| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 100 === The main purpose of this thesis is to propose a mixed-mode controlled push-pull SEPIC Power Factor Corrector (PFC). Both the continuous conduction mode (CCM) and the transition mode (TM) operate during one same line-frequency cycle in the proposed PFC. Under TM operations, quasi-resonant (QR) valley-switching on the switches can reduce the switching losses. However, the higher inductor current ripple increases the conduction losses of the switches, which is more obvious as the load increases. Under CCM operations, the output diode has reverse recovery problem that results in a higher switching loss, which is obvious at light load. Nevertheless, under CCM operations, the smaller inductor current ripple reduces the conduction losses of the switches. A mixed-mode controlled PFC controller is proposed in this thesis. By applying both CCM and TM operations during one same line-frequency cycle, the advantages can be maintained and the disadvantages be eliminated.
The operation principles of push-pull SEPIC power factor corrector are described, analyzed and discussed in detail. The computer simulation software, SIMetrix/SIMPLIS, is applied for circuit analysis. Experimental results have been verified with the theoretical analysis over an input voltage range of 90 Vac to 265 Vac and an output power of 200 V/300 W.
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