應用於液晶顯示器背光之發光二極體驅動與均流控制電路之設計

Abstract

由於發光二極體各項應用起飛，包括大型看板、車用發光二極體與背光源使用逐年提高，照明商機逐漸提高。特別是在NB面板方面，就光源成本來看，雖然發光二極體約為CCFL的2.5倍，總成本約高出70%，但採用發光二極體背光源優點為: 省電，將提升NB約40~60分鐘使用時間 ; 輕薄，背光模組約可節省一半厚度 ; 重量較輕 ; 色彩飽和度較佳。 液晶顯示技術往液晶電視快速發展的契機受限於數位顯示技術發展，而在液晶電視尺寸大型化後，必須在成本上降低，才能夠與傳統電視以及電漿電視相競爭。並且，液晶顯示技術本身為一種非自發光型的顯示技術，需依賴著背光源才能夠把影像顯示出來，在面板的應用上，背光源通常需要大量的發光二極體來提供光源，因此若能有效率佳且負載能力好之驅動電路則將可降低系統成本。 本篇論文中提出應用於液晶顯示器背光之發光二極體驅動與均流控制電路之設計，其輸入電壓為12V，而輸出電壓為40V。其中回授控制電路以脈波寬度調變之方式實現，並擁有根據發光二極體順向電壓改變的回授機制，使此電路能夠提供更高的可靠度，供發光二極體作為背光源使用。另外由於考量發光二極體作為背光源所需要的電流匹配度，均流控制電路也一併於本論文中提出。本論文之設計使用VIS 0.5um嵌入高壓5V/40V 2P3M CMOS製程技術進模擬與製作。

The commercial possibilities of the LED are increasing gradually since the applications of light-emitting diode are more and more prevalent in large scanning boards, vehicle-used light-emitting systems and backlighting-used display systems. Considering the cost of light source in the panel of notebook computer, the cost of light-emitting diode is 2.5 times than that of the cold cathode fluorescent lamp (CCFL). That is, it costs more than 70% of the original design. However, there are some important advantages by means of LED as a backlight module. Especially, energy saving improves the battery lifetime longer than 40% of the original design by means of CFFL backlight module. The LED backlight module can reduce the thickness of panel module. Thus, the weight is light and the color saturation is better than before. The impeding of liquid crystal display technique expending to the liquid crystal television is the developing of the digital display technique. After scaling up the size of the liquid crystal television, it should lower the cost to compete with the conventional television and plasma television. Besides, the liquid crystal display is a non-self-luminous technique and thus it leans on the backlight source to display the image. In the applications of the LCD panel, the backlight source usually needs large amount of light-emitting diodes to provide enough brightness. Therefore, if the driver circuit has high efficiency and good driving capability, the cost of the LED system can be reduced. This thesis proposes a LED driver with current Balance control circuit for the backlight of LCD display. This driver circuit design was simulated and fabricated in VIS 0.5□m embedded high voltage 5V/40V CMOS technology. The input voltage is 12V and the output voltage is 40V. The boost voltage regulator uses a pulse width modulation (PWM) and a reference tracking circuit according to the variation of forward voltage of LEDs. The advantage of the proposed method is to offer high reliability to the LED backlight system.