LLC諧振轉換器廣泛應用於液晶電視電源和伺服電源等功率應用，因為它具有寬零電壓切換（zero-voltage-switching, ZVS）範圍和低元件數量等諸多優點。與其他脈寬調製功率轉換器不同，LLC諧振轉換器通過調整其工作頻率來調節其輸出電壓。對於一些寬輸出範圍的應用，工作頻率範圍可能非常廣泛。此外，如果操作頻率遠離諧振頻率，則轉換效率會降低。
在本論文中，提出了一種自調適輸入電壓LLC諧振變換器。調整直流輸入電壓以保持LLC諧振轉換器操作於諧振頻率附近。通過這種方式，轉換效率可以最大化。為了驗證提出的概念的正確性，建立了一個480W原型電路。根據實驗結果，設計系統的測量轉換效率均高於91.4％。與常規LLC諧振轉換器相比，所提出的控制技術可以在輕載和滿載時分別提高1.1％和0.31％的平均轉換效率。

LLC resonant converters are widely used in medium power applications such as LCD TV power and server power, because it features many advantages such as wide zero-voltage-switching (ZVS) range and low component counts. Unlike other pulse width modulated power converters, LLC resonant converter regulates its output voltage by modulating its operating frequency. For some wide output range applications, the operating frequency may be very high. In addition, the conversion efficiency may downgrade if the operating frequency is far from the resonant frequency.
In this thesis, an adaptive input voltage LLC resonant converter is proposed. The dc-link voltage is adjusted to keep the LLC resonant converter operating at a nearly constant resonant frequency. Using this way, the conversion efficiency can be maximized. In order to validate the correctness of the proposed concept, a 480 W prototyping circuit is built. According to the experimental results, the measured conversion efficiencies of the designed system are all higher than 91.4 %. Comparing with conventional LLC resonant converter, the proposed control technique can improve the averaged conversion efficiency by 1.1 % and 0.31 % at light load and full load, respectively.

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