Adjustable Forward Voltage Technique in LED Driver for High Efficiency
|摘要:||近幾年發光二極體(LED)被廣泛使用於各項產品，例如電視、手機、NB、平板電腦等。使用LED當作背光板主要的優點有下列幾項：第一項，較節省電，比CCFL背光更省百分之四十的能源。第二項，較環保，LED背光板不含汞，比較不會造成環境污染。第三項，LED背光板有較佳的色彩飽和度能夠展現較佳的色彩表現。第四項，LED有較長使用壽命。第五項，LED背光板較輕薄，這項特點剛好與市場上消費者所需要的相符合。本篇論文提出的可調式順向電壓技術之高效率LED驅動器適合應用於在LED背光板上。這個LED驅動器使用定電流源的整流器提供LED一個穩定電流，避免了色偏現象，因為LED 的順向偏壓會隨製造與時間不同而變化，所以驅動器使用可調式順向電壓技術來克服這個問題，然後使用參考電壓追綜電路來避免脈衝電流的發生。本論文使用TSMC 0.6 um BCD製程技術來模擬。|
In recent year, light emitting diodes (LEDs) are widely used for display of various products, such as television, cellular phones, NB, tablet computer, etc. The advantages of LED backlight liquid are listed below. Firstly, it is more energy saving. LED backlight products save 40% energy, comparing with products with CCFL backlight in civilian industry. LED backlight technology, LED backlight display will be more energy saving in the future. Secondly, it is green and environment-friendly. Mercury in CCFL backlight is considerable damage to the environment, but LED backlight does not contain it. If LED backlight displays are popular in the future, it will be very helpful to improve the global environment. Thirdly, it has a wider color gamut. LED backlight module has a more pure white light and a wider color gamut, comparing with conventional CCFL backlight module. LED backlight display can display more vivid color and make a better color representation.Fourthly, it has a longer serving time. Theoretically, LED backlight has a long serving time and a longer brightness decreasing cycle, comparing with CCFL backlight. And it still can extend the serving time with the development of the technology. Fifthly, it is lighter and thinner. LED backlight products are much lighter and thinner than CCFL backlight products. The selling point of LED backlight displays in the market is ultra-thin which meets the fashion needs of consumers. This thesis proposes a LED driver with adjustable forward voltage technique in LED driver for High efficiency, and it was suitable for the LED backlight. This LED driver utilized a constant current regulator to support the LED string a stable current without color shift and a PWM dimming circuit to adjust the illuminate. Because the LED forward voltage variation occurred by time and manufacture, this driver utilized an adjustable forward voltage to overcome this problem. Then use a reference voltage tracking circuit with soft start to avoid the inrushing current issue. This LED driver circuit was simulated by TSMC 0.6um BCD 40 V process.
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