本論文旨在針對以輕薄短小為特點之小功率電子產品，應用壓電變壓器來研製一降壓式電源轉換器，俾以提供產品所需之低壓直流電源。此電源轉換器是以圓型疊層壓電變壓器為主要電能轉換元件，以最佳負載下所對應的諧振頻率為系統的操作頻率，配合適當的串聯電感值使電路具有零電壓切換的功能，藉由結合脈波寬度調變與定量模式的控制方法，俾使其有良好的負載調節特性且具有開路保護的功能。文中最後試製一降壓式電源轉換器，並經由實驗證實在輸入交流電壓100V~130V內可正常工作，輸出直流電壓15V、輸出電流0.51A~1.77A。

　　The purpose of this thesis is to present a piezoelectric transformer based power converter for small power devices, which need compact volume. This power converter based on round-shaped multi-layer piezoelectric transformer. The optimum-designed series inductor and switching frequency are able to keep power efficiency high while the converter can achieve zero voltage switching condition. A new control method of the combination of pulse width modulation and quantum mode control makes it possible to regulate the output voltage and provide open circuit protection. As a result, the step-down power converter implemented on a printed circuit board was experimentally evaluated and it allows 100V~130V AC input voltage range at output voltage of 15V, load current of 0.51A~1.77A.

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