Switching power supply is a common power supply equipment, which is widely used in various fields. However, due to prolonged use or improper operation, switching power supply may have various failures. In this article, we will introduce the common failures of switching power supply and its repair methods in detail to help readers solve the switching power supply failure.

First, let's understand the basic composition of a switching power supply. A common switching power supply is mainly composed of input filter circuit, rectifier circuit, power factor correction circuit, power conversion circuit, output filter circuit, feedback control circuit and so on. Among them, the input filter circuit is used to filter out the noise and interference signals in the input power supply; the rectifier circuit converts the AC input voltage to DC voltage; the power factor correction circuit is used to improve the power factor and reduce harmonic pollution; the power conversion circuit converts the DC voltage to the desired output voltage; the output filter circuit filters out the ripple signals in the output voltage; the feedback control circuit is used to achieve the output voltage and current Feedback control circuit is used to realize the regulation of output voltage and current.

Failure 1: switching power supply no output

When the switching power supply fails to output voltage, first check whether the input power supply is normal. Check whether the power supply voltage is in accordance with the specified value, and check whether the line of the input power supply is affected by over-voltage or over-current. If the input power supply is normal, then the fault may be inside the switching power supply.

The second step is to check whether the output voltage is short-circuited. Use a multimeter to connect the test pen to the output of the switching power supply. Under normal circumstances, the multimeter pointer should display a stable voltage value. If the display is zero or flashing, then the failure may be caused by a short circuit in the output voltage. At this point, you can disconnect the output port load one by one to determine whether there is a short-circuit load components, and then solve the problem.

Fault two: switching power supply output voltage instability

When the output voltage of the switching power supply is unstable, the first thing to check is whether the input power supply is stable. If the input power supply fluctuations or noise, then the output voltage will also be affected by fluctuations or noise. Therefore, it is very important to ensure the stability of the input power supply.

If the input power supply is normal, then the fault may be caused by a damaged inductor or capacitor inside the switching power supply. You can check if the inductor and capacitor components are working properly and replace the damaged components if necessary.

In addition, a fault in the feedback control circuit can cause the output voltage to become unstable. The feedback control circuit is used to realize the regulation of the output voltage and current, if the circuit is faulty, the output voltage and current cannot be regulated correctly. At this time, you can check whether the feedback control circuit connection and components are normal to determine whether it needs to be repaired or replaced.

Fault three: switching power supply fails to protect

When the switching power supply fails to protect and stop output voltage and current, it may be due to overcurrent protection, overvoltage protection or over-temperature protection trigger. Over-current protection will be triggered when the output current exceeds the rated value, over-voltage protection will be triggered when the output voltage exceeds the rated value, and over-temperature protection will be triggered when the temperature of the switching power supply exceeds the safe range.

First, you should check whether the output current and voltage exceed the rated value. If the rated values are exceeded, it is necessary to check whether the load exceeds the rated value of the switching power supply. In addition, the over-temperature protection may be due to poor heat dissipation or a damaged heat sink, which can be resolved by checking the heat sink connection and condition.

If the output current and voltage do not exceed the rated values, then it may be caused by a faulty overcurrent protection, overvoltage protection, or overtemperature protection element. You can use a multimeter to check whether the protection components are working properly, and replace the faulty protection components if necessary.

In summary, switching power supply is a common power supply equipment, but in the case of prolonged use or improper operation, there may be a variety of failures. This article describes in detail the common failures of switching power supplies and their repair methods, designed to help readers solve switching power supply failures. Whether the switching power supply has no output, unstable output voltage or failsafe occurs, as long as you follow the correct steps and methods to check and repair, to a large extent, you can solve the problem.