IC Design for LLC Resonant Converter

• Main Authors: Chun-HsuYang, 楊淳旭
• Other Authors: Tsorng-Juu Liang
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/41940660259405825488

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.