Research On Digital Controled Single Stage Full Bridge Power Factor Correction Technology Based On Dsp

The input and output grades of the power electronic equipment mostly use diode rectifier with capacitor filter which will cause harmonic pollution to the power grid. Active power factor correction is a method to curb harmonic pollution and improve the system's power factor. Traditional single-stage PFC converter usually adopts analog control, however with the rapid development and the drop of the price of the digital signal processor, more and more power electronic equipment use DSP instead of analog controller as the main controller. Digital control has the advantages of high reliability, strong performance of anti-interference, high integration and realizing complex algorithm easily which are the major development direction of the APFC.This article mainly talks about single-stage full-bridge isolated APFC technology with digital control strategy. It adopts full bridge topology based on the passive clamp technique. The clamping capacitor could absorb the energy released by the leakage inductor during current commutation, reduce the voltage stress of the switches, buffer the energy, lower the voltage ripples of the output side and improve the responding speed. This article does research on the principle and operating mode of the PFC based on the passive clamping technique in detail. To solve the problem of the energy storage of the inductor when starting which can't be released and the pump of the input current, this article designs a fly-back winding through circuit simulation. It provides a circuit loop for the energy-storage inductor and avoids damage of switches casing by the excessive current of the inductor when starting.When it comes to the control strategy, we choose predictive control. Predictive control doesn't need current sampling and avoids the interference from the high-frequency burrs of the current. It has the advantages of less computation, high speed of current tracking and has the ability of working under high frequency. Based on all the advantages above, it can achieve good controlling performance.According to predictive control methods, we design the software. Through analyzing the problem of electromagnetic interference of the DSP control system working under high frequency, this article does some improvement from the aspects of both the software and hardware such as adding the sampling circuits, zero-crossing detection circuits, driving circuits, and filtering circuits.We build an experimental circuit based on the theoretical analysis and software simulation which verifies that the theoretical analysis is correct. And from the experimental results, we know the converter can realize the function of single-stage power factor correction well with broad application prospects.