Hybrid PFC circuit for wide load range high efficiency server power supply unit

Wide load range high efficiency requirement challenges the design for future server power supply unit (PSU). Low line efficiency and light load efficiency are two major concerns for future server PSU design. Based on the loss analysis of the conventional boost PFC and the bridgeless PFC, a hybrid PFC circuit dedicated for the improvement of low line efficiency and light load efficiency is proposed. The hybrid PFC consists of a dual-boost-PFC (DBPFC) and a paralleled conventional boost PFC. With most of the power handled by DBPFC, low line efficiency of the PFC stage is guaranteed; and by substituting DBPFC with a baby boost PFC in light load condition, the light load efficiency of the PFC stage is obviously improved. A 1850 W PFC prototype was accomplished and the experimental results demonstrated the wide load range high efficiency merit of the proposed hybrid PFC circuit.