Soft-Switching Converter With Two Series Half-Bridge Legs to Reduce Voltage Stress of Active Switches

This paper presents a new soft-switching dc/dc converter for high-input-voltage applications. Two half-bridge converters connected in series with interleaved asymmetric pulsewidth modulation (PWM) are adopted to limit the voltage stress of each power switch at one-half of the input dc bus voltage. In each half-bridge converter, two asymmetrical dc/dc circuits with the same active switches are connected in parallel at the output side to share the load current and reduce the current stresses of the secondary windings and rectifier diodes. Since two half-bridge converters are operated with interleaved PWM, the output ripple currents partially cancel each other so that the resultant ripple current at the output side is reduced. Active switches in the proposed circuit can be turned on at zero-voltage switching during the transition interval due to the resonant behavior by the output capacitance of MOSFETs and the leakage inductance of transformers. Experiments based on a laboratory prototype with 960-W rated power are provided to demonstrate the performance of the proposed converter.