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4 defects of LED display chip with small spacing

4 defects of LED display chip with small spacing

Small spacing LED display with the LED package prices down, the price is more approachable. Relative to the LCD screen or back projection. The advantages of small spacing are: 1 arbitrary splicing seamless. 2 do not need to adjust the ambient light source. 3 picture more three-dimensional reality.

It is very important for one of the parts in addition to outside chip display lamp. If the chip is not suitable for use, then it will have some defects. The following are mainly introduced 4 kinds of chips are not suitable for the display screen.

1, block and uneven color (Pian Hong)

In indoor applications, LED screen brightness more between 300 and 1000 nits (NIT), the brightness is converted into the forward current of LED, Jordan 1~5mA, or even less than 1mA. Therefore, the small current concentration of the driver chip becomes very important. When the driver current accuracy is poor, dot pitch LED display screen is prone to block the uneven color, but the color to cover the defect, usually will be taken to improve the current LED this means to increase the brightness of the screen. But the disadvantage is that when the audience watching this LED display a period of time, the eyes easily feel uncomfortable. Figure 1 shows a small dot pitch LED display, in the use of different quality LED driver chip, the actual difference after the re image.

According to proportion, green and blue LED forward current is affected by the parasitic capacitance than the red LED, so in the low gray scale, dot pitch LED display looks red (red-tint), this is the color shift phenomenon we often say (color shift), as shown in figure 2. The right solution is used with the color compensation LED driver chip, rather than by raising the forward current of LED to hide this shortcoming.

2, low brightness image detail loss

If you do not use LED to improve the current along the way to cover the defect, gamma curve of another way is to adjust the dot pitch LED display, grayscale brightness is very important for the correct image reproduction, because in the video source brightness contain most of picture data. In Figure 3, the gamma image on the right side of the smaller, brightness represents mid tone is too high, therefore, the overall picture of white and the lack of depth, the image details of a lot of losses, compared to the left, right, dog hair less level.

3, gray scale is not smooth

Dot pitch LED display for sequential scanning (multiplexed) display, hold-type display non LCD screen, so the refresh rate for small pitch LED display is quite important, low refresh rate will not only make the dot pitch LED display screen to watch a flicker of discomfort, easy to cause the viewer halo Hyun, it will make the effect of gray scale gradient smoothing. Figure 4 as an example, the gray face gradually the effect is not smooth, have similar contour phenomenon, from gray scale figure 5 gradation test screen can also see that the continuity of the dot pitch LED display on the right than the poor.

4, LED point caused by the bright line or cross

LED epitaxial grow with each passing day and packaging technology today, but LED after a long time of use will inevitably have different damage, and the LCD screen is broken, LED will form a bright line or cross dot pitch LED display, rather than a black spot, as shown in figure 6. The LED display manufacturers, operators are concerned with the audience, is a big problem.

A good small pitch LED display must be able to eliminate the dead LED caused by annoying bright line or cross phenomenon, as Figure 7 shown on the left. Only with "bad isolation" function (dead pixel isolation) LED driver chip, in order to maintain the normal operation of dot pitch LED display, and a user can conveniently arrange the maintenance process of elastic.

These means are very common in the dot pitch LED display, knowledge and ability but limited to buyers and users for basic image processing and LED driver chip, is not easy to distinguish these differences, avoid annoying problem, the most simple way is to choose a specially designed for the dot pitch LED display LED driver chip

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