本論文提出應用於資料中心的48 V轉 12 V，操作頻率為 1.6 MHz的隔離型直流 -直流諧振轉換器。本論文採用夠在全負載範圍達到一次側功率開關零電壓切換、二次側功率開關零電流切換的全橋 LLC串聯諧振式轉換器。功率開關使用氮化鎵元件取代傳統矽元件，以降低功率開關的截止切換損耗，並將切換頻率設計在轉換器諧振頻率上，使直流轉換器的應用獲得最佳的轉換效率。本論文考量了變壓器內部的雜散電容設計功率開關之零電壓切換條件，確保在高頻的環境下功率開關皆有達成 零電壓切換。在變壓器設計的部分，使用新的設計流程改善一次側功率開關的損耗，在功率密度以及轉換效率上取得最佳點。採用四分之一圈變壓器結構，在維持相同圈比的情況下，減少一次側與二次側的直流銅損，並在低壓大電流的規格下，分析了繞組排列以減少交流阻抗，並使用磁性元件模擬軟體 ANSYS Maxwell分析漏磁通對銅損的影響。且分析繞組間距對於雜散電容的影響，減少變壓器內的雜散電容，進一步優化轉換器效率。最終完成輸出功率1600 W、切換頻率 1.6 MHz、最高效率 97.51 %、功率密度為 64 W/cm3的四分之一圈 全橋 LLC串聯諧振式轉換器。

This thesis proposes a 48 V to 12 V isolated DC-DC resonant converter operating at 1.6 MHz for data center applications. This paper adopts a full-bridge LLC series resonant converter, which can achieve zero-volt-age switching of the primary side power switch and zero-current switching of the secondary side power switch in the entire load range. The power switch used gallium nitride devices to reduce the turn-off switching loss of the power devices. The switching frequency is designed at the resonant frequency of the resonant converter for the high conversion efficiency. This thesis considers the stray capacitance inside the transformer to design the zero-voltage switching condition of the power switch to ensure that the power switch can achieve zero-voltage switching in a high-frequency environment. In the transformer design, a new design process is used to improve the loss of the primary side power switch and achieve the best point in power density and conversion efficiency. A quarter-turn transformer structure is adopted to reduce the DC copper losses on the primary and secondary sides while maintaining the same turn ratio. Magnetic component simulation software ANSYS Maxwell analyzes the influence of leakage flux on copper loss. And analyze the effect of winding spacing on stray capacitance, reduce the stray capacitance in the transformer, and further optimize the converter efficiency. Finally, a quarter-turn full-bridge LLC series resonant converter with an output power of 1600 W, a switching frequency of 1.6 MHz, maximum efficiency of 97.51 %, and a power density of 64 W/cm3 is completed.

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