Comprehensive analysis of LED display knowledge

LED definition

In the PN junction of some semiconductor materials, when the injected minority carriers recombine with the majority carriers, they release the excess energy in the form of light, thereby directly converting electrical energy into light energy. When a reverse voltage is applied to the PN junction, it is difficult for minority carriers to be injected, so no light is emitted. This type of diode made using the principle of injection electroluminescence is called a light-emitting diode, or LED for short.

The luminous color and luminous efficiency of LED are related to the materials and processes used to make LED. Currently, red, green and blue are widely used. Since LED has a low working voltage (only 1.5-3V), can actively emit light and has a certain brightness, and the brightness can be adjusted by voltage (or current), it is also impact-resistant, vibration-resistant, and has a long life (100,000 hours). Therefore, in large-scale display devices, there is currently no other display method that can match the LED display method.

The display screen that puts red and green LEDs together as a pixel is called a two-color screen or a color screen; the display screen that puts red, green and blue LED tubes together as a pixel is called a three-color screen or a full-color screen.

Whether using LED to make a single-color, two-color or three-color screen, the luminous brightness of each LED that constitutes a pixel to display the image must be adjusted, and the degree of fineness of the adjustment is the grayscale level of the display screen. The higher the grayscale level, the more delicate the displayed image, the richer the color, and the more complex the corresponding display control system. Generally, for an image with 256 grayscale levels, the color transition is very soft, while for a color image with 16 grayscale levels, the color transition boundary is very obvious. Therefore, color LED screens are currently required to be made into 256 levels of grayscale.

Working principle of LED display screen

LED electronic display screen is a high-tech product integrating optoelectronics and computer technology.

Performance characteristics of LED products

Text LED display screen and graphic LED display screen should have the moving in and out mode and display mode specified in the detailed specifications.

Computer video LED display screen should have: animation function. The animation display of LED display screen is required to be consistent with the display of the corresponding area of ​​​​the computer monitor; text display function. The text display is required to be stable and clear; grayscale function. It is required to have the grayscale level specified in the detailed specifications. In addition to animation, text display and grayscale functions, TV video LED display screen should be able to show TV and video images. Market LED display screen has the corresponding market display capability.

How to classify LED display screens

LED display screens can be classified according to the following conditions:

Use environment LED display screens are divided into indoor LED display screens and outdoor LED display screens according to the use environment.

Display color LED display screens are divided into single-primary color LED display screens (including pseudo-color LED display screens), dual-primary color LED display screens and full-color (three-primary color) LED display screens according to the display color. According to the grayscale, it can be divided into 16, 32, 64, 128, 256 grayscale LED display screens, etc.

Display performance LED display screens are divided into text LED display screens, graphic LED display screens, computer video LED display screens, TV video LED display screens and market LED display screens, etc. According to display performance, market LED display screens generally include LED display screens for securities, interest rates, futures, etc.

Among the basic luminous point non-market LED display screens, indoor LED display screens can be divided into Φ3mm, Φ375mm, Φ5mm, Φ8mm, and Φ10mm display screens according to the LED single point diameter used; outdoor LED display screens can be divided into Φ19mm, Φ22mm and Φmm26 LED display screens according to the pixel diameter used. According to the size

of the digital tube used in the market LED display screen, it can be divided into 2.0cm (0.8inch), 2.5cm (1.0inch), 3.0cm (1.2inch), 4.6cmm (1.8inch), 5.8cm (2.3inch), 7.6cm (3inch) and other LED display screens. How to evaluate the quality of LED screens?

The out-of-control point of the indoor LED display screen should not exceed 0.3%, and the out-of-control point of the outdoor LED display screen should not exceed 0.3%, and it should be discrete and strong;

consistency: the consistency of the LED screen should be good, the brightness of the whole screen should be balanced, and there should be no obvious color blocks;

safety: there should be no safety hazards and leakage current, and the ground leakage current should not exceed 3.5mA (AC effective value); anti-point strength: the LED display screen can withstand the experimental voltage Lmin of 50Hz and 1500V (AC effective value) and there should be

no insulation breakdown; at the same time, the LED display screen should have warning signs at the fuse and switch power supply; appearance: there should be no obvious scratches on the outer frame of the LED display screen. The pixel tubes of the outdoor LED display screen should be installed consistently, without looseness and tube shell cracks;

structure: the LED display screen part can be made of steel, aluminum, wood and other materials, and the structure is required to be sturdy and beautiful.