Switching power supply is an essential component of various electronic devices, and its functionality directly affects the technical specifications and safe and reliable operation of electronic devices. Due to the fact that the key components inside the switching power supply operate in high-frequency switching conditions, with low power consumption, high conversion rate, and only 20% -30% of the volume and weight of linear power supplies, it has become the mainstream product of regulated power supplies. The maintenance of electrical problems in electronic devices follows the principle of starting from easy to difficult, fundamentally starting from the power supply. After confirming that the power supply is normal, other parts of the equipment can be repaired, and power supply problems account for the majority of electrical problems in electronic devices. Therefore, understanding the basic operating principles of power supplies, as well as their maintenance techniques and common problems, is beneficial for shortening the repair time of electronic equipment problems and improving personal equipment maintenance skills.

1. No output, the fuse is normal

This phenomenon indicates that the switch power supply is not operating or has entered a maintenance condition. Firstly, it is necessary to measure whether there is engine voltage on the engine pin of the power control chip. If there is no engine voltage or the engine voltage is too low, it is necessary to check whether the engine resistance and external components of the engine pin are leaking electricity. If the power control chip is normal at this time, the above inspection can quickly detect the hair disease. If there is a starting voltage, measure whether there is a high or low level jump at the output terminal of the control chip at the moment of startup. If there is no jump, it indicates that the control chip is broken, or there are problems with the peripheral oscillation circuit components or maintenance circuit. You can replace the control chip first and then check the peripheral components; If there is a jump, it is usually due to poor or damaged switch tubes.

2. Insurance burns or explodes

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

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

This kind of problem 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, and any problem at any point will cause the output voltage to rise.

4. In addition to the voltage stabilization control circuit causing low output voltage, there are also some reasons that can cause low output voltage:

b. The failure of rectifier diodes and filtering capacitors at the output voltage terminal can be identified through substitution method.

c. The decrease in the function of the switch tube will inevitably lead to the inability of the switch tube to conduct normally, increasing the internal resistance of the power supply and reducing its load capacity.

Article source: Jiangmen Rainproof Power Switch http://www.gddpdz.com/