傳統交換式電源由於開關的硬式切換會產生嚴重的電磁干擾與轉換效率低的問題。非對稱半橋轉換器具有零電壓切換功能，可以有效降低切換損耗和雜訊，進而提高操作頻率和轉換效率。
非對稱半橋轉換器有許多優點，如架構簡單、開關應力低和柔性切換特性。然而，對於非對稱半橋拓樸而言，在輕載條件下，開關元件難以實現零電壓切換操作。本論文旨在研究在前級功率因數修正電路，利用電壓隨耦控制方法，於低交流輸入電壓和輕載條件下，降低功率因數修正電路的輸出電壓，減少電路切換損耗、提高轉換效率。
本論文實現與測試一部240W的雛型電源供應器。前級電路利用邊界電流模式功率因數修正電路，用以改善輸入功率因數；後級電路為具有零電壓切換的非對稱半橋轉換器。非對稱半橋雛型電路在低輸入電壓和輕載條件下，效率可達到92.6%。因此，240W電源供應器的整體效率可達88%。

Conventional switching power supplies have serious electromagnetic interference (EMI) problem and poor efficiency performance due to their hard-switching operation. An asymmetrical half-bridge (AHB) converter with zero-voltage-switching (ZVS) features can reduce switching losses and noises effectively, thus raise the operating frequency and conversion efficiency.
The asymmetrical half-bridge converter has many advantages such as simple structure, lower switch stresses and soft-switching features. However, the ZVS operation is difficult to achieve under light load condition for the AHB topology. This thesis aims to study a follower boost control method for pre-stage power factor corrector (PFC). Under low AC-line input and light load conditions, the conversion efficiency can be significantly raised by lower the DC bus voltage between the PFC circuit and AHB converter to reduce switching losses.
A laboratory prototype of 240W adaptor was implemented and tested. The pre-stage circuit is a transition-mode (TM) power factor corrector for improving input power factor. The post-stage circuit is an asymmetrical half-bridge converter with zero–voltage switching features. The measured efficiency for AHB prototype circuit reaches 92.6% under low-line input and light load conditions. Thus, the overall efficiency of the developed 240W adapter can be up to 88%.

[1] A. I. Pressman, “Switching Power Supply Design,” Second Edition,
McGraw-Hill, 1998.
[2] M. Brown, “Power Supply Cookbook,” Second Edition, Butterworth-
Heinemann, 2001.
[3] S. S. Ang, “Power-Switching Converters,” Second Edition, Marcel Dekker, Inc. 2005.
[4] 宋自恆、林慶仁，「功率因數修正器之原理與常用元件規格」，新電子科技雜誌217期，民國93年4月。
[5] C. Hua and F. C. Lee, “Soft Switching Techniques in PWM Converters,” IEEE Trans. on Industrual Electronics, Vol.42, No.6, pp 595-603, December 1995.
[6] J. G. Cho, “Zero-Voltage and Zero-Current Switching Full Bridge PWM Converter using Secondary Active Clamp,“ IEEE PSEC, pp 601-607, 1998.
[7] B. Amdreycak, “Active Clamp and Reset Technique Enhances Forward Converter Performance,“ Unitrode Power Supply Design Seminar, SEM-1000, 1994.
[8] J. Wittenbreder, “Zero Voltage Switching Pulse Width Modulated Power Converter,” U. S. Platent, No. 5,402,329, Mar. 1995.
[9] J. Feng, Y. Hu, W. Chen, and C. C. Wen, “ZVS Analysis of Asymmetrical Half-Bridge Converter,” IEEE PESC, Vol. 1, pp.243-247, 2001.
[10] J. H. Liang, P. C. Wang, K. C. Huang, C. L. Chen, Y. H. Leu, and T. M.
Chen, “Design Optimization for Asymmetrical Half-Bridge Converters,”
IEEE APEC, Vol. 2, pp. 697-702, 2001.
[11] P. Imberston and N. Mohan, “Asymmetrical Duty Cycle Permits Zero Switching Loss in PWM Circuits with No Conduction Loss Penalty,” IEEE Trans. Industry Application, vol. 29, no. 1, pp. 121-125, Jan/Feb.. 1993.
[12] S. Korotkov, V. Meleshin, R. Miftahutdinov, and S. Fradlin, “Soft-Switched Asymmetrical Half-Bridge DC/DC Converter: Strady-State Analysis. An Analysis of switching Processes,” IEEE INTELEC, 1997, pp. 177-184.
[13] R. Oruganti, P. C. Heng, J. T. K. Guan, and L. A. Choy, “Soft-switched DC/DC Converter with PWM Control,” IEEE Trans. Power Electronics, Vol. 13, No. 1, Jan. 1998, pp. 102-114.
[14] 曾軍浩，「高效能功率因數修正器研製」，國立台灣科技大學電子工程
系研究所碩士論文，民國95年。
[15] ST Microelectronics, “L6561 POWER FACTOR CORRECTOR”, Data Sheet, 2003.
[16] Applications Handbook, AN966, STMicroelectronics, Mar. 2003.
[17] ST Microelectronics, “L6591 PWM CONTROLLER FOR ZVS HALF-BRIDGE”, Data Sheet, 2008.
[18] M. K. Kazimierczuk and D. Czarkowski, “Resonant Power Converters,” Wiley-Interscience publication, ISBN 0-471-04706-6.
[19] 蘇英傑，「具同步整流倍流輸出之單級非對稱半橋電能轉換器」，私立中原大學電機工程學系研究所碩士論文，民國93年。
[20] P. Imberson and N. Mohan, “NEW PWM Converter Combining Zero Switching Loss With Low Conduction Loss,” IEEE INTELEC, 1990, pp. 179-185.
[21] N. Mohan, T. M. Undeland, and W. P. Robbins, “Power Electronics:
Converters, Applications and Design,” Third Edition, John Wiley &
Sons, 2003.
[22] 梁適安，「交換式電源供應器之理論與實務設計」，全華科技圖書出版，民國93年10月。
[23] 呂宜興，「不對稱半橋零電壓切換直流電源供應器之研製」，國立台灣大學電機工程系研究所碩士論文，民國89年。
[24] 曾偉碩，「空載低損耗不對稱半橋電源轉換器之研製」，國立成功大學
電機工程系研究所碩士論文，民國92年。
[25] 陳皇運，「高效率非對稱半橋轉換器之研製」，國立台灣科技大學電子
工程系研究所碩士論文，民國97年。
[26] B. Andreycak, “Active Clamp and Reset Technique Enhances Forward Converter Performance,” Unitrode Power Supply Design Seminar SEM-1000, 1994.
[27] 郭啟業，「非對稱半橋之研製」，國立台灣科技大學電子工程系研究所碩士論文，民國94年。
[28] B. Andreycak, “Practical Considerations in High Performance MOSFET, IGBT & MCT Gate Drive Circuit,” Unitrode Application Note.
[29] 劉建宏，「高效率低空載損耗之200W穩壓器研製」，國立台灣科技大學電子工程系研究所碩士論文，民國96年。