Abstract: The specific application of LED backlight instead of CCFL backlight is introduced. Through the description of CCFL backlight features. Furthermore, the actual scheme of the LED backlight and the technical effects achieved are described. And through the design and production of a 47in LED backlight . A detailed explanation is given. The test results show a central brightness of 11,230 nits, an overall power consumption of 178 W, a uniformity of 96.26%, and a color reproduction of 128.15% of the NTSC standard. It far exceeds 70% of CCFL backlights.

Introduction

The liquid crystal display is mainly composed of an LCD (liquid crystal panel) and a backlight. Since the LCD itself does not emit light, the LCD needs to be transmitted or reflected by an external light source. Most of the existing LCDs are transmissive devices with backlights. The illumination characteristics of the backlights directly affect the picture quality of the LCD display devices. Therefore, the backlight is a very important component of the liquid crystal display.

The low-cost, mature CCFL (Cold Cathode Light Tube) is still the main source of backlight for existing liquid crystal display devices. However, LED (Light Emitting Diode) is becoming more and more widely used as a display device. Especially in the situation where the function of LCD TV is getting stronger and the structure is more and more beautiful, LED is applied to various parts of LCD TV. Rapid update, high brightness, high quality and versatility are the main goals of the new products.

LED backlights can be roughly classified into direct type and side light type. The direct type is to design LED lights on the entire back of the liquid crystal display: the side light type is to design LED lights on the edge of the liquid crystal display. In general, a direct-lit backlight is used in a large-size LCD TV of 30 in. or more, and an edge-lit backlight is available below 30 in.

The direct-lit LED backlight designed in this paper, with a size of 47in, covers the backlight structure and circuit design, including the design of the arrangement of LED lights, which are based on the circuit board. At the same time, the size, shape, and component arrangement of the board are determined according to the structure of the backlight. After installing the board, cover the required optical film and install various components to assemble a complete backlight.

1 Comparative analysis with CCFL technology

1.1 Features of CCFL

The CCFL is a sealed glass tube filled with an inert gas. When a high voltage is applied to the tube, the gas ionizes to generate ultraviolet (UV) light, and the UV light excites the internal phosphor coating to generate visible light.

CCFL features white light source, low cost, long life (greater than 25,000 hours), high voltage drive, and contain toxic gas mercury.

At present, CCFL as the backlight is the mainstream of LCD TVs. However, CCFL has an essential shortcoming, that is, the color gamut that can be achieved (that is, the color performance range of the TV) is small, and the ordinary CCFL can only reach 72% of the NTSC (National Television System Committee) gamut standard, and it The toxic gas containing mercury does not meet the requirements of green environmental protection.

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