Isolated High-Frequency Link PFC Rectifier With High Step-Down Factor and Reduced Energy Circulation

Abstract

This article presents an isolated single-stage ac–dc high-frequency link full-bridge cycloconverter (HFLC) with high conversion ratio. Despite certain advantages, such topologies gen- erally suffer from transformer leakage inductance problems and lack of effective modulation methods, particularly in the ac–dc operation mode. In this study, for the input current regulation with the power factor correction of the HFLC, a novel phase-shift modulation method is used. It allows soft-switched turn-OFF of the dc-side transistors and zero current switching of the ac-side matrix switches without additional circuits or topology modifications. The introduced time-varying regulation of the peak current can be easily implemented; as a result, merely minor energy circulation occurs. Moreover, two of the ac-side transistors operate with fun- damental frequency. Design constraints of the concept are analyzed and discussed. For verification, a 1.2-kW 230 VAC to 48 VDC experimental prototype is used.