Research On High Power Factor And High Efficiency Of DCM Boost PFC Converter Based On Variable Inductor

The boost power factor correction(PFC)converter in discontinuous current mode(DCM)has the advantages of zero-current turn-on for the switch,no reverse recovery of the diode,single voltage loop fixed frequency,constant duty cycle control(CDCC),etc.However,when the input voltage is higher,the discontinuous degree of inductance current changes greatly in half line cycle.The input current waveform distortion is serious,and the power factor(PF)is significantly reduced.Variable duty cycle control(VDCC)can adjust the input current to a sinusoidal form,improve the PF and the critical inductance value,and further reduce the peak value of inductance current.However,there are still the following shortcomings: the power transmission of input voltage on the inductor does not occupy the whole switching cycle,that is,the inductor current has zero period in the switching cycle.In discontinuous mode,the inductance current peak value and effective value are large,and the current stress and conduction loss of switchs and diode components increase,which affects the improvement of converter efficiency.To solve the above problems,this paper proposes a full switching cycle utilization control(FSCUC)strategy using variable inductance.In other words,small bias current is injected into the control winding of variable inductance to change the inductance value,so that the main inductance of DCM Boost PFC converter presents different values at each moment of line cycle input voltage,and the duty cycle is changed accordingly.The utilization rate of each switching cycle in the line cycle is 1,that is,the critical conduction of the inductance current,so as to reduce the current peak and effective value,reduce the loss,improve the efficiency,keep the input current sinusoidal,and further optimize the performance of converter.In order to realize the full switching cycle utilization in a wide voltage range,the inductance change is relatively large,so that the variation range of variable inductance is not easy to realize.Therefore,a quasi switching cycle utilization control(QSCUC)strategy using variable inductance is further proposed,that is,the trade-off between switching cycle utilization and inductance variation range is realized by controlling the optimal subsection change of inductance in half line cycle,which can not only reduce the variation range of inductance under a wide range of input voltage,but also achieve high switching cycle utilization and power factor.Finally,the device selection,loss analysis and hardware circuit design of the proposed two control circuits are carried out,and a 120 W experimental prototype is made.The experimental results verify the feasibility and effectiveness of the proposed control strategy.