為了使伺服器系統獲得較好的效能，因此降壓轉換於輕中載的效率顯得相當重要。本論文所研製具非線性輸出電感的單相降壓型轉換器(Buck Converter)，利用磁性材料飽和特性將電感設計成高與低兩種感值，其與傳統線性電感轉換器相比，非線性電感轉換器具有較低的損失、低輸出漣波電壓的優點。
本論文先分析降壓型轉換器的工作原理，探討與設計非線性電感，進而實現一18W之電壓模式控制降壓轉換電路，非線性電感轉換器工作於重載時電感值為1μH；工作於輕中載，其感值可改變為2μH。以實測結果驗證本文所提之非線性電感轉換器的可行性，以達改善輕中載效率，並降低輕中載輸出漣波電壓。

The light and intermediate load efficiencies of Buck converter in server system are very important for getting better performance. This thesis focuses on the study and implementation of a single phase voltage mode Buck converter to have changeable nonlinear inductor to improve light, intermediate load efficiencies and voltage ripple. The cross section area of magnetics is advanced to realize the nonlinear inductors. The theoretical loss reduction and output voltage ripple is demonstrated by comparing of loss/output voltage ripple of a conventional Buck converter with voltage mode control circuits.
Firstly, the principles of Buck circuits are analyzed in details. Nonlinear inductor is analyzed and designed to achieve high efficiency performance. Its inductance could vary from 1 μH at full load to 2 μH at light and intermiate load. Finally, an 18W Buck converter prototype with nonlinear inductor is realized and tested to verify the feasibility of the studied scheme. The results show the nonlinear inductor with voltage mode control could improve efficiencies and ripple of light and intermediate load, the output voltage ripple also can be reduced.

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