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LED displays Technical Index


1. Types of LED display

1. According to the color classification

Single-color display: single red or single green; dual-color display: red and green dual-color, 256 gray levels, can display 65536 colors; full-color display: red, green, and blue three-color, 256 gray levels The full-color display can display more than 16 million colors.

2. Classification according to the constituent pixel units

Digital display screen: The display pixel is a 7-segment digital tube, which is suitable for making clock screens, interest rate screens, etc.;

Graphic display: The display pixel is a dot matrix module, which is suitable for playing text and image information;

Video display screen: The display pixels are composed of many light-emitting diodes, which can display various video files such as videos and animations.

3. According to the location of use

Indoor display: small luminous points, dense pixel pitch, suitable for close viewing;

Semi-outdoor display: between indoor and outdoor, not rainproof, suitable for information guidance on the door lintel;

Outdoor display screen: large luminous point, large pixel pitch, high brightness, can work in the sun, with windproof, rainproof, and waterproof functions, suitable for long-distance viewing.

4. According to the driving mode, there are static, horizontal scrolling, vertical scrolling and page turning display, etc.

2. Types, advantages and disadvantages of LEDs for display screens

According to the classification of the display screen, the pixel LEDs used can also be divided into the following types:

1. Dot matrix module

Advantages: low cost, mature processing technology, stable quality; Disadvantages: brightness and color consistency are not well controlled, and Masaige phenomenon is prone to occur;

2. Straight plug light

Advantages: Color consistency is relatively easy to control, and the pixel pitch can be freely adjusted and combined according to needs; Disadvantages: the red, green and blue color mixing effect is not good, the angle is not large, it is difficult to control the consistency of the angle, and the processing is prone to unevenness, up and down, left and right Easy to misplace

3. Patch

Advantages: display color, color mixing effect, angle consistency, etc. are the best; disadvantages: high cost of packaging and processing;

3. LED packaging technology requirements for display screens

Different application positions will use different specifications of display screens, and different display screens require LED devices with different technical requirements. So what are the technical requirements for LEDs used in display screens? The following descriptions are based on different categories:

1. SMD LED for indoor display.

SMD LEDs for indoor display screens are divided into "three-in-one" and "three-in-one". The former is mostly used in areas with relatively low cost and low display requirements, while the latter has better display effects and relatively low cost. High, the following will mainly explain the "three in one";

(1) Brightness: The first thing to consider is the appropriate ratio of product brightness. At present, the red, green and blue brightness of most full-color displays are matched according to 3:6:1 (that is, the red brightness in a pixel accounts for 30%, and the green brightness is 30%. It accounts for 60% and blue is 10%); generally speaking, packaging factories and upstream chip manufacturers almost test products according to 20mA, but when applied to displays, almost none of them are driving LED lights. Yes, generally speaking, the red, green, and blue LEDs are composed of different chip materials, and their heating, luminescence, and brightness attenuation in actual use are not proportional. Generally speaking, the red attenuation ratio is smaller, and the blue-green attenuation is larger. Therefore, in order to ensure a relatively long service life of the display, the general designer will lower the blue-green drive current than red; for example: if red is driven at 18mA, green is driven at 15mA, and blue is driven at 12mA, according to the LED Chip IV-If relationship:

Roughly we can calculate that the actual brightness of the LED, the relationship between red, green and blue is:

R: 3÷90%

G: 6÷75%

B:1÷60%

At the same time, the brightness should be classified. The purpose of the classification is to prevent the difference in brightness from being visible to the naked eye. Generally speaking, the brightness difference that the human eye can distinguish is 30%, deducted For the test error of the equipment and the error of the installation mechanism, it is better to design the light splitting according to 10%~20%.

(2) Color: According to the optical effect, the white light is decomposed into a gradual transitional color spectrum after passing through the prism. The colors are red, orange, yellow, green, cyan, blue, and purple, which is the visible spectrum. Among them, the human eye is most sensitive to red, green,
 

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