Why must the LED display be grounded? _LED display boxu200b|LED display structure
Why must the LED display be grounded? This is related to the working mode of the LED display switching power supply. Our LED display switching power supply is a series of methods such as filtering-rectification-pulse modulation-output rectification-filtering and other means to convert alternating current (AC) 220V city power into direct current (DC) ) A device with stable output of 5V DC power supply. In order to ensure the stability of the AC/DC conversion of the power supply, the power supply manufacturer connects an EMI filter circuit from the live wire to the ground wire in the circuit design of the AC220V input terminal in accordance with the national 3C mandatory standard. In order to ensure the stability of AC220V input, all power supplies will have filter leakage when working, and the leakage current of a single power supply is about 3.5mA. The leakage voltage is about 110V. When the LED display is not grounded, the leakage current may not only damage the chip or burn out the lamp. If more than 20 power supplies are used, the accumulated leakage current can 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 our LED display cannot use the leakage protector. If the leakage protection is not connected and the LED display is not grounded, the leakage current superimposed by the power supply will exceed the safety current of the human body, and the voltage of 110V is enough to cause death! After grounding, the voltage of the power supply shell is close to 0 to the human body. It shows that there is no potential difference between the power supply and the human body, and the leakage current is led to the ground. Therefore, the LED display must be grounded. The main components of the LED display are LEDs and drive chips, which are a collection of microelectronic products. The working voltage of the LED is about 5V, and the general working current is less than 20 mA. Its working characteristics determine its resistance to static electricity and abnormal voltage or current impact. This requires us to recognize this in the production and use process and pay enough attention to take measures to protect the led display. The power grounding is the most commonly used protection method for LED displays. However, customers often use wrong grounding methods to ground the display. Common ones are: 1. Think that the power supply is locked on the box, and the boxes are connected to each other with a lock, so the structure of the LED display is grounded. It means that the power supply is also grounded; 2. It is considered that the lower end of the column of the outdoor LED display column structure is connected to the earth, so there is no need to ground the LED display. There are misunderstandings in these two types of practices. Our LED display column is connected with the foundation bolts, and the anchor bolts are embedded in the concrete. The resistance of the concrete is in the range of 100-500Ω, and the grounding resistance is too high. It will cause the leakage current to discharge in time or to have residuals. The surface of our LED display cabinet is sprayed with paint, and paint is a poor conductor of electricity, which will cause poor grounding of the cabinet or increase the ground resistance, and electrical sparks may interfere with the screen signal. As time goes by, the surface of the box or structure will be oxidized and rusted, and the fixing parts such as screws will gradually loosen due to thermal expansion and contraction caused by the temperature difference. It will cause the effect of structural grounding to weaken or even fail completely. Form a safety hazard. Lead to safety accidents such as leakage current and electric shock, chip interference and damage.