採用乙太網路供電(PoE)的技術，電源設備(PD)，例如VoIP，安全攝影機和無線LAN節點系統，因為供電通過該乙太網路電纜，而沒有連接到AC電源。因此，系統的可靠性增加，並且一個DC-DC變換器在電源裝置內部。目前，反馳式變換器的拓撲結構，RCD緩衝器的是最常用的解決方案，由於它的簡單結構和低成本，所以被廣泛應用。評估相關利弊和深入的討論將在第2章中提供。
但是，由於RCD緩衝器。它佔用了寶貴的空間，並降低了電源效率。為了提高效率，一個無源無損的緩衝電路是用來替代和一個具有低輸入漣波的反馳式轉換器（FYRR）拓撲結構在PoE應用，在本文提出。除了節省對RCD損失外，還具有利用該箝位電容器和變壓器的漏電感作為嵌入陷波濾波器的輸入電流紋波抑制功能。因此，EMI噪聲等級可以用較小的EMI濾波器元件去衰減，以滿足EMI結果。
除了的操作原理的描述中，理論分析，和設計上的考慮，兩個硬體電路，具有RCD緩衝器反馳式轉換器和FYRR電路被實現，具有頻率250KHz，44-57V的輸入電壓和12V /24W輸出規格被製造和測試。

Employing Power over Ethernet (PoE) technology, power devices (PDs), such as VoIP, security cameras and wireless LAN system node are thus powered over the cable without connecting to an AC source. Therefore, system reliability is increased and a DC-DC converter is built in the power device. Currently, flyback converter with RCD clamped topology is the most commonly used in power device due to it’s simple and low cost for PoE applications. To investigate the pros and cons, a thorough discussion will be provided in the chapter 2.
However, it suffers from the power dissipations in the RCD network. It occupies precious space and degrades the power efficiency. To improve the efficiency, a lossless passive snubber circuit is used instead and a flyback converter with current ripple reduction (FYRR) topology for the PoE applications is proposed in this thesis. In addition to saving the RCD loss, it also has an input current ripple reduction function by utilizing the clamp capacitor and the leakage inductance of the transformer as an embedded notch filter. Consequently, the EMI noise level can be attenuated with smaller EMI filter components to meet the EMI regulation.
In addition to the descriptions of the operation principle, theoretical analysis, and design considerations, two hardware circuits, the flyback with RCD snubber and the FYRR, with 250 kHz, 44-57V input and 12V/24W output specifications are built and tested.

[1] 區域網路的主流-乙太網路(Ethernet). Avaiable : http://opencourse.ncyu.edu.tw/ncyu/file.php/15/week03/乙太網路.pdf
[2] 乙太網供電 : IEEE 802.3af 標準. Available : http://www.powerdsine.com/languages/cantonese/eug_cantonese.pdf
[3] LAN-Power Systems Corporation. Available: http://www.lan-power.com/
[4] Introduction the PoE and the IEEE802.3af and 802.3at Standards. Available: http://www.ieee.li/pdf/viewgraphs/introduction_to_poe_802.3af_802.3-at.pdf
[5] 陳乃塘，「不再受限於電源位置，PoE新技術顛覆乙太網路」，新電子科技雜誌232期，民國94年6月。
[6] H. Wu, Z. Wang, J. Wu, X. He, Y. Deng, “50W Power Device (PD) Power in Power over Ethernet (PoE) System with Input Current Balance in Four-pair Architecture with Two DC/DC Converters,” IEEE APEC, pp. 575-579, Feb. 2010.
[7] 黃振邦，「資料和電源共網傳輸，分析PoE技術發展及其應用」，新通信元件雜誌49期，民國94年3月。
[8] Panjit Corp., Available: http://www.panjit.com.tw/
[9] Wikipedia, http://en.wikipedia.org/
[10] Microsemi Corp. , http:/www.microsemi.com/powerdsine/.
[11] Michele Sclocchi, L.H. Mweene, Frederik Dostal,“高效能PoE返馳式電源供應系統設計”, (EE Times，電子工程專輯), Mar. 2007.
[12] C. Gobok，「滿足高功率應用需求，PoE+設計升級亟待實現」，新通信元件雜誌108期，民國99年2月。
[13] Techmosa Corp., “Introduction to PoE & PowerDsine Product,” May 2006.
[14] National Semiconductor Corp., “Power over Ethernet (PoE),” 2007.
[15] 林志賢,「返馳式電源轉換器之分析、模擬與製作」, 逢甲大學電機工程碩士在職專班碩士論文, 民國九十九年一月.
[16] Patel, H.K, “Voltage transient spikes suppression in flyback converter using dissipative voltage snubbers,” Industrial Electronics and Applications, IEEE ICIEA'08, June 2008, pp. 897-901.
[17] 鄭玉南，「返馳式轉換器緩振電路研究」，國立臺灣科技大學電子工程系研究所碩士論文，民國95年。
[18] 葉松柏，「低輸入電流漣波之返馳式轉換器」，國立臺灣科技大學電機工程碩士學位論文，民國九十九年一月。
[19] 鄭培璿，返馳式轉換器，電力電子分析與模擬，初版，全華科技圖書股份有限公司，12-1、91年11月(公元2002年)。
[20] A. Hren, H. Korelic, and M. Milanovic, “RC-RCD clamp circuit for ringing losses reduction in a flyback converter,” IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 53, Issue 5, pp. 369-373, May 2006.
[21] 朱慶隆, “返馳式轉換器之基本工作原理”, Apr. 2010.
[22] 梁適安編譯，「高頻交換式電源供應器原理與設計」，第二版，全華科技圖書出版，西元2008年1月。
[23] AN-4137 application note, “Design Guidelines for Off-line Flyback Converters Using Fairchild Power Switch (FPS)”, Fairchild semiconductor Corporation, 2003.
[24] Jin, “返馳式開關電源設計解析---15W SG6848設計實例”, Apr. 2005.
[25] AN-4147 application note, “Design Guidelines for RCD Snubber of Flyback Converters”, Fairchild semiconductor Corporation, 2006.
[26] SIMetrix Technologies Ltd. (2012). SIMPLIS Reference. [Online]. Available: http://www.simetrix.co.uk//Files/manuals/6.2/SIMPLIS_Reference.pdf
[27] SIMetrix Technologies Ltd. (2012). User’s Manual. [Online]. Available: http://www.simetrix.co.uk/Files/manuals/6.2/UsersManual.pdf
[28] High Power/High Efficiency PoE Interface and DC/DC Controller. [Online]. Available: http://www.ti.com/lit/ds/symlink/tps23756.pdf