Analysis and implementation of a hybrid ZVS converter

A new hybrid zero voltage switching (ZVS) three-level and half-bridge DC/DC converter is presented to achieve the functions of low voltage stress of switches, low circulating current during the freewheeling interval, wide ZVS range of lagging-leg switches, low output inductor and energy transfer within the whole switching period. The proposed converter includes a three-level phase-shifted pulse-width modulation converter and an un-regulated half-bridge converter. A resonant capacitor is added in conventional three-level DC/DC converter to reduce the circulating current loss to zero during the freewheeling interval. Half-bridge converter, shared the same lagging-leg switches of three-level converter, is used to extend the ZVS range of lagging-leg switches. The secondary windings of two converters are connected in series to generate two positive voltage levels at the rectified voltage instead of one positive voltage and zero voltage. Hence, the output inductance of three-level converter can be reduced. Energy transfers from input to output load through half-bridge converter during the whole switching period and through three-level converter during the active mode operation. Experiments based on a 1440W prototype are provided to validate the theoretical analysis and demonstrate the effectiveness of the proposed converter.