Using the ohmic resistance reverse conduction capability of MOSFETs in quasi-resonant converters

A technique is proposed to eliminate the external diodes used to block the MOSFET's parasitic antiparallel diode in full-wave-mode zero-current switching quasi-resonant converters (ZCS-QRCs). The method, which consists of using the ohmic resistance reverse conduction capability of MOSFETs for conducting the negative portion of the resonant inductor current, thus preventing it from flowing into the body diode, has been successfully employed in 300 W, 20 V buck and forward quasi-resonant converters. It has been verified that the method improves efficiency and reduces the cost, size, and weight of ZCS-QRCs. The feasibility of associating MOSFETs in parallel in ZCS-QRCs in order to increase power rating is also demonstrated.<
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