30 views Yuda Electronic (HK) Technology Co.,Limited. 2020-08-07
Chargers and power adapters are essential products in modern life, but what are the common faults of chargers and power adapters? How to repair them? Let’s take a look together to make life easier!
Common faults and maintenance of charger and power adapter!
One, line failure
Line faults, including the power cord is damaged and not energized, the contact port is oxidized and the contact is poor. Focus on checking whether the input line and output line are energized.
If the line fails, it can be solved by replacing the power cord.
2. The output voltage is too high
Excessive output voltage generally comes from the voltage stabilization sampling and voltage stabilization control circuit. In the closed control loop composed of DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits, any one of the parts will cause a problem to cause the output voltage to rise.
Three, the output voltage is too low
The following are the main causes of low output voltage:
1 Switching power supply load short circuit fault (especially DC/DC converter short circuit or poor performance, etc.), at this time, first disconnect all loads of the switching power supply circuit and 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, which means that the switching power supply circuit is faulty.
2 The failure of the filter capacitor or rectifier diode at the output voltage terminal can be judged by the replacement method.
3 The performance of the switch tube is reduced, 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 The poor switching transformer not only causes the output voltage to drop, but also causes insufficient excitation of the switching tube and damages the switching tube.
The 5300V filter capacitor is bad, resulting in poor load carrying capacity of the power supply, and the output voltage will drop as soon as the load is connected.
4. Insurance burned out or blown up
Mainly check the rectifier bridge, each diode, switch tube and the large filter capacitor on 300 volts. It may cause the insurance to burn and turn black, or it may be caused by a problem with the anti-interference circuit.
Special attention should be paid to the fact that the fuse is burnt due to the breakdown of the switch tube, which usually burns the power control chip and current detection resistor. The thermistor is also easy to burn out along with the insurance.
The 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, which can reduce the occurrence of failures and effectively extend the service life.
Five, 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 a protection state. The first step is to check the value of the starting voltage 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 resistor are leaking.
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 and low level jump at the output terminal 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 component is damaged or the protection circuit is faulty, and the control chip is replaced. Chips, check the peripheral components, and check them one by one; if they are changing, most of them are bad or damaged switch tubes.
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