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Causes of damage to the power adapter and treatment methods

16 views Yuda Electronic (HK) Technology Co.,Limited. 2020-09-11

With the rapid development of technology and the popularization of personal smart mobile devices, power adapters have become one of the essential daily necessities for people. There are many kinds of power supplies, such as solar batteries, lithium batteries, mobile batteries, etc., but the power adapters corresponding to different batteries are also different. During daily use, the power adapter will be damaged, so common power supplies What are the reasons for the damage of the adapter? Let’s take a look at the summary of the reasons for the damage of the power adapter that the power adapter manufacturer has compiled for you:


The first type: output voltage is too high


Excessive output voltage generally comes from 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 components will cause the output voltage to rise.


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 or low level jump at the output 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 oscillator 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.


The second type: 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.


The third type: insurance burned out or blown up


Mainly check the rectifier bridge, the diodes, the 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. It is especially worth noting that the fuse is burnt 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 insurance.


Type 4: The output voltage is too low


The following are the main causes of low output voltage:


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


2, 300V filter capacitor is poor, resulting in poor load capacity of the power supply, and the output voltage will drop when the load is connected.



3. Switching power supply load short-circuit failure (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 the load is too heavy; or it is still abnormal, it means the switching power supply circuit is faulty.



4. 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.



5. The failure of the filter capacitor or rectifier diode at the output voltage end can be judged by the replacement method.

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