Power Factor Correction Reserch On A Bridgeless Sepic Converter

In order to restrain the harmonics of the power grid,develop the power electronics technology with green energy-saving and reduce the pollution caused by the harmonic current to the power grid,the power factor correction technology has been paid more and more attention.However,the commonly used Boost PFC converter only can work in boost mode,and the rectifier bridge in the circuit will reduce the overall efficiency of the circuit,In order to solve this problem,a bridgeless PFC circuit is proposed in this paper,which can work not only in the buck mode but also in the boost mode.By reading a large number of domestic and foreign literature,this paper aims at the existing problems of the traditional PFC converter,and proposes a new type of bridgeless parallel Sepic PFC converter with reference to the existing structure.This converter can work in buck/boost mode,which is applied the input voltage in a wide range or worked on lower output voltage;and the parameter of the output side filter inductor can be designed to make freewheeling diodes work in discontinuous current mode,reduce the diode reverse recovery due to energy loss.In this paper,the average current control method is used to the circuit,and it is found that there is zero crossing distortion and the EMI noise generated by the carrier frequency and the frequency doubling.This paper chose the critical current control and fixed off time control of two kinds of frequency control mode,according to the simulation results of these two kinds of control methods can solve the problem of zero crossing distortion,but the EMI noise suppression and can not play a good inhibitory effect.In this paper,a new type of variable conductance control method is proposed.The simulation results show that the new control method has a good effect.On the basis of theoretical analysis and simulation results,the main circuit and the control of parallel bridge Sepic converter has been designed.At the same time,this paper has implemented the hardware and software system design finally built a prototype.The experiments verify the feasibility and correctness of the theoretical analysis of the control scheme.