The main components of LED display screen are LED and driver chip, which belong to the collection of microelectronic products. The working voltage of LED is about 5V, and the general working current is below 20mA. Its working characteristics determine that it is very vulnerable to static electricity and abnormal voltage or current impact. This requires us to recognize this and pay enough attention to it in the production and use process, and take measures to protect the LED display. Power grounding is the most common protection method for LED display screen.
Why should the power supply be grounded? This is related to the working mode of switching power supply. Our LED display switching power supply is a device that converts AC (AC) 220V mains power into DC (DC) 5V DC power supply for stable output through a series of means such as filtering rectifier pulse modulation output rectifier filtering.
In order to ensure the stability of AC/DC conversion of power supply, the power supply manufacturer connects an EMI filter circuit from live wire to ground wire in the circuit design of AC220V input terminal according to the national 3C mandatory standard. To ensure the stability of AC220V input, all power supplies will have filtering leakage during operation, and the leakage current of a single power supply is about 3.5mA. The leakage voltage is about 110V. When the display screen is not grounded, the leakage current may not only cause chip damage or lamp burn out. If more than 20 power supplies are used, the accumulated leakage current will reach more than 70mA.
It is enough to cause the leakage protector to act and cut off the power supply. This is also the reason why we cannot use the leakage protector on the display screen. If the leakage protector is not connected and the display screen is not grounded, the leakage current superimposed by the power supply will exceed the human safety current, and the 110V voltage is enough to kill people! After grounding, the voltage of the power supply housing is close to 0. It indicates that there is no potential difference between the power supply and the human body, and the leakage current is introduced to the ground. Therefore, the LED display must be grounded.