Research And Design Of Bidirectional Switch Totem-pole PFC Converter

The electric vehicle PFC converter is an important component of the vehicle charging system,and its working characteristics have a great impact on the power grid and the automotive electrical network.Totem-pole PFC converter has the advantages of small common mode interference,high work efficiency and high power density,which possesses become a research hotspot in this field.In this thesis,the topology structure and control method of the totem pole PFC converter are improved,which possesses theoretical engineering significance.The traditional totem-pole PFC converter can not work stably for a long time in the current continuous mode(CCM)and the power factor is reduced under light load conditions,and the dynamic characteristic of the output voltage is poor.This thesis analyzes the causes of the problem in detail,improves the traditional circuit topology,optimizes the design o f the main circuit,optimizes the control loop,and verifies the feasibility of the improved scheme from both theoretical and experimental aspects.The thesis first analyzes the operation of the traditional totem pole PFC converter in the current continuous mode.Aiming at the unfavorable phenomenon that the current flows through the MOS tube body diode during the switching period,the bidirectional switch tube is connected in series with the SiC diode in parallel,which effectively suppresses the reverse recovery current loss caused by the freewheeling of the body diode.To ensure that the converter operates reliably in the current continuous mode.In order to improve the power factor of the converter under CCM mode light load condition,this thesis adopts current phase lead compensation to compensate the converter’s own leading-loop closed-loop characteristic admittance and EMI filter current compensation scheme to improve the EMI filter input.The effect of current generation.At the same time,a fast and slow loop complementary strategy is designed for the voltage control loop to improve the dynamic characteristics of the output voltage.In the Saber software,the time domain simulation of the closed-loop control system of the converter is carried out.Compared with the bidirectional switch totem-pole PFC converter and the traditional totem-pole PFC converter working in the current continuous mode,the switching cycle alternates the dead zone of the freewheeling process The ability of the bidirectional switch structure to suppress reverse recovery current is verified..Finally,an experimental prototype was built and the experiment was carried out.The input current power factor and the dynamic characteristics of the output voltage before and after the current loop and voltage loop compensation are measured.The experimental results show that the input current power factor of the new bidirectional switch totem-pole PFC converter is improved,the lifting effect is obvious under light load conditions,and the o utput voltage dynamic characteristics are also improved.