A half-bridge pulse-width modulated zero-current-switched quasi-resonant converter

The authors present a novel half-bridge pulse-width modulated zero-current-switched quasi-resonant converter for offline application, derived from the half-bridge frequency-modulated zero-current-switched quasi-resonant converter with secondary-side resonance and a separate freewheeling diode. It is shown that the proposed converter operates under constant frequency and is regulated by pulse-width modulation, with lossless commutation. A detailed analysis, the design procedure, simulation, and experimental results are presented. A laboratory prototype rated at 140 W, operating at a switching frequency of 500 kHz and resonant frequency of 2.5 MHz, has been implemented and tested.