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Common failures and maintenance methods of 12V2A power adapter
This article describes the common failures and maintenance methods of the 12V2A power adapter
1. Line failure
If the 12V2A power adapter has a line fault, including power cord damage, no power supply, poor oxidation contact at the contact points, etc.Focus on checking whether the input and output lines are powered on.
2. Overlow output voltage
The following are the main reasons for the low output voltage of 12V2A power adapter:
1 Switch power load short-circuit fault (especially DC/DC converter short-circuit or poor performance), in which case, first disconnect all the load of the switch power circuit, check whether the switch power circuit or the load circuit is faulty.If the load circuit is disconnected and the voltage output is normal, the load is too heavy.Or if it is still not normal, the switch power circuit is faulty.
2 Failure of filter capacitance or rectifier diode at output voltage end can be judged by substitution method.
3 The performance of the switch tube decreases, resulting in the switch tube not conducting properly, which increases the internal resistance of the power supply and decreases the load capacity.
4 Bad switching transformer not only causes output voltage to drop, but also causes insufficient switching tube excitation to damage the switching tube
The poor filter capacitance of 5 300V results in poor load capacity of the power strip, and the output voltage of the power strip decreases when the load is connected.
3. Over-high output voltage
If the output voltage of 12V2A power adapter is too high, it is generally caused by the voltage regulator sampling and the voltage regulator control circuit.Closed control loops consisting of DC output, sampling resistance, error sampling amplifier such as TL431, photocouple, power control chip, etc. Any problems with any of these parts will cause the output voltage to increase.
4. The fuse is normal and there is no output voltage
If the fuse is normal, the output voltage of the 12V2A power adapter is zero, indicating that the switching power supply is not working or is in a protective state.The first step is to check the value of the start voltage of the startup foot of the power control chip. If there is no start voltage or the start voltage is too low, check if there is any leakage in the components outside the startup foot and the start resistance.
If the power control chip of 12V2A power adapter is normal, the fault can be quickly detected by the above monitoring.If there is a start voltage, measure if there is a high or low level jump in the output of the control chip at the instant of switching on. If there is no jump, it indicates that the control chip is damaged, the peripheral oscillatory circuit component is damaged or the protection circuit is faulty. Check one by one by replacing the control chip and checking the peripheral components.If jumping, most cases are bad or damaged switch tube