Design And Research On APFC Circuit Of Switch-mode Power Supplies

With the development of electronic technology, lots of power electronic equipments are accessed to the power grid, which brings to the power gird a range of serious problems. As the most important part in power electronic equipments, the pros or cons of power source quality directly effects on the stand of fall of power using devices. So, the low harmonic and high power factor green power becomes a research spot by demestic and foreign scholars.Since the birth of switch-mode power supplies, which is widely used in people’s work and life. Because of the nonlinear and low power factor, a lot of harmonic is ejected to the power grid, which leads to a distortion of input current waveforms and a serious harmonic polution of power grid day by day. APFC (active power factor correction) technology effectly improves the efficency of switch-mode power supplies and reduces the current harmonic component and decreases the effect of power grid, which is paid more and more attention.This thesis combines the knowledge of the power factor and current harmonic, compares a contrast on main circuit of APFC circuits, selects the Boost circuit as DC/DC converter. Determined to use average current control as the control strategy by analysis on general control and some advanced control method. The theory of an average current control Boost and APFC circuit is studied, also the small signal model of system is established. An analysis on stability of the voltage loop and current loop of control circuit is made. The design of circuit and parameters of a500Watt Boost APFC circuit using the UC3854are accomplished. The nolinear optimization method is used to optimize the parameters of the voltage loop and current loop compensation network and build the voltage loop and current loop compensation network optimization mathematical model. The results show that system performance has been improved. A simulation is made via using MATLAB software and analysis of simulation results, the results verifies the superiority of the model. On this basis, the build of the experimental circuit and debug the circuit are completed. Reseaech on emerging issues and solutions in the implementation process of the APFC circuit. The experiment results show that the circuit current of the design of circuit for sine wave voltage waveform and the phase is very small, the circuit of power factor is improved to0.996. Output of the circuit gets a low ripple and stable DC of400volts. Finally, improving the circuit topology, the new topology structure is stucture simple and of a high step-up ratio, an optimization design is made and new topology structurea of tapped inductor Boost converters are used in APFC circuit, which can solve the problem of the switch’s impact current and the diode’s junction temperature.