Half-bridge ZVS converter with three resonant tanks

This paper presents a zero voltage switching (ZVS) converter with three resonant tanks to reduce switching losses on power semiconductors, to achieve primary side current sharing and to lessen transformer secondary winding with a full-wave rectifier. Three resonant converters with the same power switches are adopted at low voltage side to reduce current rating on transformer windings. Using series-connection of transformer secondary windings, the primary side currents of three resonant circuits are balanced to share load power. Thus the sizes of the transformer core and bobbin are reduced. The full-wave diode rectifier is used at high voltage side to reduce the voltage stress of the rectifier diodes at V_o instead of 2V_o in the conventional center-tapped rectifier topology. Based on the circuit characteristics of resonant converter, power switches are turned on at ZVS. Rectifier diodes can be turned off at zero current switching (ZCS) if the switching frequency is less than the series resonant frequency. Thus, the reverse recovery losses on rectifier diodes are overcome. The proposed converter can be applied for DC-DC power stage in renewable energy system or fuel-cell power system. Experiments with a 1.6kW prototype are described to verify the effectiveness of the proposed converter.