| Summary: | 碩士 === 大同大學 === 電機工程學系(所) === 103 === In this thesis, a valley detection technique applied for quasi-resonant flyback converter is proposed, which not only can set a reasonable switching timing according to various loading conditions, but also improve the switching losses resulted from the increased switching frequency at light load. Comparing with the traditional hard-switching under current mode control has better conversion efficiency. In addition, a quasi-resonant flyback converter is implemented by using the proposed valley detection technique, whose specifications including output power of 20W, input voltage ranges from 90-265Vac, and output voltage of 12Vdc. Finally, the measured four-point average conversion efficiency can achieve 80% under 25%, 50%, 75% and 100% load in full region of the input voltage, as well as meet the specification requirement of the DoE level V.
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