What are the common faults of switching power supply?

Fuse fuse

Generally speaking, fuse wire indicates that there is something wrong with the internal wiring of the power supply. Because the power supply operates under the condition of high voltage and high current, the fluctuation and surge of the grid voltage will cause the instantaneous increase of the current in the power supply and cause the fuse to fuse. The emphasis should be put on checking the rectifier diode, high voltage filter electrolytic capacitor, inverter power switching transistor and so on, and checking whether there is breakdown, open circuit, damage and so on. If it's a fuse, you should first look at the components on the circuit board to see if they're burned and electrolyte spills. If you don't find the above, use a multimeter to measure whether the switch tube has a breakdown short circuit. It is necessary to pay special attention to: when a component is found to be damaged, it must not be replaced and turned on directly. This is very likely because other high-voltage components are still in trouble and will be replaced by damaged components.

No DC voltage output or voltage output instability.

If the wire is intact, there will be no DC voltage at all levels under load. This situation is mainly caused by the following reasons: open circuit, short circuit, over-voltage, over-current protection circuit fault, auxiliary power failure, oscillatory circuit is not working, the power load is too heavy, high-frequency rectifier filter circuit rectifier diode is broken down, filter capacitor leakage and so on. If the output is zero, then the control circuit of the power supply must be out of order. If a part of the voltage output indicates that the former circuit works normally, the fault is in the high frequency rectification filter circuit. The high frequency filter circuit mainly consists of rectifier diode and low voltage filter capacitor. The breakdown of rectifier diode will cause no voltage output and the leakage of filter capacitor will cause unstable output voltage. The damaged components can be detected by measuring the corresponding components with multimeter.

Poor power load capability

The poor load capacity of power supply is a common fault, which usually occurs in old-fashioned or long-time power supply. The main reason is that the components are aging, the switching tube is unstable, and there is no timely cooling. It should focus on checking whether the voltage regulator diode is heat leakage, rectifier diode damage, high-voltage filter capacitor damage.