Highly Efficient Bridgeless Dual-Mode Resonant Single Power-Conversion AC–DC Converter

This paper presents a bridgeless dual-mode single power-conversion ac-dc converter that can achieve a high conversion efficiency. By adopting a bidirectional switch, we remove a full-bridge diode rectifier from the grid side of the proposed converter, and thereby, reduce the number of components and the primary-side conduction loss. To adapt the converter to 1-kW power applications with a bidirectional switch, we used a series-resonant circuit in the output voltage doubler on the secondary side. The series-resonant circuit also provides zero-current switching turn-off at the output diode, and thereby, reduces the reverse-recovery loss. To attain medium-high power capability with an appropriate transformer, the proposed converter operates in both discontinuous conduction mode and continuous conduction mode. The operation principle of the converter is presented and analyzed. By using the dual-mode control algorithm, the proposed converter achieves a high power factor of 0.994 and maximum efficiency of 97.3$\%$. Experimental results for a prototype 1-kW ac-dc converter verify these characteristics.