基於現今擁有的技術如耦合電感及主動式箝位，論文提出一個具有開關零電壓切換及較低開關電壓應力之新穎降壓型轉換器。所提轉換器係利用耦合電感之特性，具有較傳統降壓轉換器大之降壓比。由滿載至極輕載，電路開關均具有零電壓切換之特性。因而所提轉換器於輕載時之效率不受制於切換損失，具有整體效率佳之特性。
於內文中，電路穩態特性如諧振電流公式、諧振電容電壓公式、電壓轉換比均進行推導，並和現有的電路架構進行了比較。此外，本文亦敘述了轉換器零電壓操作之條件與設計方式。透過設計適當的激磁電感與諧振電感值，可使本轉換器零開關電壓切換之範圍覆蓋整個負載區間。最後，實現以控制器TMS320F28035的電路原型，操作於156 V輸入電壓、48 V輸出電壓、200 W輸出功率，用以驗證所提轉換器之可行性。本轉換器於125 W輸出功率時，可達最高效率96.8%。

In this thesis, a novel ZVS buck converter with lower voltage stress based on coupled-inductor and active clamp techniques has been proposed. This converter utilizes coupled-inductor to obtain higher step-down ratio than the conventional buck converter. Besides, proposed converter can achieve ZVS on both switches from full load to extra-light load. Therefore, the efficiency at light load does not subject to the switching losses, which leads to high overall efficiency.
The steady-state features of the circuit are derived in this thesis, such as the equations of resonant currents, resonant voltages, and voltage conversion ratios. In addition, the ZVS conditions and the design considerations of proposed converter are described. The ZVS region can cover the full load range, if the value of the magnetic inductance and resonant inductance have been properly chosen. Finally, based on controller TMS320F28035, a converter with 156 V input voltage, 48 V output voltage, and 200 W output power is also developed to prove feasibility of the proposed converter. When the output power is around 125 W, the efficiency reaches its peak value as 96.8%.

[1] The Department of Ecology is Washington's environmental protection agency/ what is climate change? [Online]. Available: http://www.ecy.wa.gov/about.html.
[2] What is the Paris Agreement on climate change? (Sep. 2016) [Online]. Available: https://www.weforum.org/agenda/2016/what-is-the-paris-agreement-on-climate-change/.
[3] COP 21 Paris Summit (Dec.2015) [Online]. Available: http://climateparis.org/COP21.
[4] K. H. Liu, R. O. Oruganti and F. C. Lee, "Resonant switches-topologies and characteristics", Proc. Power Electronic. Spec. Conf., pp. 62-67, 1985.
[5] T. Zheng, D. Y. Chen and F. C. Lee, "Variations of quasi-resonant DC-DC converter topologies", Proc. Power Electronic. Spec. Conf., pp. 381-392, 1986.
[6] C. M. C. Duarte and I. Barbi, "A family of ZVS-PWM active-clamping Dc-to-Dc converters: Synthesis analysis design and experimentation", IEEE Trans. Circuits Syst., vol. 44, pp. 698-704, Aug. 1997.
[7] Y. Ma, X. Wu, X. Xie, G. Chen and Z. Qian, "A new ZVS-PWM buck converter with an active clamping cell," IEEE IECON'07, pp. 1592-1597, 2007.
[8] N. Lakshminarasamma and B. Swaminathan, V. Ramanarayanan, "A unified model for ZVS dc to dc converters with active clamp", Proc. PESC, pp. 2441-2447, 2004.
[9] S. Chattopadhyay and S. Baratam, H. Agrawal, "A new family of active clamp PWM dc-dc converters with ZVS for main switch and ZCS for auxiliary switch", Proc. Applied Power Electronic. Conf. Exposition, pp. 851-858, APEC 2011.
[10] K. Smith and K. Smedley, "Engineering design of lossless passive soft switching methods for PWM converters Part II. With non-minimum voltage stress circuit cells", IEEE Trans. Power Electronic, vol. 17, no. 6, pp. 864-873, Nov. 2002.
[11] K. Smith and K. Smedley, "A comparison of active and passive soft switching methods for PWM converters", Proc. 29th Power Electronic. Spec. Conf. (PESC), vol. 1, pp. 94-100, May 1998.
[12] S. A. Liang and T. F. Wu, "A systematic approach developing single-stage soft switching PWM converters", IEEE Trans. Power Electronic, vol. 16, no. 5, pp. 581-593, Sep. 2001.
[13] K. M. Smith and K. M. Smedley, "Properties and synthesis of passive lossless soft-switching PWM converters", IEEE Trans. Power Electronic, vol. 14, no. 5, pp. 890-899, Sep. 1999.
[14] H. L. Do, "Zero-voltage-switching synchronous buck converter with a coupled inductor", IEEE Trans. Ind. Electronic, vol. 58, no. 8, pp. 3440-3447, Aug. 2011.
[15] S. S. Lee, "Step-down converter with efficient ZVS operation with load variation", IEEE Trans. Ind. Electronic, vol. 61, no. 1, pp. 591-597, Jan. 2014.
[16] L. Jiang, C. C. Mi, S. Li, C. Yin and J. Li, "An improved soft-switching buck converter with coupled inductor", IEEE Trans. Power Electronic, vol. 28, no. 11, pp. 4885-4891, Nov. 2013.
[17] Y. Zhang and P. C. Sen, "A new soft-switching technique for buck boost and buck-boost converters", IEEE Trans. Ind. Appl., vol. 39, no. 6, pp. 1775-1781, Nov./Dec. 2003.
[18] K. I. Hwu, W. Z. Jiang and Y. T. Yau, "Ultrahigh step-down converter", IEEE Trans. Power Electronic, vol. 30, no. 6, pp. 3262-3274, Nov. 2015.
[19] W. Martinez, J. Imaoka, Y Itoh, M. Yamamoto and K. Umetani, "A Novel High Step-Down Interleaved Converter with Coupled Inductor", IEEE International Telecommunications Energy Conference - INTELEC, pp. 1-6, Jan. 2015.
[20] K. I. Hwu, W. Z. Jiang and Y. T. Yau, "Nonisolated coupled-inductor-based high step-down converter with zero DC magnetizing inductance current and nonpulsating output current", IEEE Trans. Power Electronic, vol. 31, no. 6, pp. 4362-4377, Jun. 2016.
[21] H. Wu, K. Sun, L. Chen, L. Zhu and Y. Xing, "High step-up/step-down soft-switching bidirectional dc–dc converter with coupled-inductor and voltage matching control for energy storage systems", IEEE Trans. Ind. Electronic, vol. 63, no. 5, pp. 2892-2903, May 2016.
[22] M. Aamir, S. Mekhilef and H. J. Kim, "High-Gain Zero-Voltage Switching Bidirectional Converter with a Reduced Number of Switches", IEEE Trans. Circuits Syst. II Express Briefs, vol. 62, no. 8, pp. 816-820, Aug. 2015.
[23] G. Chen, Y. Deng, Y. Tao, X. He, Y. Wang and Y. Hu, "Topology derivation and generalized analysis of zero-voltage-switching synchronous dc–dc converters with coupled inductors", IEEE Trans. Ind. Electronic, vol. 63, no. 8, pp. 4805-4815, Aug. 2016.
[24] Y. P. Hsieh, J. F. Chen, L. S. Yang, C. Y. Wu and W. S. Liu, "High-conversion-ratio bidirectional DC–DC converter with coupled inductor", IEEE Trans. Ind. Electronic, vol. 61, no. 1, pp. 210-222, Jan. 2014.
[25] K. Yao, Y. Ren, J. Wei, M. Xu and F. C. Lee, "A family of buck-type dc̵-dc converters with autotransformers", Proc. APEC'03, vol. 1, pp. 114-120, 2003.
[26] J. H. Park and B. H. Cho, "Nonisolation soft-switching buck converter with tapped-inductor for wide-input extreme step-down applications", IEEE Trans. Circuits Syst. I Reg. Papers, vol. 54, no. 8, pp. 1809-1818, Aug. 2007.
[27] P. Xu, J. Wei and F. C. Lee, "Multiphase coupled-buck converter-a novel high efficient 12 V voltage regulator module", IEEE Trans. Power Electronic, vol. 18, no. 1, pp. 74-82, Jan. 2003.
[28] S. Abe and T. Ninomiya, "Comparison of active-clamp and ZVT techniques applied to tapped-inductor DC-DC converter with low voltage and high current", J. Power Electronic, vol. 2, no. 3, pp. 199-205, Jul. 2002.
[29] P. C. Tsai, C. C. Feng and C. C. Chi, "A Novel Transformerless Interleaved High Step-Down Conversion Ratio DC-DC Converter With Low Switch Voltage Stress", Industrial Electronics IEEE Transactions on, vol. 61, pp. 5290-5299, Jan. 2014.
[30] F. L. de S´a, C. V. B. Eiterer, D. Ruiz-Caballero and S. A. Mussa, “Double Quadratic Buck Converter”, in Proc. Brazilian Power Electronics Conference (COBEP), 2013.
[31] X. Ruan, J. Wei and Y. Xue, "Three-level converters with the input and output sharing the ground", Proc. IEEE PESC, pp. 1919-1923, 2003.
[32] J. P. Rodrigues, I. Barbi and A. J. Perin, "Buck converter with ZVS three level boost clamping", Proc. IEEE ISIE, pp. 673-678, 2007.
[33] X. Ruan, B. Li, Q. Chen, S.C. Tan and C. K. Tse, "Fundamental Considerations of Three-Level DC-DC Converters: Topologies Analyses and Control", IEEE Transactions on Circuits and Systems, vol. 55, no. 11, pp. 3733-3743, Dec. 2008.
[34] C. Mclyman, “DC Inductor Design Using Gapped Cores,” in Transformer and inductor design handbook, 3rd ed. New York: Marcel Dekker, 2004, ch.8, pp. 254-271.
[35] L. Wuhua, L. Xiaodong, D. Yan, L. Jun and H. Xiangning, "A review of non-isolated high step-up DC/DC converters in renewable energy applications", Proc. 24th Annu. IEEE Appl. Power Electronic Conf. Expo., pp. 364-369, 2009-Feb.-15–19.
[36] N. Mohan, T. M. Undel and W. P. Robbins, PowerElectronics:Converters, Applications and Design, Second Edition, John Wiley & Sons, 1995.
[37] C. Mclyman, “DC Inductor Design Using Gapped Cores,” in Transformer and inductor design handbook, 3rd ed. New York: Marcel Dekker, 2004, ch.8, pp. 254-271.