Summary of common faults of LED switching power supply

　　In the process of research and development and application of LED switching power supply, engineers not only need to make the designed products meet the corresponding testing standards, but also need to deal with the failures of LED switching power supply products in time. Electronics summarizes some common LED switching power supply operating failures and correction methods here, and shares them with you here.

　　1. The fuse is blown

　　During the normal operation of the LED switching power supply, the most common power failure is the blown fuse. Under normal circumstances, if the fuse inside the switching power supply is blown, it means that some problems have occurred in the line of the power supply. Because the switching power supply often works in the state of high voltage and high current, the fluctuation and surge of the grid voltage will cause the current in the power supply to increase instantaneously and cause the fuse to blow. After the fuse is blown, we should focus on checking the rectifier diodes, high-voltage filter electrolytic capacitors, inverter power switch tubes, etc. at the power input end, and check whether these components have breakdown, open circuit, damage, etc. If the fuse is indeed blown, you should first check the various components on the circuit board to see if the surface of these components is burnt and whether there is electrolyte overflow. If the above situation is not found, use a multimeter to measure whether the switch tube has a breakdown . It should be noted that when a component is found to be damaged, it must not be turned on directly after replacement. It is very likely that other high-voltage components are still faulty and the replaced components will be damaged. Be sure to conduct a comprehensive inspection of all high-voltage components of the above circuit. After checking and measuring, the fault of blown fuse can be completely ruled out.

　　2. No DC voltage output or unstable voltage output

　　In the process of practical application of LED switching power supply, there is another type of problem that is prone to occur, that is, there is no DC voltage output, or the voltage output is unstable. In the process of inspection, if the fuse of the power supply is found to be in good condition, then there is no output of DC voltage at all levels under load conditions. This situation is mainly caused by the following reasons: open circuit and short circuit in the power supply; overvoltage, overvoltage The current protection circuit is faulty; the auxiliary power supply is faulty; the oscillation circuit is not working, the power supply is overloaded, etc. After measuring the secondary components with a multimeter and ruling out the breakdown of the high-frequency rectifier diode and the short-circuit of the load, if the output is zero at this time, it is basically certain that the control circuit of the power supply is faulty. If there is some voltage output, it means that the pre-stage circuit is working normally, and the fault is in the high-frequency rectifier and filter circuit. The high-frequency filter circuit is mainly composed of a rectifier diode and a low-voltage filter capacitor to form a DC voltage output. The breakdown of the rectifier diode will cause no voltage output in the circuit, and the leakage of the filter capacitor will cause the output voltage to be unstable and other faults. The damaged components can be detected by statically measuring the corresponding components with a multimeter.

　　3. Poor power load capacity

　　In the actual application process of LED switching power supply, poor power supply load capacity is also a very common fault, which generally occurs in old-fashioned or long-working power supplies. The main reason for the decrease in load capacity is the aging of various components inside the power supply, the unstable operation of the switch tube, and the lack of timely cooling. Once the load capacity drop problem is found, the engineer should focus on checking whether the Zener diode generates heat and leakage, the rectifier diode is damaged, and the high-voltage filter capacitor is damaged.

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