Talk about what faults may occur in the power adapter and wh

Source:AdminAuthor:WPOWER Addtime:2019-12-13 Click:
Talk about what faults may occur in the power adapter and what are the solutions to them?
  What faults will occur in the power adapter, and how can I solve them? Maybe we will encounter some in our daily life. Next, the professional manufacturer of power adapters, Wei Da Yuan Technology, made a detailed list for everyone.
  1. Short-circuit failure of the power supply load (especially short-circuit or poor performance of the DC / DC converter, 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 positive, it means that the load is too heavy; or it is still abnormal, it means that 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 reduced, which causes the switch tube to fail to conduct normally, increasing the internal resistance of the power supply and reducing the load capacity.
  4. Defective 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, 300V filter capacitor is bad, causing the power supply with poor load capacity, the output voltage will drop as soon as the load is connected.
   The high output voltage usually comes from the regulated sampling and regulated control circuit. In the closed control loop composed of DC output, sampling resistor, and 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.
  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 startup voltage of the startup pin of the power control chip. If there is no startup voltage or the startup voltage is too low, check the components external to the startup pin and the startup resistor for leakage.
  If the power control chip is normal, the fault can be quickly detected through the above monitoring. If there is a startup voltage, measure whether there is a high or low level transition at the output of the control chip at the moment of power-on. If there is no transition, it means that the control chip is damaged, the peripheral oscillation circuit components are damaged, or the protection circuit is faulty. Chips, inspection of peripheral components, inspection one by one; if the transition, most cases are defective or damaged switch.
  Mainly check the rectifier bridge, diodes, switching tubes and large filter capacitors on 300 volts. It may cause the fuse to burn or black, or it may be caused by a problem with the anti-interference circuit. It is particularly worth noting that the fuse burned due to the breakdown of the switch tube usually burns out the power control chip and the current detection resistor. Thermistors are also easily controlled by burnout power with fuses.     

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