Three-level converter with wide ZVS operation and low circulating loss

A new DC/DC converter with wide range of zero voltage switching is studied, designed and implemented in this paper. The circuit topology of the proposed converter includes a three-level pulse-width modulation converter and an unregulated half-bridge converter. The three-level pulse-width modulation converter and half-bridge converter share the lagging-leg switches of three-level converter in order to extend the ZVS range from light load to full load. The output voltage of the half-bridge converter is connected to the secondary rectified voltage of three-level converter. Therefore, a positive voltage instead of zero voltage is generated on the transformer secondary rectified point and the circulating current during the freewheeling interval is reduced to zero. Finally, the effectiveness and performance of the proposed converter are verified by the experiments for a 1.44kW prototype converting 800V input to an output voltage 24V/60A.