Study And Design On Boost-type Power Factor Correction Circuits

Power factor correction(PFC)is necessary for restraining harmonic pollution in the grid.And the input current ripple of the PFC circuit can be mitigated by the application of interleaved technology.In the meanwhile,interleaved technology can increase the equivalent switching frequency.The equivalent switching frequency is twice of the actual switching frequency in the parallel interleaved boost PFC.Due to the divided input current,both the inductor volume and the conducting losses can be decreased.What's more,the power density can be improved and the current stress of switches can be decreased,which is benefit to capacity expansion.This paper focused on the interleaved Boost PFC which is implemented in digital onboard charger.The working principles of the converter and the design methods of the main circuits are analyzed,and the small-signal model is established to describe this converter.Finally,the simulation model and the 3300W experimental prototype are built to verify the theoretical analysis.Considering the sampling speed limitation of the digital controllers,usually,the halfway value of the rise of inductor current is sampled to represent the average value of the input current.There will be serious degradation in performance when it works in a wide load range.In order to solve this problem,duty-ratio feed-forward control method is proposed.The influence of input current of average current mode and duty-ratio feed-forward control mode in different load is compared by simulation.And the correctness of theoretical analysis is verified by experiment.Commonly,higher switching frequency is preferred to decrease the converter size and weight.However,this will increase the switching loss due to the reverse recovery of the diode.In this paper,a new topology is proposed,in which an auxiliary loop is established using a coupling inductor.The ZVS of the main loop switch can be achieved by the auxiliary loop.The design method of self-inductance,mutual-inductance and dead time is discussed in detail.And a 220V input/3300W PFC circuit is built to verify the correctness of theoretical analysis.The experiment results show that the soft-switching operation is achieved in the whole range.