Zero-Voltage-Switching PWM Full-Bridge Converter Employing Auxiliary Transformer to Reset the Clamping Diode Current

Introducing clamping diodes into the zero-voltage-switching (ZVS) pulsewidth-modulation (PWM) full-bridge (FB) converters can eliminate the voltage oscillation across the output rectifier diodes; however, the clamping diodes result in increase in conduction loss and suffer from serious reverse recovery at light load. In order to solve these problems, the clamping diode current should be reset rapidly. This paper proposes a scheme of resetting the clamping diode current over the full-load range by introducing an auxiliary transformer into the ZVS PWM FB converter. The operation principles of the proposed scheme under heavy-load and light-load conditions are analyzed in details. The design considerations of the introduced auxiliary transformer are also given. A performance comparison among the proposed scheme of resetting the clamping diode current and other ones are addressed. Experimental results verify the effectiveness of the analysis and prove that the proposed converter has improved reliability and reduced conduction loss compared with the classical one.