本論文目標為對 LLC 諧振式電能轉換器進行優化，研製一台具寬電壓增益範圍且不影響穩態轉換器效率的串聯諧振式直流轉換器。
本文先從傳統 LLC 諧振式轉換器的動作區間與設計上進行分析，傳統 LLC 諧振式轉換器應用在寬範圍輸入場合下，通常僅能夠透過降低激磁電感來滿足對於操作頻率範圍的需求，然而降低激磁電感會造成額外的損失。因此本文先以體積相同的變壓器，藉由改變氣隙達成不同的激磁電感量的做法對其繞組損耗進行分析與模擬，並探討過去文獻對於改變激磁電感量的方式進行分析與比較；接著提出次級側相移調變控制，該控制方式可以提升 LLC 諧振式轉換器操作低於諧振頻率時的電壓增益，同時不會影響當轉換器操作於諧振點時的效率；另外本文亦探討次級側相移調變控制對於諧振式轉換器的影響，分析過度相移對於電路動作所帶來的影響，利用時域分析法推導出相移邊界。根據傳統 LLC 諧振式轉換器的設計流程與次級側相移控制的相移邊界整合出一優化設計流程，使設計者可以利用輸入規格設計出合理的諧振槽參數。最終本論文利用該設計流程實現輸入電壓為 400 VDC – 290 VDC、輸入電壓為 12 VDC、輸出功率為 1.5 kW，最高效率為97.2 %的 LLC 諧振式直流/直流轉換器。

The purpose of this dissertation is to implement the LLC resonant converter with wide input voltage range without reducing the overall efficiency. The dissertation analyzed the operation and design procedure of traditional LLC resonant converters. In wide range input applications, traditional LLC resonant converters can only satisfy the frequency range requirements by reducing the excitation inductance, which causes additional losses. Therefore, this dissertation analyzes and simulates the winding loss of a transformer with the same volume by changing the air gap to achieve different excitation inductance levels, and explores previous literature on analyzing and comparing different methods of changing the excitation inductance.
Then, this dissertation purposed a secondary-side phase-shift control to further improve the voltage gain without reducing the overall efficiency of the LLC resonant converter. Furthermore, this dissertation explores the impact of secondary-side phase-shift control on the resonant converter and analyzes the influence of excessive phase shift on the circuit operation, deriving the phase-shift boundary using time interval analysis. Combining the design process of traditional LLC resonant converters and the phaseshift boundary of secondary-side phase-shift control, this dissertation develops an optimized design process to enable designers to design reasonable resonant tank parameters based on specifications. Last, this paper implements an LLC resonant DC/DC converter with input voltage ranging from 400 VDC to 290 VDC, input voltage of 12 VDC, output power of 1.5 kW, and a maximum efficiency of 97.2%.

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