Research On Pseudo-Boost Converter

Power factor correction (PFC) is a state-of-art technique for reducing harmonic distortion and increasing the efficiency of power supply. Power factor (PF) is an important characteristic index of electric equipment, and the active power factor correction (APFC) technique is the fundamental way to improve it. In recent years, with the increasing of quality requirement of electric equipment, this technique has become the focus in the power electronics research field and has been widely applied.A novel high-efficiency bridgeless PFC converter, pseudo-boost PFC converter, is studied in this thesis. It consists of one boost inductor, one bidirectional switch, two fast recovery diodes, a resonant tank and a storage capacitor. The principle, operating mode and DC static characteristics of DCM pseudo-boost converter are analyzed in detail in the thesis. It is found that the voltage transfer ratio of pseudo-boost PFC converter is similar to that of conventional boost converter, and it has no relationship with the resonant parameters and switching frequency.However, it is found that it will produce a serious voltage spike which is caused by the step change of the boost inductor current during the working process of pseudo-boost converter, and it seriously limit the application of pseudo-boost converter. In order to avoid the boost inductor is connected in series with resonant inductor, which makes a step change of inductor current when the switch is turned off. In this thesis, an improved Pseudo-Boost converter, Improve-Pseudo-Boost converter, is proposed by connecting a switch in parallel with the resonant inductor to avoid connecting the two inductors in series at the time when the power switch is turned off. It is a good solution to solve the voltage spike problem and has been significantly improved the performance of the converter.Pseudo-boost converter has bipolar voltage gain, it can get stable dc output voltage no matter the input voltage is positive or negative. The bipolar gain Boost converter can be applied directly to the PFC converter. The characteristics of input current and power factor are analyzed in detail and the influence of the resonant inductor, the boost inductor, input voltage and output voltage on the input current and power factor are studied. Furthermore, comparative analyses of the Improve-Pseudo-Boost PFC converter are presented. Finally, experimental results are provided to verify the theoretical analyses results.