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Summary of common faults of LED switching power supply

Source:AdminAuthor:WPOWER Addtime:2019-06-05 Click:
   Summary of common faults of LED switching power supply
 
In the 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 faults of LED switching power supply products in use. Good Power - Weida Source Electronics here summarizes some common LED switching power supply operation failures and correction methods, and share them with everyone here.
 
1, the fuse is blown
    In the normal operation of the LED switching power supply, the most common power failure is that the fuse is blown. Under normal circumstances, the fuse inside the switching power supply is blown, indicating that some problems have occurred in the power supply line. Since the switching power supply tends to work under high voltage and high current conditions, the fluctuations and surges of the power grid voltage will cause the current in the power supply to increase instantaneously and the fuse to be blown. After the fuse blows, we should focus on the rectifier diode, high-voltage filter electrolytic capacitor, inverter power switch, etc. at the input of the power supply, and check whether the component has breakdown, open circuit, damage, etc. If the fuse is really blown, you should first check the components on the board to see if the appearance of these components is burnt and there is no electrolyte overflow. If the above is not found, use a multimeter to measure whether the switch has a breakdown short circuit. . It is important to note that it is forbidden to directly turn on the power after the component is damaged. It is very likely that the other high-voltage components will still be damaged and the replacement components will be damaged. It is necessary to comprehensively apply all the high-voltage components of the above circuit. After the measurement is checked, the fuse blowout can be completely eliminated.
 
2, no DC voltage output or voltage output is unstable
    In the process of practical application of LED switching power supply, there is a kind of problem that is easy to occur, that is, there is no DC voltage output, or the voltage output is unstable. During the inspection process, if the fuse of the power supply is found to be intact, then there is no output of the DC voltage at all levels under load. This situation is caused by the following reasons: open circuit or short circuit in the power supply; overvoltage, over The flow protection circuit is faulty; the auxiliary power supply is faulty; the oscillating circuit is not working, the power supply is overloaded, and so on. After measuring the secondary component with a multimeter and eliminating 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 has failed. If some of the voltage output indicates that the pre-stage circuit is working properly, the fault is in the high-frequency rectification and filtering circuit. The high-frequency filter circuit mainly consists of a rectifier diode and a low-voltage filter capacitor to form a DC voltage output. The breakdown of the rectifier diode causes the circuit to have no voltage output, and the leakage of the filter capacitor causes the output voltage to be unstable. Statically measure the corresponding component with a multimeter to check the damaged component.
 
3, poor power supply capacity
     In the actual application of LED switching power supply, the poor load capacity of the power supply is also a very common fault, which is usually found in old-fashioned or long-running power supplies. The main reason for the decrease in load capacity is that the components inside the power supply are aging, the operation of the switch tube is unstable, and heat dissipation is not performed in time. Once the load capacity is found to be degraded, the engineer should focus on checking whether the Zener diode is hot or leaky, the rectifier diode is damaged, and the high voltage filter capacitor is damaged.

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