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Common Faults and Troubleshooting Methods of Power Adapter

  • Line Failure.
    Line failure, including power line damage and lack of power, contact oxidation contact and so on. Focus on the input line, the output line is electrified. If the line failure, can be through the replacement of power lines and other ways to solve.
  • Output Voltage is Too Low.
    The following are the main reasons for the low output voltage:
  1. short circuit fault of switching power supply load (especially DC/DC converter short circuit or poor performance etc.), at which time, all load of switching power supply circuit is disconnected first, Check whether the switching power circuit fault or load circuit failure. If the load circuit is disconnected and the voltage output is normal, it is overloaded; or it is still abnormal indicating that the switching power supply circuit is out of order.
  2. The output voltage end filter capacitor or rectifier diode failure can be judged by substitution method.
  3. The performance of the switch tube is decreased, which leads to the failure of the normal conduction of the switch tube, the increase of the internal resistance of the power supply and the decrease of the load capacity.
  4. The bad switching transformer not only causes the output voltage to decrease, but also leads to the insufficient excitation of the switch tube and thus damages the switch tube.
  5. 300V filter capacitance of the switch tube, which results in the poor load capacity of the power supply and the decrease of the output voltage of the power supply as soon as the load is connected.
  • Output Voltage is Too High.
    High output voltage generally comes from voltage-stabilized sampling and voltage-stabilized control circuit. The closed control loop composed of DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and so on, will cause the output voltage to rise if any part of the circuit has a problem.
  • Safety tube normal, no output voltage
    The safety tube is normal and no output voltage indicates that the switching power supply is not working or in a protective state. The first step is to check the value of the starting voltage of the starting pin of the power supply 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 resistance are leaking. If the power control chip is normal, the fault can be quickly found through the above monitoring. If there is a startup voltage, the output of the control chip is measured if there is a high or low level jump at the start of the chip. 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 broken. By replacing the control chip, the peripheral components are checked and checked one by one; In the event of a jump, most of the cases are bad or damaged switch tubes
  • Fuse Burned
    Mainly check rectifier bridge, each diode, switch tube and large filter capacitance over 330v and other parts. Lead to fuse burn, blackening, may also be caused by problems with anti-jamming circuits. It is important to note that the breakdown of the switch leads to the burning of the power supply control chip and the current detection resistor. Thermistors are also easily burned out with fuse.

 

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