Chargers and power adapters are indispensable items in modern life, but what are the common faults of chargers and power adapters? How to repair? Let's take a look together to facilitate life!
1. Line fault
Line failure, including the situation that the power cord is damaged and not powered, and the contact port is poorly oxidized. Focus on checking whether the input and output lines are energized.
If it is a line failure, it can be solved by replacing the power cord.
Second, the output voltage is too high
The output voltage is too high generally comes from the voltage regulation sampling and voltage regulation 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 one of the parts will cause the output voltage to rise.
3. The output voltage is too low
The following are the main causes of low output voltage:
1 Short-circuit fault of switching power supply load (especially short circuit of DC / DC converter or poor performance, etc.), at this time, first disconnect all loads of 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 abnormal, indicating that the switching power supply circuit is faulty.
2 The output voltage filter capacitor or rectifier diode failure, etc., can be judged by the replacement method.
3 The performance of the switch is reduced, which causes the switch to fail to conduct normally, which increases the internal resistance of the power supply and reduces the load capacity.
4 bad switching transformer not only causes the output voltage to drop, but also causes insufficient excitation of the switch to damage the switch.
5300V filter capacitor is bad, resulting in poor load capacity of the power supply, the output voltage will drop once connected to the load.
Fourth, the insurance burned out or blown up
Mainly check the rectifier bridge, each diode, switch tube and large filter capacitor at 300 volts and other parts. The fuse and blackening of the fuse may also be caused by a problem with the anti-interference circuit.
Pay special attention to the following: the fuse is burnt due to the breakdown of the switch tube, and the power control chip and the current detection resistor are usually burned out. The thermistor is also easily burnt out together with the fuse.
Common faults and repairs of the charger / power adapter are here. In addition, we should pay attention to the daily maintenance and maintenance of the charger / power adapter. This can reduce the occurrence of failures and also effectively extend the service life.
Fifth, the insurance tube 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 start voltage of the start pin of the power control chip. If there is no start voltage or the start voltage is too low, check whether the external components of the start pin and the start resistance leak.
If the power control chip is normal, the fault can be quickly found through the above monitoring. If there is a starting voltage, measure whether there is a high or low level transition at the output of the control chip at the moment of startup. If there is no transition, it means that the control chip is damaged, the peripheral oscillation circuit component is damaged or the protection circuit is faulty. By replacing the control Check the chip and peripheral components one by one; if it is jumping, most of the cases are bad or damaged switch.