相較於傳統全橋轉換器，隔離雙倍降壓轉換器可以達到更高的降壓倍率，但在輸出功率維持不變的情況下，由於進入變壓器一次側的電壓降低，將導致流入變壓器的電流上升，使一次側開關電流應力提高，並增加一次側環路損失。為解決上述問題，本論文提出架構由雙倍降壓和倍流整流技術組成，透過倍流整流技術減少變壓器二次側輸出電流峰值，達到減少一次側環路電流，且倍流整流電路的二極體數目為橋式整流電路的一半，可減少二極體導通造成的損失。
研究主要有兩個目標，首先透過一次側電容達成雙倍降壓，同時開關元件具低電壓應力；接著二次側採用倍流整流技術，減少變壓器環路損失與降低輸出負載的連波電流，達到一次側低電流應力，同時整流二極體上皆達到零電壓切換，降低切換損失，進而提升轉換器效率。本論文透過模擬和實驗結果的綜合驗證，證實高降壓轉換器的可行性，實際量測負載範圍內的效率最高為93.4%，突顯本論文架構的潛力。

Isolated double step-down converter can achieve a higher step-down ratio which compared to traditional Full-Bridge converter. Because maintaining the same output power, the primary circulating current will be increased while reducing input voltage to the primary side of transformer. This results is increasing current stress on the primary side switches and the line loss on the primary side. To solve these issues, this paper proposes a structure composed of double step-down and current-doubler rectifier. By utilizing the current-doubler rectifier, the peak current on the secondary side of transformer is reduced, thereby decreasing the current on primary-side. Additionally, the current-doubler rectifier circuit only requires half the amount of diodes compared to the bridge rectifier circuit, it can decrease the losses caused by diode.
The study has two main objectives: first, to achieve step-down through primary-side capacitor energy, while reducing voltage stress of switches; and second, proposed topology adopt current-doubler rectifier on the secondary side which can reduce the secondary circulating currents and ripple voltage, while achieving low current stress on primary side and zero-voltage switching on the rectifier diodes which can promote the conversion efficiency. The feasibility of the proposed topologies is confirmed through comprehensive verification using simulation and experimental results. According to actual measurements within the load range, the highest efficiency of proposed circuit is 93.4%, which highlights the significant potential of the proposed topology.

摘要......i
Abstract......ii
誌謝......iii
目錄......iv
表目錄......vi
圖目錄......vii
第一章 緒論......1
1.1、 研究背景與動機......1
1.2、 論文架構與貢獻......1
第二章 降壓轉換器簡介......3
2.1、 全橋式轉換器......3
2.2、 隔離雙倍降壓轉換器......3
2.3、 具倍流整流之全橋式轉換器......4
第三章 電路架構與分析......6
3.1、 具倍流整流之隔離雙倍降壓轉換器架構......6
3.2、 電路動作原理......6
3.3、 電壓增益......12
3.4、 元件上的電壓應力......13
3.5、 電容Ci設計......14
3.6、 電路模擬......15
3.6.1、25%負載率模擬波形......15
3.6.2、 50%負載率模擬波形......18
3.6.3、 75%負載率模擬波形......20
3.6.4、 100%負載率模擬波形......23
第四章 實驗結果與分析......27
4.1、 轉換器參數......27
4.2、 電路實測結果......28
4.2.1、 25%負載率實測波形......28
4.2.2、 50%負載率實測波形......32
4.2.3、 75%負載率實測波形......37
4.2.4、 100%負載率實測波形......41
4.3、 效率分析......46
第五章 結論與未來展望......47
5.1、 結論......47
5.2、 未來展望......47
References......48

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