Switching power supply is an indispensable component of various electronic devices, and its performance is directly related to the technical indicators of electronic devices and whether they can work safely and reliably. Due to the key components inside the switching power supply working in the high-frequency switching state, low power consumption, high conversion rate, and only 20 percent -30 percent of the volume and weight of linear power supplies, it has become the mainstream product of regulated power supplies. The maintenance of electrical faults in electronic equipment follows the principle of starting from easy to difficult. Basically, it starts with the power supply, and after confirming that the power supply is normal, other parts of the equipment can be repaired. Power supply faults account for the majority of electrical faults in electronic equipment. Therefore, understanding the basic working principle of the starting power supply, familiarizing oneself with its maintenance skills and common faults, is beneficial for shortening the repair time of electronic equipment faults and improving personal equipment maintenance skills.

1. No output, safety tube is normal

2. Safe burning or frying

Mainly inspect the large filtering capacitor, rectifier bridge diodes, switch tubes, and other parts on the 300V. If there are problems with the anti-interference circuit, it can also cause fuse burning and blackening. It should be noted that fuse burning caused by switch tube breakdown usually burns out the current detection resistor and power control chip. Negative temperature coefficient thermistors are also easily burned out along with the fuse.

3. There is an output voltage, but the output voltage is too high

This type of fault usually comes from the voltage stabilization sampling and voltage stabilization control circuit. The DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip, and other circuits together form a closed control loop. Any problem at any point will cause an increase in output voltage.

4. If the output voltage is too low, besides the voltage stabilizing control circuit, there are also some reasons that can cause low output voltage: