LED large screen core components are composed of LED lamp beads and IC driver. Because LED is very sensitive to static electricity, static electricity will cause LED breakdown. Therefore, it is necessary to do grounding measures when installing LED large screen to avoid dead lights. risks of.

The working voltage of the LED large screen is about 5V, and the general working current is below 20 mA. The working characteristics of the LED determine that it is very vulnerable to static electricity and abnormal voltage or current impact. This requires us to recognize this in the process of production and use, and give enough attention to take effective measures to protect the LED large screen. Power grounding is a common protection method for LED large screens.

Why is the power supply grounded? This is related to the working mode of the switching power supply. Our LED large-screen switching power supply is a kind of means to convert the alternating current (AC) 220V mains into DC through a series of means such as filtering-rectifying-pulse modulation-output rectification-filtering. (DC) A device that stabilizes the output of a 5V DC power supply. In order to ensure the stability of the AC/DC conversion of the power supply, the power supply manufacturer crosses an EMI filter circuit from the live line to the ground line in the circuit design of the AC220V input terminal according to the national 3C mandatory standard. In order to ensure the stability of the AC220V input, all the 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 approximately 110V. In the case where the LED large screen is not grounded, leakage current may not only cause chip damage or burnout of the lamp.

       If more than 20 power supplies are used, the accumulated leakage current reaches 70 mA or more. Sufficient to cause the leakage protector to operate and cut off the power supply. This is also the reason why our LED large screen cannot use the leakage protector. If the leakage protection is not connected and the LED large screen is not grounded, the current superimposed by the power supply will exceed the safe current of the human body, and the voltage of 110V is enough to cause death! After grounding, the voltage of the power supply casing is close to zero to the human body. It indicates that there is no potential difference between the power source and the human body, and the leakage current is introduced into the earth. Therefore, the LED large screen must be grounded.

However, customers often use the wrong grounding method to ground the LED large screen. Common ones are:

1. It is considered that the lower end of the column of the outdoor column structure is connected to the earth, so there is no need to do the LED large screen grounding;

2. It is considered that the power supply is locked on the box body, and the boxes are connected with each other by a lock and a structure, so the structure grounding means that the power source is also grounded.

There are some misunderstandings in these two types of practices. Our columns are connected to the anchor bolts of the foundation. The anchor bolts are embedded in the concrete. The resistance of the concrete is in the range of 100-500 Ω. If the grounding resistance is too high, it will lead to leakage. Current bleed is not timely or there is residue. The surface of our cabinet is sprayed with paint, and the paint is a poor conductor of electricity, which will lead to poor contact of the cabinet to the ground or an increase in the grounding resistance. It is possible that the spark interferes with the LED large screen signal. As time goes by, the LED large-screen box or structural surface will appear oxidized and rusted, and the fixing parts such as screws will gradually loosen due to the thermal expansion and contraction caused by the temperature difference. The effect of grounding the LED large screen structure will be weakened or even completely disabled. Form a safety hazard. A safety accident such as leakage current or chip damage.

Then, what should the standard grounding be? The power input has three terminals, which are the live terminal, the neutral terminal and the ground terminal. The correct grounding method is to use a ground-specific yellow-green two-color cable to connect and lock all the power ground terminals in series, and then lead them out to the ground.

If there is no grounding terminal at the site, it can be connected to a pipe such as an iron tap pipe or an iron sewer pipe buried in the earth and in good contact with the earth. To ensure good contact, the terminal block should be welded on such a natural grounding body, and then The ground wire is locked to the terminal block and must not be bundled. However, pipes that are flammable and explosive, such as gas, must not be used. Or bury the grounding body on site. The grounding body can be made of angle steel or steel pipe. It can be buried horizontally or vertically into the earth as a simple grounding point. The grounding point should be chosen in a remote place to prevent pedestrians or vehicles from damaging the grounding body.

When grounding, the grounding resistance must be less than 4 ohms to ensure timely discharge of leakage current. It should be noted that the lightning protection grounding terminal needs a certain time due to the diffusion of the earth current when discharging the lightning current. In a short time, the earth potential will rise. If the LED large screen is grounded to the lightning protection grounding terminal, then the ground potential It is higher than the LED large screen, and the lightning current will be transmitted to the LED screen along the ground line, causing damage to the equipment. Therefore, the protective grounding of the LED large screen must not be connected to the lightning protection grounding terminal. The protective grounding terminal must be more than 20 meters away from the lightning protection grounding terminal. Prevent counterattack of ground potential.

Source: HC LED screen