How to prevent the failure of LED display dead light
LED large screen core components are composed of LED lamp beads and IC drivers, because the LED is very sensitive to static electricity, static electricity too large lead to LED breakdown, so the installation of LED large screen must do a good job of grounding measures to avoid the risk of dead lights.
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 its resistance to static electricity and abnormal voltage or current impact. This requires us to recognize this point in the production and use process, and pay enough attention to take effective measures to protect the LED screen. Power grounding is a common protection method for LED large screens.
Why should the power supply be grounded? This is related to the working mode of the switching power supply, our LED large screen switching power supply is a kind of equipment that converts AC (AC)220V mains power into DC (DC)5V DC power supply stable output through a series of means such as filtering – rectification – pulse modulation – output rectification – filtering. 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 line to the ground line in the circuit design of the AC220V input in accordance with the national 3C mandatory standard. In order to ensure the stability of the AC220V input, all power supplies will have filter leakage at work, and the leakage current of a single power supply is about 3.5mA. The leakage voltage is about 110V.
In the case that the LED screen is not grounded, the leakage current may not only cause chip damage or lamp burning. If more than 20 power supplies are used, the cumulative leakage current reaches more than 70mA. Enough to cause the leakage protector to operate, cut off the power supply. This is also the reason why our LED large screen can not use the leakage protector. If the leakage protection is not connected and the LED screen is not grounded, the current superimposed by the power supply will exceed the human safety current, and the voltage of 110V is enough to kill people! After grounding, the voltage of the power supply shell to the human body is close to 0. 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 screen must be grounded.
The correct approach and misunderstanding of LED display grounding
However, customers often use the wrong grounding method for the LED large screen grounding, common are:
1. It is believed that the lower end of the column of the outdoor column structure is connected with the earth, so there is no need to do LED large screen grounding;
2, it is believed that the power supply is locked on the box, and the box is connected with the structure with each other’s locks, so the structure is grounded on behalf of the power supply is also grounded.
These two kinds of practices exist misunderstanding, our column is connected with the foundation bolt, and the anchor bolt is embedded in the concrete, the concrete resistance in the range of 100-500Ω, the ground resistance is too high will lead to leakage current leakage time or residual. The surface of our box has spray paint, and the paint is a poor conductor of electricity, which will lead to poor contact or grounding resistance of the box connection, and there may be electrical spark interference with the LED large screen body signal. Over time, LED large screen box or structural surface will appear oxidation and rust, screws and other fixed parts are also gradually loosened with the temperature change caused by thermal expansion and contraction. It will cause the effect of the grounding of the LED large screen structure to weaken or even completely fail. Create security risks. Resulting in leakage current electric shock, chip interference damage and other safety accidents.
So, what should the standard grounding look like?
The power input terminal has three wiring terminals, which are live wire terminal, neutral wire terminal, and ground terminal. The correct grounding practice is to use a yellow-green two-color cable dedicated to grounding to connect all power ground terminals in series and lock them, and then lead out and connect them to the grounding terminal. If no ground terminal is available onsite, connect it to a pipe, such as an iron water supply pipe or an iron sewer pipe, that is buried and in good contact with the ground. To ensure good contact, weld wiring terminals on such natural grounding body, and then lock the ground cable to the wiring terminal. Do not bind the grounding terminal. However, flammable and explosive pipelines such as gas shall not be used. Or bury the ground body onsite. The ground body can be buried horizontally or vertically into the ground as a simple ground point. The ground point should be in a remote place to prevent pedestrians or vehicles from damaging the ground body. When we ground, the grounding resistance must be less than 4 ohms to ensure the timely discharge of leakage current. It should be noted that when the lightning protection grounding end release the lightning strike current, because the diffusion of the telluric current takes a certain time, it will lead to the rise of the geodetic potential in a short time. If the LED screen is grounded to the lightning protection grounding end, the geodetic potential is higher than the LED screen, and the lightning strike current will be transmitted to the LED screen along the ground wire, causing equipment damage. Therefore, the protective grounding of the LED large screen shall not be connected to the lightning protection grounding terminal, and the protective grounding terminal must be more than 20 meters away from the lightning protection grounding terminal. Prevent ground potential counterattack.
