A forward pulse-width modulated quasi-resonant converter: analysis, design and experimental results

The authors propose a forward pulse-width modulated zero-current switching quasi-resonant converter (F-PWM-ZCS-QRC), which, in contrast to the conventional forward frequency-modulated zero-current switching quasi-resonant converter (F-FM-ZCS-QRC), provides output voltage and power control at a constant operating frequency. The topology is generated by inserting an additional current-bidirectional switch in the conventional F-FM-ZCS-QRC. The operation principle and design-oriented analysis are presented, with normalized design curves, design procedure, numerical examples, simulations, and experimental results. Theoretical analysis was verified experimentally with a prototype rated at 100 W, operating at the resonant frequency of 1.56 MHz and a switching frequency of 500 kHz. It has been experimentally demonstrated that the proposed converter operates from full load down to 2% of full load, with a constant switching frequency of 500 kHz