Common faults and troubleshooting methods of wall plug in adapter:
1. Circuit fault
Line fault, including power line failure, poor contact oxidation contact, etc. Check whether the input line and output line are energized.
If the line fault, it can be solved by the power line replacement or other ways.
2. The output voltage is too low
The main causes of output voltage depression are as follows:
2.1 load short circuit fault of the switching power supply (especially short circuit or poor performance of DC/DC converter). At this time, first of all, disconnect all the load of the switching power supply circuit, and check whether there is a fault of the switching power supply circuit or the load circuit. If the load circuit is disconnected and the voltage output is normal, the load is too heavy; If it is still abnormal, the switch power circuit is out of order.
2.2 Filter capacitance or rectifier diode failure at the output voltage end can be determined by the substitution method.
2.3 The performance of the switch tube decreases, resulting in the failure of the switch tube to conduct normally, increasing the internal resistance of the power supply and decreasing the load capacity.
2.4 Poor switching transformer, which not only causes output voltage drop but also causes insufficient excitation of switching tube and damages the switching tube.
2.5 300v filter capacitor is bad, resulting in poor load capacity of the power supply, and the output voltage will drop once the load is connected.
3. The output voltage is too high
High output voltage usually comes from stable voltage sampling and control circuit.
4. The fuse is normal without output voltage
The fuse is normal and no output voltage indicates that the switching power supply is not working or is in the protection state. The first step is to check the starting voltage value of the starting pin of the power supply control chip. If there is no starting voltage or the starting voltage is too low, check the external components of the starting pin and whether the starting resistance is leakage.
If the power control chip is normal, the fault can be quickly detected through the above monitoring. If there is a starting voltage, measure whether there is a jump of a high or low level at the output end of the control chip at the moment of starting. If in the jump, most cases are the switch tube is bad or damaged.
5. Insurance burn out or blow up
Check the rectifier bridge, diodes, switching tubes and large filter capacitance over 300 volts. Causes of insurance burning, blackening, can be possibly the anti-interference circuit problems. In particular, the safety burn due to the breakdown of the switch tube usually burns out the power supply control chip and the current detection resistor. Thermistors can easily burn out with insurance.