Troubleshooting of switching power supply is easy or difficult, but as long as we grasp its core things and fully understand the basic structure and characteristics of switching power supply, it can quickly solve the fault of switching power supply equipment and achieve multiplier effect.

1. Check whether the large filter capacitor, rectifier bridge diode, and switch tube on the 300V have safety burns or explosions. The anti-interference circuit problem will also cause safety burns and blackening. It should be noted that the current detection resistor and the power control chip are generally burned out due to the breakdown of the switch tube. Negative temperature coefficient thermistors are also easy to burn out together with the insurance.

2. For no output, the phenomenon that the safety tube is normal indicates that the switching power supply does not work or enters a protective state. First, measure whether the start pin of the power control chip has a start voltage. If there is no starting voltage or the starting voltage is too low, the starting resistor and the components connecting the starting resistor should be checked for leakage. At this time, if the power control chip is normal, the above inspection can quickly detect the failure. If there is a startup voltage, measure the output of the manipulation chip to see if there are jumps of high and low levels at startup. If there is no trip, it means that the control chip is not good, the peripheral oscillation circuit components or the protection circuit are defective, and the control chip can be replaced first, and the peripheral components are re-checked; if there is a trip, the general switch tube is not good or damaged.

3. For the output voltage, but the output voltage is too high and other faults are generally from the sampling and voltage regulator manipulation circuit. The DC output, the sampling resistor, the sampling error amplifier, the coupler, and the power supply control circuit chip together form a closed control loop, any one of which will cause the problem of the output voltage rising.

4. There is a short circuit fault in the load of the switching power supply system (especially the short circuit of the DC/DC converter or poor performance, etc.), at this time, all loads of the switching power supply module circuit should be disconnected to distinguish whether the switching power supply design circuit is mainly or can be The load circuit is faulty. If the output of the voltage signal of the disconnected load circuit is normal, it means that the load is too heavy.

5. For the output voltage of the rectifier diode, the failure of the filter capacitor can be determined by the replacement method.