New Seamless Switching Control Technique Between CCM and DCM for Boost PFC Without Additional Zero Crossing Point Sensing Circuit

A new seamless switching control technique for power factor correction (PFC) is presented for efficiency improvement, especially in discontinuous conduction mode (DCM) operation. Seamless transition between continuous conduction mode (CCM) and DCM can be automatically achieved without requiring additional zero crossing point detection circuit of inductor current. The cost and losses can therefore be reduced. The proposed switching control method calculates the "quasi-SR" duty based upon the input and output voltages. As the "quasi-SR" duty is smaller than the complementary duty, the calculated "quasi-SR" duty is used for the synchronous rectification power device switching control. Otherwise, conventional complementary duty is used. A 3 kW totem-pole PFC is set up for test. The experimental results show the efficiency can be significantly improved as input ac voltage = 110, 230, and 264 V rms , and 99.28% of peak efficiency is achieved.