具高功因修正之自激式單級LED驅動電路探討

Investigation of A Self-Excited Single-Stage LED Driver with High Power Factor Correction.

邱思哲(Sse-Che Chiu)

指導教授 ： 張永農

共同指導教授 ： 詹舜宇

國立虎尾科技大學/電機資訊學院/電機工程研究所/碩士(2015年)

摘要

本論文提出利用自激觸發方式控制切換式轉換器作為LED驅動電路切換控制使用。其中切換式轉換器為單級架構，結合主動式功率因數修正(APFC)與諧振轉換器，達到輸入高功因與直流輸出作為LED驅動電路之效能。本論文使用之自激觸發方式為在諧振電路中加入一個自激式觸發之變壓器，其具有易飽和之特性。在製作電路時可利用變壓器飽和之特性作為BJT功率開關之切換頻率操作與導通週期控制，達到節省電路之成本，增加其競爭力。利用單級架構既可達到節省元件的使用且能降低功率開關的切換損失，達到低成本、高效率之特色。而在單級架構下兩BJT功率開關之導通電流大小不一致時，將影響其導通週期不相等之特性，因此本文利用一簡單之測試平台，設計出控制變壓器飽和之特性使功率開關導通週期與頻率達到最佳化之目的。本論文使用LC半橋諧振電路，利用其諧振電流經過作為自激式觸發源，可達到較穩定之自激觸發訊號且能使BJT功率開關達到軟切換之優點，降低電路損耗達到高效率之性能。本文實際製作一28瓦具高功率因數與功率開關達到軟切換之自激式觸發之LED驅動電路，其功因達0.989與效率到82.3%之效能。

關鍵字

自激式觸發 ； LED驅動電路 ； 單級架構 ； 主動式功率因數修正 ； 諧振轉換器

並列摘要

This paper proposes an LED drive circuit using self-excited trigger switching control. The switching converter, therein, makes use of a single-stage structure, in combination with automatic power factor corrector (APFC) and resonant converter, to achieve a dc output voltage for driving LED with high efficiency. The self-excited mechanism is accomplished by introducing a transformer within the resonant circuit to trigger the BJT power switches. By utilizing the saturation characteristics of self-excited transformer, the switching frequency and duty cycle of the power BJT can be controlled accordingly, thus reducing the circuit cost and enhancing the competitiveness. Also, the employment of the single-stage mechanism can both curtail the amount of component and lower the switching loss of power switches. Therefore, the lost cost and high-efficiency advantages can be achieved. However, for overcoming the unequal conduction time of two BJTs in the single-stage circuit arising from uneven conduction current in between, a simple test platform is developed to optimize the duty cycle and switching frequency of power switches by controlling the saturation of transformer. In this paper, the LC type half-bridge resonant circuit is used and the resonant current within is served as the triggering signal source. It can offer a more stable self-excited trigger signal source and, thereby, provide the BJTs with soft switching advantage by the reduction of switching loss. In the end, a simple and low-cost 28W prototype self-excited LED drive circuit with soft-switching feature and high power-factor will be realized and implemented. Expectedly, the power-factor will be as high as 0.99 and the operating efficiency will reach 82.3%.

並列關鍵字

self-excited trigger ； LED drive circuit ； single-stage topology ； automatic power factor correction ； resonant converter

參考文獻

[31] 黃登群，2014， “單級高功因全橋諧振式LED驅動電路研製”， 國立虎尾科技大學電機工程系碩士論文，7月。

[20] 鄭榮霈，2007， “具定電流控制與無燈管保護電路之自激式全橋電子安定器”， 國立成功大學電機工程學系碩士論文，7月。

[11] Y. T. Hsieh, B. D. Liu, J. F. Wu, C. L. Fang, H. H. Tsai and Y. Z. Juang, 2012, “A High-Dimming-Ratio LED Driver for LCD Backlights”, IEEE Transactions on Power Electronics, Vol. 27, No. 11, pp.4562-4570, November.

[3] C. Y. Chen, T. H. Yang, C. H. Hsu, C. C. Sun, 2013, “High-Efficiency White LED Packaging with Reduced Phosphor Concentration”, IEEE Photonics Technology Letters, Vol. 25, No. 7, pp. 694-696, April.

[4] L. Yuan,S. Liu, M. Chen, X. Luo, 2006, “Thermal Analysis of High Power LED Array Packaging with Microchannel Cooler”, International Conference on Electronic Packaging Technology, pp. 1-5, April.