本論文以傳統 LLC 諧振電路為架構，並提出新式波谷切換控制策略應用於寬範圍電壓輸出規格與輕載策略。有別於傳統變頻控制策略，本論文提出之波谷切換策略使電路操作區間加入一次側開關元件汲極-源極間電容與激磁電感之諧振區間，進而阻擋主諧振槽之能量傳遞，達到低電壓輸出與輕載之目的。由於所加入之諧振區間一次側開關與本體二極體皆為截止狀態。因此，此方法將大大降低了有別於傳統相移控制策略環流損問題。除此之外，由於波谷切換之特性，一次側主開關將於所選擇之波谷點開啟，致使 LLC 諧振電路切換損及切換頻率下降。相較於傳統突衝控制策略，可以解決硬切、高頻切換問題。並增加電壓調節率、降低輸出電壓漣波，提升電力品質。
本論文將針對波谷切換控制策略以時間為維度進行分析，除了表示正規化開關導通時間 φon 與電壓增益之曲線外，亦分析諧振槽參數對電路電壓應力、操作頻率之影響。最終，提出完整之輕載應用與寬範圍應用之設計流程，並分別完成一台全橋 LLC 諧振式轉換器規格為 600W/48V，與一台半橋 LLC 諧振式轉換器規格為輸入 100-240 VAC，輸出5/9/15/20 VDC，最高功率65W，以確保本論文廣泛應用上之可靠性。

The dissertation uses the traditional LLC resonant converter as the architecture, and proposes a novel control strategy for wide output voltage application and light-load application. Different from the traditional PFM control strategy, the VSC control strategy proposed in this dissertation makes the magnetizing inductance resonate with the drain-source capacitance of the primary switchings. Thereby, the converter is able to block the energy transfer and achieves strait specifications. Due to the resonant interval for magnetizing inductance and drain-source capacitance, the primary side switchings have no circulating loss. The efficiency will be thus improved compared with the phase-shifted control strategy. In addition, with VSC control strategy, the primary switchings achieves the characteristic of LVS. Compared with the traditional burst control strategy, It can help converter to ease the hard-switching and regulation problems, reduce the output voltage ripple, and improve the power quality.
The dissertation depicts the VSC control strategy with the time-domain analysis. In addition, the gain curve is also described with normalized pulse-width φon. The influence of voltage stress on components and operating frequency will be discussed according to different designed parameter. Finally, a completed design process for light-load applications and wide output voltage applications are proposed. In the implement, a full-bridge LLC resonant converter with a DC input of 400-VDC, an output voltage of 48-VDC, an output current of 12.5-A, and a half-bridge LLC resonant converter with a AC input of 100~240-VAC, an output voltage of 5/9/15/20-VDC, an output current of 3-A were constructed for the prototype converters.

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