Analysis and implementation of a soft switching DC/DC converter with three asymmetric PWM circuits

This paper presents a soft switching converter with three buck-type active clamp circuits (or asymmetric half-bridge circuits) to achieve the functions of the low power rating on the transformers and power semiconductors and low current rating on the rectifier diodes and output inductors. Three half-bridge circuits are stacked at the high voltage side to reduce the voltage stress of each power switch at one-half of input voltage and connected in parallel at the low voltage side to share load current and reduce the current rating on each magnetic component and the rectifier diode. Thus, the size of the output chokes is reduced. In each half-bridge converter, the asymmetric pulse-width modulation is adopted to control power switches. Power MOSFETs can be turned on with zero voltage during the transition interval due to the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers. Experiments based on a laboratory prototype with 1 kW rated power are provided to demonstrate the performance of proposed converter. Copyright (c) 2012 John Wiley & Sons, Ltd.