fields larger than the earth’s field, and show that each cell can switch very rapidly (in <0.2 s) between a fast and a slow swimming mode. Close to a glass surface, a variety of trajectories were observed, from straight swimming that systematically deviates from field lines to various helices. A model in which fast (slow) swimming is solely due to the rotation of the trailing (leading) flagellum can account for these observations. We determined the magnetic moment of this bacterium using a to our knowledge new method, and obtained a value of (2.0±0.6)×10−16 A · m2. This value is found to be consistent with parameters emerging from quantitative fitting of trajectories to our model. PMID:24411235

  4. The mode switching of PSR B2020+28

    NASA Astrophysics Data System (ADS)

    Wen, Z. G.; Wang, N.; Yan, W. M.; Yuan, J. P.; Liu, Z. Y.; Chen, M. Z.; Chen, J. L.

    2016-08-01

    This paper reports on polarimetric radiation properties based on the switching modes of normal PSR B2020+28 by analyzing the data acquired from the Nanshan 25-m radio telescope at 1556 MHz. With nearly 8 hours quasi-continuous observation, the data presented some striking and updated phenomena. The change of relative intensity between the leading and trailing components is the predominant feature of mode switching. The intensity ratio between the leading and trailing components are measured for the individual profiles averaged over 30 seconds. It is found that there is an excess of high ratios over the normal distribution, which indicates that two modes exist in the pulsar. The distribution of abnormal mode has a narrower width indicating that the abnormal mode is more stable than the normal mode. A total of 76 mode switching events are detected in our data. It spends 89 % in the normal mode and 11 % in the abnormal mode. The intrinsic distributions of mode timescales are constrained with power-law distributions. The significant difference in the index of the duration distribution between normal and abnormal modes possibly indicates that the timescale for the abnormal mode to get stable is shorter than that for the normal mode. The frequent switching between both modes may indicate that the oscillations between different magnetospheric states are rapid.

  5. Mode-selective optical packet switching in mode-division multiplexing networks.

    PubMed

    Diamantopoulos, N P; Hayashi, M; Yoshida, Y; Maruta, A; Maruyama, R; Kuwaki, N; Takenaga, K; Uemura, H; Matsuo, S; Kitayama, K

    2015-09-01

    A novel mode-selective optical packet switching, based on mode-multiplexers/demultiplexers and multi-port optical micro-electro-mechanical systems (MEMS) switches, has been proposed and experimentally demonstrated. The experimental demonstration was performed using the LP(01), LP(11a) and LP(11b) modes of a 30-km long mode-division multiplexed few-mode fiber link, utilizing 40 Gb/s, 16-QAM signals. PMID:26368463

  6. DC-DC power converter research for Orbiter/Station power exchange

    NASA Technical Reports Server (NTRS)

    Ehsani, M.

    1993-01-01

    This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented.

  7. Cryogenic Evaluation of an Advanced DC/DC Converter Module for Deep Space Applications

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Hammoud, Ahmad; Gerber, Scott S.; Patterson, Richard

    2003-01-01

    DC/DC converters are widely used in power management, conditioning, and control of space power systems. Deep space applications require electronics that withstand cryogenic temperature and meet a stringent radiation tolerance. In this work, the performance of an advanced, radiation-hardened (rad-hard) commercial DC/DC converter module was investigated at cryogenic temperatures. The converter was investigated in terms of its steady state and dynamic operations. The output voltage regulation, efficiency, terminal current ripple characteristics, and output voltage response to load changes were determined in the temperature range of 20 to -140 C. These parameters were obtained at various load levels and at different input voltages. The experimental procedures along with the results obtained on the investigated converter are presented and discussed.

  8. Adaptive output voltage tracking controller for uncertain DC/DC boost converter

    NASA Astrophysics Data System (ADS)

    Lee, Byoung-Seoup; Kim, Seok-Kyoon; Park, Jin-Hyuk; Lee, Kyo-Beum

    2016-06-01

    This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.

  9. Compact Low Cost Hybrid DC/DC Converter Controller For Space Applications

    NASA Astrophysics Data System (ADS)

    Volpi, Gian Franco; Contissa, Alessandro; Mantegazza, Massimiliano

    2011-10-01

    The need for low cost, space qualified (ESA requirements), compact DC/DC converters is becoming increasingly important both for commercial market and programs controlled by space administration. Market is also showing request for large scale production. To face market needs, the design of low power multi- output DC/DC converters can be based on small and low mass hybrid controllers for better mechanical optimization. Moreover, this approach, maintaining robust performances against harsh space environment, allows taking the advantages typical of recurrent design: high reliability and reduction of cost. Also, using the hybrid controller allows designers to focus just on power transformer and filters, reducing the time necessary to complete the design. This paper shall provide description of the standard Thales Alenia Space hybrid controller in its two variants: 40V-760V (HYLPSC03RAD) and 20.5V-43V (HYLPSC04RAD) bus voltage.

  10. Analysis of a transformer-less, multi-level DC-DC converter for HVDC operation

    SciTech Connect

    Karady, G.G.; Devarajan, S.

    1998-12-31

    HVDC systems require DC step up and DC step down units. The traditional approach is the application of twelve-pulse thyristor bridges with transformers. The developments of fast switching IGBT devices permit the development of transformer-less, multi-level converters. A multi-level circuit was suggested by Limpaecher. This paper presents a detailed simulation of the proposed circuit together with the analysis of its performance. The converter consists of a set of capacitors, air core inductors and solid state switches arranged in a ladder network. In the step-up mode, the closing of solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches connect the capacitors in series and discharge them through an air-core inductor to the load. In the step-down mode the capacitors are charged in series and discharged in parallel. The circuit has three modes of operation in each cycle: charge, inversion, and discharge. The circuit operation is analyzed in each mode using SPICE simulations. The selection of the components is discussed and output voltage regulation is analyzed. The results show that the proposed circuit promises significant reduction of losses, because of the zero current switching. The investment cost is reduced because of the elimination of transformers.

  11. High performance dc-dc conversion with voltage multipliers. [using transformerless capacitor diode circuit

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1974-01-01

    An experimental 100W 1000V dc-dc converter using a capacitor diode voltage multipler (CDVM) with a nominal frequency of 100 kHz is studied. A component weight of about 1 kg/kW was obtained. Design equations for current, output -ripple and -power, efficiency and output voltage are derived. Agreement between experimental results and calculations is fairly good except for ripple.

  12. Mode switching in a gyrotron with azimuthally corrugated resonator.

    PubMed

    Nusinovich, G S; Sinitsyn, O V; Antonsen, T M

    2007-05-18

    The operation of a gyrotron having a cylindrical resonator with an azimuthally corrugated wall is analyzed. In such a device, wall corrugation cancels the degeneracy of the modes with azimuthally standing patterns. The coupling between these modes depends on the radius of electron beam. It is shown that such a gyrotron can be easily switched from one mode to another. When the switching is done with the repetition frequency equal to the rotational frequency of magnetic islands, this sort of operation can be used for suppression of neoclassical tearing modes in large-scale tokamaks and stellarators. PMID:17677705

  13. Mode Switching in a Gyrotron with Azimuthally Corrugated Resonator

    SciTech Connect

    Nusinovich, G. S.; Sinitsyn, O. V.; Antonsen, T. M. Jr.

    2007-05-18

    The operation of a gyrotron having a cylindrical resonator with an azimuthally corrugated wall is analyzed. In such a device, wall corrugation cancels the degeneracy of the modes with azimuthally standing patterns. The coupling between these modes depends on the radius of electron beam. It is shown that such a gyrotron can be easily switched from one mode to another. When the switching is done with the repetition frequency equal to the rotational frequency of magnetic islands, this sort of operation can be used for suppression of neoclassical tearing modes in large-scale tokamaks and stellarators.

  14. DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

    NASA Astrophysics Data System (ADS)

    Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

    2013-06-01

    Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

  15. A 1 MW, 100 kV, less than 100 kg space based dc-dc power converter

    NASA Technical Reports Server (NTRS)

    Cooper, J. R.; White, C. W.

    1991-01-01

    A 1 MW dc-dc power converter has been designed which has an input voltage of 5 kV +/-3 percent, an output voltage of 100 kV +/- 0.25 percent, and a run time of 1000 s at full power. The estimated system mass is 83.8 kg, giving a power density of 11.9 kW/kg. The system exceeded the weight goal of 10 kW/kg through the use of innovative components and system concepts. The system volume is approximately 0.1 cu m, and the overall system efficiency is estimated to be 87 percent. Some of the unique system features include a 50-kHz H-bridge inverter using MOS-controlled thyristors as the switching devices, a resonance transformer to step up the voltage, open-cycle cryogenic hydrogen gas cooling, and a nonrigid, inflatable housing which provides on-demand pressurization of the power converter local environment. This system scales very well to higher output powers. The weight of the 10-MW system with the same input and output voltage requirements and overall system configuration is estimated to be 575.3 kg. This gives a power density of 17.4 kW/kg, significantly higher than the 11.9 kW/kg estimated at 1 MW.

  16. Electron dynamics in the process of mode switching in gyrotrons

    SciTech Connect

    Dumbrajs, O.; Kominis, Y.; Nusinovich, G. S.

    2009-01-15

    The present paper is devoted to the analysis of electron interaction process in the course of gyrotron switching from one mode to another. This analysis is based on the use of the Hamiltonian formalism that allows one to construct Poincare plots for different instants of switching time. The study is carried out for a 170 GHz, MW-class gyrotron for the International Thermonuclear Experimental Reactor (ITER) [ITER web site: http://www.iter.org].

  17. Advanced medium-voltage bidirectional dc-dc conversion systems for future electric energy delivery and management systems

    NASA Astrophysics Data System (ADS)

    Fan, Haifeng

    2011-12-01

    switching loss and conduction loss are must-haves for high efficiency, while bidirectional power flow capability is a must for power management requirement. To address the demand, the phase-shift dual-halfbridge (DHB) is proposed as the constituent module of ISOP configuration for MV application. The proposed ISOP DHB converter employs zero-voltage-switching (ZVS) technique combined with LV MOSFETs to achieve low switching and conduction losses under high frequency operation, and therefore high efficiency and high power density, and bidirectional power flow as well. Secondly, a large load range of high efficiency is desired rather than only a specific load point due to the continuous operation and large load variation range of utility application, which is of high importance because of the rising energy cost. This work proposes a novel DHB converter with an adaptive commutation inductor. By utilizing an adaptive inductor as the main energy transfer element, the output power can be controlled by not only the phase shift but also the commutation inductance, which allows the circulating energy to be optimized for different load conditions to maintain ZVS under light load conditions and minimize additional conduction losses under heavy load conditions as well. As a result, the efficiency at both light and heavy load can be significantly improved compared with the conventional DHB converter, and therefore extended high-efficiency range can be achieved. In addition, current stress of switch devices can be reduced. The theoretical analysis is presented and validated by the experimental results on a 50 kHz, 1 kW dc-dc converter module. Thirdly, input-voltage sharing and output-current sharing are critical to assure the advantages of the ISOP modular configuration. To solve this issue, an identically distributed control scheme is proposed in this work. The proposed control scheme, using only one distributed voltage loop to realize both input-voltage and output-current sharing

  18. A High Power Density DC-DC Converter for Distributed PV Architectures

    SciTech Connect

    Agamy, Mohammed S; Chi, Song; Elasser, Ahmed; Harfman-Todorovic, Maja; Jiang, Yan; Mueller, Frank; Tao, Fengfeng

    2012-06-01

    In order to maximize solar energy harvesting capabilities, power converters have to be designed for high efficiency and good MPPT and voltage/current performance. When many converters are used in distributed systems, power density also becomes an important factor as it allows for simpler system integration. In this paper a high power density string dc-dc converter suitable for distributed medium to large scale PV installation is presented. A simple partial power processing topology, implemented with all silicon carbide devices provides high efficiency as well as high power density. A 3.5kW, 100kHz converter is designed and tested to verify the proposed methods.

  19. DC-DC Converter Topology Assessment for Large Scale Distributed Photovoltaic Plant Architectures

    SciTech Connect

    Agamy, Mohammed S; Harfman-Todorovic, Maja; Elasser, Ahmed; Sabate, Juan A; Steigerwald, Robert L; Jiang, Yan; Essakiappan, Somasundaram

    2011-07-01

    Distributed photovoltaic (PV) plant architectures are emerging as a replacement for the classical central inverter based systems. However, power converters of smaller ratings may have a negative impact on system efficiency, reliability and cost. Therefore, it is necessary to design converters with very high efficiency and simpler topologies in order not to offset the benefits gained by using distributed PV systems. In this paper an evaluation of the selection criteria for dc-dc converters for distributed PV systems is performed; this evaluation includes efficiency, simplicity of design, reliability and cost. Based on this evaluation, recommendations can be made as to which class of converters is best fit for this application.

  20. Combustion mode switching with a turbocharged/supercharged engine

    SciTech Connect

    Mond, Alan; Jiang, Li

    2015-09-22

    A method for switching between low- and high-dilution combustion modes in an internal combustion engine having an intake passage with an exhaust-driven turbocharger, a crankshaft-driven positive displacement supercharger downstream of the turbocharger and having variable boost controllable with a supercharger bypass valve, and a throttle valve downstream of the supercharger. The current combustion mode and mass air flow are determined. A switch to the target combustion mode is commanded when an operating condition falls within a range of predetermined operating conditions. A target mass air flow to achieve a target air-fuel ratio corresponding to the current operating condition and the target combustion mode is determined. The degree of opening of the supercharger bypass valve and the throttle valve are controlled to achieve the target mass air flow. The amount of residual exhaust gas is manipulated.

  1. Architectures and Control of Submodule Integrated DC-DC Converters for Photovoltaic Applications

    SciTech Connect

    Olalla, C; Clement, D; Rodriguez, M; Maksimovic, D

    2013-06-01

    This paper describes photovoltaic (PV) module architectures with parallel-connected submodule-integrated dc-dc converters (subMICs) that improve efficiency of energy capture in the presence of partial shading or other mismatch conditions. The subMICs are bidirectional isolated dc-dc converters capable of injecting or subtracting currents to balance the module substring voltages. When no mismatches are present, the subMICs are simply shut down, resulting in zero insertion losses. It is shown that the objective of minimum subMIC power processing can be solved as a linear programming problem. A simple close-to-optimal distributed control approach is presented that allows autonomous subMIC control without the need for a central controller or any communication among the subMICs. Furthermore, the proposed control approach is well suited for an isolated-port architecture, which yields additional practical advantages including reduced subMIC power and voltage ratings. The architectures and the control approach are validated by simulations and experimental results using three bidirectional flyback subMICs attached to a standard 180-W, 72-cell PV module, yielding greater than 98% module-level power processing efficiency for a mismatch less than 25%.

  2. Effective switching frequency multiplier inverter

    SciTech Connect

    Su, Gui-Jia; Peng, Fang Z.

    2007-08-07

    A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

  3. Temperature switching of cavity modes in InN microcrystals

    SciTech Connect

    Kazanov, D. R. Kaibyshev, V. H.; Davydov, V. Yu.; Smirnov, A. N.; Jmerik, V. N.; Kuznetsova, N. V.; Kopiev, P. S.; Ivanov, S. V.; Shubina, T. V.

    2015-11-15

    InN optical cavities supporting low-order whispering-gallery modes up to room temperature are formed by molecular-beam epitaxy on patterned substrates. The observed switching of the mode type with increasing temperature is explained in terms of changes in the optical parameters due to a shift of the absorption edge and modification of its shape. Modeling taking into account a variation in the refractive index reproduces the typical distributions of the electromagnetic-field intensity in the cavities.

  4. A Cryogenic Dc-Dc Power Converter for a 100 kW Synchronous HTS Generator at Liquid Nitrogen Temperatures

    NASA Astrophysics Data System (ADS)

    Bailey, Wendell; Wen, Hauming; Yang, Yifeng; Forsyth, Andrew; Jia, Chungjiang

    A dc-dc converter has been developed for retrofitting inside the vacuum space of the HTS rotor of a synchronous generator. The heavy copper sections of the current leads used for energising the HTS field winding were replaced by cryogenic power electronics; consisting of the converter and a rotor control unit. The converter board was designed using an H-bridge configuration with two 5A rated wires connecting the cryogenic boards to the stator control board located on the outside of the generator and drawing power from a (5A, 50 V) dc power source. The robustness of converter board was well demonstrated when it was powered up from a cold start at 82K. When charging the field winding with moderate currents (30A), the heat in-leak to the 'cold' rotor core was only 2W. It continued to function down to 74K, surviving several quenches. However, the quench protection function failed when injecting 75A into the field winding, resulting in the burn out of one of the DC-link capacitors. The magnitudes of the critical currents measured with the original current leads were compared to the quench currents, which was defined as the current which triggered quench protection protocol. The difference between the two currents was rather large, (∼20A). However, additional measurements using a single HTS coil in liquid nitrogen found that this reduction should not be so dramatic and in the region of 4A. Our conclusions identified the converter's switching voltage and its operating frequency as two parameters, which could have contributed to lowering the quench current. Magnetic fields and eddy currents are expected to be more prominent the field winding and its impact on the converter also need further investigation.

  5. Anisotropic nanolaminated CoNiFe cores integrated into microinductors for high-frequency dc-dc power conversion

    NASA Astrophysics Data System (ADS)

    Kim, Jooncheol; Kim, Minsoo; Kim, Jung-Kwun; Herrault, Florian; Allen, Mark G.

    2015-11-01

    This paper presents a rectangular, anisotropic nanolaminated CoNiFe core that possesses a magnetically hard axis in the long geometric axis direction. Previously, we have developed nanolaminated cores comprising tens to hundreds of layers of 300-1000 nm thick metallic alloys (i.e. Ni80Fe20 or Co44Ni37Fe19) based on sequential electrodeposition, demonstrating suppressed eddy-current losses at MHz frequencies. In this work, magnetic anisotropy was induced to the nanolaminated CoNiFe cores by applying an external magnetic field (50-100 mT) during CoNiFe film electrodeposition. The fabricated cores comprised tens to hundreds of layers of 500-1000 nm thick CoNiFe laminations that have the hard-axis magnetic property. Packaged in a 22-turn solenoid test inductor, the anisotropic core showed 10% increased effective permeability and 25% reduced core power losses at MHz operation frequency, compared to an isotropic core of the identical geometry. Operating the anisotropic nanolaminated CoNiFe core in a step-down dc-dc converter (15 V input to 5 V output) demonstrated 81% converter efficiency at a switching frequency of 1.1 MHz and output power of 6.5 W. A solenoid microinductor with microfabricated windings integrated with the anisotropic nanolaminated CoNiFe core was fabricated, demonstrating a constant inductance of 600 nH up to 10 MHz and peak quality factor exceeding 20 at 4 MHz. The performance of the microinductor with the anisotropic nanolaminated CoNiFe core is compared with other previously reported microinductors.

  6. High-Voltage 1-kW dc/dc Converter Developed for Low-Temperature Operation

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.

    1998-01-01

    Recently, Lewis developed and demonstrated a high-voltage, 1-kW dc/dc converter that operates from room temperature to -184 C. A power supply designed for use in a NASA ion beam propulsion system was utilized as a starting point for the design of a low- (wide-) temperature dc/dc converter. For safety, we decided to halve the output voltage and power level, so the converter was designed for an 80-Vdc input and a 550-Vdc output at 1 kW.

  7. Construction of a dc-dc transformer - A model of transitory behavior under load

    NASA Astrophysics Data System (ADS)

    Louail, G.

    A numerical model is presented for the construction of high performance dc-dc transformers for industrial applications, taking into account a variety of control techniques. Control logic to minimize fluctuations during load dumping intervals are defined. Problems linked to the demagnetization of the core are investigated and solutions are proposed. Attention is given to the selection of a commutator for a given application of a transformer, and functional characteristics of bipolar and MOS transistors are described. The principles are applied to the construction of a prototype second order transformer which is amenable to modular use. Finally, two methods of numerical modeling are presented: the first with simplified hypotheses for use with a hand calculator, and the second more rigourous, using discretized equations in a static regime. It is shown that a sudden power surge is the most critical phase for a power commutator. Progressively loading logic is devised, and the fabrication of 150 A commutators is indicated

  8. Low Temperature Performance of High Power Density DC/DC Converter Modules

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Hammond, Ahmad; Gerber, Scott; Patterson, Richard L.; Overton, Eric

    2001-01-01

    In this paper, two second-generation high power density DC/DC converter modules have been evaluated at low operating temperatures. The power rating of one converter (Module 1) was specified at 150 W with an input voltage range of 36 to 75 V and output voltage of 12 V. The other converter (Module 2) was specified at 100 W with the same input voltage range and an output voltage of 3.3 V. The converter modules were evaluated in terms of their performance as a function of operating temperature in the range of 25 to -140 C. The experimental procedures along with the experimental data obtained are presented and discussed in this paper.

  9. Low-temperature operation of a Buck DC/DC converter

    NASA Technical Reports Server (NTRS)

    Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

    1995-01-01

    Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials.

  10. DC-DC converters in 0.35μm CMOS technology

    NASA Astrophysics Data System (ADS)

    Michelis, S.; Allongue, B.; Blanchot, G.; Faccio, F.; Fuentes, C.; Orlandi, S.; Saggini, S.; Cengarle, S.; Ongaro, F.

    2012-01-01

    In view of the upgrade of the LHC experiments, we are developing custom DC/DC converters for a more efficient power distribution scheme. A new prototype have been integrated in ASICs in the selected 0.35μm commercial high voltage technology that has been successfully tested for all radiation effects: TID, displacement damage and Single Event Burnout. This converter has been optimized for high efficiency and improved radiation tolerance. Amongst the new features the most relevant are the presence of internal linear regulators, protection circuits with a state-machine and a new pinout for a modified assembly in package in order to reduce conductive losses. This paper illustrates the design of the prototype followed by functional and radiation tests.

  11. A 0.04 mm (2) Buck-Boost DC-DC Converter for Biomedical Implants Using Adaptive Gain and Discrete Frequency Scaling Control.

    PubMed

    George, Libin; Gargiulo, Gaetano Dario; Lehmann, Torsten; Hamilton, Tara Julia

    2016-06-01

    This paper presents the design of a reconfigurable buck-boost switched-capacitor DC-DC converter suitable for use in a wide range of biomedical implants. The proposed converter has an extremely small footprint and uses a novel control method that allows coarse and fine control of the output voltage. The converter uses adaptive gain control, discrete frequency scaling and pulse-skipping schemes to regulate the power delivered to a range of output voltages and loads. Adaptive gain control is used to implement variable switching gain ratios from a reconfigurable power stage and thereby make coarse steps in output voltage. A discrete frequency scaling controller makes discrete changes in switching frequency to vary the power delivered to the load and perform fine tuning when the output voltage is within 10% of the target output voltage. The control architecture is predominately digital and it has been implemented as part of a fully-integrated switched-capacitor converter design using a standard bulk CMOS 0.18 μm process. Measured results show that the converter has an output voltage range of 1.0 to 2.2 V, can deliver up to 7.5 mW of load power and efficiency up to 75% using an active area of only 0.04 mm (2), which is significantly smaller than that of other designs. This low-area, low-complexity reconfigurable power converter can support low-power circuits in biomedical implant applications. PMID:26600247

  12. 75 FR 446 - In the Matter of Certain DC-DC Controllers and Products; Notice of Investigation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-05

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION In the Matter of Certain DC--DC Controllers and Products; Notice of Investigation AGENCY: U.S... claims of U.S. Patent Nos. 7,315,190; 6,414,470; and 7,132,717; and by reason of trade...

  13. Analysis of mode switching algorithms in dual chamber pacemakers.

    PubMed

    Israel, Carsten W

    2002-03-01

    Dual chamber systems are currently implanted in an increasing number of patients with a pacing indication and paroxysmal atrial tachyarrhythmias (ATAs). To avoid tracking of high atrial rates during ATA while providing AV synchronous pacing during sinus rhythm and AV block, automatic mode switching (MS) to a nontracking mode has been developed. Several concepts of MS algorithms have been introduced differing in sensitivity and specificity of ATA detection, delay between ATA onset and MS, pacing mode during MS, rapidity of MS termination upon detection of sinus rhythm, and special algorithms pertinent to MS. This review classifies and analyzes algorithms that are integrated into MS concepts and outlines considerations on optimal MS performance. Based on simulations and clinical studies, fast MS concepts avoiding high paced ventricular rates seem preferable but require special functions to avoid loss of AV synchrony by inappropriate MS. Similarly, fast return to tracking mode after ATA cessation seems preferable but requires algorithms to prevent mode oscillations. Sudden ventricular rate changes have to be avoided by rate smoothing functions, and an appropriate ventricular rate during nontracking mode has to be provided by rate responsive pacing. Programming of the device includes individual optimization of atrial sensitivity, atrial blanking times, and tachycardia detection rates. In addition, a high signal-to-noise ratio by careful atrial lead implantation, narrowly spaced bipolar atrial leads and a good sensing amplifier, together with special algorithms for atrial sensing adjustment improve the performance of MS algorithms. PMID:11990674

  14. Design of piezoelectric transformer for DC/DC converter with stochastic optimization method

    NASA Astrophysics Data System (ADS)

    Vasic, Dejan; Vido, Lionel

    2016-04-01

    Piezoelectric transformers were adopted in recent year due to their many inherent advantages such as safety, no EMI problem, low housing profile, and high power density, etc. The characteristics of the piezoelectric transformers are well known when the load impedance is a pure resistor. However, when piezoelectric transformers are used in AC/DC or DC/DC converters, there are non-linear electronic circuits connected before and after the transformer. Consequently, the output load is variable and due to the output capacitance of the transformer the optimal working point change. This paper starts from modeling a piezoelectric transformer connected to a full wave rectifier in order to discuss the design constraints and configuration of the transformer. The optimization method adopted here use the MOPSO algorithm (Multiple Objective Particle Swarm Optimization). We start with the formulation of the objective function and constraints; then the results give different sizes of the transformer and the characteristics. In other word, this method is looking for a best size of the transformer for optimal efficiency condition that is suitable for variable load. Furthermore, the size and the efficiency are found to be a trade-off. This paper proposes the completed design procedure to find the minimum size of PT in need. The completed design procedure is discussed by a given specification. The PT derived from the proposed design procedure can guarantee both good efficiency and enough range for load variation.

  15. Lightweight DC-DC Converter with Partial Power Processing and MPPT for a Solar Powered Aircraft

    NASA Astrophysics Data System (ADS)

    Diab-Marzouk, Ahmad

    A lightweight dc-dc partial power processing converter is demonstrated for solar aerospace applications. A system-level model is conceived to determine conformity to payload and target distance objectives, with the Solarship aircraft used as an application example. The concept of partial power processing is utilized to realize a high efficiency lightweight converter that performs Max Peak Power Tracking (MPPT) to transfer power from the aircraft solar array to the high-voltage battery bus. The isolated Cuk is determined to be a suitable converter topology for the application. A small-signal model is derived for control design. The operation of a 400V, 2.7 kW prototype is verified at high frequency (200 kHz), high efficiency (> 98%), small mass (0.604 kg), and uses no electrolytic capacitors. MPPT operation is verified on a 376 V commercial solar installation at The University of Toronto. The prototype serves as an enabling technology for solar aerospace applications.

  16. Multiphase High-Frequency Isolated DC-DC Converter for Industrial Applications

    NASA Astrophysics Data System (ADS)

    Maurya, Rakesh; Srivastava, S. P.; Agarwal, Pramod

    2014-01-01

    Industrial applications such as welding, plasma cutting, and surface hardening require a large DC current at low voltage. In such applications, the rating of power supply varies from few kilowatts to hundreds of kilowatts. The power supply employs in such applications particularly in arc welding process is expected to operate from open-circuit (no-load) to short-circuit (when the electrode sticks to the workpiece for a short span of time) quickly. In this paper, high-frequency isolated multiphase DC-DC converter is proposed which is well suited for aforementioned applications. Based on mathematical analysis, a simulation study with 5 kW, 5 V/1,000 A proposed model is carried out using Simulink block set and Sim Power System tool box and its performances are evaluated under symmetrical control methods. To verify the simulation results, scaled prototype model of rating 1.5 V/100 A is developed and tested with aforementioned control method under different operating conditions. In comparison with conventional welding power supply employed in many industries, the performance of proposed converter is improved significantly in terms of size and weight, efficiency and dynamic response.

  17. Developments on DC/DC converters for the LHC experiment upgrades

    NASA Astrophysics Data System (ADS)

    Abbate, C.; Alderighi, M.; Baccaro, S.; Busatto, G.; Citterio, M.; Cova, P.; Delmonte, N.; De Luca, V.; Fiore, S.; Gerardin, S.; Ghisolfi, E.; Giuliani, F.; Iannuzzo, F.; Lanza, A.; Latorre, S.; Lazzaroni, M.; Meneghesso, G.; Paccagnella, A.; Rampazzo, F.; Riva, M.; Sanseverino, A.; Silvestri, R.; Spiazzi, G.; Velardi, F.; Zanoni, E.

    2014-02-01

    Prototypes of DC/DC power and Point of Load (PoL) converters were designed and built with the aim of satisfying the foreseen working parameters of the High Luminosity (HL) LHC experiments, using both Silicon (Si) MOSFETs and/or more recent devices substantiated of better power performance, like Silicon Carbide (SiC) and Gallium Nitride (GaN) transistors. Optimization of their design, based on the comparison between the simulated and measured thermal, electrical and mechanical performance, is in progress, and many improvements with respect to the previous versions are under implementation. We discuss in this paper the results of the last modifications. In addition, many tens of discrete component samples, chosen among the devices commercially available in the three different technologies (Si, SiC and GaN), were electrically characterized and tested under γ-rays, neutron, proton and heavy ion radiation, also using a combined run method. We have also planned to test some commercial DC/DCs under the extreme conditions of radiation and magnetic field expected in the upgrades of the LHC experiments. Here we show the first results on few samples.

  18. Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model

    NASA Astrophysics Data System (ADS)

    Suskis, P.; Rankis, I.

    2012-01-01

    The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software.

  19. Development of a Novel Bi-Directional Isolated Multiple-Input DC-DC Converter

    SciTech Connect

    Li, H.

    2005-10-24

    There is vital need for a compact, lightweight, and efficient energy-storage system that is both affordable and has an acceptable cycle life for the large-scale production of electric vehicles (EVs) and hybrid electric vehicles (HEVs). Most of the current research employs a battery-storage unit (BU) combined with a fuel cell (FC) stack in order to achieve the operating voltage-current point of maximum efficiency for the FC system. A system block diagram is shown in Fig.1.1. In such a conventional arrangement, the battery is sized to deliver the difference between the energy required by the traction drive and the energy supplied by the FC system. Energy requirements can increase depending on the drive cycle over which the vehicle is expected to operate. Peak-power transients result in an increase of losses and elevated temperatures which result in a decrease in the lifetime of the battery. This research will propose a novel two-input direct current (dc) dc to dc converter to interface an additional energy-storage element, an ultracapacitor (UC), which is shown in Fig.1.2. It will assist the battery during transients to reduce the peak-power requirements of the battery.

  20. An Integrated High Efficiency Switched Mode Laser Power Supply

    NASA Astrophysics Data System (ADS)

    Merz, S. Spencer

    1987-05-01

    An ideal laser power supply should bring a capacitive storage medium to a programmable voltage level at a constant rate. This voltage level must be maintained until the laser is fired, at which time the charging source must be immune to severe transients. Considerations include efficiency, size, cost, and reliability. A switched mode charging source is described which has been in commercial production for several years, and which will transfer 5KW of average power to a value of capacitance ranging from 20 to 100nF at approximately 32KV with repetition rates to 500Hz.

  1. Mode switching in volcanic seismicity: El Hierro 2011-2013

    NASA Astrophysics Data System (ADS)

    Roberts, Nick S.; Bell, Andrew F.; Main, Ian G.

    2016-05-01

    The Gutenberg-Richter b value is commonly used in volcanic eruption forecasting to infer material or mechanical properties from earthquake distributions. Such studies typically analyze discrete time windows or phases, but the choice of such windows is subjective and can introduce significant bias. Here we minimize this sample bias by iteratively sampling catalogs with randomly chosen windows and then stack the resulting probability density functions for the estimated b>˜ value to determine a net probability density function. We examine data from the El Hierro seismic catalog during a period of unrest in 2011-2013 and demonstrate clear multimodal behavior. Individual modes are relatively stable in time, but the most probable b>˜ value intermittently switches between modes, one of which is similar to that of tectonic seismicity. Multimodality is primarily associated with intermittent activation and cessation of activity in different parts of the volcanic system rather than with respect to any systematic inferred underlying process.

  2. Mode-selection and mode-switching of an autonomous motor composed of a camphor rotor and a mobile loop

    NASA Astrophysics Data System (ADS)

    Nakata, Satoshi; Tenno, Ryoichi; Ikura, Yumihiko S.

    2011-09-01

    Mode-selection and mode-switching of self-motion were investigated for a loop driven by the movement of a camphor rotor on water, as a simple autonomous system. Three modes of self-motion (caterpillar motion, translation, and alternating mode-switching between them) were selectively generated depending on the state of a knot of the loop. The experimental results were numerically reproduced and categorized by using a differential equation of rotation with a fold bifurcation.

  3. A High Efficiency DC-DC Converter Topology Suitable for Distributed Large Commercial and Utility Scale PV Systems

    SciTech Connect

    Agamy, Mohammed S; Harfman-Todorovic, Maja; Elasser, Ahmed; Steigerwald, Robert L; Sabate, Juan A; Chi, Song; McCann, Adam J; Zhang, Li; Mueller, Frank

    2012-09-01

    In this paper a DC-DC power converter for distributed photovoltaic plant architectures is presented. The proposed converter has the advantages of simplicity, high efficiency, and low cost. High efficiency is achieved by having a portion of the input PV power directly fed forward to the output without being processed by the converter. The operation of this converter also allows for a simplified maximum power point tracker design using fewer measurements

  4. A brief review of models of DC-DC power electronic converters for analysis of their stability

    NASA Astrophysics Data System (ADS)

    Siewniak, Piotr; Grzesik, Bogusław

    2014-10-01

    A brief review of models of DC-DC power electronic converters (PECs) is presented in this paper. It contains the most popular, continuous-time and discrete-time models used for PEC simulation, design, stability analysis and other applications. Both large-signal and small-signal models are considered. Special attention is paid to models that are used in practice for the analysis of the global and local stability of PECs.

  5. Quasi-Periodicity, Chaos and Coexistence in the Time Delay Controlled Two-Cell DC-DC Buck Converter

    NASA Astrophysics Data System (ADS)

    Koubaâ, Karama; Feki, Moez

    In addition to border collision bifurcation, the time delay controlled two-cell DC/DC buck converter is shown to exhibit a chaotic behavior as well. The time delay controller adds new design parameters to the system and therefore the variation of a parameter may lead to different types of bifurcation. In this work, we present a thorough analysis of different scenarios leading to bifurcation and chaos. We show that the time delay controlled two-cell DC/DC buck converter may also exhibit a Neimark-Sacker bifurcation which for some parameter set may lead to a 2D torus that may then break yielding a chaotic behavior. Besides, the saturation of the controller can also lead to the coexistence of a stable focus and a chaotic attractor. The results are presented using numerical simulation of a discrete map of the two-cell DC/DC buck converter obtained by expressing successive crossings of Poincaré section in terms of each other.

  6. Exponential synchronization of coupled switched neural networks with mode-dependent impulsive effects.

    PubMed

    Wenbing Zhang; Yang Tang; Qingying Miao; Wei Du

    2013-08-01

    This paper investigates the synchronization problem of coupled switched neural networks (SNNs) with mode-dependent impulsive effects and time delays. The main feature of mode-dependent impulsive effects is that impulsive effects can exist not only at the instants coinciding with mode switching but also at the instants when there is no system switching. The impulses considered here include those that suppress synchronization or enhance synchronization. Based on switching analysis techniques and the comparison principle, the exponential synchronization criteria are derived for coupled delayed SNNs with mode-dependent impulsive effects. Finally, simulations are provided to illustrate the effectiveness of the results. PMID:24808570

  7. 275 C Downhole Switched-Mode Power Supply

    SciTech Connect

    Chris Hutchens; Vijay Madhuravasal

    2008-08-31

    A vee-square (V2) control based controller IC is developed for a switch mode power supply capable of operating at extreme temperature/harsh environment conditions. A buck type regulator with silicon carbide power junction field effect transistors (JFET) as power devices is used to analyze the performance of controller. Special emphases are made on the analog sub-blocks--voltage reference, operational transconductance amplifier and comparator as individual building blocks. Transformer coupled gate drives and high temperature operable magnetic cores and capacitors are identified and tested for use in the design. Conventional ceramic chip packaging of ICs combined with lead carrier type mounting of passive filter components is introduced for hybrid packaging of the complete product. The developed SMPS is anticipated to support the operation of down-hole microcontrollers and other electronics devices that require low/medium power filtered dc inputs over an operating temperature of 275 C.

  8. Experience from design, prototyping and production of a DC-DC conversion powering scheme for the CMS Phase-1 Pixel Upgrade

    NASA Astrophysics Data System (ADS)

    Feld, L.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Schmitz, S.; Wlochal, M.

    2016-02-01

    The CMS collaboration has adopted a DC-DC conversion powering scheme for the Phase-1 Upgrade of its pixel detector. DC-DC buck converters with a conversion ratio of around 3 are installed on the support structures, outside of the sensitive tracking region, requiring a re-design of the low and high voltage distribution to the pixel modules. After several years of R&D, the project has entered the production phase. A total of 1800 DC-DC converters are being produced, and rigorous quality assurance and control is being employed during the production process. The testing program is outlined, results from mass production are presented and issues that have been encountered are described. In addition, two system level challenges, namely the choice of output voltage in the presence of large, load-dependent voltage drops, and the thermal management required to remove the heat load caused by the DC-DC converters, are discussed.

  9. Analysis, design and implementation of an interleaved three-level PWM DC/DC ZVS converter

    NASA Astrophysics Data System (ADS)

    Lin, Bor-Ren; Liu, Chien-Hung

    2016-02-01

    This paper presents a new parallel three-level soft switching pulse-width modulation (PWM) converter. The proposed converter has two circuit cells operated by the interleaved PWM modulation. Thus, the ripple currents at input and output sides are reduced. Each circuit cell has two three-level zero voltage switching circuits sharing the same power switches. Therefore, the current and power rating of the secondary side components are reduced. Current double rectifier topology is selected on the secondary side to decrease output ripple current. The main advantages of the proposed converter are soft switching of power switches, low ripple current on the output side and low-voltage rating of power switches for medium-power applications. Finally, the performance of the proposed converter is verified by experiments with 1 kW prototype circuit.

  10. An Approach to Average Modeling and Simulation of Switch-Mode Systems

    ERIC Educational Resources Information Center

    Abramovitz, A.

    2011-01-01

    This paper suggests a pedagogical approach to teaching the subject of average modeling of PWM switch-mode power electronics systems through simulation by general-purpose electronic circuit simulators. The paper discusses the derivation of PSPICE/ORCAD-compatible average models of the switch-mode power stages, their software implementation, and…

  11. Single-switch 3{phi} PWM low harmonic rectifiers

    SciTech Connect

    Ismail, E.H.; Erickson, R.

    1996-03-01

    Existing 3{phi} ac-dc low-harmonic rectifiers are costly and require complex control schemes to minimize input current harmonics. Introduced here are two new classes of low cost 3{phi} ac-dc high power factor/low harmonic controlled rectifiers. These are derived from parent dc-dc converter topologies containing boost-type inputs and buck-type inputs. With a single active switch in addition to the diode bridge rectifier, the converters are capable of drawing a high-quality input current waveform naturally at nearly unit power factor. Thus, a simple 3{phi} ac-dc high power factor rectifier is obtained. Two algorithms are introduced in this paper for constructing a 3{phi} ac-dc high-quality rectifier. These algorithms depend on the simple switched-mode boost-type input converter and buck-type input converter modified by an input filter. For most known dc-dc converters which belong to these classes, there are corresponding 3{phi} ac-dc high power factor topologies, which use the same number of transistors and use six additional fast diodes. Analytical and simulation results are supplied to demonstrate the validity of the concept.

  12. High efficiency DC-DC converter using GaN transistors

    NASA Astrophysics Data System (ADS)

    Tómaş, Cosmin-Andrei; Grecu, Cristian; Pantazicǎ, Mihaela; Marghescu, Ion

    2015-02-01

    The paper presents a new high-efficiency power switching supply using the Gallium Nitride (GaN) technology. There are compared two solutions, the first using standard MOS transistors and the second using the new GaN transistor. The actual green technologies for obtaining the maximum energy and minimum losses have pushed the semiconductor industry into a continuous research regarding high power and high frequency devices, having uses in both digital communications and switching power supplies.

  13. Switching deformation mode during natural faulting in Carrara marbles.

    NASA Astrophysics Data System (ADS)

    Molli, Giancarlo

    2010-05-01

    A study on meso- and microstructural features of a high angle normal fault observed in the Alpi Apuane NW Tuscany (Italy) is presented to document switching in the deformation mode during different evolutionary stages of a fault zone growth in naturally deformed Carrara marble. The studied fault was formed at c.3 Km of depth and belongs to structures related to the most recent deformation history of the Alpi Apuane metamorphic core (from c.4 Ma until now, Fellin et al. 2007; Molli, 2008). On the basis of deformation mechanisms and their chronology interpreted from cross-cutting relationships, different stages of the fault zone evolution have been recognized. An early stage of deformation (stage 1) was associated with extensional and shear veins now observable in both hangingwall and footwall blocks as part of the deformation zone developed at decameter-scale. Geochemical data indicate vein-development in a locally closed system where a "stationary" fluid phase migrates over meter scale distances (Molli et al., in press). During stage 2, a localization of the deformation, possibly in precursory coarse grained calcite/quartz shear veins of stage 1, took place. During this second stage crystal-plastic deformation affected areas at the head and along the hanging wall rim of fractures accommodating fault tip distorsions in a way recalling the mode-II geometry of stable crack propagation (Atkinson, 1987; Vermilye and Scholtz, 1993; Kim et al., 2004). Following pervasive cataclasis (stage 3) characterizes a plurimeter-wide dilational jog between two non-parallel main slip surfaces with brecciation and far-derived fluids channelling leading to significant geochemical alteration of the fault rocks with respect to the protolith (Molli et al., in press). Cataclastic deformation produced a grain size refinement and a decimetric thick fault core asymmetrically bounded by the upper main slip surface. Deformation was then localized within ultracataclasite of the fault core where

  14. Study of a piezoelectric transformer-based DC/DC converter with a cooling system and current-doubler rectifier

    NASA Astrophysics Data System (ADS)

    Su, Yu-Hao; Liu, Yuan-Ping; Vasic, Dejan; Costa, Francois; Wu, Wen-Jong; Lee, Chuih-Kung

    2013-09-01

    The objective of this study was to increase the output current and power in a piezoelectric transformer (PT)-based DC/DC converter by using a cooling system. It is known that the output current of a PT is limited by temperature build-up because of losses, especially when driving at high vibration velocity. Although connecting different inductive circuits at the PT secondary terminal can increase the output current, the root cause of the temperature build-up problem has not yet been solved. This paper presents a study of a PT with cooling system in a DC/DC converter with a commonly used full-bridge rectifier and current-doubler rectifier. The advantages and disadvantages of the proposed technique were investigated. A theoretical-phenomenological model was developed to explain the relationship between the losses and the temperature rise. It will be shown that the vibration velocity as well as heat generation increases the losses. In our design, the maximum output current capacity can increase by 100% when the temperature of operation of the PT is kept below 55 ° C. The study comprises a theoretical part and experimental proof-of-concept demonstration of the proposed design method.

  15. Reliability and performance studies of DC-DC conversion powering scheme for the CMS pixel tracker at SLHC

    NASA Astrophysics Data System (ADS)

    Todri, A.; Perera, L.; Rivera, R.; Kwan, S.

    2010-12-01

    The upgrades of the Large Hadron Collider (LHC) introduce a significant challenge to the power distribution of the detectors. DC-DC conversion is the preferred powering scheme proposed to be integrated for the CMS tracker to deliver high input voltage levels and performing a step-down conversion nearby the detector modules. In this work, we propose a step-up/step-down powering scheme by performing voltage step up at the CAEN supply unit and voltage step down near the detector. We designed step-up converters and investigate the pixel performance and power loss on the FPIX power distribution system. Tests are performed using the PSI46 pixel readout chips on a forward pixel panel module and the DC-DC converters developed at CERN and Fermilab. Reliability studies include the voltage drop measurements on the readout chips and the power supply noise generated from the converter. Performance studies include pixel noise and threshold dispersion results. Comparison between step-down only and step-up/step-down conversion powering schemes are provided.

  16. A study of DC-DC converters with MCT's for arcjet power supplies

    NASA Technical Reports Server (NTRS)

    Stuart, Thomas A.

    1994-01-01

    Many arcjet DC power supplies use PWM full bridge converters with large arrays of parallel FET's. This report investigates an alternative supply using a variable frequency series resonant converter with small arrays of parallel MCT's (metal oxide semiconductor controlled thyristors). The reasons for this approach are to: increase reliability by reducing the number of switching devices; and decrease the surface mounting area of the switching arrays. The variable frequency series resonant approach is used because the relatively slow switching speed of the MCT precludes the use of PWM. The 10 kW converter operated satisfactorily with an efficiency of over 91 percent. Test results indicate this efficiency could be increased further by additional optimization of the series resonant inductor.

  17. Monte Carlo calculations of switching-time statistics in a two-mode laser

    SciTech Connect

    Murthy, K.P.N.; Dattagupta, S.

    1985-12-01

    A two-mode laser operating in the bistable region switches spontaneously from one mode to the other under the influence of quantum fluctuations. We present here a Monte Carlo simulation of the coupled Langevin equations describing the dynamics of a two-mode laser. We present results on the variation of average switching time with pump parameter. We show that if fluctuations in the pump parameter are incorporated, the Monte Carlo estimates agree well with measured switching times. To further check this observation we reanalyze the results of a recent analytical study and show that by including the same pump parameter fluctuations, the agreement with measurements becomes much better.

  18. Design of Current Source Dc/Dc Converter for Interfacing a 5 Kw Pem Fuel Cell / Paaugstinošā Strāvas Avota Līdzsprieguma Pārveidotāja Izstrāde 5 Kw Ūdeņraža Degvielas Elementam

    NASA Astrophysics Data System (ADS)

    Andreičiks, A.; Steiks, I.; Krievs, O.

    2013-08-01

    In domestic applications the low DC output voltage of a hydrogen fuel cell used as the main power supply or a backup power source has to be matched to the level and frequency of the AC voltage of utility grid. The interfacing power converter system usually consists of a DC/DC converter and an inverter. In this work, a DC/DC step-up converter stage is designed for interfacing a 5kW proton exchange membrane (PEM) fuel cell. The losses of DC/DC conversion are estimated and, basing on the relevant analysis, the most appropriate configuration of converter modules is selected for a DC/DC converter stage of increased efficiency. The authors present the results of experimental analysis and simulation for the selected configuration of four double inductor step-up push-pull converter modules Ūdeņraža degvielas elementa invertoru sistēmas mājsaimniecības pielietojumiem parasti sastāv no līdzsprieguma paaugstināšanas un invertēšanas mezgliem. Šis raksts ir veltīts paaugstinošā līdzsprieguma pārveidotāja izstrādei 5 kW protonu apmaiņas membrānas degvielas elementam. Rakstā izpētīts divu induktoru divtaktu strāvas avota paaugstinošais līdzsprieguma pārveidotājs, aplūkojot gan datormodelēšanas, gan eksperimentālos rezultātus. Lai palielinātu DC/DC pārveidotāja efektivitāti var izmantot vairākus pārveidotāja moduļus, kam ieejas savienotas paralēli un izejās - virkne. Analīze Šajā raksta ir veikta analīze, balstoties uz kuras var izvēlieties skaitu pārveidotāj moduļu skaitu, kuri nodrošina vislabāko efektivitāti DC/DC pārveidotāja posmā. Kopējais eksperimentāli noteiktais izstrādātās degvielas elementa pārveidotāju sistēmas fizikālā modeļa lietderības koeficients ir 93%

  19. A Low-Cost Soft-Switched DC/DC Converter for Solid-Oxide Fuel Cells

    SciTech Connect

    Jason Lai

    2009-03-03

    A highly efficient DC to DC converter has been developed for low-voltage high-current solid oxide fuel cells. The newly developed 'V6' converter resembles what has been done in internal combustion engine that split into multiple cylinders to increase the output capacity without having to increase individual cell size and to smooth out the torque with interleaving operation. The development was started with topology overview to ensure that all the DC to DC converter circuits were included in the study. Efficiency models for different circuit topologies were established, and computer simulations were performed to determine the best candidate converter circuit. Through design optimization including topology selection, device selection, magnetic component design, thermal design, and digital controller design, a bench prototype rated 5-kW, with 20 to 50V input and 200/400V output was fabricated and tested. Efficiency goal of 97% was proven achievable through hardware experiment. This DC to DC converter was then modified in the later stage to converter 35 to 63 V input and 13.8 V output for automotive charging applications. The complete prototype was tested at Delphi with their solid oxide fuel cell test stand to verify the performance of the modified DC to DC converter. The output was tested up to 3-kW level, and the efficiency exceeded 97.5%. Multiple-phase interleaving operation design was proved to be reliable and ripple free at the output, which is desirable for the battery charging. Overall this is a very successful collaboration project between the SECA Core Technology Team and Industrial Team.

  20. Investigation of Timing to Switch Control Mode in Powered Knee Prostheses during Task Transitions

    PubMed Central

    Zhang, Fan; Liu, Ming; Huang, He

    2015-01-01

    Current powered prosthetic legs require switching control modes according to the task the user is performing (e.g. level-ground walking, stair climbing, walking on slopes, etc.). To allow prosthesis users safely and seamlessly transition between tasks, it is critical to determine when to switch the prosthesis control mode during task transitions. Our previous study defined critical timings for different types of task transitions in ambulation; however, it is unknown whether it is the unique timing that allows safe and seamless transitions. The goals of this study were to (1) systematically investigate the effects of mode switch timing on the prosthesis user’s performance in task transitions, and (2) identify appropriate timing to switch the prosthesis control mode so that the users can seamlessly transition between different locomotion tasks. Five able-bodied (AB) and two transfemoral (TF) amputee subjects were tested as they wore a powered knee prosthesis. The prosthesis control mode was switched manually at various times while the subjects performed different types of task transitions. The subjects’ task transition performances were evaluated by their walking balance and success in performing seamless task transitions. The results demonstrated that there existed a time window within which switching the prosthesis control mode neither interrupted the subjects’ task transitions nor disturbed their walking balance. Therefore, the results suggested the control mode switching of a lower limb prosthesis can be triggered within an appropriate time window instead of a specific timing or an individual phase. In addition, a generalized criterion to determine the appropriate mode switch timing was proposed. The outcomes of this study could provide important guidance for future designs of neurally controlled powered knee prostheses that are safe and reliable to use. PMID:26197084

  1. Generalized computer-aided discrete time domain modeling and analysis of dc-dc converters

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Iwens, R. P.; Yu, Y.; Triner, J. E.

    1977-01-01

    A generalized discrete time domain modeling and analysis technique is presented for all types of switching regulators using any type of duty-cycle controller, and operating in both continuous and discontinuous inductor current. State space techniques are employed to derive an equivalent nonlinear discrete time model that describes the converter exactly. The system is linearized about its equilibrium state to obtain a linear discrete time model for small signal performance evaluations, such as stability, audiosusceptibility and transient response. The analysis makes extensive use of the digital computer as an analytical tool. It is universal, exact and easy to use.

  2. Automatic Mode Switching Method for Torque Priority Control of IPMSM by Considering Voltage Saturation

    NASA Astrophysics Data System (ADS)

    Nakama, Takao; Hanada, Toshihiro; Ohishi, Kiyoshi; Makishima, Shingo; Uezono, Keiichi; Yasukawa, Shinobu

    This paper proposes a new current control method for interior permanent magnet synchronous motor (IPMSM). In the case of AC motor control, two axis current feedback control is performed to control the voltage amplitude and phase. When the inverter voltage is saturated, current control is achieved by controlling the voltage phase. Conventional techniques require switching the mode of the control system from variable-voltage mode to voltage-saturation mode. However, in conventional techniques, the transient voltage saturation occurs by switching the control system. The proposed method achieves the current control in variable voltage mode and voltage saturation mode without switching the control system. Moreover, the current response is not affected by the rotor speed. The numerical simulation results and experimental results confirm the effectiveness of proposed current control method.

  3. On Optimal Control of Non-Autonomous Switched Systems with a Fixed Mode Sequence

    NASA Technical Reports Server (NTRS)

    Kamgarpour, Maryam; Tomlin, Claire

    2012-01-01

    We consider differentiability with respect to the switch times of the value function of an optimal control problem for a non-autonomous switched system. The control variables are the switch times between the modes and the input in each mode. We provide a method to compute the derivative of the cost function given a nominal input. Then, we view the optimal control problem as a parametrized optimization problem in which the switch times are the parameters and the optimization is over the set of feasible inputs of each mode. From this point of view, we provide conditions under which the continuity and differentiability of the optimal value function, that is the cost function optimized over the inputs, can be guaranteed.

  4. Isolated and soft-switched power converter

    DOEpatents

    Peng, Fang Zheng; Adams, Donald Joe

    2002-01-01

    An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

  5. Doubly active Q switching and mode locking of an all-fiber laser.

    PubMed

    Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, Jose L; Andrés, Miguel V

    2009-09-15

    Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train. PMID:19756079

  6. IGBT convertor with active snubber for soft switching. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Masserant, B. J.; Shriver, J.; Stuart, T. A.

    1991-01-01

    This full bridge dc-dc convertor with IGBTs uses zero voltage switching (ZVS) for one leg of the bridge and zero current switching (ZCS) for the other. It is shown that an active snubber greatly improves the performance over previous methods. Experimental results are shown for a 6 kW circuit switching at 20 kHz.

  7. Modular DC-DC converter system for energy harvesting with EAPs

    NASA Astrophysics Data System (ADS)

    Eitzen, L.; Graf, C.; Maas, J.

    2013-04-01

    Energy harvesting with EAPs requires an energy-efficient power electronics providing a bidirectional energy transfer and operating voltages of up to several kilovolts. A possibility to achieve a high energy-efficiency for high voltage conversion is the use of a modular converter system consisting of several bidirectional converter modules, which are connected in series on the converter output side and in parallel at the input side. Since each converter stage provides only a part of the overall converter output voltage, the converter module output voltages can effectively be reduced by choosing the number of cascaded converter modules appropriately. This allows the use of standard semiconductor switches with superior electrical characteristics compared to high voltage semiconductors, enabling a high energy-efficiency and smaller passive components. Since EAP devices exhibit a mainly capacitive behavior and a limitation of the operating current is required for electrode protection, the utilized converter structure/topology has to be operated as a controllable current source on the lowest control level, which is achieved by operating the converter modules of the modular converter system with a subordinate closed-looped current control scheme. In order to avoid voltage unbalances among the single converter modules, a method for voltage balancing is presented. For validation, experimental results of a realized bidirectional flyback converter prototype are presented and discussed.

  8. Noisy inflows cause a shedding-mode switching in flow past an oscillating cylinder.

    PubMed

    Lucor, Didier; Karniadakis, George Em

    2004-04-16

    Vortex streets formed behind oscillating bluff bodies consist of arrays of groups of two, three, or four vortices classified as 2S, P+S, and 2P shedding modes, respectively. The prevailing dominant mode depends primarily on the amplitude and the frequency of the oscillation and on the Reynolds number. We investigate the effect of noise at the inflow on the stability of these vortex modes in laminar flow past a circular cylinder. We employ stochastic simulations based on a new polynomial chaos method to study the shedding-mode switching from a P+S pattern to a 2S mode in the presence of noise. PMID:15169289

  9. Modelling of nonisolated high-voltage gain boost converters using the PWM switch model

    NASA Astrophysics Data System (ADS)

    Janeth Acosta Alcazar, Yblin; Lessa Tofoli, Fernando; de Souza Oliveira, Demercil, Jr.; Pastor Torrico-Bascopé, René

    2014-08-01

    This paper presents the small-signal models for nonisolated dc-dc boost converters based on the three-state switching cell (3SSC) and voltage multiplier cells (VMCs) by using the concept of pulse-width modulation switch introduced by Vorpérian. Two possible topologies are analysed in the study using one multiplier cell (VMC = 1) and two multiplier cells (VMC = 2). The models are validated by properly comparing the theoretical curves with those obtained in simulation tests. Besides, conventional average current-mode control is implemented in practice for the topology with VMC = 2. An experimental prototype rated at 1 kW is evaluated so that it can be seen that the control system is stable and the dynamic response of the converter is satisfactory.

  10. Analysis of polarization switching in ferroelectric crystals in the injection mode

    SciTech Connect

    Maslovskaya, A. G. Kopylova, I. B.

    2009-07-15

    We report on the results of experiments on polarization switching in a ferroelectric TGS crystal during injection of electron beams from a scanning electron microscope under a surface layer. A series of models reflecting the polarization switching dynamics of a ferroelectric crystal under the action of an injected charge is constructed. The implementation of these models is based on the principles of evolution of domain structures taking into account analysis of possible polarization switching mechanisms for ferroelectric samples. A mathematical model developed using these principles demonstrates qualitative similarity of model current pulses and those obtained experimentally in the injection mode.

  11. Prognostic health monitoring in switch-mode power supplies with voltage regulation

    NASA Technical Reports Server (NTRS)

    Hofmeister, James P (Inventor); Judkins, Justin B (Inventor)

    2009-01-01

    The system includes a current injection device in electrical communication with the switch mode power supply. The current injection device is positioned to alter the initial, non-zero load current when activated. A prognostic control is in communication with the current injection device, controlling activation of the current injection device. A frequency detector is positioned to receive an output signal from the switch mode power supply and is able to count cycles in a sinusoidal wave within the output signal. An output device is in communication with the frequency detector. The output device outputs a result of the counted cycles, which are indicative of damage to an a remaining useful life of the switch mode power supply.

  12. Integrated photonic emitter with a wide switching range of orbital angular momentum modes

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Zhao, Peng; Feng, Xue; Xu, Yuntao; Cui, Kaiyu; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-03-01

    Due to the nature of infinite dimensionality, the orbital angular momentum (OAM) has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications such as optical telecommunication, quantum information, particle manipulation and imaging. In recent years, the integrated photonic OAM emitters have been actively investigated due to both compactness and tunability. Essentially, the number of available OAM modes by dynamic switching should be large enough so that the dimensionality of OAM could be explored as much as possible. In this work, an integrated photonic emitter with a wide switching range of OAM modes is theoretically developed, numerically simulated, and experimentally verified. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = -4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect.

  13. High frequency switched-mode stimulation can evoke post synaptic responses in cerebellar principal neurons

    PubMed Central

    van Dongen, Marijn N.; Hoebeek, Freek E.; Koekkoek, S. K. E.; De Zeeuw, Chris I.; Serdijn, Wouter A.

    2015-01-01

    This paper investigates the efficacy of high frequency switched-mode neural stimulation. Instead of using a constant stimulation amplitude, the stimulus is switched on and off repeatedly with a high frequency (up to 100 kHz) duty cycled signal. By means of tissue modeling that includes the dynamic properties of both the tissue material as well as the axon membrane, it is first shown that switched-mode stimulation depolarizes the cell membrane in a similar way as classical constant amplitude stimulation. These findings are subsequently verified using in vitro experiments in which the response of a Purkinje cell is measured due to a stimulation signal in the molecular layer of the cerebellum of a mouse. For this purpose a stimulator circuit is developed that is able to produce a monophasic high frequency switched-mode stimulation signal. The results confirm the modeling by showing that switched-mode stimulation is able to induce similar responses in the Purkinje cell as classical stimulation using a constant current source. This conclusion opens up possibilities for novel stimulation designs that can improve the performance of the stimulator circuitry. Care has to be taken to avoid losses in the system due to the higher operating frequency. PMID:25798105

  14. Anisotropic mechanism on distinct transition modes of tip-activated multipolorizaion switching in epitaxial BiFeO3 films

    NASA Astrophysics Data System (ADS)

    Shi, Y. P.; Soh, A. K.; Weng, G. J.

    2011-01-01

    Based on the extended Kittel's law, an anisotropic mechanism has been developed to investigate the complex multipolarization switching in (001) and (110) epitaxial BiFeO3 films, under a biased-tip field. Switching inhomogeneity and domain wall width evolution have been specifically accounted for. It has been found that distinct switching modes, i.e., the breakdown mode of 71°-switched domain and the activation mode of 180°/109° switching, exist and dominate the switching orders within switching process. Our predicted switching orders show excellent agreements with the existing experimental data and phase-field results. A two-step procedure is also proposed to fabricate single-phase 71° ferroelastic domain array of controllable density using (001) BiFeO3 films, which is favored in practice to significantly enhance the magnetoelectric coupling and photovoltage.

  15. Microprocessor control of multiple peak power tracking DC/DC converters for use with solar cell arrays

    NASA Technical Reports Server (NTRS)

    Frederick, Martin E. (Inventor); Jermakian, Joel (Inventor)

    1991-01-01

    A method and an apparatus is provided for efficiently controlling the power output of a solar cell array string or a plurality of solar cell array strings to achieve a maximum amount of output power from the strings under varying conditions of use. Maximum power output from a solar array string is achieved through control of a pulse width modulated DC/DC buck converter which transfers power from a solar array to a load or battery bus. The input voltage from the solar array to the converter is controlled by a pulse width modulation duty cycle, which in turn is controlled by a differential signal controller. By periodically adjusting the control voltage up or down by a small amount and comparing the power on the load or bus with that generated at different voltage values a maximum power output voltage may be obtained. The system is totally modular and additional solar array strings may be added to the system simply by adding converter boards to the system and changing some constants in the controller's control routines.

  16. A general unified approach to modelling switching dc-to-dc converters in discontinuous conduction mode

    NASA Technical Reports Server (NTRS)

    Cuk, S.; Middlebrook, R. D.

    1977-01-01

    A method for modelling switching converters in the discontinuous conduction mode is developed, whose starting point is the unified state-space representation, and whose end result is a complete linear circuit model which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small signal). While the method is generally applicable to any switching converter operating in the discontinuous conduction mode, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model.

  17. Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

    NASA Astrophysics Data System (ADS)

    Lim, Sungkeun

    of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is

  18. A novel adaptive switching function on fault tolerable sliding mode control for uncertain stochastic systems.

    PubMed

    Zahiripour, Seyed Ali; Jalali, Ali Akbar

    2014-09-01

    A novel switching function based on an optimization strategy for the sliding mode control (SMC) method has been provided for uncertain stochastic systems subject to actuator degradation such that the closed-loop system is globally asymptotically stable with probability one. In the previous researches the focus on sliding surface has been on proportional or proportional-integral function of states. In this research, from a degree of freedom that depends on designer choice is used to meet certain objectives. In the design of the switching function, there is a parameter which the designer can regulate for specified objectives. A sliding-mode controller is synthesized to ensure the reachability of the specified switching surface, despite actuator degradation and uncertainties. Finally, the simulation results demonstrate the effectiveness of the proposed method. PMID:24954808

  19. Non-linear adaptive sliding mode switching control with average dwell-time

    NASA Astrophysics Data System (ADS)

    Yu, Lei; Zhang, Maoqing; Fei, Shumin

    2013-03-01

    In this article, an adaptive integral sliding mode control scheme is addressed for switched non-linear systems in the presence of model uncertainties and external disturbances. The control law includes two parts: a slide mode controller for the reduced model of the plant and a compensation controller to deal with the non-linear systems with parameter uncertainties. The adaptive updated laws have been derived from the switched multiple Lyapunov function method, also an admissible switching signal with average dwell-time technique is given. The simplicity of the proposed control scheme facilitates its implementation and the overall control scheme guarantees the global asymptotic stability in the Lyapunov sense such that the sliding surface of the control system is well reached. Simulation results are presented to demonstrate the effectiveness and the feasibility of the proposed approach.

  20. Electro-optic mode switch based on lithium-niobate Mach-Zehnder interferometer.

    PubMed

    Zhang, Mengruo; Chen, Kaixin; Jin, Wei; Chiang, Kin Seng

    2016-06-01

    We propose an electro-optic mode switch based on an optical waveguide Mach-Zehnder interferometer fabricated with x-cut lithium niobate by the annealed proton exchange process. The device can switch between the fundamental mode and the higher-order mode with a low driving voltage. Our typical fabricated device, which has a total length of ∼24  mm, shows a mode extinction ratio of ∼35  dB and a 20-dB bandwidth of ∼12  nm at the wavelength 1552 nm, when driven at a voltage of 1.7 V at 26°C. High performance can be obtained at any wavelength in the C+L band with a driving voltage varying by no more than 3 V. The proposed mode switch is easy to fabricate and could find applications in reconfigurable mode-division-multiplexing systems. PMID:27411197

  1. Generalized Simulation Model for a Switched-Mode Power Supply Design Course Using MATLAB/SIMULINK

    ERIC Educational Resources Information Center

    Liao, Wei-Hsin; Wang, Shun-Chung; Liu, Yi-Hua

    2012-01-01

    Switched-mode power supplies (SMPS) are becoming an essential part of many electronic systems as the industry drives toward miniaturization and energy efficiency. However, practical SMPS design courses are seldom offered. In this paper, a generalized MATLAB/SIMULINK modeling technique is first presented. A proposed practical SMPS design course at…

  2. 1 kW, 9 kV dc-dc converter module with time-sharing control of output voltage and input current

    SciTech Connect

    Borgatti, R.; Stefani, R.; Bressan, O.; Bicciato, F.; Tenti, P.; Rossetto, L.

    1993-10-01

    The paper describes a dc-dc power module based on a single-stage current-fed converter structure. Control is made according to a time-sharing strategy allowing simultaneous regulation of output voltage and input current. This solution is suitable for high-performance space and avionic applications, giving high efficiency, compactness, and accuracy, speed and robustness of control. Theoretical analysis, design criteria, and experimental results are reported. Application to radar supplies is discussed.

  3. Micro-Fabrication and Circuit Optimization for Magnetic Components of High-Efficiency DC-DC Converters

    NASA Astrophysics Data System (ADS)

    Tian, Rui

    Magnetic components are essential parts of power converters. Inductors with magnetic cores are investigated. An eddy current loss model for pot-core inductors is developed with finite elemental analysis (FEA). The reliability of inductors using magnetic cores in a high-temperature environment is investigated. Working in up to 150°C circumstance for a short periods is not destructive for the inductors. Optimization of toroidal inductors in a DC-DC converter is investigated. Parasitic capacitance and the capacitive loss in toroidal inductors are modeled. Standard circuit optimization is performed to explore the energy conversion efficiency of the toroidal inductors. Thermal analysis, light-load efficiency and relative permeability of the toroidal inductor design are also investigated. The toroidal inductor can achieve about 85% efficiency for 3 A DC current and 1 W/mm2 power density. Inductor-only efficiency of toroidal inductors is investigated with revised model. At 100 MHz operating frequency, toroidal inductors can achieve more than 97% inductor efficiency with power density range of 0.7 W/mm2 to 6 W/mm2. The performance of our nanograngular magnetic core is dependent on the angle of the poling magnetic field compared to the field during operation. Experiments on a serious of samples show that the poling angle can deviate by up to 15 degrees from ideal with only a small penalty in performance. The field-angle experiment is intended to prove integrated toroidal inductor process possible. A magnetic fixture model is proposed for large-scale toroidal inductor processing.

  4. Fast electrical switching of orbital angular momentum modes using ultra-compact integrated vortex emitters.

    PubMed

    Strain, Michael J; Cai, Xinlun; Wang, Jianwei; Zhu, Jiangbo; Phillips, David B; Chen, Lifeng; Lopez-Garcia, Martin; O'Brien, Jeremy L; Thompson, Mark G; Sorel, Marc; Yu, Siyuan

    2014-01-01

    The ability to rapidly switch between orbital angular momentum modes of light has important implications for future classical and quantum systems. In general, orbital angular momentum beams are generated using free-space bulk optical components where the fastest reconfiguration of such systems is around a millisecond using spatial light modulators. In this work, an extremely compact optical vortex emitter is demonstrated with the ability to actively tune between different orbital angular momentum modes. The emitter is tuned using a single electrically contacted thermo-optical control, maintaining device simplicity and micron scale footprint. On-off keying and orbital angular momentum mode switching are achieved at rates of 10 μs and 20 μs respectively. PMID:25229882

  5. Mode-switching induced super-thermal bunching in quantum-dot microlasers

    NASA Astrophysics Data System (ADS)

    Redlich, Christoph; Lingnau, Benjamin; Holzinger, Steffen; Schlottmann, Elisabeth; Kreinberg, Sören; Schneider, Christian; Kamp, Martin; Höfling, Sven; Wolters, Janik; Reitzenstein, Stephan; Lüdge, Kathy

    2016-06-01

    The super-thermal photon bunching in quantum-dot (QD) micropillar lasers is investigated both experimentally and theoretically via simulations driven by dynamic considerations. Using stochastic multi-mode rate equations we obtain very good agreement between experiment and theory in terms of intensity profiles and intensity-correlation properties of the examined QD micro-laser’s emission. Further investigations of the time-dependent emission show that super-thermal photon bunching occurs due to irregular mode-switching events in the bimodal lasers. Our bifurcation analysis reveals that these switchings find their origin in an underlying bistability, such that spontaneous emission noise is able to effectively perturb the two competing modes in a small parameter region. We thus ascribe the observed high photon correlation to dynamical multistabilities rather than quantum mechanical correlations.

  6. Novel Trajectory Control for Human Cooperation Robot Based on Behavior Mode Switching

    NASA Astrophysics Data System (ADS)

    Seki, Hirokazu; Takahashi, Kazuki; Tadakuma, Susumu

    This paper describes a novel trajectory control system for human cooperation robots based on behavior mode switching. Human cooperation robots have the great possibility to serve as useful support systems for elderly people and physically handicapped people and it is expected to realize the smooth and human-friendly support movements. This study defines three behavior modes in human cooperation motion and their respective trajectory control system are designed. In the trajectory design, minimum jerk model is introduced to realize the smooth and human-friendly cooperation movements. In addition, the initial value compensation at the mode switching is also developed. Some experiments on two-axis plane robot and performance evaluation by trial subjects show the effectiveness of the proposed trajectory control system.

  7. Five simultaneously Q-switch mode-locked passive laser modulators

    NASA Astrophysics Data System (ADS)

    Chen, Junewen

    2007-02-01

    Five types of passive Q-switched as well as simultaneously Q-switch mode-locked modulators: plastic dye sheets ( Kodak 9850 cellulose acetate dye sheets), lithium fluoride crystals containing F II - color centers ( LiF: F II -), chromium doped yttrium aluminum garnet crystals ( Cr 4+:YAG), ionic color filter glass ( Schott RG1000 color filter glass) and the single crystal semiconductor wafers ( GaAs, Fe doped InP, Zn doped InP, S doped InP, etc.) used for the modulation of the Nd:hosted(Nd:YAG, Nd:YVO 4, and Nd:LSB) lasers have been investigated in detail in our researches. We have also investigated into the applications of the Q-switch mode-locked pulses train for the development of higher resolution solid state laser range finder. We will also present the high accuracy laser ranging results, the micro-motor that driven mechanical parts from the stepping digital ranging readout, to precisely control the best focus of a miniature zoom lens modular. The core simultaneously Q-switch mode-locked modulators microchip laser is the key part of our automatic optical inspection system.

  8. Vibration modes and acoustic noise in a 4-phase switched reluctance motor

    SciTech Connect

    Colby, R.S.; Mottier, F.; Miller, T.J.E.

    1995-12-31

    Acoustic noise in the switched reluctance motor is caused primarily by the deformation of the stator lamination stack. Acoustic noise is most severe when the periodic excitation of the SRM phases excites a natural vibration mode of the stack. The natural vibration modes and frequencies of a 4-phase, 8/6 switched reluctance motor are examined. Structural finite element analysis is used to compute the natural modes and frequencies. Impulse tests on the stator stack verify the calculations and show which modes are excited. Heuristic arguments are developed to predict the operating conditions that will excite the natural modes. Measurement of vibration while the machine is under load shows which operating conditions excite the natural modes and verifies the predictions. An approximate formula is derived to predict the frequency of the fundamental vibration mode in terms of lamination dimensions and material properties. The formula is validated by comparison with finite element calculations for several laminations, and hence is shown to be useful in design trade-off studies.

  9. Ionic bipolar resistive switching modes determined by the preceding unipolar resistive switching reset behavior in Pt/TiO2/Pt

    NASA Astrophysics Data System (ADS)

    Yoon, Kyung Jean; Song, Seul Ji; Seok, Jun Yeong; Yoon, Jung Ho; Kim, Gun Hwan; Lee, Jong Ho; Hwang, Cheol Seong

    2013-04-01

    Various types of bipolar resistive switching (BRS) at the filament ruptured region by the unipolar resistive switching (URS) reset in the structure Pt/TiO2/Pt were categorized in terms of operation polarity and switching parameters. The differences in BRS behavior, even under identical current-voltage switching, are closely related to the previously performed URS reset parameter, especially the power consumed during the reset process. Various modes of BRS from the URS reset status in the structure Pt/TiO2/Pt are reported, and interpreted in terms of a distinct oxygen vacancy configuration in the ruptured region of a Magnéli filament.

  10. Soft switch-avalanche IGBT convertor. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Chen, K.; Stuart, T. A.

    1990-01-01

    A full bridge dc-dc converter using a zero voltage and zero current switching technique is described. This circuit utilizes the characteristics of the IGBT to achieve power and frequency combinations that are much higher than those previously reported for this device. Experimental results are included for a 1.5 kW, 100 kHz converter with 94 percent efficiency.

  11. Thresholds, Mode-Switching, and Emergent Pseudo-Equilibrium in Geomorphic Systems

    NASA Astrophysics Data System (ADS)

    Phillips, J. D.

    2012-04-01

    Many geomorphic systems exhibit mode shifts as they evolve, or react to disturbances, from an initial mode of dynamically unstable, divergent evolution, to a mode of convergent evolution. These trends are often interpreted as progression toward a normative equilibrium. However, these mode shifts are shown to arise from two basic principles: gradient (or resistance) selection, and threshold-mediated modulation. In early stages of system development positive feedbacks associated with gradient selection are dominant, and dynamical instability, chaos, and divergence result. Eventually, however, as the system approaches limiting thresholds, negative feedback associated with the thresholds becomes stronger than the positive feedbacks, and the system becomes stable, with convergent evolution. The unstable-to-stable mode switches are an emergent outcome of the gradient selection and threshold modulation principles, not a goal function of Earth surface systems. These principles are illustrated with two examples—fluvial dissection of the Cumberland Plateau, Kentucky, and channel development in deltas of the Texas coastal plain.

  12. Design of a high voltage input - output ratio dc-dc converter dedicated to small power fuel cell systems

    NASA Astrophysics Data System (ADS)

    Béthoux, O.; Cathelin, J.

    2010-12-01

    Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andújar, F. Segura, Renew. Sust. Energy Rev. 13, 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained, 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51, 56 (2010)]. This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the

  13. Vertical cavity surface emitting laser based optoelectronic asynchronous transfer mode switch

    SciTech Connect

    Wilmsen, C.W.; Duan, C.; Collington, J.R.; Dames, M.P.; Crossland, W.A.

    1999-07-01

    Large broadband asynchronous transfer mode (ATM) switching nodes require novel hardware solutions that could benefit from the inclusion of optical interconnect technology, since electronic solutions are limited by pin out and by the capacitance/inductance of the interconnections. We propose, analyze and demonstrate a new three stage free space optical switch that utilizes vertical cavity surface emitting lasers (VCSELs) for the optical interconnections, a liquid crystal spatial light modulator (SLM) as a reconfigurable shutter and relatively simple optics for fan out and fan in. A custom complementary metal oxide semiconductor (CMOS) chip is required to introduce a time delay in the optical bit stream and to drive the VCSELs. Analysis shows that the switch should be scalable to 1024{times}1024, which would require 2048 {approximately}2 mW VCSELs. {copyright} {ital 1999 Society of Photo-Optical Instrumentation Engineers.}

  14. Cavity length dependence of mode beating in passively Q-switched Nd-solid state lasers

    NASA Astrophysics Data System (ADS)

    Zameroski, Nathan D.; Wanke, Michael; Bossert, David

    2013-03-01

    The temporal intensity profile of pulse(s) from passively Q-switched and passively Q-switched mode locked (QSML) solid-state lasers is known to be dependent on cavity length. In this work, the pulse width, modulation depth, and beat frequencies of a Nd:Cr:GSGG laser using a Cr+4:YAG passive Q-switch are investigated as function cavity length. Measured temporal widths are linearly correlated with cavity length but generally 3-5 ns larger than theoretical predictions. Some cavity lengths exhibit pulse profiles with no modulation while other lengths exhibit complete amplitude modulation. The observed beat frequencies at certain cavity lengths cannot be accounted for with passively QSML models in which the pulse train repetition rate is τRT-1, τRT= round-trip time. They can be explained, however, by including coupled cavity mode-locking effects. A theoretical model developed for a two section coupled cavity semiconductor laser is adapted to a solid-state laser to interpret measured beat frequencies. We also numerically evaluate the temporal criterion required to achieve temporally smooth Q-switched pulses, versus cavity length and pump rate. We show that in flash lamp pumped systems, the difference in buildup time between longitudinal modes is largely dependent on the pump rate. In applications where short pulse delay is important, the pumping rate may limit the ability to achieve temporally smooth pulses in passively Q-switched lasers. Simulations support trends in experimental data. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. All-solid-state passively Q -switched mode-locked Nd-doped fiber laser

    SciTech Connect

    Zenteno, L.A.; Po, H.; Cho, N.M. )

    1990-01-15

    We report the generation of {ital Q}-switched mode-locked pulses from a Nd-doped fiber laser that uses a solid-state solution of BDN-I dye as the saturable absorber and is pumped by a GaAlAs laser diode. For an absorbed pump power of 110 m W, pulses of 8-nsec duration at a repetition rate of 14 MHz can be generated under an 800-nsec-wide {ital Q}-switched envelope at a repetition rate of 100 kHz, yielding an average output power of 8 m W near 1.06 {mu}m. This corresponds to approximately 9 W of peak power in the main mode-locked pulse.

  16. High Resolution Switching Mode Inductance-to-Frequency Converter with Temperature Compensationti

    PubMed Central

    Matko, Vojko; Milanović, Miro

    2014-01-01

    This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85–100 μH to 2–560 kHz. PMID:25325334

  17. Polarization switch of four-wave mixing in large mode area hybrid photonic crystal fibers.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2015-02-15

    Degenerate spontaneous four-wave mixing is considered in a large mode area hybrid photonic crystal fiber. Numerical and experimental results show birefringence assisted four-wave mixing for a certain polarization state of the pump field. The parametric gain can be turned on and off by switching the polarization state of the pump field between the two principal axis of the hybrid photonic crystal fiber. PMID:25680131

  18. Generation of single longitudinal mode in a pulsed passively Q -switched Nd:YAG laser

    SciTech Connect

    Hariri, A.; Soltanmoradi, F.; Nayeri, M. )

    1990-08-01

    It is shown that a single longitudinal mode in a passively {ital Q}-switch Nd:YAG laser can be obtained by adjusting an intracavity saturable absorber gelatin film (BDN) to work as a mirror in a three-mirror Fabry--Perot resonator. With a 0.13-mm-thick gelatin film of 40% unsaturated transmission, a temporally smooth single-laser pulse of {similar to}10 ns duration has been obtained.

  19. Speed control of switched reluctance motor using sliding mode control strategy

    SciTech Connect

    John, G.; Eastham, A.R.

    1995-12-31

    A robust speed drive system for a switched reluctance motor (SRM) using sliding mode control strategy (SLMC) is presented. After reviewing the operation of an SRM drive, a SLMC based scheme is formulated to control the drive speed. The scheme is implemented using a micro-controller and a high resolution position sensor. The parameter insensitive characteristics are demonstrated through computer simulations and experimental verification.

  20. Spontaneous mode switching in coupled oscillators competing for constant amounts of resources.

    PubMed

    Hirata, Yoshito; Aono, Masashi; Hara, Masahiko; Aihara, Kazuyuki

    2010-03-01

    We propose a widely applicable scheme of coupling that models competitions among dynamical systems for fixed amounts of resources. Two oscillators coupled in this way synchronize in antiphase. Three oscillators coupled circularly show a number of oscillation modes such as rotation and partially in-phase synchronization. Intriguingly, simple oscillators in the model also produce complex behavior such as spontaneous switching among different modes. The dynamics reproduces well the spatiotemporal oscillatory behavior of a true slime mold Physarum, which is capable of computational optimization. PMID:20370272

  1. Spontaneous mode switching in coupled oscillators competing for constant amounts of resources

    NASA Astrophysics Data System (ADS)

    Hirata, Yoshito; Aono, Masashi; Hara, Masahiko; Aihara, Kazuyuki

    2010-03-01

    We propose a widely applicable scheme of coupling that models competitions among dynamical systems for fixed amounts of resources. Two oscillators coupled in this way synchronize in antiphase. Three oscillators coupled circularly show a number of oscillation modes such as rotation and partially in-phase synchronization. Intriguingly, simple oscillators in the model also produce complex behavior such as spontaneous switching among different modes. The dynamics reproduces well the spatiotemporal oscillatory behavior of a true slime mold Physarum, which is capable of computational optimization.

  2. Integrated photonic emitter with a wide switching range of orbital angular momentum modes

    PubMed Central

    Wang, Yu; Zhao, Peng; Feng, Xue; Xu, Yuntao; Cui, Kaiyu; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-01-01

    Due to the nature of infinite dimensionality, the orbital angular momentum (OAM) has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications such as optical telecommunication, quantum information, particle manipulation and imaging. In recent years, the integrated photonic OAM emitters have been actively investigated due to both compactness and tunability. Essentially, the number of available OAM modes by dynamic switching should be large enough so that the dimensionality of OAM could be explored as much as possible. In this work, an integrated photonic emitter with a wide switching range of OAM modes is theoretically developed, numerically simulated, and experimentally verified. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = −4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect. PMID:26936327

  3. Integrated photonic emitter with a wide switching range of orbital angular momentum modes.

    PubMed

    Wang, Yu; Zhao, Peng; Feng, Xue; Xu, Yuntao; Cui, Kaiyu; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-01-01

    Due to the nature of infinite dimensionality, the orbital angular momentum (OAM) has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications such as optical telecommunication, quantum information, particle manipulation and imaging. In recent years, the integrated photonic OAM emitters have been actively investigated due to both compactness and tunability. Essentially, the number of available OAM modes by dynamic switching should be large enough so that the dimensionality of OAM could be explored as much as possible. In this work, an integrated photonic emitter with a wide switching range of OAM modes is theoretically developed, numerically simulated, and experimentally verified. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = -4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect. PMID:26936327

  4. Domain switching emission from the mixed-mode crack in ferroelectrics by birefringence measurement and phase field modeling

    NASA Astrophysics Data System (ADS)

    Li, Qun; Pan, Suxin; Liu, Qida; Wang, Jie

    2016-07-01

    The spatial and temporal evolution of domain switching near the tip of a mixed-mode crack (e.g., an inclined crack) is observed in ferroelectrics. The birefringence technique is used to measure the optical quantities to demonstrate the domain switching near the crack tip. The results show an intriguing feature that there appears electrical creep and domain switching emission from the crack tip. The actual time-dependence of domain switching emission and its anisotropic velocity is approximately measured. Moreover, the phase field modeling is developed to simulate polarization distribution and domain switching near the crack tip where the time-dependent Ginzburg–Landau equation is used to describe the change of polarization. The phase field results indicate the same features of domain switching emission from the mixed-mode crack. A good agreement between phase field simulation and birefringence measurement is concluded by setting the appropriate kinetic coefficient in the time-dependent Ginzburg–Landau equation.

  5. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  6. Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

    PubMed

    Hermsen, W; Hessels, J W T; Kuiper, L; van Leeuwen, J; Mitra, D; de Plaa, J; Rankin, J M; Stappers, B W; Wright, G A E; Basu, R; Alexov, A; Coenen, T; Grießmeier, J-M; Hassall, T E; Karastergiou, A; Keane, E; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Noutsos, A; Serylak, M; Pilia, M; Sobey, C; Weltevrede, P; Zagkouris, K; Asgekar, A; Avruch, I M; Batejat, F; Bell, M E; Bell, M R; Bentum, M J; Bernardi, G; Best, P; Bîrzan, L; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Ciardi, B; Duscha, S; Eislöffel, J; Falcke, H; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; de Gasperin, F; de Geus, E; Gunst, A W; Heald, G; Hoeft, M; Horneffer, A; Iacobelli, M; Kuper, G; Maat, P; Macario, G; Markoff, S; McKean, J P; Mevius, M; Miller-Jones, J C A; Morganti, R; Munk, H; Orrú, E; Paas, H; Pandey-Pommier, M; Pandey, V N; Pizzo, R; Polatidis, A G; Rawlings, S; Reich, W; Röttgering, H; Scaife, A M M; Schoenmakers, A; Shulevski, A; Sluman, J; Steinmetz, M; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Vermeulen, R; van de Brink, R H; van Weeren, R J; Wijers, R A M J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P

    2013-01-25

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories. PMID:23349288

  7. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  8. Repetition rate switching in a passively mode-locked fibre laser

    NASA Astrophysics Data System (ADS)

    Tian, X. L.; Tang, M.; Gong, Y. D.; Shum, P.

    2006-09-01

    Here we demonstrated a dispersion stretched passively mode-locked fiber laser. The laser was mode-locked by nonlinear polarization rotation (NPR) technical. Both dispersion managed soliton and noise-like pulses were observed in the experiment. Harmonic mode-locked noise-like pulses were observed. By changing the pump power or rotating the waveplates, noise-like pulse could split and always form equally spaced pulse train, thus the repetition rate of the output pulse could be switched among different orders of harmonic frequency. The experiment results were analyzed. We found that peak power clamping caused by NPR module led to pulse splitting, the pulse interaction through the Raman light drives the pulse to space equally.

  9. Experimental research of heavy ion and proton induced single event effects for a Bi-CMOS technology DC/DC converter

    NASA Astrophysics Data System (ADS)

    Anlin, He; Gang, Guo; Shuting, Shi; Dongjun, Shen; Jiancheng, Liu; Li, Cai; Hui, Fan

    2015-11-01

    This paper tested and analyzed heavy ion and proton induced single event effects (SEE) of a commercial DC/DC converter based on a 600 nm Bi-CMOS technology. Heavy ion induced single event transients (SET) testing has been carried out by using the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. Proton test has been carried out by using the Canadian TRIUMF proton accelerator. Both SET cross section versus linear energy transfer (LET) and proton energy has been measured. The main study conclusions are: (1) the DC/DC is both sensitive to heavy ion and proton radiations although at a pretty large feature size (600 nm), and threshold LET is about 0.06 MeV·mg/cm2 (2) heavy ion SET saturation cross section is about 5 magnitudes order larger than proton SET saturation cross section, which is consistent with the theory calculation result deduced by the RPP model and the proton nuclear reaction model; (3) on-orbit soft error rate (SER) prediction showed, on GEO orbit, proton induced SERs calculated by the heavy ion derived model are 4-5 times larger than those calculated by proton test data.

  10. 1400, +/- 900V PEAK PULSE SWITCH MODE POWER SUPPLIES FOR SNS INJECTION KICKERS.

    SciTech Connect

    LAMBIASE,R.ENG,W.SANDBERG,J.DEWAN,S.HOLMES,R.RUST,K.ZENG,J.

    2004-03-10

    This paper describes simulation and experimental results for a 1400A, {+-} 900V peak rated, switch mode power supply for SNS Injection Kicker Magnets. For each magnet (13 m{Omega}, 160{micro}H), the power supply must supply controlled pulses at 60 Hz repetition rate. The pulse current must rise from zero to maximum in less than 1 millisec in a controlled manner, flat top for up to 2 millisec, and should fall in a controlled manner to less than 4A within 500{micro}s. The low current performance during fall time is the biggest challenge in this power supply. The simulation results show that to meet the controlled fall of the current and the current ripple requirements, voltage loop bandwidth of at least 10 kHz and switching frequency of at least 100 kHz are required. To achieve high power high frequency switching with IGBT switches, a series connected topology with three phase shifted (O{sup o}, 60{sup o} & 120{sup o}) converters each with 40 kHz switching frequency (IGBT at 20kHz), has been achieved. In this paper, the circuit topology, relevant system specifications and experimental results that meet the requirements of the power supply are described in detail. A unique six pulse SCR rectifier circuit with capacitor storage has been implemented to achieve minimum pulse width to meet required performance during current fall time below 50A due to the very narrow pulse width and non-linearity from IGBT turn-on/off times.

  11. Resistance switching of Cu/SiO2 memory cells studied under voltage and current-driven modes

    NASA Astrophysics Data System (ADS)

    Bernard, Y.; Gonon, P.; Jousseaume, V.

    2010-05-01

    Resistance switching in Cu/SiO2-based conductive-bridging random access memories is studied under voltage and current-driven modes. These two modes are used to study memory cycling and time-dependent switching. Voltage-current (V-I) cycles (logarithmic current ramp) are compared to I-V cycles (linear voltage ramp). The Off-On transition in V-I cycles is governed by device capacitance. The Off-On switching time (in the 10-1-103 s range) was studied under constant voltage and constant current stresses. The switching time varies as exp(V0/V) and as 1/I. Switching kinetics is discussed considering a Fowler-Nordheim tunneling injection law and a field-induced nucleation theory.

  12. Note. Switch-Mode Hybrid Current Controllers for Quantum Cascade Lasers

    SciTech Connect

    Taubman, Matthew S.

    2013-01-07

    Chemical sensing in the mid-infrared has been revolutionized by the advent of quantum cascade lasers. Their higher current and voltage demands compared to laser diodes however, negatively impact size, weight and power footprint for fieldable systems, particularly in hot environments. This letter presents a switch-mode/linear hybrid controller design, furnishing low-noise drive current up to 2 amperes at compliance voltages up to 15 volts, with noise levels close to the Johnson noise of the internal resistors. Current modulation from near zero to 1.8 Amps is also demonstrated at frequencies up to a kilohertz.

  13. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, Charles L.

    1996-01-01

    A method and apparatus for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential element is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits.

  14. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, C.L.

    1997-09-23

    A method and apparatus are disclosed for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential dement is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits. 4 figs.

  15. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, Charles L.

    1997-01-01

    A method and apparatus for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential dement is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits.

  16. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, C.L.

    1996-12-31

    A method and apparatus are disclosed for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential element is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits. 4 figs.

  17. The effect of the depth of single longitudinal mode modulation in Q-switching pre-Pr3+:YLF laser

    NASA Astrophysics Data System (ADS)

    Qing-Song, Li; Ling-Xi, Zhu; Xi-He, Zhang; Yuan, Dong; Yong-Ji, Yu; Guang-Yong, Jin

    2016-08-01

    The single longitudinal mode (SLM) can be obtained under the condition of Q-switching pre-lase. In this paper, the model of Q-switching pre-lase is firstly established. Taking the Pr3+:YLF laser as an example, the process of Q-switching pre-lase is simulated and optimized, then the optimized parameters and best output characteristics under different depth of SLM modulation are obtained. Comparing with the normal Q-switching laser, the SLM pulse energy can reach to 79.29%, the pulse width exceeds 16.45% and the depth of SLM modulation get to be 20. The results show that the Q-switching pre-lase output characteristics can be effected obviously by the SLM modulation depth, and the pulse energy and pulse width can be close to the normal Q-switching laser as long as the depth of SLM modulation is optimized.

  18. An analysis toolbox to explore mesenchymal migration heterogeneity reveals adaptive switching between distinct modes

    PubMed Central

    Shafqat-Abbasi, Hamdah; Kowalewski, Jacob M; Kiss, Alexa; Gong, Xiaowei; Hernandez-Varas, Pablo; Berge, Ulrich; Jafari-Mamaghani, Mehrdad; Lock, John G; Strömblad, Staffan

    2016-01-01

    Mesenchymal (lamellipodial) migration is heterogeneous, although whether this reflects progressive variability or discrete, 'switchable' migration modalities, remains unclear. We present an analytical toolbox, based on quantitative single-cell imaging data, to interrogate this heterogeneity. Integrating supervised behavioral classification with multivariate analyses of cell motion, membrane dynamics, cell-matrix adhesion status and F-actin organization, this toolbox here enables the detection and characterization of two quantitatively distinct mesenchymal migration modes, termed 'Continuous' and 'Discontinuous'. Quantitative mode comparisons reveal differences in cell motion, spatiotemporal coordination of membrane protrusion/retraction, and how cells within each mode reorganize with changed cell speed. These modes thus represent distinctive migratory strategies. Additional analyses illuminate the macromolecular- and cellular-scale effects of molecular targeting (fibronectin, talin, ROCK), including 'adaptive switching' between Continuous (favored at high adhesion/full contraction) and Discontinuous (low adhesion/inhibited contraction) modes. Overall, this analytical toolbox now facilitates the exploration of both spontaneous and adaptive heterogeneity in mesenchymal migration. DOI: http://dx.doi.org/10.7554/eLife.11384.001 PMID:26821527

  19. Near perfect mode overlap between independently seeded, gain-switched lasers

    NASA Astrophysics Data System (ADS)

    Comandar, L. C.; Lucamarini, M.; Fröhlich, B.; Dynes, J. F.; Yuan, Z. L.; Shields, A. J.

    2016-08-01

    We drastically improve the mode overlap between independently seeded, gain-switched laser diodes operating at gigahertz repetition rates by implementing a pulsed light seeding technique. Injecting pulsed light reduces the emission time jitter and enables frequency chirp synchronization while maintaining random optical phases of the emitted laser pulses. We measure interference of these pulsed sources both in the macroscopic regime, where we demonstrate near perfect mode overlap, and in the single photon regime, where we achieve a Hong-Ou-Mandel dip visibility of 0.499+/-0.004, thus saturating the theoretical limit of 0.5. The measurement results are reproduced by Monte-Carlo simulations with no free parameters. Our light source is an ideal solution for generation of high rate, indistinguishable coherent pulses for quantum information applications.

  20. Coordinated control for regulation/protection mode-switching of ducted rockets

    NASA Astrophysics Data System (ADS)

    Qi, Yiwen; Bao, Wen; Zhao, Jun; Chang, Juntao

    2014-05-01

    This study is concerned with the coordinated control problem for regulation/protection mode-switching of a ducted rocket, in order to obtain the maximum system performance while ensuring safety. The proposed strategy has an inner/outer loop control structure which decomposes the contradiction between performance and safety into two modes of regulation and protection. Specifically, first, the mathematical model including the actuator (gas regulating system) and the plant (ducted rocket engine) is introduced. Second, taking the inlet buzz for instance, the ducted rocket coordinated control problem for thrust regulation and inlet buzz limit protection is formulated and discussed. Third, to solve the problem, based on the main inner loop, a limit protection controller (outer loop) design method is developed utilizing a linear quadratic optimal control technique, and a coordinated control logic is then presented. At last, the whole coordinated control strategy is applied to the ducted rocket control model, and simulation results demonstrate its effectiveness.

  1. Common mechanics of mode switching in locomotion of limbless and legged animals

    PubMed Central

    Kuroda, Shigeru; Kunita, Itsuki; Tanaka, Yoshimi; Ishiguro, Akio; Kobayashi, Ryo; Nakagaki, Toshiyuki

    2014-01-01

    Crawling using muscular waves is observed in many species, including planaria, leeches, nemertea, aplysia, snails, chitons, earthworms and maggots. Contraction or extension waves propagate along the antero-posterior axis of the body as the crawler pushes the ground substratum backward. However, the observation that locomotory waves can be directed forward or backward has attracted much attention over the past hundred years. Legged organisms such as centipedes and millipedes exhibit parallel phenomena; leg tips form density waves that propagate backward or forward. Mechanical considerations reveal that leg-density waves play a similar role to locomotory waves in limbless species, and that locomotory waves are used by a mechanism common to both legged and limbless species to achieve crawling. Here, we report that both mode switching of the wave direction and friction control were achieved when backward motion was induced in the laboratory. We show that the many variations of switching in different animals can essentially be classified in two types according to mechanical considerations. We propose that during their evolution, limbless crawlers first moved in a manner similar to walking before legs were obtained. Therefore, legged crawlers might have learned the mechanical mode of movement involved in walking long before obtaining legs. PMID:24718452

  2. Using the Virtual Heart Model to validate the mode-switch pacemaker operation.

    PubMed

    Jiang, Zhihao; Connolly, Allison; Mangharam, Rahul

    2010-01-01

    Artificial pacemakers are one of the most widely-used implantable devices today, with millions implanted worldwide. The main purpose of an artificial pacemaker is to treat bradycardia, or slow heart beats, by pacing the atrium and ventricles at a faster rate. While the basic functionality of the device is fairly simple, there are many documented cases of death and injury due to device malfunctions. The frequency of malfunctions due to firmware problems will only increase as the pacemaker operations become more complex in an attempt to expand the use of the device. One reason these malfunctions arise is that there is currently no methodology for formal validation and verification of medical device software, as there are in the safety-critical domains of avionics and industrial control automation. We have developed a timed-automata based Virtual Heart Model (VHM) to act as platform for medical device software validation and verification. Through a case study involving multiple arrhythmias, this investigation shows how the VHM can be used with closed-loop operation of a pacemaker to validate the necessity and functionality of the complex mode-switch pacemaker operation. We demonstrate the correct pacemaker operation, to switch from one rhythm management mode to another, in patients with supraventricular tachycardias. (1). PMID:21096077

  3. Common mechanics of mode switching in locomotion of limbless and legged animals.

    PubMed

    Kuroda, Shigeru; Kunita, Itsuki; Tanaka, Yoshimi; Ishiguro, Akio; Kobayashi, Ryo; Nakagaki, Toshiyuki

    2014-06-01

    Crawling using muscular waves is observed in many species, including planaria, leeches, nemertea, aplysia, snails, chitons, earthworms and maggots. Contraction or extension waves propagate along the antero-posterior axis of the body as the crawler pushes the ground substratum backward. However, the observation that locomotory waves can be directed forward or backward has attracted much attention over the past hundred years. Legged organisms such as centipedes and millipedes exhibit parallel phenomena; leg tips form density waves that propagate backward or forward. Mechanical considerations reveal that leg-density waves play a similar role to locomotory waves in limbless species, and that locomotory waves are used by a mechanism common to both legged and limbless species to achieve crawling. Here, we report that both mode switching of the wave direction and friction control were achieved when backward motion was induced in the laboratory. We show that the many variations of switching in different animals can essentially be classified in two types according to mechanical considerations. We propose that during their evolution, limbless crawlers first moved in a manner similar to walking before legs were obtained. Therefore, legged crawlers might have learned the mechanical mode of movement involved in walking long before obtaining legs. PMID:24718452

  4. Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy

    PubMed Central

    Takahashi, Yasufumi; Shevchuk, Andrew I.; Novak, Pavel; Babakinejad, Babak; Macpherson, Julie; Unwin, Patrick R.; Shiku, Hitoshi; Gorelik, Julia; Klenerman, David; Korchev, Yuri E.; Matsue, Tomokazu

    2012-01-01

    We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5–100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5–3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences. PMID:22611191

  5. Electrochemical treatment of tannery effluent using a battery integrated DC-DC converter and solar PV power supply--an approach towards environment and energy management.

    PubMed

    Iyappan, K; Basha, C Ahmed; Saravanathamizhan, R; Vedaraman, N; Tahiyah Nou Shene, C A; Begum, S Nathira

    2014-01-01

    Electrochemical oxidation of tannery effluent was carried out in batch, batch recirculation and continuous reactor configurations under different conditions using a battery-integrated DC-DC converter and solar PV power supply. The effect of current density, electrolysis time and fluid flow rate on chemical oxygen demand (COD) removal and energy consumption has been evaluated. The results of batch reactor show that a COD reduction of 80.85% to 96.67% could be obtained. The results showed that after 7 h of operation at a current density of 2.5 A dm(-2) and flow rate of 100 L h(-1) in batch recirculation reactor, the removal of COD is 82.14% and the specific energy consumption was found to be 5.871 kWh (kg COD)(-1) for tannery effluent. In addition, the performance of single pass flow reactors (single and multiple reactors) system of various configurations are analyzed. PMID:24844896

  6. Codimension-Two Big-Bang Bifurcation in a ZAD-Controlled Boost DC-DC Converter

    NASA Astrophysics Data System (ADS)

    Amador, A.; Casanova, S.; Granada, H. A.; Olivar, G.; Hurtado, J.

    In this paper, we study some nonlinear behaviors in a two-dimensional system defined by a Boost Converter controlled by CPWM (Centered Pulse-Width Modulation) and a ZAD (Zero Average Dynamics) strategy. The dynamics was analyzed using a discrete-time map, which consists of a sampled system at each switching cycle. The structure of the two-parametric space is characterized analytically. This allows proving the existence and stability of an infinite number of codimension-one curves that intersect at the same point in the two-parametric space. This phenomenon has been called a big-bang bifurcation.

  7. All-optical scanhead for ultrasound and photoacoustic imaging-Imaging mode switching by dichroic filtering.

    PubMed

    Hsieh, Bao-Yu; Chen, Sung-Liang; Ling, Tao; Guo, L Jay; Li, Pai-Chi

    2014-03-01

    Ultrasound (US) and photoacoustic (PA) multimodality imaging has the advantage of combining good acoustic resolution with high optical contrast. The use of an all-optical scanhead for both imaging modalities can simplify integration of the two systems and miniaturize the imaging scanhead. Herein we propose and demonstrate an all-optical US/PA scanhead using a thin plate for optoacoustic generation in US imaging, a polymer microring resonator for acoustic detection, and a dichroic filter to switch between the two imaging modes by changing the laser wavelength. A synthetic-aperture focusing technique is used to improve the resolution and contrast. Phantom images demonstrate the feasibility of this design, and show that axial and lateral resolutions of 125 μm and 2.52°, respectively, are possible. PMID:25302154

  8. Switch mode power supply for microwave heating based on the Boucherot effect.

    PubMed

    Georghiou, G E; Meredith, R; Metaxas, A C; Gurwicz, D

    1999-01-01

    This paper describes a new self-resonating switch-mode power-supply for driving CW magnetrons, based on the Boucherot effect. A detailed circuit analysis is given and its performance is evaluated for an 800 W/2450 MHz magnetron, whilst work at high power driving a magnetron up to 40 kW is reported. A comparison of the supply with the conventional power-supply used in microwave ovens is made and the principal features of the new design are found to be: low energy dissipation under short-circuit conditions, low ripple current and voltage waveforms that result in more precise control in the range 20-100% of rated power, high efficiencies and small size and weight. PMID:10687152

  9. Transverse field-induced nucleation pad switching modes during domain wall injection

    SciTech Connect

    Bryan, M. T.; Fry, P. W.; Schrefl, T.; Gibbs, M. R. J.; Allwood, D. A.; Im, M.-Y.; Fischer, P.

    2010-03-12

    We have used magnetic transmission X-ray microscopy (M-TXM) to image in-field magnetization configurations of patterned Ni{sub 80}Fe{sub 20} domain wall 'injection pads' and attached planar nanowires. Comparison with micromagnetic simulations suggests that the evolution of magnetic domains in rectangular injection pads depends on the relative orientation of closure domains in the remanent state. The magnetization reversal pathway is also altered by the inclusion of transverse magnetic fields. These different modes explain previous results of domain wall injection into nanowires. Even more striking was the observation of domain walls injecting halfway across the width of wider (>400 nm wide) wires but over wire lengths of several micrometers. These extended Neel walls can interact with adjacent nanowires and cause a switching in the side of the wire undergoing reversal as the domain wall continues to expand.

  10. Methods for testing automatic mode switching in patients implanted with DDD(R) pacemakers.

    PubMed

    Lau, Chu-Pak; Mascia, Franco; Corbucci, Giorgio; Padeletti, Luigi

    2004-01-01

    The assessment of automatic mode switching (AMS) algorithms is impossible in vivo, due to a low chance of seeing the patient at the onset of a spontaneous episode of atrial fibrillation (AF). As the induction of AF to test AMS has clinical concerns, three alternative and non-invasive techniques may be proposed for this purpose: myopotentials, chest wall stimulation, and an external supraventricular arrhythmia simulator. The first method is simple and does not require additional equipment, even though in some patients adequate signals cannot be generated with a soft effort such as handgrip or hand compression. The main advantage of the chest wall stimulation method is the possibility that it be performed in every implanting center, since it is based on the use of standard devices for cardiac stimulation. The method based on the external supraventricular arrhythmia simulator allows the most detailed of the ECG traces, but it needs a dedicated electronic device. PMID:15080575

  11. In-Plane Switching Mode for Liquid Crystal Displays Using a DNA Alignment Layer.

    PubMed

    Cha, Yun Jeong; Gim, Min-Jun; Oh, Kyunghwan; Yoon, Dong Ki

    2015-06-24

    We successfully fabricated the in-plane switching mode (IPS) LC display (LCD) based on a double stranded DNA (dsDNA) alignment layer. As widely known, the DNA has the right-handed double helical structure that has naturally grown grooves with a very regular period, which can be used as an alignment layer to control the orientation of liquid crystal (LC) molecules. The LC molecules on this topographical layer of DNA material align obliquely at a specific angle with respect to the direction of DNA chains, providing an instant and convenient tool for the fabrication of the IPS display compared to the conventional ways such as rubbing and mechanical shearing methods. The electro-optical performance and response time of this device were also investigated. Our result will be of great use in further exploration of the electro-optical properties of the other biomaterials. PMID:26066312

  12. Sandia`s network for supercomputing `95: Validating the progress of Asynchronous Transfer Mode (ATM) switching

    SciTech Connect

    Pratt, T.J.; Vahle, O.; Gossage, S.A.

    1996-04-01

    The Advanced Networking Integration Department at Sandia National Laboratories has used the annual Supercomputing conference sponsored by the IEEE and ACM for the past three years as a forum to demonstrate and focus communication and networking developments. For Supercomputing `95, Sandia elected: to demonstrate the functionality and capability of an AT&T Globeview 20Gbps Asynchronous Transfer Mode (ATM) switch, which represents the core of Sandia`s corporate network, to build and utilize a three node 622 megabit per second Paragon network, and to extend the DOD`s ACTS ATM Internet from Sandia, New Mexico to the conference`s show floor in San Diego, California, for video demonstrations. This paper documents those accomplishments, discusses the details of their implementation, and describes how these demonstrations supports Sandia`s overall strategies in ATM networking.

  13. Maximizing Data Quality using Mode Switching in Mixed-Device Survey Design: Nonresponse Bias and Models of Demographic Behavior

    PubMed Central

    Axinn, William G.; Gatny, Heather H.; Wagner, James

    2016-01-01

    Conducting survey interviews on the internet has become an attractive method for lowering data collection costs and increasing the frequency of interviewing, especially in longitudinal studies. However, the advantages of the web mode for studies with frequent re-interviews can be offset by the serious disadvantage of low response rates and the potential for nonresponse bias to mislead investigators. Important life events, such as changes in employment status, relationship changes, or moving can cause attrition from longitudinal studies, producing the possibility of attrition bias. The potential extent of such bias in longitudinal web surveys is not well understood. We use data from the Relationship Dynamics and Social Life (RDSL) study to examine the potential for a mixed-device approach with active mode switching to reduce attrition bias. The RDSL design allows panel members to switch modes by integrating telephone interviewing into a longitudinal web survey with the objective of collecting weekly reports. We found that in this design allowing panel members to switch modes kept more participants in the study compared to a web only approach. The characteristics of persons who ever switched modes are different than those who did not – including not only demographic characteristics, but also baseline characteristics related to pregnancy and time-varying characteristics that were collected after the baseline interview. This was true in multivariate models that control for multiple of these dimensions simultaneously. We conclude that mode options and mode switching is important for the success of longitudinal web surveys to maximize participation and minimize attrition. PMID:26865882

  14. Observer-based robust finite time H∞ sliding mode control for Markovian switching systems with mode-dependent time-varying delay and incomplete transition rate.

    PubMed

    Gao, Lijun; Jiang, Xiaoxiao; Wang, Dandan

    2016-03-01

    This paper investigates the problem of robust finite time H∞ sliding mode control for a class of Markovian switching systems. The system is subjected to the mode-dependent time-varying delay, partly unknown transition rate and unmeasurable state. The main difficulty is that, a sliding mode surface cannot be designed based on the unknown transition rate and unmeasurable state directly. To overcome this obstacle, the set of modes is firstly divided into two subsets standing for known transition rate subset and unknown one, based on which a state observer is established. A component robust finite-time sliding mode controller is also designed to cope with the effect of partially unknown transition rate. It is illustrated that the reachability, finite-time stability, finite-time boundedness, finite-time H∞ state feedback stabilization of sliding mode dynamics can be ensured despite the unknown transition rate. Finally, the simulation results verify the effectiveness of robust finite time control problem. PMID:26777336

  15. Digitally Controlled 4-Phase Bi-Directional Interleaved Dc-Dc Converter with Coupled Inductors / Digitāli Vadāms 4 Fāžu Divvirziena Līdzstrāvas Pārveidotājs Ar Saistītajām Droselēm

    NASA Astrophysics Data System (ADS)

    Kroics, K.; Sirmelis, U.; Grigans, L.

    2015-08-01

    The main advantages of multiphase interleaved DC-DC converters over single-phase converters are reduced current stress and reduced output current ripple. Nevertheless, inductor current ripple cannot be reduced only by an interleaving method. The integrated magnetic structure can be used to solve this problem. In this paper, the application of 2-phase coupled inductor designed in a convenient way by using commercially manufactured coil formers and ferrite cores is analysed to develop a 4-phase interleaved DC-DC converter. The steady state phase and output current ripple in a boost mode of the interleaved bidirectional DC-DC converter with integrated magnetics are analysed. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper. Šajā rakstā piedāvāta magnētiski saistīta drosele, kas izveidota, izmantojot plaša patēriņa ferrīta serdi un tinuma formētāju. Izmantojot šādas droseles, var tikt izveidots vairākfāžu pārveidotājs ar mazām izejas un iejas strāvas pulsācijām, kā arī samazinātām strāvas pulsācijām droselē. Rakstā sīkāk apskatīts līdzstrāvas pārveidotājs, kas sastāv no četrām fāzēm. Šim gadījumam izvestas teorētiskās formulas strāvas pulsāciju aprēķinam, kā arī rakstā parādīti eksperimentālie rezultāti, kas iegūti, testējot prototipu. Teorētiskie rezultāti sakrīt ar eksperimentālajiem

  16. How to test mode switching in pacemakers implanted in patients: the MOST study.

    PubMed

    Padeletti, Luigi; Gasparini, Maurizio; Porciani, Maria Cristina; Pieragnoli, Paolo; Colella, Andrea; Michelucci, Antonio; Proclemer, Alessandro; Tognarini, Stefano; Mantica, Massimo; Coltorti, Fernando; Corbucci, Giorgio; Sutton, Richard

    2002-02-01

    Optimal management of atrial arrhythmias with dual chamber pacemakers requires proper performance of automatic mode switching (AMS). The aim of this study was to develop a reliable technique to test the AMS function by using an external electronic device capable of mimicking the occurrence of supraventricular arrhythmias (Supraventricular Arrhythmia Simulator [SAS]). The SAS delivers low voltage pulse trains (200 mV, 20 ms) through two skin electrodes. Each pulse train lasts 15 seconds and starts synchronously with a pacing pulse of the implanted pacemaker to avoid interference from the operator. The pulse train rate is set at 350, 250, and 160 beats/min to simulate AF, atrial flutter, and atrial tachycardia (AT), respectively. Thirty-five patients implanted with Vitatron pacemakers, whose AMS system has been previously validated, were enrolled. Atrial and ventricular sensing were programmed in unipolar mode at 0.5 mV and in bipolar mode at > 2 mV, respectively. All pulses from the SAS were detected by the atrial channel at an amplitude ranging from 1 to 3 mV. The test proved to be safe and reliable at rest and during exercise. AMS occurred immediately at onset or at offset of atrial arrhythmias, and no adverse interference on pacemaker function was seen from the SAS. In conclusion, the described technique and the SAS are safe and reliable for patient and pacemaker function and can be proposed as a useful method to verify proper performance of AMS function irrespective of the type of implanted devices. PMID:11915981

  17. THE LIGHT CURVE AND INTERNAL MAGNETIC FIELD OF THE MODE-SWITCHING PULSAR PSR B0943+10

    SciTech Connect

    Storch, Natalia I.; Lai, Dong; Ho, Wynn C. G.; Bogdanov, Slavko; Heinke, Craig O.

    2014-07-10

    A number of radio pulsars exhibit intriguing mode-switching behavior. Recent observations of PSR B0943+10 revealed correlated radio and X-ray mode switches, providing a new avenue for understanding this class of objects. The large X-ray pulse fraction observed during the radio-quiet phase (Q-mode) was previously interpreted as a result of changing obscuration of X-rays by dense magnetosphere plasma. We show that the large X-ray pulse fraction can be explained by including the beaming effect of a magnetic atmosphere, while remaining consistent with the dipole field geometry constrained by radio observations. We also explore a more extreme magnetic field configuration, where a magnetic dipole displaced from the center of the star produces two magnetic polar caps of different sizes and magnetic field strengths. These models are currently consistent with data in radio and X-rays and can be tested or constrained by future X-ray observations.

  18. Q-switching and mode-locking in a diode-pumped frequency-doubled Nd : YAG laser

    SciTech Connect

    Donin, Valerii I; Yakovin, Dmitrii V; Gribanov, A V

    2012-02-28

    A new method for obtaining Q-switching simultaneously with mode-locking using one travelling-wave acousto-optic modulator in a frequency-doubled Nd : YAG laser cavity is described. Further shortening of output laser pulses (from 40 to 3.25 ps) is achieved by forming a Kerr lens in the frequency-doubling crystal. At an average power of {approx} 2 W and a Q-switching rate of 2 kHz, the peak power of the stably operating reached {approx} 50 MW.

  19. Multi-mode to single-mode switching caused by self-heating in bottom-emitting intra-cavity contacted 960 nm VCSELs

    NASA Astrophysics Data System (ADS)

    Blokhin, Sergey A.; Maleev, Nikolai A.; Kuzmenkov, Alexander G.; Lott, James A.; Kulagina, Marina M.; Zadiranov, Yurii M.; Gladyshev, Andrey G.; Nadtochiy, Alexey M.; Nikitina, Ekaterina V.; Tikhomirov, Vladimir G.; Ledentsov, Nikolai N.; Ustinov, Viktor M.

    2012-03-01

    Detailed investigation of anomalous modal behavior in fabricated bottom-emitting intra-cavity contacted 960 nm range vertical cavity surface emitting lasers (VCSELs) have been performed. At low currents the broad-aperture VCSELs show multi-mode operation at 945 nm via whispering gallery-like modes. Subsequent increase of pump current results in rapid increase of fundamental mode intensity and switching to a pure single transverse mode lasing regime at 960 nm with the higher slope efficiency. As a result record single transverse mode output power of 15 mW with a side-mode-suppressionratio (SMSR) above 30 dB was achieved. The observed phenomena cannot be explained by oxide-index guiding or changes in current pumping. 2D heat transport simulations show a strong temperature gradient inside the microcavity due to an effective lateral heat-sinking. This creates an effective waveguide and results in lower optical losses for the fundamental mode. At fixed pump current in pulsed regime (pulse width < 400 ns) high-order modes dominate, however the subsequent increase of pulse width leads to a rapid rise of optical power for the fundamental mode and SMSR increasing. Thus the self-heating phenomena play a crucial role in observed VCSEL unusual modal behavior.

  20. Dual-mode ion switching conducting polymer films as high energy supercapacitor materials

    SciTech Connect

    Naoi, Katsuhiko; Oura, Yasushi

    1995-12-31

    The electropolymerized polypyrrole films formed from micellar solution of anionic surfactants, viz., Dodecylbenzene sulfonate (DBS), showed potential-dependent anion and cation ion switching behavior and the peculiar columnar structure. The formation process and the redox of the polypyrrole was studied with the in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods. In-situ AFM observation clearly indicated that such a columnar structure started to form around critical charge densities of 60--100 mC cm{sup {minus}2}. The cyclic voltammogram for the PPy doped with DBS{sup {minus}} film showed two redox couples, each of which corresponds to a cation and an anion exchange process. Thus, the film behaves as a dual-mode ion doping/undoping exchanger. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. three orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a peculiar structure of the polymer formed. The feasibility of such polypyrrole in use of supercapacitor material was discussed.

  1. Analysis of mode wavefront characteristics for passively Q-switched slab Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang; Wang, Jie; Hu, Zhiqiu; Su, Likun

    2016-01-01

    The eigenmode of resonators with symmetric circular mirrors used in solid-state lasers is investigated. Further experiments on output beam quality on a passive Q-switched zigzag slab Nd:YAG laser have been performed by adopting Hartmann-Shack and Zernike-mode reconstruction methods. By the means of peak-valley and root mean square errors of the wavefront distribution, each order of Zernike aberrations are achieved accurately. Moreover, the distribution of circle energy in the far-field and corresponding beam evaluation factors can also be obtained by further calculation. Experimental results indicate that the wavefront aberration is mainly concentrated in the first 10 Zernike aberrations, which mainly includes the defocus Z3, the low-order astigmatism Z5, the coma aberration Z6, and the spherical aberration Z10, because of the crystal thermal effect and the intracavity phase perturbation. The method can be used to further analyze the compensation of intracavity aberration and optimal design for such lasers.

  2. Power Quality Improvement in Bridgeless Ac-Dc Converter Based Multi-output Switched Mode Power Supply

    NASA Astrophysics Data System (ADS)

    Singh, Shihka; Singh, Bhim; Bhuvaneswari, G.; Bist, Vashist

    2014-12-01

    Computer power supplies are required to have multiple isolated regulated dc voltages with low ripple content and high input power factor at the utility interface. A dc-dc converter is used for obtaining these isolated multi-output dc voltages with excellent regulation. In this paper, a non-isolated ac-dc converter is proposed as the first stage converter to obtain a regulated dc output rather than using a simple uncontrolled diode bridge rectifier at the front end. A dc-dc converter is used at the second stage that has a high frequency transformer with multiple secondary windings to obtain different dc voltage levels at the output. The proposed bridgeless converter based power supply is designed using fundamental design equations, and different component values are calculated. Extensive simulations are carried out to demonstrate the improved performance of the proposed bridgeless converter based multi-output computer power supply at varying source voltages and load conditions. Experimental validation of the power supply is carried on a developed hardware prototype, and the test results are compared with the simulated performance for design verification.

  3. Ultrafast, low-power, all-optical switching via birefringent phase-matched transverse mode conversion in integrated waveguides.

    PubMed

    Hellwig, Tim; Epping, Jörn P; Schnack, Martin; Boller, Klaus-J; Fallnich, Carsten

    2015-07-27

    We demonstrate the potential of birefringence-based, all-optical, ultrafast conversion between the transverse modes in integrated optical waveguides by modelling the conversion process by numerically solving the multi-mode coupled nonlinear Schroedinger equations. The observed conversion is induced by a control beam and due to the Kerr effect, resulting in a transient index grating which coherently scatters probe light from one transverse waveguide mode into another. We introduce birefringent phase matching to enable efficient all-optically induced mode conversion at different wavelengths of the control and probe beam. It is shown that tailoring the waveguide geometry can be exploited to explicitly minimize intermodal group delay as well as to maximize the nonlinear coefficient, under the constraint of a phase matching condition. The waveguide geometries investigated here, allow for mode conversion with over two orders of magnitude reduced control pulse energy compared to previous schemes and thereby promise nonlinear mode switching exceeding efficiencies of 90% at switching energies below 1 nJ. PMID:26367581

  4. Q-switched mode-locked and azimuthally polarized Nd:GdVO4 laser with semiconductor saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Hong, Kun-Guei; Hung, Bi-Jin; Lin, Shih-Ting; Wei, Ming-Dar

    2016-06-01

    A Q-switched mode-locked Nd:GdVO4 laser with azimuthal polarization was generated using a semiconductor saturable absorber mirror. On the basis of the birefringence of the laser crystal inducing different equivalent lengths for ordinary and extraordinary rays, beams were azimuthally polarized around the edge of a stable cavity region. At a pump power of 9 W, the repetition rate and width for the Q-switched envelope were 318 kHz and 0.91 µs, and the mode-locked pulse repetition rate and pulse width were 455 MHz and 65 ps, respectively. The degree of polarization was controllable up to 95.4 ± 1.4%.

  5. Nanosecond pulses in a THz gyrotron oscillator operating in a mode-locked self-consistent Q-switch regime.

    PubMed

    Alberti, S; Braunmueller, F; Tran, T M; Genoud, J; Hogge, J-Ph; Tran, M Q; Ansermet, J-Ph

    2013-11-15

    An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE(7,2) transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations. PMID:24289692

  6. 183 WTEM00 mode acoustic-optic Q-switched MOPA laser at 850 kHz.

    PubMed

    Liu, Qiang; Yan, Xingpeng; Fu, Xing; Gong, Mali; Wang, Dongsheng

    2009-03-30

    We report a high-power, high-repetition-rate TEM00 mode MOPA laser using acoustic-optic Q-switching. Seed laser from the dual-end- pumped Nd:YVO4 oscillator was scaled up to 183.5 W average power at 850 kHz after behind amplified by the four-stage power amplifiers. The stable Q-switching operation worked at different pulse repetition rate from 60 kHz to 850 kHz while the pulse duration increased from 12.8 ns to 72 ns. The beam quality was near diffraction-limit with M2 factors measured as M2x = 1.28 and M2y = 1.21. In CW operation, 195 W TEM00 mode output was achieved corresponding to the total optical-optical efficiency of 44.7% and the absorbed pump power to output power efficiency of 53.3% respectively. PMID:19333332

  7. Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous LaHoO{sub 3} thin films

    SciTech Connect

    Sharma, Yogesh; Pavunny, Shojan P.; Katiyar, Ram S.; Fachini, Esteban; Scott, James F.

    2015-09-07

    We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO{sub 3} (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high R{sub ON}/R{sub OFF} ratios (in the range of ∼10{sup 4}–10{sup 5}) and non-overlapping switching voltages (set voltage, V{sub ON} ∼ ±3.6–4.2 V and reset voltage, V{sub OFF} ∼ ±1.3–1.6 V) with a small variation of about ±5–8%. Temperature dependent current-voltage (I–V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that the formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I–V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state.

  8. Diode pumped Nd:YAG laser with active Q-switching and mode locking for hole drilling

    NASA Astrophysics Data System (ADS)

    Solokhin, S. A.; Sirotkin, A. A.; Garnov, S. V.

    2011-06-01

    A diode-pumped Nd:YAG laser operating with active-passive Q-switch mode locking, has been developed. The acousto-optic repetition train was one kilohertz with generated pulse train widths 65 ns, single pulse widths 200 ps and an average power of 6.5 W. Improvement of efficiency of small diameter deep holes laser drilling in different materials was studied.

  9. Electro-optic characteristics of fringe-field-switching mode with controllable anchoring strength of liquid crystal alignment

    NASA Astrophysics Data System (ADS)

    Lin, T.-C.; Chang, K.-H.; Song, Y.; Hsieh, C.; Lo, C.-C.; Lee, C.; Lien, S.-C. Alan; Hasebe, H.; Takatsu, H.; Chien, L.-C.

    2015-11-01

    A photoalignment technique used in preparation of fringe-field-switching (FFS) mode cells is presented. The azimuthal anchoring energy (AAE) of photoalignment is controllable by tuning the UV exposure and if the value of AAE is as strong as that of the rubbing method. The electro-optical properties of FFS cells are optimized with different electrode configurations and high quality dark states of various types of cells are achieved to create the high contrast ratio. The great thermal stability shown after applying voltage and heat confirms that photoalignment is suitable for FFS mode applications.

  10. Intrinsic Neuronal Properties Switch the Mode of Information Transmission in Networks

    PubMed Central

    Gjorgjieva, Julijana; Mease, Rebecca A.; Moody, William J.; Fairhall, Adrienne L.

    2014-01-01

    represent and propagate information, and suggests a role for background synaptic noise in switching the mode of information transmission. PMID:25474701