Phase-shifted full bridge converter featuring ZVS over the full load range

A new full-bridge circuit which can achieve zero voltage switching (ZVS) for all the primary side switches over the full load range and a wide input voltage range is proposed. The ZVS is achieved by the energy stored in the auxiliary inductor and the magnetizing inductance of the transformer. Because the leakage inductance is relatively small, there is no severe duty ratio loss or severe voltage ringing across the output rectifier. As the assistant current for achieving ZVS is almost the same for any duty ratio, the conduction losses at light load are reduced. The principal operation of the converter is described, and the optimal design is discussed. Finally, the operation of the converter is verified on a 1kW prototype.