The Research On Control Algorithm On PFC Circuit Of Switch Power Supply

Active power factor correction (APFC) technique is an effective method forreducing harmonic current and increasing power factor. The research of Active PowerFactor Correction technology is mainly focused on circuit topology, control strategy andmodeling analysis. The research of control strategy is to optimize the performance ofthe circuit and simplify the control circuit by different mathematical and modelinganalysis on a particular topology.This paper first analyzes the principle of active power factor system ofconventional average current control. Designing the main circuit and the voltage、current controller of power factor correction system based on the establish of the smallsignal model and the power transfer function of the main circuit. Simulation resultsdemonstrate the effectiveness of the system.Because the traditional APFC system based on the control of double loop controlneed to detect the input voltage、input current and output voltage, it has a complexstructure, and it also need to sample the voltage and current、calculate the voltage errorsignal and current error signal、adjust the voltage loop and current loop、calculate theduty ratio, so it has a lot of operation time requirement. In order to solve thisshortcoming, designing one method calculating the duty cycle directly. This methoddoes not need the current sensor and much calculation and sampling, so it greatly reducethe computation of time requirements.Regardless of the traditional double loop control APFC system or the improvedalgorithm APFC system are both based on the the precise mathematical model. But PFCsystem is a nonlinear and time variable system, so it is difficult to establish its accuratemathematical model.And the conventional control algorithms can’t achieve high controlrequirements When the input voltage or load changes greatly. But the fuzzy control doesnot need precise mathematical model and it is not sensitive to the process parameters, ithas a good robustness. Based on the above reasons, designing the power factorcorrection device based on fuzzy adaptive PI control. Simulation results show that thefuzzy adaptive PI controller has better control effect than the conventional PI controller.