Influence Of Inductor High-frequency Parasitic Parameters On Boost-type PFC Input Current And Improment Measures

PFC(Power Factor Correction) circuit is usually applied as the preceding circuit of switching power supply. It is used to suppress harmonic wave of the input current of switching power supply, which could achieve unit power factor and avoid more pollutions to the grid. With the number of switching power supplies increasing, this kind of method which eliminates the pollutions from their origins is drawing more and more attention. So far, researches on PFC mainly focus on circuit topology and current control method. However, despite advanced topologies and current control methods, the performance of PFC is not good enough due to unexpected parasitic parameters caused on account of high frequency switching circumstance. Therefore, it is of great significance to study the influence of parasitic parameters on circuit performance and find ways to improve the situation.Firstly the thesis studied the working mechanism of PFC circuit by simulation, through which the meaning of average current method and closed-loop control was understood. Then with small signal analysis transfer function of every part of the circuit was derived to establish the model. Design of circuit was accomplished on the basis of the model and after that prototype was made and debugged to meet the design requirements. Afterwards, the thesis compared several kinds of inductors in terms of their core materials, shapes and winding styles and concluded their relations with high frequency parasitic parameters. Finally, having built the models of inductor and the whole circuit, the thesis analyzed the influence of parasitic parameters due to inductor on input current of PFC circuit and concluded that the parasitic resistor has an obvious influence on system stability rather than THD(Total Harmonic Distortion) of input current, whereas parasitic capacitor has evident effect on THD of input current while it affects system stability little. Furthermore, the thesis proposed several measures to improve the waveform of input current with the results verified by simulation.