本論文提出一「具主動箝位之高升壓順向/返馳式轉換器」。此電路架構包含：變壓器、開關元件、諧振電容、主動箝位電路及輸出倍壓電路所組成。藉由採用變壓器與輸出倍壓電路使得轉換器具有高電壓增益，以及兼具順向式轉換器之儲能特性與返馳式轉換器之釋能特性。此外使用主動箝位電路，使儲存在變壓器漏感上的能量可以被回收至輸入端，降低主開關在截止時的電壓應力並使開關元件具有零電壓切換，故可有效地提升轉換器的效率。最後，經由實作一雛型電路，輸入電壓為24 V，輸出為 200 V/ 400 W，以驗證所提出轉換器之可行性與正確性。

In this thesis, a high step-up forward/flyback converter with active-clamp circuit is proposed. The circuit topology of the proposed converter consists of a transformer, switch, resonant capacitor, an active-clamp circuit, and the output voltage doubler circuit. By utilizing the transformer and output voltage doubler, the proposed converter can achieve high voltage gain. The proposed converter functions as the forward and flyback integrated converter. In additional the active-clamp circuit is employed to recycle the leakage-inductance energy of the transformer and thus the stresses on the switches are reduced and zero-voltage-switching (ZVS) are achieved. Thus, the system efficiency can be improved. Finally, a prototype circuit with 24-V input voltage, 200-V/ 400-W output power is implemented to verify the performance.

[1] S. K. Changchien, T. J. Liang, J. F. Chen, and L. S. Yang, “Novel high step-up DC–DC converter for fuel cell energy conversion system,” IEEE Trans. Industrial Electronics, vol. 57, no. 6, pp. 2007–2017, Jun. 2010.
[2] C. T. Pan and C. M. Lai, “A high efficiency high step-up converter with low switch voltage stress for fuel cell system applications,” IEEE Trans. Industrial Electronics, vol. 57, no. 6, pp.1998-2006, Jun. 2010.
[3] S. V. Araujo, R. P. Torrico-Bascope, and G. V. Torrico-Bascope, “Highly efficient high step-up converter for fuel-cell power processing based on three-state commutation cell,” IEEE Trans. Industrial Electronics, vol. 57, no. 6, pp. 1987–1997, Jun. 2010.
[4] K. B. Park, G. W. Moon, and M. J. Youn, “Non-isolated high step-up boost converter integrated with sepic converter”, IEEE Trans. Power Electronics, 2010.[5] R. J. Wai, C. Y. Lin, R. Y. Duan, and Y. R. Chang, “High-efficiency power conversion system for kilowatt-level stand-alone generation unit with low input voltage,” IEEE Trans. Industrial Electronics, vol.55, no.10, pp.3702-3714, Oct. 2008.
[6] W. Li and X. He, “A family of interleaved DC–DC converters deduced from a basic cell with winding-cross-coupled inductors (WCCIs) for high step-up or step-down conversions”, IEEE Trans. Power Electronics, vol. 23, no. 4, pp. 1791-1801, Jul. 2008.
[7] M. Prudente, L. L. Pfitscher, G. Emmendoerfer, E. F. Romaneli, and R. Gules, “Voltage multiplier cells applied to non-isolated DC–DC converters”, IEEE Trans. Power Electronics, vol. 23, no. 2, pp. 871-887, Mar. 2008.
[8] R. J. Wai, C. Y. Lin, R. Y. Duan, and Y. R. Chang, “High-efficiency DC-DC converter with high voltage gain and reduced switch stress,” IEEE Trans. Industrial Electronics, vol. 54, no. 1, pp. 354–364, Feb. 2007.
[9] W. Li, J. Liu, J. Wu, and X. He, “Design and analysis of isolated ZVT boost converters for high-efficiency and high-step-up applications”, IEEE Trans. Power Electronics, vol. 22, no. 6, pp. 2363-2374, Nov. 2007.
[10] R. J.Wai and R. Y. Duan, “High step-up converter with coupled-inductor,” IEEE Trans. Power Electronics, vol. 20, no. 5, pp. 1025–1035, Sep. 2005.
[11] Q. Zhao and F. C. Lee, “High-efficiency, high step-up dc–dc converters”, IEEE Trans. Power Electronics, vol. 18, no. 1, pp. 65–73, Jan. 2003.
[12] O. Abutbul, A. Gherlitz, Y. Berkovich, and A. Ioinovici, “Step-up switching-mode converter with high voltage gain using a switched capacitor circuit,” IEEE Trans. Circuit System I, vol. 50, no. 8, pp. 1098–1102, Aug. 2003.
[13] I. Barbi and R. Gules, “Isolated DC-DC converters with high-output voltage for TWTA telecommunication satellite applications”, IEEE Trans. Power Electronics, vol. 18, no. 4, pp. 975-984, Jul. 2003.
[14] L. S. Yang, T. J. Liang, and J. F. Chen, “Transformerless DC–DC converters with high step-up voltage gain,” IEEE Trans. Industrial Electronics, vol. 56, no. 8, pp. 3144–3152, Aug. 2009.
[15] K. C. Tseng and T. J. Liang, “Novel high-efficiency step-up converter,” IEE Proc. Electric Power Applications, vol. 151, no. 2, pp. 182-190, Mar. 2004.
[16] René P. Torrico-Bascopé, Francisco A. A. de Souza, Cícero M. T. Cruz, Luiz H. C. Barreto, Grover V. Torrico-Bascopé, and Carlos G. C. Branco, “A new isolated DC-DC Boost converter using three-state switching cell,” IEEE APEC, pp. 607-613, Feb. 2008.
[17] J. M. Kwon and B. H. Kwon, “High step-up active-clamp converter with input-current doubler and output-voltage doubler for fuel cell power systems”, IEEE Trans. Power Electronics, vol. 24, no. 1, pp. 108-115, Jan. 2009.
[18] J. J. Lee, J. M. Kwon, E. H. Kim, and B. H. Kwon, “Dual series-resonant active-clamp converter”, IEEE Trans. Industrial Electronics, vol. 55, no. 2, pp. 699–710, Feb. 2008.
[19] T. S. Kim, S. K. Han, G. W. Moon, and M. J. Youn, “High efficiency active clamp forward converter for sustaining power module of plasma display panel”, IEEE Trans. Industrial Electronics, vol. 55, no. 4, pp. 1874-1876, Apr. 2008.
[20] S. S. Lee, S. W. Choi, and G. W. Moon, “High-efficiency active-clamp forward converter with transient current build-up (TCB) ZVS technique”, IEEE Trans. Industrial Electronics, vol. 54, no. 1, pp. 310-318, Feb. 2007.
[21] Y. K. Lo and J. Y. Lin, “Active-clamping ZVS flyback converter employing two transformers,” IEEE Trans. Power Electronics, Vol. 54, no. 4, pp. 2416-2423, Nov. 2007.
[22] Y. K. Lo, T. S. Kao, and J. Y. Lin, “Analysis and design of an interleaved active clamping forward converter,” IEEE Trans. Industrial Electronics, Vol. 54, no. 4, pp. 2323-2332, Aug. 2007.
[23] B. R. Lin and F. Y. Hsieh, “Soft-switching zeta–flyback converter with a buck-boost type of active clamp”, IEEE Trans. Industrial Electronics, Vol. 54, no. 5, pp. 2813–2822, Oct. 2007.
[24] S. S. Lee, S. W. Choi and G. W. Moon, “High-efficiency active-clamp forward converter with transient current build-up (TCB) ZVS technique”, IEEE Trans. Industrial Electronics, vol. 54, pp. 310-318, Feb. 2007.
[25] V. Tuomainen and J. Kyyrä, “Effect of resonant transition on efficiency of forward converter with active clamp and self-driven SRs,” IEEE Trans. Power Electronics, vol. 20, no. 2, pp. 315-323, Mar. 2005.
[26] Q. M. Li and F. C. Lee, “Design consideration of the active-clamp forward converter with current mode control during large-signal transient”, IEEE Trans. Power Electronics, vol. 18, pp. 958-965, Jul. 2003.
[27] K. W. Lee, S. W. Choi, B. H. Lee, and G. W. Moon, “Current boosted active clamp forward converter without output filter,” IEEE ECCE, pp. 2873-2880, Sep. 2009.
[28] H. Huang, “Design guidelines on the effect of resonant transitions of forward converter on efficiency with active clamp,” IEEE APEC, pp. 600-606, Feb. 2008.
[29] P. Alou, A. Bakkali, I. Barbero, J. A. Cobos, and M. Rascon, “A low power topology derived from flyback with active clamp based on a very simple transformer,” IEEE APEC, pp. 627-632, Mar. 2006.
[30] Y. Wen, H. Mao, and I. Batarseh, “DC bias anaIysis and small-signal characteristic of active-clamp forward-flyback DC-DC converter with a current doubIer rectifier,” IEEE APEC, pp. 1531-1536, Mar. 2005.
[31] R. Watson, F. C. Lee, and G. C. Hua, “Utilization of an active-clamp circuit to achieve soft switching in flyback converters,” IEEE Trans. Power Electronics, vol. 11, no. 1, pp. 162-169, Jan. 1996.
[32] UCC2893 Datasheet, Texas Instrument, 2009.