Study On Discontinuous Conduction Mode Boost PFC Converters Considering Parasitic Parameters

There is a parasitic oscillation problem in discontinuous conduction mode Boost PFC converters,especially for CCM Boost PFC converters operating in DCM.This paper focus on the parasitic effects and its improvement methods on input current distortion of discontinuous conduction mode Boost PFC converters.Firstly,the research background of PFC technology is introduced and the working mode and the research status of Boost PFC converters are summarized.The working principle of DCM Boost PFC converters is described as well.Movever,a detailed analysis and comparison of three kinds of discontinuous mode control strategies are done to select the predictive current control scheme.And its digital implementation method is introduced.Secondly,based on the design of main power circuit of Boost converter,an equivalent model is built considering the main parasitic parameters,and the measurement method of equivalent series resistance of the inductor is given.The oscillation process is analyzed accurately,including the derivation of cut-off point voltage and duration in oscillation period,and the calcultion of the initial value of the inductor current in each switching cycle.Through the average inductor current model,the effects of parasitic parameters on the input current waveform and THD are given in theory,as well as the primary causes of the parasitic oscillation on input current distortion.Then,the possible improving methods are presented,including the optimization of inductor design,selection of switching devices with lower parasitic capacitance and adding of the RC/RCD circuit.And a series diode method of suppressing oscillation is proposed.The modeling of the equivalent circuit is analyzed,the improvement of the input current is given in theory,and the recommendations for the selection of the series diode is given meanwile.Finally,the experiment is carried out for the verification.The experimental waveforms and the test results indicate that the theoretical analysis is in agreement with the experimental results,which proves the accuracy of the established model and the feasibility of the proposed method.