What Is LED Backlighting?

LED backlight refers to the use of LED (light-emitting diode) as the backlight source of the liquid crystal display. Compared with the traditional CCFL (cold-cathode tube) backlight, LED has the characteristics of low power consumption, low heat generation, high brightness, long life and so on. It is expected to completely replace the traditional backlight system in recent years.

LED backlight

Backlit Chinese characters are interpreted as "light cannot be directly irradiated" or "direct light to avoid light".

In the electronics industry, backlighting is a form of lighting often used in LCD displays. The difference between the backlight type and the front light type is that the backlight is illuminated from the side or the back, and the front light is illuminated from the front as the name implies. They are used to increase the brightness in low-light environments and the brightness of computer monitors and LCD screens to produce light in a manner similar to CRT displays.

Its light source may be an incandescent light bulb, an electro-optic panel (ELP),

The main structure of LED backlight

LED backlight refers to the use of LED (light emitting diode) as the backlight source of the liquid crystal display, and the LED backlight display is only the backlight source of the liquid crystal display from the traditional CCFL cold light tube (similar to fluorescent lamps) to LED (light emitting diode). The imaging principle of liquid crystal can be simply understood as the application of external voltage to deflect liquid crystal molecules like a gate to block the transparency of the light emitted by the backlight, and then project the light into color filters of different colors to form an image.

LED display is a combination of microelectronic technology, computer technology and information processing. With its colorful, wide dynamic range, high brightness, long life, stable and reliable work, LED display has become the most advantageous public display media. LED display It has been widely used in large squares, commercials, stadiums, information dissemination, news releases, securities trading, etc., which can meet the needs of different environments. An LED display is a display method by controlling a semiconductor light emitting diode. Its approximate appearance is composed of a plurality of usually red light emitting diodes, and the characters are displayed by the light on and off. Display screen for displaying various information such as text, graphics, images, animations, quotes, videos, video signals, etc.

OLED displays are self-luminous, do not require backlight, high contrast, thin thickness, wide viewing angle, fast response speed, can be used for flexible panels, wide temperature range, simple structure and manufacturing process, etc. It is considered to be the emerging application technology of next-generation flat panel displays.

Many netizens easily associate OLEDs with LED backlights that are more hyped by manufacturers. In fact, OLEDs and LED backlights are completely different display technologies. The OLED emits light by driving the organic thin film by electric current. The light emitted can be monochromatic colors such as red, green, blue, and white, and can also achieve the effect of full color. So OLED is a new light-emitting principle different from CRT, LED and liquid crystal technology.

In general, LED displays, LED backlights, and OLEDs are three completely different imaging technologies.

The latest survey data from the Consumer Electronics Product Survey Office of the China Electronics Chamber of Commerce shows that consumers have already paid 75% attention to LED LCD TV products, ranking first in the list. In particular, LGD s 240HZ Straight LED Backlight technology has injected a heartbeat into the LED LCD TV industry, making consumers eager. So, what kind of cutting-edge quality and charm do LED LCD TVs have to gain such a strong development momentum? According to the data of Zhongyikang's sample survey of consumers in 22 provinces across the country, more than 70% of consumers choose LED LCDs. The TV thinks that it looks stylish, thin and light, which is more in line with modern home style. Indeed, the ultra-thin appearance of LED LCD TVs has challenged the limits of people's awareness of "thinness" and fully meets consumer demand for personalized products. For example, LG s new direct-lit LED LCD TV is the thinnest at 24.8mm, while traditional LCD TVs are technically difficult to cross and it is difficult to achieve such an ultra-thin design. In addition to its thin and light appearance, LED-backlit LCD TVs have also made a qualitative leap in terms of picture performance. Especially LGDisplay's flagship

The brightness of the LED backlight is high, and the brightness does not decrease for a long time. The body of the LED backlight is thinner and the appearance is beautiful.

LED backlight, soft color, with the color of the hard screen panel can make the eyes more comfortable.

Another advantage is that all LED backlights have low power consumption and environmental protection.

* Automotive: Backlight indication of car DVD button and switch

* Communication equipment: mobile phone, telephone, fax machine key backlight

* Indoor signboard

* Handheld device: Signal indication

* Mobile phone: key backlight indication, flashlight

* Small and medium size LCM: backlight

* PDA: Key backlight indication

Designers must strike a balance between system requirements, power sources, and circuit architecture before selecting the appropriate LED drive circuit structure. Therefore, the designer must weigh the available budget against the final product.
In addition, size and height impose another technical limitation. Only high-frequency charge pumps and inductive DC / DC boost solutions can use smaller external components. In particular, a charge pump-based LED drive circuit, because charge pumps and parallel LED power supplies require very small external capacitors, will use parallel LED power supplies to reduce the size of external components. Whether to reduce the external component size of a charge pump or an inductive solution, the main consideration is

Since 2008, LED backlight has gradually entered the industrialization, and its market share has been expanding. Since its application in notebook computers, in 2012, it has been used in displays and LCD TVs. LED backlight products have continued to emerge and the market share has continued to increase.

The maturity and popularity of LED technology will become a new driving force for the growth of the LCD industry. "From the consumer level, it will create new selling points and applications for LCD displays, which will stimulate consumer demand; from the producer level, it will promote the technological upgrade and industrial transformation with LEDs, and continue to attract talent and capital investment. Du Guanglei believes.

Compared with cold cathode lamp, LED has many advantages. The first is energy saving. The photoelectric efficiency of cold-cathode lamps is around 60lm / W, and the current commercial LED efficiency has reached twice this value, and samples in the laboratory can be doubled. Secondly, LED will bring great changes in the mechanical structure design of the backlight. Because the LED is small in size and has good light directivity, the thickness of the light guide plate in the traditional backlight can be greatly reduced, or the light guide plate can be eliminated.

In addition, mercury in cold-cathode lamps is a substance that is costly and harmful to the environment. From an environmental perspective, the gradual replacement of cold cathode lamps by LEDs will also be an inevitable result.

The application of LED may bring subversive changes to the backlight. "3M started to use the company's core technology platform 5 years ago to develop optical and

Status in 2009:

There are not many domestic upstream LCD supporting factories. If a new LCD production line is established, new upstream supporting factories must be built to ensure the supply of goods and reduce costs. For domestic upstream supporting factories, production and processing are basically the main focus, and they cannot keep up with the international situation and develop new technologies. Like the more popular ultra-thin backlight technology and dynamic backlight technology, domestic backlight manufacturers have almost no new product launches, and new products using these new technologies have been repeatedly used by major international companies (Samsung, LG, etc.).

Domestic LCD panel manufacturing companies should focus on research to improve the transmittance of liquid crystals and reduce energy consumption from the source. LED research and development institutions and manufacturing enterprises should strive to improve the luminous efficiency of LEDs, narrow the gap with the world's advanced level, and catch up with the world level as soon as possible. Otherwise, LED backlights seem to be a big cake, while domestic LED manufacturers

In terms of color expressiveness, LED backlight is also far superior to CCFL. The original CCFL backlight did not perform well in color gradation due to color purity issues. This has led to LCDs not performing as well as CRTs in grayscale and color transitions. LEDs make up for the shortcomings of CCFL backlights in the red spectrum and increase the color saturation of LCD products to levels close to 100%.

Both Sharp and Sony have introduced products using LED backlight technology. It achieves a high contrast ratio comparable to that of a plasma TV, which greatly improves the color reproduction while bringing a thinner and lighter body. It is just that the production of LED is high, and the white LED devices are monopolized by several major manufacturers, and the output cannot be increased, so the price is high.

The direct-type backlight is simple in process and does not require a light guide plate. The LED array is placed at the bottom of the light box, and the light emitted from the LED is reflected by the bottom surface and the side, and then uniformly emitted through the surface diffusion plate and optical module. The thickness of the direct type backlight is determined by the distance between the bottom of the light box and the diffuser plate. Generally, the thicker the thickness, the better the light uniformity of the backlight. In the case of a thin backlight, color and brightness uniformity have become the key to direct-type backlight technology. The type of light field distribution of LED lights plays an important role in the color and brightness uniformity of the backlight source. L ED lamps used in backlight sources usually have two types: Lambertian and edge-emitting. Because edge-emitting LEDs are more beneficial Light uniformity, most of direct-lit backlights use edge-emitting LEDs. However, the large-angle edge-emitting LEDs are liable to cause dark spots due to their low intermediate light intensity, which affects the uniformity of the backlight.

The edge-lit backlight module is to set the point light source on the side of the specially designed light guide plate as the backlight source, using fewer LEDs; and because the light source is placed on the side of the light guide plate, the LED is limited by the number and brightness. When the light is evenly distributed on the entire plane, it will form that when the panel area is larger, the light source light source light source brightness application is more limited. Because the LED backlight is placed on the side of the product, the appearance thickness of the LCD product can be made very thin by simply adding a light guide plate. For example, Sony's ZX1 series uses an edge-lit backlight module.

Generally speaking, there are three main types of LED backlight sources, namely E, CCF and LED. At the same time, it can also be divided according to the distribution position of the light source, and there are edge-lit and bottom-backlit. The following is the classification of LED backlight sources.

Classification of LED backlight source one: edge light type.

That is, a linear or point light source is arranged on the side of a specially designed light guide plate as a backlight source. According to the needs of practical use, it can be made into a bilateral type or even a trilateral type.

1. LED backlight.

LED lights are also called light emitting diodes, and the power consumption of a single LED light is minimal. LED lights come in many colors from blue to red. In various colors, it can be roughly divided into two types: high light and low light. Because white is a mixed color and has no identifiable wavelength value, it is represented by its coordinate value on the chromaticity diagram. We customize it as "cool white" and "warm white". In various colors, there is a problem of color deviation, especially white, and LED suppliers cannot control it effectively.

2. CCFL backlight.

The biggest advantage of this kind of backlight is its high brightness, so it has basically adopted large black and white negative phase, blue mode negative phase and color liquid crystal display devices. In theory, it can make a variety of colors based on the principle of matching the three primary colors. The disadvantage is that the power consumption is large, the inverter circuit needs to be driven, and the operating temperature is narrow, between 0 ~ 60 degrees, and other backlight sources such as LED can reach between -20 ~ 70.

Classification of LED backlight source 2: bottom backlight.

It is a flat surface light source with a certain structure. It can be a continuous and uniform surface light source, such as EL or flat fluorescent lamp. It can also be composed of more point light sources, such as dot matrix LED or incandescent backlight. Commonly used are LED dot matrix and EL backlight.

1. EL backlight. That is, electroluminescence is a cold light source that emits light by the intrinsic emission of phosphors under the excitation of an alternating electric field. Its biggest advantage is that it is thin, and can achieve a thickness of 0.2 ~ 0.6mm. Disadvantages are low brightness, short life (generally 3000 ~ 5000 hours), inverter drive is required, and flicker, noise and other defects will occur due to circuit interference.

2. LED bottom backlight. The advantages are good brightness and good uniformity. The disadvantage is that the thickness is larger (more than 4.0mm), the number of LEDs used is large, and the heating phenomenon is obvious. Generally, low-bright colors are used for design, and high-bright colors are basically not considered due to high costs. WA products are Weizhidi backlight.