Analysis of common faults of switching power supply
In general, a blown fuse indicates a problem with the internal wiring of the power supply. Due to the high voltage and high current operation of the power supply, fluctuations and surges in the grid voltage can cause an instantaneous increase in the current inside the power supply, leading to the melting of fuses. The key should be to check the rectifier diode, high-voltage filter electrolytic capacitor, inverter power switch tube, etc. at the input end of the power supply, and check whether these components have breakdown, open circuit, damage, etc. If the fuse is indeed blown, you should first check the various components on the circuit board to see if their surfaces have been burnt or if there is electrolyte overflow. If the above situation is not found, use a multimeter to measure whether the switch tube has a breakdown or short circuit. It is important to note that when a component is found to be damaged, it should not be replaced and turned on directly. This is likely to cause damage to the replaced component due to other high-voltage components still having faults. It is necessary to inspect and measure all high-voltage components of the above circuit before completely eliminating the problem of fuse melting. Humidity sensor probe, stainless steel electric heating tube PT100 sensor, cast aluminum heater, heating coil fluid solenoid valve
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.
