串聯諧振轉換器(Series Resonant Converter, SRC)因一次側功率開關可達成零電壓切換(ZVS)的緣故，其可降切換低損失進而提升效率。但SRC串聯諧振轉換器在輕載時操作頻率會變高，因此需要輕載時的頻率改善對策。輸出側若使用同步整流取代傳統的二極體整流，可減少導通損並進一步提升效率。
本文實際研製一台500 W同步整流SRC串聯諧振轉換器，利用虹冠電子所開發的一二次側整合控制晶片CM6901實現一次側開關的變頻控制以及二次側同步整流開關的驅動。本文針對輕載時控制方式與同步整流控制信號深入探討，並分析元件設計上的考量。根據實測結果，當輕載控制模式與變頻控制模式轉態時，輸出電壓上會有非預期的突波出現，針對此突波進行改善，卻會影響輕載時的效率，最後以更換功率開關的寄生電容，來達到符合輕載效率的目標規格。

The SRC resonant converter allows for zero voltage switching (ZVS) of the main switches; therefore, the switching losses can be lowered and the efficiency can be improved. However, SRC series resonant converters operate at a higher frequency at light loads, so they need to be improved at light load. By replacing the traditional secondary side diode rectifier with a synchronous rectifier switch, the efficiency can further be improved.
In this thesis, a 500 W SRC resonant converter with synchronous rectification is implemented and studied. The variable frequency control of the primary switches and the driving scheme of the synchronous rectifier are all implemented by a controller CM6901 from Championmicro. Detail analysis of light load control mode and synchronous rectification control signal are given, and then the design considerations are discussed. According to the experimented results, when the transition of light load control mode and frequency control mode, there exist an unexpected spike imposed on the output voltage. A solution is included successfully to improve this spike voltage, but it will reduce the efficiency of light load. Finally, another secondary switch with different output capacitance is replaced to change the output capacitance to meet the requirement of efficiency at light load.

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