Phase-Shifted Full-Bridge Converter with an Improved Coupled Inductor Rectifier

Abstract

A phase-shifted full-bridge (PSFB) converter with coupled inductor rectifier (CIR) structure has the advantage that eliminate freewheeling current in the primary side of the PSFB converter. However, during freewheeling period, the output current flows through high-voltage-rated diodes, resulting in large conduction loss. Also, the converter should be designed with a small magnetizing inductance to achieve zero-voltage switching (ZVS) for the lagging-leg switches, resulting in increased transformer loss. This article proposes a modified PSFB converter to mitigate the drawbacks of the conventional CIR PSFB converter. By employing two diodes in the secondary side, the output current is transferred to the primary side during the freewheeling period, facilitating ZVS for the lagging-leg switches. Moreover, the output current during the freewheeling period flows through the low-voltage-rated diodes. Therefore, the proposed converter achieves high efficiency. The performance of the proposed converter was verified using prototypes with 320–400-V input and 56-V/700-W output specifications.