USB電力傳輸( Power Delivery)透過單一電源供應器與統一化之連接埠，能滿足各種3C裝置供電需求，同時接頭的無方向性更增進使用上之便利性，改善眾多傳統3C產品充電配件之缺點。傳統電源裝置大多使用返馳式轉換器，達到體積小及成本低之效益，然而，其輸出功率隨負載的變換，導致轉換器效率常處於非最佳之狀態。因此本論文設計新型效率修正控制之準諧振返馳式電源轉換器，並且可適用於不同輸出電壓，以改善上述問題。
本論文以Mathcad計算主要元件損耗，而電路主架構為邊界導通模式升壓型功率因數修正器做前級穩壓器，使輸入直流電壓升至260V或400V，可降低導通損失；關閉功率因數修正器輸入直流電壓為163V或325V，能降低切換損失，減少電路整體損耗。假設導通損失小於切換損失時，預期關閉功率因數修正器；相反之，當導通損失遠大於切換損失時，預期開啟功率因數修正器，以此方式提高整體效率。後級準諧振返馳式轉換器，具有波谷切換特性，可有效減少開關損耗。最後實測整體系統效能，當輸出功率50W，而輸入交流電壓為230V且25%負載時，功率因數修正器關閉時的效率比開啟時提高7.4%；當輸出功率100W，而輸入交流電壓為115V且負載100%載時，功率因數修正器開啟時的效率比關閉時提升2.67%，本文均符合新式能源之星法規標準。

Power delivery of a universal serial bus (USB) can meet power supply requirements in a variety of 3C devices by a single power supply and a unified port. At the same time, the non-directional joint can increase the convenience of use and improve the shortcomings of charging accessories in many conventional computers, communications, and consumer electronics (3C) products. Most of the traditional power supply devices use the flyback converter to achieve the small size and the benefits of low cost. However, the output power with the changes in the load, resulting in converter efficiency is often in the non-optimal state. Therefore, a new type of quasi-resonant flyback power converter with efficiency correction control is designed in this thesis and can be applied for different output voltages to improve the above problems.
In this thesis, Mathcad is used to calculate the losses of main components. The circuit main structure is a boost type power factor correction device with the border conduction mode as a regulator in the front stage. The input DC voltage roses to 260V or 400V and the conduction loss can be reduced. The input DC voltage of 163V or 325V can decrease the switching loss and reduce the overall circuit loss after turning off the power factor correction device. When the conduction loss is less than the switching loss, the power factor corrector is turned off. When the conduction loss is much greater than the switching loss, the power factor correction is turned on. The overall efficiency is improved by this way. The quasi-resonant flyback converter in the rear stage with valley switching characteristics can effectively reduce the switching losses. Finally, the overall system performance is tested. When the output power is 50W and the input AC voltage is 230V with the 25% load, the efficiency of the power factor correction device which is turned off is 7.4% higher than it which is turned on. When the output power is 100W and the input AC voltage is 115V with the 100% load, the efficiency of the power factor correction device which is turned on is 2.67% higher than it which is turned off. Accordingly, the system performance entirely satisfies the new type of Energy-Star regulations.

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