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.

/pdf/development-of-a-microcontroller-based-photovoltaic-maximum-1r79o424xa.pdf

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 current switching transistor controlling a load in its collector circuit receives from a drive circuit sufficient base current necessary to render the transistor conductive. A low loss inductor and switching means are connected to the base of the transistor such that when switching means are rendered nonconductive, current from the inductor flows into the base of the transistor to render it conductive, thus energizing the load. Regulating means coupled between a source of relatively high DC potential and the inductor together with unidirectional feedback path means provide a continuous current into the inductor such that when regulating means are substantially nonconductive, current is diverted away from the base of the high current transistor and circulates through the unidirectional feedback path and low loss inductor.

Efficient base drive circuit for high current transistors

A control system of a dc separately excited motor for electric vehicle drive is described. The armature of the motor is controlled by a thyristor chopper, whereas the field is regulated by a highfrequency transistor chopper. The control scheme combines the advantages of both series and shunt motors and permits maximum possible acceleration within the transient thermal ratings of the motor. In addition, motor torque becomes smoother under all operating conditions. A complete drive system has been formulated, designed, and analyzed, and performances have been evaluated on a hybrid computer. At present, the breadboard of the drive system is being tested in the laboratory.

A DC Motor Control System for Electric Vehicle Drive

A secondary-side controlled series resonant AC voltage controlled module (VRM) converts an AC distribution bus voltage to a low DC voltage for providing power to high speed microprocessors and integrated circuits, with minimal conduction and switching losses, providing high efficiency even at low output voltage, high current and high switching frequency.

Secondary-side controlled resonant AC voltage regulator module

An improved battery charger circuit for rapidly charging batteries by increasing the rate of battery charge acceptance through periodic battery discharge pulses during the charging process includes first and second chopper circuits coupled in parallel through an inductor across the DC source for coupling to a battery. The first chopper circuit controls the amplitude of battery charge current while the second chopper circuit controls the amplitude of battery discharge current and provides a low impedance conduction path for discharge current to be returned to the DC source, thus realizing an efficient battery charger circuit.

High efficiency circuit for rapidly charging batteries

An apparatus for rapid charging using onboard power electronics includes a DC bus, a first energy storage device coupled to the DC bus and configured to output a DC voltage, a first bi-directional voltage modification assembly coupled to the DC bus, and a high-impedance voltage source coupleable to the DC bus. The apparatus further includes a charging system having a first receptacle coupled to the DC bus and a second receptacle coupled to the first bi-directional voltage modification assembly. The first receptacle is constructed to mate with a first connector coupled to the high-impedance voltage source and the second receptacle is constructed to mate with a second connector coupled to the high-impedance voltage source. A controller is programmed to control a simultaneous transfer of charging energy through the first and second receptacles of the charging system to the DC bus.

Robert Louis Steigerwald

Papers

Efficient base drive circuit for high current transistors

A DC Motor Control System for Electric Vehicle Drive

Secondary-side controlled resonant AC voltage regulator module

High efficiency circuit for rapidly charging batteries

Apparatus for rapid charging using onboard power electronics and method of manufacturing same