應用新穎的電流均衡電路於LED照明

Applying a Novel Current Balancing Circuit to LED Lighting

周勝千(Sheng-Chien Chou)

指導教授 ： 胡國英

國立臺北科技大學/電資學院/電機工程系所/碩士(2009年)

摘要

本論文提出一個應用於LED strings並聯之電流平衡電路。由於近來大量LED照明被用來取代白熾燈泡及鹵素燈泡且應用層面擴大到路燈照明，單純的LED串聯驅動方式已經不敷使用，LED串聯後並聯使用已經成為趨勢，LED特性是亮度與驅動電流成正比且極小的電壓變化會造成電流的極大變化，故目前驅動方式的發展為採用定電流驅動。由於考量效率高及體積小之需求，故採用電力電子電路進行電能轉換是必然的趨勢，然而目前的LED並聯驅動方式是採用每一串聯路徑單獨進行定電流控制其電路架構複雜且成本高。然而採用本論文所提之驅動電路具有特點如：(i)架構簡單；(ii)可適用於多種電路架構，降壓式轉換器、前向式轉換器、共振式轉換器等；(iii)擴充容易可同時進行多路電流平衡控制；(iv)前端為一個降壓型轉換器用以提供LED所須之電流，後端採用本論文所提之電流平衡電路用以作為平衡LED電流。
最後，藉由數學推導與軟體驗證所提架構之可行性；並藉由實驗進一步驗證此架構之有效性。

關鍵字

電流平衡電路LED strings ； 白幟燈泡 ； 鹵素燈泡

並列摘要

In this paper, a current balancing cicuit is presented and applied to driving paralleled light-emitting diode (LED) strings. As generally acknowledged, LEDs are getting more and more popular instead of incandescent lamps, halogen light bulbs and street lights. Therefore, a single LED string does not provide enough illumination, and hence paralleled LED strings are indispensable. There are some features of the LED given as follows: (i) LED illumination is proportional to the driving current; and (ii) slight variations in voltage on the LED cause significant variations in current in the LED. Based on the mention above, the constant current control has been widely used to drive the LED up to now. Concerning the high efficiency and small volume of the LED product, it is indispensable for using the power electronics circuit to tackle energy conversion. However, up to the present the paralleled LED strings are driven based on the fact that each LED string is independently controlled, thereby causing the corresponding circuit to be complicated and the resulting cost to be high. Consequently, the proposed LED driving circuit is presented herein and has the following features: (i) it is simple in structure; (ii) it is suitable for different types of converters, such as buck converter, forward converter, resonant converter, etc.; (iii) there are two stages in such a LED driving circuit, one is a front-ended buck converter to provide a constant current for LED strings, and the other is a current balancing circuit to balance current among LED strings; and (iv) it has easy expansion by modifying the current balancing circuit. In this paper, mathematical derivation and software simulation are used to verify the feasibility of the proposed topology whereas some experimental results are provided to further demonstrate its effectiveness.

並列關鍵字

LED String ； Current Balancing Circuit

參考文獻

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