Hybrid Soft-Switching Step-Down Totem Pole PFC With Redundant Switch Multiplexing

Totem pole power factor correction rectifiers (TPPFC) have gained popularity with the advantage of a minimal number of devices for optimal performance, but cause a high output voltage due to the inherent step-up characteristic, limiting the single-stage applications. As the switched capacitor converters (SCCs) feature low voltage stress and high-power density, a hybrid soft-switching step-down PFC rectifier is proposed in this paper, which integrates TPPFC with ladder SCC by redundant switch multiplexing. Similar to the traditional TPPFC, the proposed converter can achieve unity power factor and comply with IEC61000-3-2 Class C in universal-input applications. With critical conduction mode (CRM) control, some active switches are turned ON and OFF under soft-switching condition. Therefore, high efficiency performance is realized. Besides, an adaptive synchronous timing multiplexing control strategy is presented, achieving low voltage gain and natural capacitor voltage balance characteristics. Finally, a 300W step-down prototype with 97% peak efficiency and PF of 0.99 is built to verify the theoretical analysis results.