Buck-type current-fed push-pull converter with ZCS for high voltage applications

A buck-type current-fed push-pull converter with zero current switching (ZCS) is proposed in this paper. The proposed converter is comprised of two buck switches, two flywheel diodes, a current-fed push-pull converter, and a high-voltage transformer. The proposed converter using buck switches to reduce the startup inrush current and to operate with constant switching frequency compare with the L-type half-bridge isolated boost converter. The buck converters regulate the output voltage and operate with PWM modulation, while the push-pull switches operate with constant switching frequency and a fixed duty-ratio. The proposed converter also utilizes the leakage inductance and parasitic capacitance of a high voltage transformer to achieve ZCS operation of push-pull switches. Finally, a laboratory prototype converter with a 200 V input and a 4 kV/1 kW output is implemented to verify the performance of the proposed converter. The experimental results show that the proposed converter can achieve a high output voltage and an efficiency of 90% at full load.