LLC諧振轉換器因主開關可達成零電壓切換(ZVS)的緣故，其可降低損失進而提升效率。LLC諧振轉換器的優點還包括在窄頻率變化範圍時能擁有寬負載變化範圍，並在無載的情況下也可能達到ZVS。輸出側若使用同步整流取代傳統的二極體整流，效率還能可進一步的提升。
本文實際研製一台432 W數位控制同步整流LLC諧振轉換器，利用Microchip所開發的低成本數位控制器dsPIC33FJ16GS502實現一次側開關的變頻控制以及同步整流開關的驅動。本文首先針對所提出的系統深入探討硬體及軟體的部分，並分析元件設計上的考量。除此之外，也對二次側開關之盲時區間對效率的影響進行研究。根據實測結果，所得之效率與盲時區間成反比關係，當二次側盲時區間為50 ns時，在任一負載情況下，數位控制同步整流LLC諧振轉換器效率均能達94%以上。

The LLC 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. Other advantages of the LLC resonant converter are narrow frequency variation range over wide load range and ZVS even at no load condition. By replacing the traditional secondary side diode rectifier with a synchronous rectifier switch, the efficiency can further be improved.
In this thesis, a 432 W LLC 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 digitally using a low cost digital signal controller dsPIC33FJ16GS502 from Microchip corp. Detailed description about the hardware and firmware parts of the proposed system are presented first , and then the design considerations are discussed. In addition, the effect caused by dead time values of the secondary side on the converter efficiency will also be investigated. According to the experimental results, the measured efficiency is inversely proportional to the dead time value, and the proposed digitally-controlled LLC resonant converter with synchronous rectifier can achieve efficiencies higher than 94 % under all load conditions when secondary side dead time value is 50 ns.

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