Full color LED out of control is a relatively common problem. What is the cause of this phenomenon and how to solve it? Today Lianchengfa Xiaobian (www.lcf-led.cn) and everyone come together Analyze it.

Analysis of pixel out-of-control reasons for full-color LED display

The pixel out of control of the LED display means that the smallest imaging unit (pixel) of the display is not working properly. The ratio of out-of-control pixels to the total number of full-screen pixels is called the “out-of-control pixel control rate”. There are two types of pixel out-of-control mode. One is blind spot, that is, the blind spot. When it needs to be bright, it is not bright, which is called blind spot. The second is the constant bright spot. It’s a constant highlight.

LED lights out of control can not be found in the regular inspection test of LED sign parts. Under severe conditions such as high temperature, low temperature, and rapid temperature changes, it is caused by the difference in thermal expansion coefficients of LED chips, epoxy resin, brackets, inner leads, die-bonding adhesives, PPA cups and other materials, resulting in different internal stresses. The mechanism of LEDs get out of control due to electrostatic discharge is very complicated. Equipment, tools, utensils, and the human body may carry static electricity and discharge it. This static electricity ranges from hundreds of volts to tens of thousands of volts. The discharge time is at the nanosecond level. . If the blue-green tube is out of control, it is often that the LED-PN junction is penetrated by electrostatic discharge. Due to the complicated production process of LED display screens, electrostatic discharge cannot be prevented. Therefore, electrostatic protection must run through the entire production process.

In general, the common LED display pixel composition is 2R1G1B (2 red lights, 1 green light and 1 blue light, the same reasoning below) and 1R1G1B, and out of control is generally not the same red, green, The blue lights are all out of control at the same time, but as long as one of the lights is out of control, we consider that the pixel is out of control. Therefore, it can be concluded that the main cause of the out-of-control pixels of full-color LED display screens is the out-of-control LED lights. The main reasons for the failure of LED lights can be divided into two aspects: one is the poor quality of the LED itself; the other is the improper use of the LED.

At present, domestic LED displays are subject to aging tests before leaving the factory. The LED lights of out-of-control pixels are repaired and replaced. The “out-of-control pixel control rate” is controlled within 1/104 and the “out-of-control pixel control rate” is controlled at 3 / It is no problem within 104, and even some manufacturers’ enterprise standards require that out-of-control pixels are not allowed before leaving the factory, but this will inevitably increase the manufacturer’s manufacturing and maintenance costs and extend the shipping time.

In different occasions, the actual requirements for pixel out-of-control rate are different. Full-color LED display indicators are required to be controlled within one percent; monochrome LED display indicators are required to be controlled within one-tenth. At present, there is no good solution for Novastar full color LED display pixels. It is recommended to contact the service manufacturer to return to the factory for repair. If the repair cost is too high, you can consider replacing the defective module unit board.