Common faults and maintenance of chargers and power adapters!

Time of issue:2022-04-22
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Common faults and maintenance of chargers and power adapters!

Chargers and power adapters are essential in modern life, but what are the common faults of chargers and power adapters? How to repair them? Let’s take a look at it together to make life easier!

1. Line failure

Line failure, including power cord damage, no electricity, poor contact port oxidation, etc. Focus on checking whether the input line and output line are powered on.

If the line is faulty, it can be solved by replacing the power cord.

Second, the output voltage is too high

The high output voltage generally comes from the voltage-stabilizing sampling and voltage-stabilizing control circuits. In the closed control loop formed by the DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits, any problem in any of these parts will cause the output voltage to rise.

3. The output voltage is too low

The following are the main reasons for the 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 if it is still abnormal, the switching power supply circuit is faulty.

2. The failure of the filter capacitor or rectifier diode at the output voltage end 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. The poor switching transformer will not only cause the output voltage to drop, but also cause insufficient excitation of the switch tube and damage the switch tube.

The 5300V filter capacitor is not good, resulting in poor load capacity of the power supply, and the output voltage will drop as soon as the load is connected.

Fourth, the insurance burns out or blows up

Mainly check the rectifier bridge, diodes, switch tubes and large filter capacitors on 300 volts. It may cause the fuse to burn and become black, or it may be caused by a problem with the anti-jamming circuit.

In particular, it should be noted that the fuse is burned due to the breakdown of the switch tube, which usually burns the power control chip and the current detection resistor. The thermistor is also easy to burn out along with the fuse.

The common faults and maintenance of the charger/power adapter are mentioned here. In addition, we should pay attention to the daily maintenance and maintenance of the charger/power adapter, which can reduce the occurrence of faults and effectively prolong 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 start-up voltage of the start-up pin of the power control chip. If there is no start-up voltage or the start-up voltage is too low, check whether the components connected to the start-up pin and the start-up resistor are leaking.

If the power control chip is normal, the fault can be quickly found through the above monitoring. If there is a start-up voltage, measure whether the output terminal of the control chip has high and low level jumps at the moment of power-on. If there is no jump, it means that the control chip is damaged, the peripheral oscillation circuit components are damaged or the protection circuit is faulty. Chip, check peripheral components, check one by one; if it is jumping, in most cases, the switch tube is bad or damaged.

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