Three DC/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, lower turn-off peak currents in the power devices and lower RMS current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable. >

A three-phase soft-switched high power density DC/DC converter for high power applications

The half-bridge series-resonant, parallel-resonant, and combination series-parallel resonant converters are compared for use in low-output-voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, avoids the main disadvantages of each of them. Analyses and breadboard results show that the combination converter can run over a large input voltage range and a large load range (no load to full load) while maintaining excellent efficiency. A useful analysis technique based on classical AC complex analysis is introduced. >

A comparison of half-bridge resonant converter topologies

A surgical instrument including a handle assembly, a first endoscopic portion, a motor, and a first end effector is disclosed. The first endoscopic portion is selectively connectable to a distal portion of the handle assembly and defines a longitudinal axis. The first endoscopic portion includes a housing adjacent its proximal portion and includes an actuation member. The motor is disposed in mechanical cooperation with the housing of the first endoscopic portion and is operatively connected to the actuation member for moving the actuation member substantially along the longitudinal axis. The first end effector is selectively connectable to a distal portion of the first endoscopic portion and is configured to perform a first stapling function.

Powered surgical instrument

Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the proposed MPPT system and other techniques used in the past is that the PV array output power is used to directly control the DC/DC converter, thus reducing the complexity of the system. The resulting system has high-efficiency, lower-cost and can be easily modified to handle more energy sources (e.g., wind-generators). The experimental results show that the use of the proposed MPPT control increases the PV output power by as much as 15% compared to the case where the DC/DC converter duty cycle is set such that the PV array produces the maximum power at 1 kW/m/sup 2/ and 25/spl deg/C.

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Development of a microcontroller-based, photovoltaic maximum power point tracking control system

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

/pdf/step-up-dc-dc-converters-a-comprehensive-review-of-voltage-6dlytctzg2.pdf

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

A high power factor converter system comprises an input rectifier, a converter and a booster circuit. The input rectifier is configured for rectifying an input ac voltage. The converter is configured for generating an output voltage for the high power factor converter system. The converter comprises several converter switches and inverse parallel diodes. The booster circuit comprises an inductor and at least one converter switch and an inverse parallel diode of the converter. The inductor is coupled between the input rectifier and the converter. The booster circuit is configured for controlling the supply of a booster current through the inductor to be discontinuous when the instantaneous voltage level is less than a predetermined fraction of a dc voltage level across the converter and continuous when the instantaneous voltage level is greater than the predetermined fraction of the dc voltage level.

High power factor converter with a boost circuit having continuous/discontinuous modes

A control circuit for a full bridge switching converter including power FET switching devices. The control circuit including a gate driver with a voltage sensor circuit which senses the precise instant to gate the power FET on in order to achieve substantially lossless switching by the converter.

Gate driver for a full-bridge lossless switching device

A circuit for "resetting" snubbers in a series resonant bridge inverter maintains lossless snubber action during light-load and no-load inverter operation and during operation near resonance Series resonant circuit operation is controlled to be above the resonant frequency to ensure operation at a lagging power factor The snubber-resetting operation is facilitated by a relatively small inductor connected across the output terminals of the series resonant inverter

Series resonant inverter with lossless snubber-resetting components

A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/in/sup 3/) and low profile (height 40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors requires a special ring down measurement set-up which is also described. >

High-efficiency, high-density MHz magnetic components for low profile converters

A high efficiency, high power factor, low voltage power converter includes a dual active bridge converter (DABC) having transformer-coupled primary-side and secondary-side bridge connections of switching devices and providing two output voltages. One output voltage drives a resonant boost converter coupled in series between an ac rectifier for rectifying an ac line voltage and the DABC. The boost converter, which is controlled by frequency modulation, boosts a dc bus voltage above the peak line voltage, thereby providing a high power factor. The other output is a low dc voltage which is regulated by controlling the phase shift between the voltages respectively produced by the primary-side and secondary-side connections of switching devices of the DABC. Advantageously, the leakage inductance of the DABC transformer coupling the primary and secondary sides of the DABC is efficiently used for energy transfer therebetween such that an output filter inductor is not needed. Moreover, use of synchronous rectifiers in the DABC allows for active control on the secondary side of the DABC transformer, further increasing efficiency. Zero-voltage switching of the switching devices of the DABC allows for an increase in operating frequency and hence an increase in power density.

Robert Louis Steigerwald

Papers

High power factor converter with a boost circuit having continuous/discontinuous modes

Gate driver for a full-bridge lossless switching device

Series resonant inverter with lossless snubber-resetting components

High-efficiency, high-density MHz magnetic components for low profile converters

Efficient, high power density, high power factor converter for very low dc voltage applications