| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 105 === 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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