Zero-voltage and zero-current-switching full bridge PWM converter for high-power applications

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulse-width modulated (PWM) converter is proposed. The new converter overcomes the limitations of the zero-voltage-switching (ZVS)-FB-PWM converter, such as high circulating energy, loss of duty cycle, and limited ZVS load range for the lagging-leg switches. By using the DC blocking capacitor and adding a saturable inductor, the primary current during the freewheeling period is reduced to zero, allowing the lagging-leg switches to be operated with zero-current-switching (ZCS). Meanwhile, the leading-leg switches are still operated with ZVS. The new converter is attractive for high-voltage (400-800 V), high-power (2-10 kW) applications where IGBTs are predominantly used as the power switches. The principle of operation, features, and design considerations of the new converter are described and verified on a 2-kW, 100-kHz, IGBT-based experimental circuit.