A Novel Soft-Switching Full-Bridge Converter With a Combination of a Secondary Switch and a Nondissipative Snubber

In this paper, a novel soft-switching full-bridge converter with an additional secondary switch and a nondissipative energy recovery snubber is proposed. Thanks to the combination of an active switch and the capacitor-diode-diode snubber employed at the secondary side of the converter, the proposed converter can achieve zero-voltage zero-current switching for all of the primary switches and rectifier diodes over the entire load range. As a result, the rectifier diodes have no reverse-recovery problem and their ringing voltage is clamped. In addition, since no phase shift is used for the gate signals of the primary-side switches, the converter control can be implemented easily and it has no circulating current inherently. The converter exhibits a significant improvement in terms of efficiency, especially under light-load conditions, which is difficult to achieve with conventional phase-shift full-bridge converters. A 3-kW prototype circuit is implemented to verify the superior performance of the proposed converter.