A Novel Zero-Voltage-Switching PWM Full-Bridge Converter

Introducing resonant inductance and clamping diodes into the full-bridge converter can eliminate the voltage oscillation across the rectifier diodes and increase the load range for zero- voltage-switching (ZVS) achievement. The resonant inductance is shorted and its current keeps constant when the clamping diode is conducting, and the clamping diodes are hard turned-off and cause significant reverse recovery loss if the output filter inductance is relatively larger. This paper improves the full-bridge converter by introducing a reset winding in series with the resonant inductance to make the clamping diode current decay rapidly when it conducts. The reset winding not only reduces the conduction losses, but also makes the clamping diodes naturally turn-off and avoids the reverse recovery. The operation principle of the proposed converter is analyzed. The design of the turns ratio of transformer is discussed. A 1kW prototype converter is built to verify the operation principle and the experimental results are also demonstrated.