LED display chip 4 kinds of defects of small spacing

by:Xinyao LCD     2020-04-08
Small spacing of LED display screen as LED encapsulation lower price, the price is more approachable. Relative to the LCD screen or the back projection. The advantages of small spacing are: 1. Any stitching without aperture. 2. Don't need to adjust the environment light. 3. More stereo true picture. In addition to a lamppost chip for display is one of the important parts. If the chip is not suitable for use, can produce some defects. Below mainly introduces four kinds of chips are not suitable for display problem. 1, uneven blocks and color ( Partial red) In indoor applications, the brightness of the LED display at between 300 and 1000 ( nit) , converting the brightness LED downstream current, Jordan in 1 ~ 5 ma, even less than 1 ma. Therefore, drive chip small current concentration becomes important. When the driver chip current poor accuracy, smaller spacing LED display is easy to appear uneven blocks of color piece, but to hide color piece this defect, usually adopt the means to improve the LED current, to increase the brightness of the display screen. But the disadvantage is that when watching on the LED display after a period of time, eyes feeling ill easily. Figure 1 illustrates the smaller distance between the LED display, when use different quality of LED driver chip, image after making real differences. According to the proportion, green and blue leds forward current is affected by the parasitic capacitance is bigger than red light LED, in low gray-scale, partial red dot spacing LED display looks ( 红色- - - - - - tint) , this is we often say that the color of partial phenomenon ( 颜色的转变) As shown in figure 2. The right solution is to use a compensation of LED driver chip color, rather than by LED forward current increases to hide this shortcoming. 2, under the low brightness of image details loss if we do not adopt the way of improving LED forward current to cover up the above shortcomings, another way is to adjust the dot pitch LED display gamma curve, the brightness of the gray-scale image for correct weight system is very important, because in the video source brightness contains most of the image data. As shown in figure 3, the right of the image gamma value is small, represents the middle color brightness is too high, therefore, the overall picture white-washed and lack of depth, the details of the image loss, compared with left, right in the dog hair less have layers. 3, not smooth performance of gray-scale dot spacing LED display as the sequential scanning ( 多路复用) Hold - display of the LCD screen Type display, so the refresh rate is quite important to smaller spacing LED display, the lower the refresh rate will not only make small LED display viewing point spacing are flashing discomfort, easy to cause the viewer dizzy dazzle, and can make the gray-scale layered effect is not smooth. To 4 as an example, the right face of gray-scale layered effect is left is not smooth, there are similar to the phenomenon of contour, the gray-scale from figure 5 layer test images can also see the picture on the right of dot spacing LED display the continuity of the inferior to the left. 4, LED light line caused by bad points or the cross LED epitaxy and encapsulation technology growing today, but the LED after long time of use is still hard to avoid can have damaged, with LCD screen, the broken LED LED display will be in a small point spacing form bright line or cross, rather than a black dot, as shown in figure 6. The LED display manufacturers, operators and viewers, is a big trouble. A good bit spacing LED display caused by LED bad point must be able to eliminate the aggravating bright line or cross phenomenon, as shown in figure 7 left. Only (with 'bad isolation' function is 死像素隔离) LED driver chips, to maintain the dot spacing LED display normal operation, and convenient user flexibility to arrange maintenance schedule. The above means in dot spacing LED display is very common, but limited to buyers and users for the basic knowledge of image processing and the LED driver chip and ability, it is not easy to distinguish the differences and avoid annoying problem above, the most simple way, is to choose a specially designed for smaller spacing LED display LED driver chip.
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