本論文實現一具有輕載效率提升之半橋LLC諧振直流轉換器控制器。在輕載狀況下，因為高頻率的切換及在諧振槽中的環路電流使得LLC諧振轉換器效率不佳，傳統的突衝模式控制應用於輕載效率提升效果有限。為了進一步提升效率，本文中實現了一個改良的突衝模式控制，在驅動訊號突衝的區間，切換頻率逐漸降低使得相同輸出漣波下所需的切換次數較少。此外，於控制訊號突衝過程中的第一個訊號用於驅動上臂電晶體，且脈寬受限以抑制諧振槽的初始電流。在突衝區間之最後一個切換週期，必須確保完整的上下臂功率開關切換，使每次突衝週期的初始條件一致。藉由上述控制達到降低切換損失之目的，使輕載效率提升，並採用TSMC 0.25um CMOS高壓製程實現此控制晶片。

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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