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May 26,2021| LED Knowledge
Assembled LED large screen is easy to ignore the problem, many customers for the first time assembled LED large screen when there is no concept of selection, process connection method is not really understand, so there have LED screen some unusual happens. We as
Senior people in the LED industry can give you some insights to avoid the waste of time and materials caused by the overlooked problems of LED large screens. As an electronic product, large LED screens are understandable for some failures during normal use.
There are integrated circuits and chips on the LED screen, and the phenomenon that the integrated circuit chip is burnt due to smoke is a relatively common failure. full-color smoke and burnt LED large-screen chip What is the reason for the of the ? Let's talk about it in detail below.
1. The power supply voltage is too large: the rated working voltage of the LED module is usually 4.5V-5V, the maximum limit working voltage of the integrated chip on the module is generally not higher than 7V, and the maximum reverse voltage of the LED lamp bead is also 7V the following. Therefore, the supply above 7V
Electric voltage can damage the integrated chip and the LED tube. When the voltage reaches about 9V, the conventional constant current/constant voltage drive chip will often start to heat up sharply and may smoke. Normally, when the voltage is 10-11V, continue to power on for about 2 seconds,
Chips will burn to varying degrees. Since the large LED screen uses a constant voltage switching power supply with an output voltage of 5V, the possibility of overvoltage is not very large. Even if the control circuit of the switching power supply fails, its output voltage is abnormal and reaches
The possibility of going above 9V is also very slim (doesn't mean it's impossible!). It is worth mentioning that even if the high output voltage ripple of some low-quality switching power supplies cannot cause the chip to smoke and burn, it is still enough to cause the chip to fail.
2. Abnormal control signal: It is also common for a full-color LED large screen to have a line of constant light and highlight failure, which is often caused by abnormal cable contact or error in debugging parameters. Strictly speaking, a well-designed LED large screen product should have
Avoid protection circuits with line highlights and always on. For products without protection circuit, after the line highlight is always on, if it is not eliminated in time, the line driver chip (such as 4953) of the module may be burned out due to the continuous high current operation and the temperature rises sharply.
Of course, compared with previous products, the current industry's full-color LED large-screen modules, the load power consumption of the row driver chip is relatively low (below 2A), and the maximum operating current of most row driver chips is about 3A. The module appears to be erratic
It is less likely that the line driver chip will be burnt when the light is on. Therefore, most products on the market no longer design protection circuits.
3. Reverse connection of the positive and negative poles of the power supply: Electronic products designed according to the specifications will have "VCC" and "GND" marks (or "+", "-") at the power terminal position, indicating the positive and negative wiring positions respectively . However, for operators who lack the basic knowledge of electrical engineering and electronics, it is still possible that the positive and negative poles of the power supply are reversed unconsciously, and even qualified technicians may make operational mistakes. Reverse connection of the positive and negative poles of the power supply will often cause most of the constant current/constant voltage drive chips on the module to smoke and burn.
Summary: In practical applications, most of the reasons that cause the chip to smoke and burn are the reverse connection of the positive and negative electrodes, followed by abnormal control signals, but this situation will become less and less common, and finally a very small number of power supply overvoltages. Some of these failures are caused by humans. Whether it is LED large-screen manufacturers or end users, in order to reduce the occurrence of full-color LED large-screen chip failures, it is very necessary to improve the technical level of operators.