Research On A Passive Soft Switching Power Factor Corrector

This thesis describes the main characters and development of power correction (PFC) technology. Its investigative necessity and importance are clarified. Several topology and control circuits are studied.With the enhancement of frequency, Electro-Magnetic Interference (EMI) problem produces, the dissipation of the main power switch increases as well. How to improve the operation circumstance of the switch, how to decrease the current and voltage stress of the main switch during turn on and turn off transient become one of the focus people study.The efficient approach to solve switching dissipation is to use soft switching technique. In the active soft-switching method, because of introduction of the additional switch, the control circuit of the converter becomes complex and the amount of the added parts and cost increases. While using passive soft switching technique, the control circuit of the original converter is not changed too much, the amount of the added parts is small, and the cost is reduced.According to the above discussion of the single-phase active power correction, the PFC system with passive soft switching technique, which adopts Boost power converter circuit and Average Current Mode control scheme is indicated.Small signal analysis is an efficient tool for the study of power converter. After building a small signal model of a converter, one can deeply and thoroughly study its operation process. The transfer functions between input, output and control can be presented. These transfer functions are the premise of design the control circuit. In this thesis the small signal model of the convener was established and analyzed. The relative transfer functions were presented.In this thesis, one topology of a so-called passive, soft-switching technique with minimum voltage stress was studied. The operation mode of the circuit is analyzed and the condition of how to achieve soft switch is discussed.In the end simulation and experiment results were presented. The results showed that this converter can get high quality factor, with the effect achieving zero current switching when the main switch turned on and zero voltage switching when it turned off in wide input voltage range.