| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 101 === In this thesis, a controller for a half-bridge LLC resonant DC-DC converter with light-load efficiency improvement is realized. The high switching frequency and circulating current in the resonant tank result the poor efficiency of a LLC resonant converter under light load condition. The light-load efficiency improvement is limited with the conventional burst-mode control. To improve efficiency further, a modified burst-mode control is implemented in the proposed controller. The switching frequency decreases gradually during burst-on time to reduce the number of switching cycles under the same output ripple. Moreover, in burst-on time, the first pulse drives the MOSFET at high side with limited pulse width to suppress the initial current in resonant tank. The last switching cycle in burst-on time must be complete to ensure that initial conditions of each burst cycle are the same. Consequently, the switching losses are reduced by proposed control strategy, and light-load efficiency is improved. This chip is fabricated with TSMC 0.25um CMOS high voltage mixed signal general purpose process.
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