Pixel out of control of full-color LED display screen is a common problem. What is the reason for this phenomenon and how to solve it?
The pixel point of LED display screen is out of control, which means that the smallest imaging unit (pixel) of the display screen is not working normally. The ratio of out of control pixels to the total number of pixels on the whole screen is called "out of control rate of pixels on the whole screen". There are two modes of pixel out of control. One is blind spot, that is, blind spot. When it needs to be bright, it is not bright, which is called blind spot; The second is the constant bright spot. When it needs not to be bright, it is always bright, which is called the constant bright spot.
Generally, the common pixels of LED display screen are 2R1G1B (two red lights, one green light and one blue light, the same below) and 1R1G1B. Generally, out of control will not mean that all the red, green and blue lights in the same pixel are out of control at the same time, but as long as one of the lights is out of control, we think that this pixel is out of control. Therefore, it can be concluded that the main reason for the out of control of pixels of full-color LED display screen is the out of control of LED lights. The main causes of LED lamp failure can be divided into two aspects: first, the poor quality of LED itself; The second is the improper use of methods.
The LED lamp out of control cannot be found in the routine inspection and test of LED. Under bad conditions such as high temperature, low temperature and rapid temperature change, due to the difference of thermal expansion coefficient of LED chip, epoxy resin, support, inner lead, solid crystal adhesive, PPA cup and other materials, it is caused by the difference of internal stress. The mechanism of led out of control caused by electrostatic discharge is very complex. Equipment, tools, utensils and human body may carry static electricity and discharge it. This static electricity is as low as hundreds of volts, as high as tens of thousands of volts, and the discharge time is at the nanosecond level. If the blue-green tube is out of control, it is often caused by the electric breakdown of the led-pn junction by electrostatic discharge. Due to the complex production process of LED display screen, electrostatic discharge prevention is impossible. Therefore, electrostatic protection must run through the whole production process.
In different occasions, the actual requirements of pixel out of control rate are different, and the index of full-color LED display screen is required to be controlled within 1%; The indicators of monochrome LED display screen shall be controlled within one tenth. At present, there is no good solution for the pixels of full-color LED display. It is recommended to contact the service manufacturer to return to the factory for maintenance. If the maintenance cost is too high, consider replacing the faulty module unit board.At present, domestic LED displays are subject to aging test before leaving the factory, and the LED lights of out of control pixels are repaired and replaced. It is no problem to control the "out of control rate of whole screen pixels" within 1 / 104 and the "out of control rate of regional pixels" within 3 / 104. Even the enterprise standards of individual manufacturers require that out of control pixels are not allowed before leaving the factory, However, this is bound to increase the manufacturing and maintenance costs of manufacturers and prolong the delivery time.In different applications, the actual requirements of pixel out of control rate can vary greatly. Generally speaking, LED display screen is used for video playback, and the index requirement is acceptable and achievable within 1 / 104; If it is used for simple character information release, it is reasonable to control the index within 12 / 104.