全橋相移諧振式冷陰極燈管驅動電路之設計與分析

Design and Analysis of Phase-Shift Full-Bridge Quasi-Resonant Inverter for Cold-Cathode Fluorescent Lamps Driver

周威任(Wei-Jen Chou)

指導教授 ： 涂世雄 ； 涂世雄

中原大學/工學院/電機工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400118

摘要

摘要
近幾年來，隨著TFT-LCD面板技術的提升，使得其應用的範圍越來越廣泛，特別是桌上型電腦顯示器及平面多媒體電視的應用。面板的尺寸也越來越大，為了達到高亮度的表現，其背光源的冷陰極燈管數也愈來愈多，因此多燈管的驅動控制，驅動電路的效率及散熱，電路的信賴性，燈管的發光效率及壽命的維持都面臨考驗。
本篇論文中，我們使用全橋相移諧振式冷陰極燈管驅動電路配合簡單的多燈管電流平衡電路來驅動多組燈管的背光源。我們設計的驅動電路具有以下特色：
1. 提供一個單級高效率的驅動電路。
2. 提供一個簡單的燈管電流平衡電路來降低不同燈管間電流的差異。
3. 輸出近似弦波且對稱波形的電壓與電流來驅動冷陰極燈管，以提高燈管的發光效率及壽命。
4. 提供一個低成本的設計。
相信本篇論文的研究結果，將對大尺寸多燈管的背光電源驅動電路設計會有相當大的助益。

關鍵字

全橋相移諧振式電源轉換器 ； 冷陰極燈管

並列摘要

Abstract

In this thesis, a quasi-resonant inverter with high efficiency, low cost and simplified circuit scheme for the multiple cold cathode fluorescent lamps as the TFT-LCD backlight is presented. The proposed topology is phase-shift full-bridge quasi-resonant inverter. The design example is also presented.
The proposed inverter is a one-stage phase-shift full-bridge quasi-resonant DC-AC power converter compared with the conventional two-stage current-fed push-pull DC-AC power converter and the component count can be reduced. The high efficiency of zero-voltage switching (ZVS) and zero-current switching (ZCS) technique is also provided to eliminate the switching losses of the power MOSFETs over the whole dimming range. A phase-shift modulation between the switches is optimized to regulate the CCFL power, and then the switching frequency and the switching duty cycle of the switches can be fixed at steady state.
The design of secondary resonant tank circuit determines the resonant frequency and operating frequency. A sweeping frequency technique can be used to ignite the CCFLs by accounting for the parasitic capacitance and leakage inductance in the resonant tank circuit. The resonant tank also acts as a low-pass or band-pass filter after the CCFL is ignited, then the preferred sinusoidal operating voltage and current waveform can be provided to increase the lifetime and luminance of CCFLs.
Additionally, for multiple CCFLs, a simplified resonant current balance circuit scheme is proposed for the single control loop DC-AC power inverter to reduce the total component count.
Finally, a prototype circuit for 4 cold cathode fluorescent lamps is built and tested to verify the analytical prediction.
The chief results of our work are shown below. (1) The single stage resonant inverter operates with high efficiency, and the thermal issue will be solved easily. (2) The current between multiple cold cathode fluorescent lamps can be balanced easily by the simplified resonant current balance circuit. (3) Sinusoidal and symmetric current and voltage waveforms are provided for the fluorescent lamps to increase its lifetime and luminance. (4) A low cost solution for multiple lamps backlight driver is proposed.

並列關鍵字

Cold Cathode Fluorescent Lamps ； Phase-Shift Full-Bridge

參考文獻

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