1.Line failure

The line is faulty, including the power cable is damaged, the contact port is not powered on, and the oxidation contact is poor. Focus on checking whether the input and output lines are powered on.

If the line is faulty, replace the power cable.

Second, the output voltage is too low

The following are the main causes of low output voltage:

2.1 Switching power supply load short-circuit fault (especially DC/DC converter short-circuit or poor performance, etc.), at this time, first disconnect all the load of the switching power supply circuit, check whether the switching power supply circuit fault or the load circuit fault. If the load circuit is disconnected and the voltage output is normal, it indicates that the load is too heavy; Or the switching power supply circuit is faulty.

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

2.3 The performance of the switch tube deteriorates, causing the switch tube to fail to perform normally, which increases the internal resistance of the power supply and decreases the load capacity. 2.4 Bad switching transformer not only causes the output voltage to drop, but also causes the switching tube to be understimulated, which damages the switching tube 2.5300V filter capacitance, resulting in poor load capacity of the power supply, and the output voltage will drop once the load is connected.

3.The output voltage is too high

The high output voltage usually comes from the voltage regulator sampling and voltage regulator control circuit. In the DC output, sampling resistance, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits composed of closed control loop, any part of the problem will cause the output voltage rise.

Four, the safety pipe is normal

No output voltage fuse is normal, no output voltage indicates that the switching power supply is not working or entered the 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 components and starting resistance connected to the starting pin 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, the output end of the control chip is measured whether there is a high or low level jump at the start of the moment, if there is no jump, it indicates that the control chip is damaged, the peripheral oscillation circuit is damaged or the protection circuit is faulty, by replacing the control chip and checking the peripheral components, check one by one; If in the jump, most cases for the switch tube is bad or damaged.

5.The insurance is burned or blown up

Mainly check the rectifier bridge, the diode, the switch tube and the large filter capacitor on 300 volts. Lead to burning, blackening, may also be caused by a problem with the anti-interference circuit. Of particular note is that the breakdown of the switching tube causes the ignition, which usually burns out the power control chip and the current detection resistor. Thermistors can also easily be burned out along with the safety.