Research On Single-stage PFC Based Onactive Clamp Forward Converter

A single-stage power factor correction(PFC) converter is combined by the PFC stage and a DC/DC converter into one stage with shared switch and controller,They can be improved by the input current shape and regulate the output voltage rapidly. It is suitable for the application of a variety of occasions because of the advantage of simple structure and low cost.To reduce the component counts and the cost, the PFC techniques have been attracted more and more attention.A prototype of single-stage PFC based on active clamp forward converter is taken as an example in the paper.Firstly,the passive PFC approach, the active two-stage PFC approach and the active single-stage PFC approach are analyzed and compared. The virtues, defects and the scope of application of them are point out. Then, the operation process of various working mode of the single-stage PFC based on active clamp forward converter is analyzed in detail.The control principle and control method of the converter are introduced at the same time. Then, with the help of simulation software Saber,several key parts of the system are simulated. Through the steady-state simulation of the topology structure of the main circuit,simulation of timing of control signal and simulation of the time-lapse and drive circuit,the correctness and feasibility of the theoretical analysis is verified. Then, A prototype of single-stage PFC based on active clamp forward converter is designed,separately from the main circuit, control circuit, time-lapse and drive circuit and other parts of the design.The calculation method of parameter of the major components and the specific selection of the main components are given in the paper.The circuit schematics of the main parts of the prototype are also given.Then, by the testing of PWM drive waveform, the main MOSEFT waveform of DS and GS, the second side waveform of transformer,the input voltage and input current waveform and the output voltage waveform, the correctness of the theoretical analysis and simulation analysis are verified.Finally,the power factor,efficiency,input regulation and load regulation are tested respectively, and the harmonics are analyzed, that the performance index of the prototype achieve the design requirements is proved.