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Common faults of power supply

Chargers and power adapters are necessary in modern life, but what are the common faults of chargers and power adapters? How to repair them? Let's learn about them together, and it's convenient for life!



1、 Line fault
Line fault, including power line damage, no power supply, poor contact oxidation, etc. It is important to check whether the input line and output line are energized.
If there is a line fault, it can be solved by replacing the power cord.

2、 Output voltage too high
The high output voltage generally comes from the stabilized voltage sampling and stabilized voltage control circuit. In the closed control loop composed of DC output, sampling resistance, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits, any problem of any part will cause the output voltage to rise.

3、 Output voltage too low

The following are the main causes of low output voltage:
1 switch power supply load short circuit fault (especially DC / DC converter short circuit or poor performance, etc.), at this time, first disconnect all loads of switch power circuit, check whether the switch power circuit fault or load circuit fault. If the load circuit is disconnected and the voltage output is normal, it means that the load is too heavy; or if it is still abnormal, it means that the switch power circuit is faulty.
2. The failure of filter capacitor or rectifier diode at output voltage end can be judged by replacement method.
3. The performance of the switch tube decreases, which leads to the failure of normal conduction of the switch tube, the increase of internal resistance of the power supply and the decrease of load capacity.
4. The poor switch transformer not only causes the output voltage to drop, but also causes the insufficient excitation of the switch tube and damages the switch tube.
5300v filter capacitor is poor, resulting in poor load capacity of the power supply, and the output voltage of the load connected will drop.

4、 Insurance burned or blown up
Mainly check the rectifier bridge, diodes, switch tubes and large filter capacitors on 300 v. It may also be caused by the problem of anti-interference circuit.
In particular, it should be noted that the fuse burns due to the breakdown of the switch tube, which usually burns the power control chip and the current detection resistance. Thermistors are also easily burned with the fuse.
This is all for the common faults and maintenance of charger / power adapter. In addition, we should pay attention to the daily maintenance of charger / power adapter, so as to reduce the occurrence of faults and effectively extend the service life.

5、 The fuse is normal, no output voltage
The fuse is normal, no output voltage indicates that the switching power supply is not working or in the protection state. The first step is to check the starting voltage value of the starting pin of the power control chip. If there is no starting voltage or the starting voltage is too low, check whether the external components of the starting pin and the starting resistance are leaking.
If the power control chip is normal, the fault can be quickly found through the above monitoring. If there is starting voltage, measure whether there is high or low level jump at the output end of the control chip at the moment of power on. If there is no jump, it means that the control chip is damaged, the peripheral oscillation circuit components are damaged or the protection circuit is faulty. Check one by one by replacing the control chip and checking the peripheral components. If there is a jump, the switch tube is poor or damaged in most cases.