A new type of color TV with LED backlight |dimmable led bulkhead light

Shenzhen Allolux Lighting Co., Ltd provide  focus on triproof light fixture and LED triproof ligh. Dimmable Led Bulkhead Light Suppliers .You can browse related products and initiate consultations on our website.
The LED backlight strings used for Dimmable Led Bulkhead Light Suppliers. The LED light strings work at high level (more than 100 volts), high current (above 300MA), and each LED lamp bead has a high temperature when it emits light. These factors lead to LED The lamp string has a high frequency of failures, and the type of failure: the common cause is that the lead of a certain LED lamp bead in the lamp string is soldered, soldered, open, and short-circuited. The backlight driver board that powers the LED light string is a constant current circuit, which maintains the current flowing through the LED light string to remain stable at the optimal operating current value.
At the same time, there are complete over voltage, over current, open circuit, and short circuit protection circuits in the backlight driver board. Once the LED string has a fault such as virtual welding, open circuit, or short circuit of a certain bulb, it will cause the protection circuit in the backlight driver board quickly Start: The circuit in the backlight driver board stops working and cuts off the LED backlight driver voltage to prevent the expansion of the fault and burn the backlight driver board. Because there are hundreds of LED lamp beads in an LED screen, any weak soldering or open circuit of any lamp bead will cause the backlight drive circuit to enter the stop working and protection state. Therefore, the occurrence rate of such failures is quite high. Because the backlight LED string is in a closed, narrow, and small backlight box, the heat dissipation is poor, and the temperature is very high during normal operation, and the temperature drops to room temperature after shutdown. This temperature difference is large because the solder of the LED lamp beads is very soft, The intensity is very low, and the temperature is very high all year round. Dimmable Led Bulkhead Light Suppliers will try to fix the problem.
In actual maintenance, a defective backlight panel will cause the backlight string drive voltage to fail to output, and a defective LED string will cause the backlight board circuit to enter a protective shutdown and cause the backlight string drive voltage to also not output. Both will cause the backlight drive circuit board to fail. There is no power output from the LED light string. At this time, the most important thing for  Dimmable Led Bulkhead Light Suppliers maintenance personnel is to distinguish clearly: the backlight string has no driving voltage, is it caused by the backlight driver board, or the LED string is bad. Because the backlight circuit enters the protection stop working state as soon as the fault occurs, so when you see the fault phenomenon and immediately detect it, you cannot judge the fault location.
And the most important thing is: if the LED light string has weak welding of the lamp beads, it is often turned on normally in the cold state, and the fault appears from time to time after the warm-up. It may fail after 1 hour of starting up, or it may fail after 4 hours, or it may not fail after being turned on for a few days, and it may fail after 7 days. In short, the timing of failure is random and not fixed. When the backlight board is bad, the main board is bad, and the power board is bad, the same failure phenomenon will occur. As a result, maintenance is very difficult.
In order to judge whether the failure is caused by the poor backlight string of the screen, the best way is to find a stabilized power supply (the stabilized power supply does not have the protection function of load open circuit and load false welding), and adjust the output voltage of the stabilized power supply to the lamp. The standard voltage when the string is working normally, the stabilized power supply is used to provide a stable and constant voltage for the backlight string. When the power is turned on for a long time, when a fault occurs: for example, when the backlight is automatically turned off, or when the backlight is flickering unstable, because the stabilized power supply is not protected, the power supply voltage applied to the LED string is stable, and immediately Detect the power supply voltage at both ends of the light string. If the power supply voltage is normal and the light string does not light up, then it is obvious that the fault must be caused by a bad light string.
As we all know: the regulated power supply sold on the market is generally below 32V. When repairing the LED backlight string, the output voltage of the regulated power supply is required to be continuously adjustable from 50V to 150V, so as to cover all Various brands and models of screens. To buy such a regulated power supply is not available in the market, even if it is available, the price is very high, so that ordinary maintenance personnel can not accept it.
To this end, I found a very suitable method: now every maintenance person has a discarded CRT switching power supply board or motherboard (some CRT switching power supplies are integrated with the motherboard), and the CRT switching power supply board or The thick film block or switch tube of the switching power supply circuit on the main board is removed and not used, and replaced with a 3-wire universal power supply module. The price of the Dianyuan module is very low, only more than a dozen yuan, and there is an adjustable potentiometer on the power module to adjust the output voltage. The adjustable range of the measured output voltage is 50V------- 170V, the output power of the CRT color TV switching power supply is related to the screen size of the CRT. The output power of the 34-inch CRT switching power supply is about 270W and the output voltage is 140V. The output power of the switching power supply for 25-inch color TV motherboards is also around 200W, and the output voltage is also 140V. The output voltage of the 21-inch color TV main board switching power supply is 110V, and the output power is about 150W. The power required by the LED color TV backlight string is related to the size of the screen. Even for an 80-inch LED color TV, the power required for the backlight string is generally below 150W, and about 40-inch LED color TVs, the power required for the backlight string is 50W. Therefore, using a CRT color TV switching power supply to supply power to the LED light string during maintenance is fully competent and no problem.
In order to prevent accidental burning of the switching power supply for maintenance, such as accidentally short-circuiting during maintenance, accidentally connecting the positive and negative voltages when powering the LED light string, etc., string a 100 ohms at the CRT color TV switching power supply + B output terminal. The 5W current-limiting resistor can prevent the LED string from over current on the one hand, and on the other hand, it can also prevent the switching power supply from being burned out when the wrong positive and negative electrode leads are connected.
In order to go out for maintenance and carry, you can cut off the other useless printed circuit parts on the color TV switch power supply board, and remove the useless parts. The circuit board carried in this way is small in size and convenient to use.




 

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