1. Line failure
Wiring failure, including the power cord is damaged and not powered, the touch port is oxidized and the touch is poor. Focus on checking whether the input line and output line are energized.
If a wiring problem occurs, it can be resolved by replacing the power cord.
2. The output voltage is too high
Excessive output voltage usually comes from voltage stabilization sampling and voltage stabilization control circuits. In a closed control loop composed of DC output, sampling resistor, error sampling amplifier (such as TL431), optocoupler, power control chip and other circuits, any one component will cause the output voltage to rise.
Third, the output voltage is too low
The following are the main reasons for low output voltage:
1 Switching power supply load short-circuit failure (especially DC/DC converter short-circuit or failure, etc.), at this time, first disconnect all loads of the switching power supply circuit, and then check whether the switching power supply circuit is faulty or whether the load circuit is faulty. If the load circuit is disconnected and the voltage output is normal, it means the load is too heavy; or if it is still abnormal, it means the switching power supply circuit is faulty.
2 The filter capacitor or rectifier diode failure at the output voltage end can be judged by replacing it.
3 The function of the switching tube is reduced, causing the switching tube to fail to conduct normally, and the internal resistance of the power supply increases, which can reduce the load.
4 The switching transformer is defective, not only the output voltage drops, but the switching tube is insufficiently excited, which damages the switching tube.
The 5300V filter capacitor is not enough to form a load power supply. After connecting the load, the output voltage will drop.
four. Burn or blow up safely
First look at the 300-volt rectifier bridge, diodes, switching tubes and large filter capacitors. It may cause safe burning and blackening, or it may be caused by a problem with the anti-interference circuit.
Special attention: due to the failure of the switch tube, the power control chip and the current detection resistor are usually burned out. The thermistor is also very simple and safe to burn out.
Common faults and repairs of the charger/power adapter are here. Otherwise, you should pay attention to the daily maintenance and maintenance of the charger/power adapter to reduce the occurrence of failures and effectively expand the scope of use. life.
5. The safety tube is normal and has no output voltage
The safety tube is normal, and there is no output voltage to indicate that the switching power supply is not running or under maintenance. The step is to check the start voltage value of the start pin of the power control chip. If there is no starting voltage or the starting voltage is too low, please check the external components of the starting pin and the starting resistance for leakage.
