Analysis, Design, and Implementation of a Soft-Switching Converter With Two Three-Level PWM Circuits

This paper proposes a new soft-switching circuit for high-input-voltage applications to achieve zero voltage switching (ZVS), implement load current sharing, reduce the voltage stress of switches at $V_{\rm in}$ /2, and decrease current rating of the rectifier diodes and the output inductors. Two three-level pulse-width modulation (PWM) circuits with the same active switches are operated with the phase-shift PWM scheme. Two center-tapped rectifiers are adopted at the secondary side such that the current rating of the transformer windings, rectifier diodes, and output filter inductors are reduced and have only one diode conduction loss in the forward current path. Based on the resonant behavior by the output capacitance of active switches and the leakage inductance (or external inductance), all power switches are turned ON at ZVS. The operation principle, circuit analysis, and design example are discussed in detail. Finally, experiments with 1-kW prototype are provided to verify the effectiveness of the proposed converter.