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What is the main reason for the low output voltage caused by the power adapter?
Time:2018-3-3 Read:
The following are the main reasons for the low output voltage caused by the power adapter.
1, switching power supply load short circuit fault (especially DC/DC converter short circuit or poor performance), at this time, first disconnect all load of switch power circuit, check whether switch power circuit fault or load circuit fault. If the load circuit is disconnected and the voltage output is normal, it is the overload of the load; or it is still unnormal to indicate that the switch power circuit has a failure.
2, the output voltage end filter capacitor or the failure of the rectifier diode can be judged by the replacement method.
3, the performance of the switch tube decreases, which leads to the failure of the switch tube to operate normally. The internal resistance of the power supply is increased and the load capacity is reduced.
4. The switching transformer is bad, which not only causes the drop of the output voltage, but also causes the switch tube to be insufficient to damage the switch tube.
5, 300V filter capacitor is bad, resulting in poor power supply capacity, and the load output voltage will decrease.
Exorbitant output voltage
The high output voltage is generally derived from the steady voltage sampling and the voltage control circuit. A closed loop is composed of DC output, sampling resistance, error sampling amplifier, such as TL431, optocoupler, power supply control chip and other circuits. Any part of the problem will cause output voltage to rise.
The safety pipe is normal and no output voltage
The safety pipe is normal and there is no output voltage indicating that the switching power is not working or entering the state of protection. The first step is to check the starting voltage value of the power supply control chip's boot pin. If there is no starting voltage or low starting voltage, check whether the external components of the boot pin and the starting resistor are leakage.
If the power control chip is normal, the fault can be detected quickly by the above monitoring. If the starting voltage, the measured output end of the control chip at the moment of starting the existence of high and low level of the jump, if no jump, the fault control chip damage, peripheral components damage and oscillation circuit protection circuit, by replacing the control chip, peripheral component inspection, the inspection is performed; if the jump in most cases, as the switch tube is bad or damaged.
Burn out or blow up
Mainly check the rectifier bridge, the diode, the switch tube and the large filter capacitor on the 300 volt. It causes insurance to burn, blacken, and may also be caused by an anti-jamming circuit. It is particularly noteworthy that the switch tube breakdown causes the insurance to burn and usually burns the power control chip and the current detection resistance. The thermistor is also easily burnt out with the insurance.
Keywords: smart card + USB | desktop power adapter | USB charger | wall adapter | car charger | mobile phone clip | power supply
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