Study On Tri-state Boost Power Factor Correction Converter

In recent years,a large number of power supply equipment cause harmonic pollution.This problem can be solved by active power factor correction technology,which can improve the grid side power factor and solve the problem of harmonic pollution.In the range of load and the transient response,tri-state Boost PFC has the better performance than CCM and DCM Boost PFC converter,however,its power factor with existing methods control is low.To solve this problem,this paper studies the control method of improving the power factor from the operating principle of the converter.Firstly,DC steady-state characteristics and the basic operating principle are analyzed,and based on the state space modeling theory,the small signal model is given.Meanwhile,based on the two control degrees of freedom of converter and decoupling theory,the regulation method of main switch and freewheeling switch is analyzed for unit power factor.Secondly,by deriving the relationship between the input current,the reference current and the duty cycle of the main switch,the parameter design of the reference current,the main switch and the freewheeling switch corresponding to the power factor close to unity power factor is studied.By introducing the non-sinusoidal reference current into the current control loop,and using Taylor series expansion to simplify the voltage control loop.Compared with the decoupling control method,the power factor can be improved by the variable duty cycle non-sinusoidal reference current control.Thirdly,based on the decoupling control theory and the input current of the tri-state Boost PFC converter,sinusoidal reference current is applied into the current control loop to control the freewheeling switch,and the voltage control loop controls the Boost switch.Realize the decoupling of the two control loops,the amplitude of the reference current and the design method of the main switch control circuit are studied.On this basis,the mixed-mode control tri-state Boost PFC converter is studied,which means the converter operates two operation mode according to its load.Variable duty cycle sinusoidal reference current control has less input current distortion when the input voltage increases.the hybrid control mode has higher light load efficiency.Finally,according to the voltage stress and current stress analysis results of power devices and the design method of PFC converter inductance and output capacitance,the circuit parameters and device selection are determined,and a 400 W experimental prototype is built.The experimental results verify the theoretical analysis.