相對於傳統諧振轉換器，LLC諧振轉換器具有許多優點，包含能在較小切換頻率範圍內調節輸出電壓，以及可在較寬的操作範圍內實現零電壓切換，並利用功率開關上的寄生元件達成零電壓切換而不需額外電路。由於LLC諧振轉換器於輕載時效率不佳，因此本文提出一種全橋LLC諧振轉換器混合控制策略，此控制策略使全橋LLC諧振轉換器在10%負載以內使用混合脈衝之簡化最佳化軌跡控制(Simplified Optimal Trajectory Control, SOTC)，並在大於10%負載之後使用變頻控制，使全負載範圍內都能達到良好的轉換效率。本文首先詳細分析傳統LLC諧振轉換器之動作原理與設計考量，接著介紹混合脈衝SOTC之原理，並將兩種方法結合於同一台LLC諧振轉換器上。
為了驗證本文所提方法之正確性與可行性，實際完成一台1 kW之LLC諧振轉換器。並根據實測結果與變頻控制、突衝模式、減少責任週期控制進行比較，於4%負載時效率分別提升了12.77%、19.62%、0.34%，輸出電壓漣波分別降低81.4%、92.9%與88.4%，且10%負載以下之輸出電壓漣波為所有控制法中最低者，並於變頻模式時能達到本電路最佳轉換效率95.36%。

Compared to traditional resonant converters, LLC resonant converters have many advantages, including the ability to regulate the output voltage with small switching frequency range, zero voltage switching (ZVS) with wide operating range, and the use of parasitic elements on power switches which achieve zero voltage switching without additional circuitry. Because the LLC resonant converter cannot achieve a good light-load efficiency, this thesis proposes a full-bridge LLC resonant converter with hybrid control strategy. This control strategy enables the full-bridge LLC resonant converter to use mixed-pulse simplified optimized trajectory control (SOTC) before 10% of the load, and uses variable frequency control after 10% of the load, so that the full-load range can achieve good conversion efficiency. First, this thesis analyzes the operation principle and design considerations of the traditional LLC resonant converter in detail, then introduces the principle of mixed pulse SOTC, and combines the two methods on the same LLC resonant converter.
In order to verify the correctness and feasibility of the method proposed in this thesis, a 1kW LLC resonant converter with 1 kW was actually completed. The experimental results are measured and compared with variable frequency control, burst mode and reduced duty cycle control. At 4% load, the efficiency is improved by 12.77%, 19.62% and 0.34%, besides the output voltage ripple is reduced by 81.4%, 92.9% and 88.4% respectively. The output voltage ripple at light load is the lowest in all control methods, and can reach the best conversion efficiency of this circuit in the frequency conversion mode, 95.36%.

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