Analysis And Design Of CCM Totem-pole Bridgeless PFC Converter

Due to the primary current path includes one fast switch and one slow switch,totem-pole bridgeless PFC in continuous current mode that enabled by GaN with low reverse-recovery charge is a very promising topology.However,inherent challenges exist in totem-pole bridgeless PFC at AC voltage zero-crossing where inductor current spike is observed,which may cause higher harmonics and EMI issue.Therefore,the research of current spike at AC voltage zero-crossing is of great significance to promote the totem-pole bridgeless PFC.In this thesis,a CCM totem-pole bridgeless PFC converter with eliminated current spike is designed,and three part of works are completed in this thesis.Firstly,the structure features and operating principle of the CCM totem-pole bridgeless PFC converter are analyzed,and the mechanism of the problem of the current spike at zero-crossing are found:the transition delay of low frequency leg and the minimum pulse width limit of high frequency leg.Secondly,a DSP-based digital modulator is designed to address those two issues by applying lead time to the low frequency leg and digital dithering to increase equivalent resolution at the high frequency leg.Finally,a lkw prototype of the CCM totem-pole bridgeless PFC converter with eliminated current spike is made by hardware and software design.Based on the lkW prototype of the converter,the analysis and design of this thesis is tested.The test results show that,the converter works with the frequency of 100kHz,and has a THD of 3.7%,achieves a PF value high than 0.96 and the overall efficiency high than 96.4%.