An improved zero-voltage and zero-current-switching full-bridge PWMconverter using a simple resonant circuit

An improved zero-voltage and zero-current-witching full-bridge pulsewidth modulation (ZVZCS-FB-PWM) DC-to-DC converter is presented and analyzed. An auxiliary resonant circuit, which consists of a switch and a capacitor, are added to provide zero-current switching (ZCS) conditions to the primary lagging-leg switches. Due to the auxiliary circuit, when the primary current is being extinguished, the voltage applied on the leakage inductance of the transformer is larger than DC-link voltage. This large voltage increases the maximal output current that can be handled in ZCS. Furthermore, the auxiliary switch softly turns on and turns off.