What is the reason for the low output voltage of the power adapter?

1. Switching power supply load short-circuit fault (especially short circuit of DC/DC converter). At this time, first disconnect all the load of the switching power supply circuit, check whether the switching power supply circuit is faulty or the load circuit is faulty. If the load circuit is disconnected and the voltage output is normal, it means that the load is too heavy; or it is still not normal, indicating that the switching power supply circuit is faulty.

2. The output voltage terminal filter capacitor or rectifier diode is invalid, etc., which can be judged by the replacement method.

3. The performance of the switch tube is degraded, which causes the switch tube to fail to conduct normally, which increases the internal resistance of the power supply and reduces the load capacity.

4. Defective switching transformer not only causes the output voltage to drop, but also damages the switching tube.

5, 300V filter capacitor is poor, resulting in poor power supply load capacity, the load output voltage will drop when connected.

The fuse is normal, no output voltage

The fuse is normal and no output voltage indicates that the switching power supply is not working or has entered the protection state. The first step is to check the value of the starting voltage of the start 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 resistor are leaking.

Insurance burned or blown up

Mainly check the rectifier bridge, each diode, switch tube and large filter capacitors on 300 volts. It may also be caused by a problem with the anti-interference circuit. It is particularly noteworthy that the power supply control chip and the current sense resistor are usually burned out due to the breakdown of the switch tube. The thermistor is also easily burned out together with the insurance.