Zero-Voltage-Switching PWM Hybrid Full-Bridge Three-Level Converter with Clamping Diodes

Hybrid full-bridge three-level converter can realize zero-voltage-switching for the switches with the use of the leakage inductance and the intrinsic capacitors of the switches. As it can operate in three-level mode and two-level mode, the secondary rectified voltage is very close to the output voltage over the input voltage range, so the output filter inductance can be reduce significantly. Moreover the voltage stress of the rectifier diodes can also be reduced as well. So the converter is very attractive for wide input range applications. However there is voltage oscillation across the rectifier diodes resulted by the reverse recovery. In this paper a resonant inductance and two clamping diodes are introduced to the converter to achieve ZVS in a wide load range, and meanwhile to clamp the secondary rectified voltage at the reflected input voltage in three-level mode and reflected half input voltage in two-level mode respectively, thus the voltage oscillation across the rectifier diodes is eliminated. The operation principle of the proposed converter is analyzed in details in this paper. A 1.2 kW prototype converter is built and the experimental results have shown the validity of the proposed converter