在發光二極體(Light-emitting diode, LED)照明系統中，傳統直流調光模式的效率差，所以現今LED照明系統中採用脈波寬度調變(Pulse Width Modulation, PWM)來控制LED驅動器，透過PWM控制使平均電流的大小隨著導通時間改變，此驅動方法在能改變LED亮度的同時也保持了LED色彩品質，但是隨著LED順向電流上升，發光效率會減小。
本文研製一高效率雙匯流排調光電路(Twin bus dimmer circuit)，根據雙匯流排電路開關電壓低應力的特性，分析雙匯流排電路的兩電壓源並選出適合的電壓源數值，以達到更好的效率。另外雙輸出返馳式轉換器藉由一組回授電路並靠著軟體控制的方式使雙輸出電壓能有最小的電壓誤差，並分析雙輸出返馳式轉換器之電壓調節率(Cross Regulation)之模型。
本文提出之LED驅動器包含功率因數修正器以及數位控制之雙輸出返馳式轉換器和雙匯流排調光電路。由實驗結果顯示，功率因數修正器之最高效率達96.8 %，功率因數可達0.998 ; 雙輸出返馳式轉換器之最高效率達93.6%，輸出電壓調節率小於5%; 調光電路各通道皆可達均流效果，電路最高效率達98.6%。整體平均效率為88.9%，並且雙匯流排調光相較於PWM調光有更佳的效率和調光線性度。

In light-emitting diode (LED) lighting systems, the efficiency of the traditional DC dimming mode is poor, so pulse width modulation (PWM) is used to control the LED driver. Through PWM control, the average current varies with the on-time. This driving method can change the brightness of the LED while maintaining the color quality of the LED. However, as the forward current of the LED increases, the luminous efficiency will decrease.
This paper develops a high-efficiency twin bus dimmer circuit. According to the characteristics of the low stress of the switching voltage of the twin bus dimmer circuit, the two voltage sources of the twin bus dimmer circuit are analyzed and the value of the voltage source is selected to achieve better efficiency. In addition, the dual output flyback converter uses a set of feedback circuits and relies on software control to make the dual output voltage have the smallest voltage error, and analyzes the model of the cross regulation of the dual output flyback converter.
The LED driver proposed in this paper includes a power factor correction, a digitally controlled dual output flyback converter, and a twin bus dimming circuit. The experimental results show that the maximum efficiency of the power factor correction reaches 96.8%, and the power factor can reach 0.998; the maximum efficiency of the dual-output flyback converter reaches 93.6%, and the cross regulation is less than 5% ;the highest circuit efficiency reaches 98.6%. The overall average efficiency is 88.9%, and the twin bus dimmer has better efficiency and dimming linearity than PWM dimming.

[1] C. Michael Bourget, "An Introduction to Light-emitting Diodes", HortScience horts, 43(7), pp. 1944-1946, Dec, 2008.
[2] Mary Yamada, Julie Penning, Seth Schober, Kyung Lee, and Clay Elliott, Energy Savings Forecast of Solid-State Lighting in General Illumination Application, U.S. Department of Energy, Dec, 2019.
[3] Chuanwen Ji, M. Smith, K. M. Smedley and K. King, "Cross regulation in flyback converters: analytic model and solution," in IEEE Transactions on Power Electronics, vol. 16, no. 2, pp. 231-239, March 2001.
[4] Q. Chen, F. C. Lee and M. M. Jovanovic, "Analysis and design of weighted voltage-mode control for a multiple-output forward converter," Proceedings Eighth Annual Applied Power Electronics Conference and Exposition, pp. 449-455, 1993.
[5] R. Y. -W. Chan, J. W. Hill and D. D. -C. Lu, "Time Multiplexing Control for Power Converters," 2007 2nd IEEE Conference on Industrial Electronics and Applications, pp. 126-131, 2007.
[6] Dongsheng Ma, Wing-Hung Ki, Chi-Ying Tsui and P. K. T. Mok, "Single-inductor multiple-output switching converters with time-multiplexing control in discontinuous conduction mode," in IEEE Journal of Solid-State Circuits, vol. 38, no. 1, pp. 89-100, Jan. 2003.
[7] J. Liu, T. Wei and N. Chen, "A new pulse width modulation-based digital control for single-inductor multi-output DC–DC converters with low cross-regulation," 2020 IEEE 9th International Power Electronics and Motion Control Conference (IPEMC2020-ECCE Asia), pp. 2605-2609, 2020.
[8] L. Chen, L. Xu, L. Zhang, Y. Huang and Y. Wang, "Cross Regulation Analysis of Voltage-Mode Controlled SIDO Buck LED Driver," 2021 IEEE 16th Conference on Industrial Electronics and Applications (ICIEA), 2021.
[9] H. -J. Wang and L. -R. Chang-Chien, "Low cross regulation voltage-mode controlled single-inductor dual-outputs (SIDO) voltage regulator," 2013 1st International Future Energy Electronics Conference (IFEEC), pp. 149-154, 2013.
[10] B. Wang, V. R. K. Kanamarlapudi, L. Xian, X. Peng, K. T. Tan and P. L. So, "Model Predictive Voltage Control for Single-Inductor Multiple-Output DC–DC Converter With Reduced Cross Regulation," in IEEE Transactions on Industrial Electronics, vol. 63, no. 7, pp. 4187-4197, July 2016.
[11] K. Modepalli and L. Parsa, "A Scalable N-Color LED Driver Using Single Inductor Multiple Current Output Topology," in IEEE Transactions on Power Electronics, vol. 31, no. 5, pp. 3773-3783, May 2016.
[12] Leng, C.-M.; Chiu, H.-J. Three-Output Flyback Converter with Synchronous Rectification for Improving Cross-Regulation and Efficiency. Electronics 10, 430, 2021.
[13] T. Anitha and S. Arulselvi, "Study of cross-regulation and intelligent control of a flyback quasi resonant converter," 2009 4th IEEE Conference on Industrial Electronics and Applications, pp. 2014-2019, 2009.
[14] M. Tahan and T. Hu, "Multiple String LED Driver With Flexible and High-Performance PWM Dimming Control," in IEEE Transactions on Power Electronics, vol. 32, no. 12, pp. 9293-9306, Dec. 2017.
[15] Ho, K.-C.; Wang, S.-C.; Liu, Y.-H. Dimming Techniques Focusing on the Improvement in Luminous Efficiency for High-Brightness LEDs. Electronics 2021, 10, 2163.
[16] Q. Wang, T. Li and Q. -H. He, "Dimmable and Cost-Effective DC Driving Technique for Flicker Mitigation in LED Lighting," in Journal of Display Technology, vol. 10, no. 9, pp. 766-774, Sept. 2014.
[17] W. -H. Yang, H. -A. Yang, C. -J. Huang, K. -H. Chen and Y. -H. Lin, "A High-Efficiency Single-Inductor Multiple-Output Buck-Type LED Driver With Average Current Correction Technique," in IEEE Transactions on Power Electronics, vol. 33, no. 4, pp. 3375-3385, April 2018.
[18] Y. Wang, X. Wu, Y. Hou, P. Cheng, Y. Liang and L. Li, "Full-Range LED Dimming Driver With Ultrahigh Frequency PWM Shunt Dimming Control," in IEEE Access, vol. 8, pp. 79695-79707, 2020.
[19] Lin, Yu‐Liang & Leng, Chung‐Ming & Wang, Jian‐Min. (2015). A simple LED driver with low dimming switch stress: A Simple LED Driver with Low Dimming Switch Stress. International Journal of Circuit Theory and Applications. 44. 10.1002/cta.2100.
[20] W. Yu, J. -S. Lai, H. Ma and C. Zheng, "High-Efficiency DC–DC Converter With Twin Bus for Dimmable LED Lighting," in IEEE Transactions on Power Electronics, vol. 26, no. 8, pp. 2095-2100, Aug. 2011.
[21] 陳聰暉，「使用雙匯流排調光技術之高效率LED驅動器研製」，國立台灣科技大學電機工程系碩士學位論文，民國 110 年 7 月。
[22] K. I. Hwu, W. Z. Jiang and C. W. Hsiao, "Dimmable LED Driver Based on Twin-Bus Converter and Differential-Mode Transformer," in Journal of Display Technology, vol. 12, no. 10, pp. 1122-1129, Oct. 2016.
[23] A. Sarkar, N. Deshmukh and S. Anand, "Modified PWM Scheme to Reduce Reverse Conduction Loss in GaN-Based Independently Controlled Multiple Output Flyback Converter," in IEEE Transactions on Power Electronics, vol. 37, no. 11, pp. 12968-12972, Nov. 2022.
[24] Texas Instruments Inc, UC3854 datasheet, 1999.
[25] 黃俊瑋，「高頻準諧振返馳式電源轉換器研製」。國立臺灣科技大 學電子工程系碩士學位論文，2019。
[26] Cree Inc, XLamp CXA2540 LED datasheet, 2018.
[27] ON Semiconductor Multi-Output Flyback Off-Line Power Supply，網址: https://www.onsemi.com/pub/Collateral/TND351-D.PDF
[28] 群燿光學股份有限公司，「全方位手持式分光光譜計」， 網址: https://www.uprtek.com/zh-TW/product/lighting-measurement-system-handheld-spectrometer/mk350s-advanced-spectrometer