Study On The Forward-Flyback PFC Converter With Quasi-Resonant(QR) Control

With the use of switching power supply,the current harmonics increases,affected the reliability of the power supply network seriously,which has become a major source of pollution on the grid harmonics.To alleviate the problem,the power factor correction(PFC)attracted people's attention increasingly.Power Factor Correction(PFC)is the AC input current waveform track the AC input voltage waveform fully,the phase and the period are same as the input voltage waveform,so that the system power factor close to 1.With the increasing demands of switching power,PFC has been to the core technology for the converter efficiency and harmonics current,and the "green energy" can be achieved by the technology.In this paper,the development of the PFC made a brief introduction,and the PFC converter operation mode,the basic topology,quasi-resonant(QR)control method started to analyze.Pointed out that current research experts and scholars in this field direction and research priorities,and to determine the object of study of this subject is based on the quasi-resonant forward converter PFC control,the bridgeless forward converter and forward-flyback PFC converter have been studied.This paper analyzes the bridgeless forward PFC converter firstly,the input rectifier bridges are eliminated and QR control is applied,and then high power factor and high efficiency can be achieved.An improved constant on time control(COT)is applied to the converter to achieve high power factor.The operation processes with the proposed converter detail analysis,and also the resonant processes are depicted in detail.The design consideration and the losses analyzation have been presented,and then analyze features with the bridgeless converter.Then analyzed the forward-flyback PFC converter,that merges the forward and the flyback converter through a shared transform,the dead zones are eliminated and high power factor can be achieved.Study the Boundary Conduction Mode(BCM)forward-flyback converter,and two QR control schemes have been designed;detail operation principle,design consideration,and comparison for these two different control modes are presented.The conventional forward converter and bridgeless PFC forward converter,two different QR control modes of forward-flyback converter experiment prototypes were built up.Compare the performance of the prototype to verify the efficiency of bridgeless Forward superiority and the theory of the forward-flyback converter operate in BCM.