本論文旨在研製高功率密度功率轉換器，以主動箝位返馳式轉換器做為電路架構。消除傳統返馳式轉換器開關上電壓突波，減少電磁干擾以及開關電壓應力，並介紹主開關在高頻操作下，零電壓切換條件與激磁電感的關係。且使用氮化鎵元件取代傳統之矽功率開關，減少轉換器體積以及高頻開關造成的切換損耗，增加整體電路的功率密度。在薄型平板變壓器的基礎上，藉由改變繞組設計方式，降低二次側電流造成之線損以及電流應力，並改變繞組走線寬度比，改善一次側之繞組線損，同時減少板層間的積熱。分析繞組次序以及不同繞組線寬的改善，以達到繞組之最佳化。
透過理論分析與電路模擬，完成主動箝位返馳式轉換器之設計及實作，在全域輸入電壓條件、輸出19 V/ 65 W的規格下，低壓效率達到93 %，功率密度為1.879 W/ cm3，並驗證繞組走線寬度比對損耗之影響。

This thesis presents a high power density power converter. The voltage spike in the conventional flyback converter can be eliminated to reduce electromagnetic interference and voltage stresses on power switches by using active-clamped circuit. The relationship between zero-voltage-switching condition of high frequency power switches and magnetizing inductance and leakage inductance is analyzed and discussed. Gallium nitride devices are used both at primary and secondary switches to reduce the converter volume and switching losses to achieve high power density. Based on the planar transformer design, reducing the conduction losses and current stresses of secondary switches by changing the winding configuration. The losses and heat in the inner winding layers can be reduced by adjusting track-width-ratio design. The winding performance can be improved by the sequences and trace width of windings.
With theoretical analysis and circuit simulation, a 65 W (19 V/ 3.3 A) active-clamped flyback converter with universal input voltage range is developed and tested to verify the track-width-ratio design with efficiency comparison. The peak efficiency can be up to 93 % at low line voltage and the power density is 1.879 W/ cm3.

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