Analysis of common faults of switching power supplies
No DC voltage output or unstable voltage output
If the fuse is intact, there will be no output of DC voltage at all levels under load. This situation is mainly caused by the following reasons: open circuit and short circuit in the power supply, overvoltage and overcurrent protection circuit failure, auxiliary power supply failure, oscillation circuit not working, excessive power load, breakdown of rectifier diodes in the high-frequency rectification and filtering circuit, leakage of filtering capacitors, etc. After measuring the secondary components with a multimeter and ruling out the breakdown of high-frequency rectifier diodes and load short circuits, if the output is zero at this time, it can be confirmed that there is a fault in the control circuit of the power supply. If there is partial voltage output, it indicates that the front-end circuit is working normally, and the fault lies in the high-frequency rectification and filtering circuit. The high-frequency filtering circuit is mainly composed of rectifier diodes and low-voltage filtering capacitors to output DC voltage. The breakdown of rectifier diodes will cause the circuit to have no voltage output, and the leakage of filtering capacitors will cause faults such as unstable output voltage. By using a multimeter to statically measure the corresponding components, damaged components can be detected.
Poor power load capacity
Poor load capacity of power supply is a common fault, which usually occurs in old or long-term power supplies. The main reasons are aging of various components, unstable operation of switch tubes, and failure to dissipate heat in a timely manner. Special attention should be paid to checking whether the voltage regulator diode is overheating or leaking electricity, whether the rectifier diode is damaged, and whether the high-voltage filter capacitor is damaged.
