| Power factor correction circuit is designed to control the harmonic waves. At present, stricter and stricter harmonic waves'standards are defined on the electrical equipment for electrical safety. Power factor correction circuit is needed to lower the content of the harmonic waves. For most power supply, the harmonic waves come from the current flows through the rectifying diodes which don't have current flow through when the voltage doesn't reach the break-over voltage. By Fourier analysis, this distorted current contains very high content of harmonic waves. Currently, although the circuit designed to improve the power factor can get a high power factor, at the same time, it needs high cost, and the switching losses of the entire circuit are too high. For this, this paper does research on the power factor correction topology, the main contents are:First, this paper studies the most widely used current most widely used passive power factor correction circuit topology and active power factor correction circuit topology, analyzes their working principle, points their advantages and disadvantages separately, and tells their limitations of application. Besides it focuses on a typical part of the active power factor correction circuit, analyzes its structure, working principle, the final waveform and its working efficiency.Then, combining the charge pump and the active power factor correction circuit topology, this paper designs a new part of active power factor correction circuit topology. And then it gives the analysis of its topological structure and working principle, establishes its working state model and its control algorithm.In addition, the paper designs over-current protection circuit and over voltage protection circuit, designs EMI filter circuit, tells how to select the capacitors and inductors used in the circuit, combining with the circuit and control algorithm, builds the simulation model, gets the simulation waves when its load changes from 0 to 20Ω, and from 20Ωto 40Ω, gets the simulation waveform of the output current's harmonic content map. Finally, it analyzes these simulation waves and the output current's harmonic content map.Simulation results show that:the new part of the active power factor correction circuit topology can achieve a high power factor, and when the loads changes, the circuit can respond quickly to adapt to the new voltage waveform. |
