An improved ZVS PWM full-bridge converter with clamping diodes

Phase-shifted ZVS PWM full-bridge converter realizes ZVS and eliminates the voltage oscillation caused by the reverse recovery of the rectifier diodes by introducing a resonant inductance and two clamping diodes. This paper improves the converter just by exchanging the position of the resonant inductance and the transformer such that the transformer is connected with the lagging leg. The improved converter has several advantages over the original counterpart, e.g., the clamping diodes conduct only once in a switching cycle, and the resonant inductance current is smaller in zero state, leading to a higher efficiency and reduced duty cycle loss. A blocking capacitor is usually introduced to the primary side to prevent the transformer from saturating, this paper analyzes the effects of the blocking capacitor in different positions, and a best scheme is determined. A 2850 W prototype converter is built to verify the effectiveness of the improved converter and the best scheme for the blocking capacitor.