LED becomes mainstream? A complete analysis of LED backlight TV technology

What is LED?

Although there are more and more LED TV products, many consumers do not have a particularly clear concept of the "LED TV" that is coming, except that they know that LED TV is a new product and most of them are expensive. Faced with LED TVs that are flooding major electrical appliance stores, what should consumers do? What is the origin of the "LED TV" that is now selling well on the market? Now the editor will take you to the real world of LED TV.

In the strict sense, LED TV refers to a TV that completely uses LED (light-emitting diode) as a display device, which is generally used for low-precision display or outdoor large screen. At present, the strict name of LED TV commonly referred to in the home appliance industry in mainland China is "LED backlight LCD TV", which uses LED light source instead of traditional fluorescent tubes, with better picture quality, longer theoretical life, more environmentally friendly manufacturing process, and can make the LCD display panel thinner.


Samsung LED TV

In order to improve the picture quality of LCD TVs, TV manufacturers have begun to use LED as the backlight source of LCD TVs. Compared with traditional LCD TVs that use fluorescent tubes as backlight sources, LED LCD TVs can display more realistic colors. In addition to improving color saturation, the dynamic adjustment of the picture can dynamically correct the brightness and contrast when displaying different pictures to achieve better picture quality.

How does LED work?

LED stands for "Light Emitting Diode", which is a semiconductor component. Since LED is very sensitive to the passage of electric current, a very small current can make it emit light, and it has a long life and can flash for a long time without damage, so it is widely used as an indicator light in electronic products. The green bean-sized indicator lights that we see on electronic products that can flash quickly are generally made of LEDs.

LED white light bulb

Due to the excellent light-emitting properties of LED, LED components have long been made into direct display devices and are widely used in the lighting field and various large-scale display devices.

Large LED display

In recent years, LED has been gradually introduced into existing flat panel display technology, especially liquid crystal display technology. However, the current application of LED technology in the field of liquid crystal mainly uses LED light-emitting components to replace the previous CCFL fluorescent light source as the backlight source of liquid crystal display devices. So to be precise, the LED TV currently promoted by merchants should be accurately called "LED backlight TV".

What are the main advantages and disadvantages of LED backlight TVs?

Why has LED backlight technology received so much attention? The most important reason is that the LCD using LED backlight technology has significantly improved the color vividness. In the video field, people generally use NTSC as a standard to measure the color reproduction characteristics of video equipment. This indicator refers to the saturation of various colors that the display device can display in the entire color space, that is, the degree of blue, green, and red that can be displayed.

Comparison of LED LCD and ordinary LCD on the same screen at the exhibition

Traditional LCD TVs usually use CCFL as light source, which can only cover 65% to 75% of the NTSC color gamut. However, LED backlight technology can expand the color gamut of LCD TVs to 105% of the NTSC standard, which can basically reproduce most of the natural scenes observed by people.

The thickness of the LED TV is only 1.99cm

Compared with traditional CCFL backlight sources, LED backlight technology has leading advantages, which are mainly reflected in the following aspects.

★ Stronger color gamut performance LED backlight has better color gamut, and its color expression is stronger than CCFL backlight;

★ Longer service life The service life of LED can be up to 100,000 hours, which greatly extends the service life of LCD TV;

★ More energy-saving and environmentally friendly LED light source does not produce any rays, nor does it contain toxic substances such as mercury. It is green and environmentally friendly. At the same time, it has high brightness and can achieve high brightness output with very little power consumption. If the power saved by dynamic backlight control is added, it is also better in energy saving.

★ More beautiful and thin The thickness of traditional LCD TVs is usually about 10cm. The application of LED backlight in TVs has made a qualitative leap in the thickness of the body, which can easily reach half the thickness of traditional flat-panel TVs.

Of course, no one is perfect, and no gold is pure. LED LCD also has its own defects. First of all, the sense of hierarchy is insufficient, and the dark details in dark scenes are not well performed. Secondly, the price is relatively high. Currently, the price of a 46-inch LED TV is usually in the tens of thousands of yuan range, which is more than 20% higher than that of a traditional CCFL backlight TV, so the cost performance is not very high.

LED backlight TV classification

If you want to subdivide LED backlight TVs, there are usually two ways to classify them. According to the color of the light source emitted by the LED, it can be divided into white light LED backlight and RGB-LED backlight. According to the incident position, it can be divided into two categories: direct-down type (the entire back of the display screen is replaced with LED) and side-in type (LED is placed around the periphery).

Direct-type LED backlight LED light-emitting body adopts dot matrix layout, with uniform brightness, high contrast, natural color, high resolution, long service life, and can realize the adjustment of independent light-emitting units through chips, with obvious energy-saving effect. But its disadvantages are thick body, high technical cost and high price.

Direct-type LED TV can be divided into white light LED and RGB three-color LED according to the type of backlight source. White light LED TV can be regarded as an upgraded version of ordinary LCD TV, except that the CCFL backlight source is replaced by LED backlight source. Therefore, this type of LED TV is relatively cheap, and there is no obvious difference in appearance from ordinary LCD TV (that is, it is not very thin). Most of the entry-level LED TVs on the market belong to this category.

RGB three-color LED backlight

RGB three-color LED TV uses red, green, blue and RGB three-color LED backlight. Due to the structure, RGB three-color LED TV currently only has direct-down type, otherwise the RGB three-color LED will not be able to mix light. RGB three-color LED TV has a very strong performance, and only the top LED TVs will adopt this solution.

At present, many LED LCDs on the market use side-entry white light types. There is only one type of side-entry LED backlight side-entry LED TV at present. According to the side position of the backlight, it is also divided into single-side, double-side, four-side and other side-entry structures. Because the backlight source is side-mounted, the volume of the TV, especially the thickness, can be greatly reduced, so all kinds of ultra-thin LED TVs on the market belong to this type. This type of TV does not have a particularly big advantage over ordinary LCD in terms of picture quality, but it wins in appearance. However, after the LED light source is side-mounted, the light must be introduced through the light guide plate. If the manufacturer's manufacturing process level is not high, the TV screen will appear "bright around and dark in the middle". As the use time increases, the darkening of the middle of the screen will become more serious.

LED and LCD

Many service personnel who sell LED TVs will give a description like "LED is more advanced and more advanced than LCD, and is a technology that can replace LCD", but it must be clear that all home LED TVs on the market are actually a type of LCD TV, but the backlight source is different. The above statement seriously replaces the concept.

LCD: The full name is "Liquid Crystal Display", which is translated as liquid crystal display, abbreviated as "liquid crystal display".

Liquid crystal is a substance between solid and liquid. It cannot emit light by itself and needs the help of additional light sources. The structure of LCD is to place liquid crystals between two parallel pieces of glass. There are many vertical and horizontal fine wires between the two pieces of glass. The rod-shaped crystal molecules change direction by powering on or off, and refract the light to produce a picture.

Classification of LCD types by backlight source

It was introduced earlier that liquid crystals must rely on additional light sources to emit light. At present, the commonly used backlight sources for LCD TVs include CCFL (cold cathode fluorescent lamp, which is our common fluorescent lamp), LED (light-emitting diode), HCFL (hot cathode fluorescent lamp), etc. Among them, CCFL is the most commonly used LCD backlight source, which is usually also called traditional backlight source.

Therefore, if we classify LCD TVs by the type of backlight, they can be divided into:

CCFL backlight LCD (also commonly known as "traditional LCD TV", "LCD")

LED backlight LCD (also commonly known as "LED TV")

HCFL backlight LCD (suitable for larger TVs, can be applied to 66-inch products, less available on the market)