A Novel Wide-Input-Range Quasi-Resonant Forward-Flyback DC/DC Converter

The paper addresses a novel quasi-resonant Forward-Flyback DC/DC converter featuring wide input range. In the proposed topology, Forward part and Flyback part share a same primary winding. Major part of power is transferred through the Forward part, while Flyback part takes responsibility to realize magnetic resetting and voltage regulation. Gain of the converter is derived. Also, characteristics in wide input range and valley-switching phenomenon is analyzed in the paper. Based on the analysis, a PWM-COT hybrid control strategy is proposed to secure a fully-resonant operation of the converter, which improves the efficiency and enhances the robustness. Design guidelines are elaborated in the paper. A 360 ~ 440 V input, 48 V/300 W output prototype is fabricated in the laboratory, which achieves a peak efficiency of 90.19%.