The Research On DCM Buck PFC Converter With High Input Power Factor

As the rapid development of power electronics recently,it has become more and more mature.In the meantime,a mass of power electronic devices and equipments were applied in the power system,the industrial products,the transportation and the household applications.With the comprehensive introduction of nonlinear components,the problem of harmonic pollution has raisen the intention of governments and relevant organizations all over the world.In order to ensure the qulity of power grid and keep the electric equipments out of harmonic pollution,mang countries and institutions made there own limits,in which the IEC61000-3-2 is the most popular one.Firstly,some concepts are explained in this paper.After the introduction of Power Factor Correction(PFC)and the comparison of different topologies and control methdes,the Discontinuous Current Mode(DCM)Buck PFC converter is chose as the object of study.The method of sinusoidal current control(SCC)with constant duty cycle is analyzed in the second part.There are three kinds of operation mode with the converter works on DCM.The rising slope and the falling slope of the inductor current,the peak value of inductor current during one switching cycle,as well as the average value of input current,the duty cycle and the input power factor are derived in the second part.From the curve of relationship between the input PF and a,we can find that the PF of DCM Buck PFC converter with SCC is low.After harmonic analysis,it's clear that the input cxrrrent contains rich harmonic and the negative 3rd one covers the most part of harmonics.Thus the optimum 3rd harmonic injection during non-dead-zone and its control implementation are proposed,which called the optimum third current harmonic control(OTCHC)method.The comparison between the proposed OTCHC and SCC is made in terms of the average value of input current,the input PF,harmonics,the output voltage ripple,the peak and rms value of inductor current.From which it is cdear that OTCHC achieves a lower peak value of input current,a smaller value of Total Harmonic Disstortion(THD),a higher PF during the whole input range,a smaller ripple of output voltage and a larger efficience.In order to verify the proposed OTCHC control and SCC control scheme,the prototypies are designed respectively.The experimental results agree with the theoretical analysis well.