Common failures of adjustable switching power supply include fuse burnout, no output, high or low output voltage, poor load capacity, and failure of output voltage rectifier diode and filter capacitor. So how to repair the common faults of these adjustable switching power supplies?
The general process of troubleshooting for adjustable switching power supply:
1) Check whether the fuse of the power supply is blown, whether the capacitor is bulged, whether the resistance is black, etc .; 2) Smell whether there is "odd smell" inside the power supply, such as paste smell; 3) Ask the user about the use process and before the power supply is damaged Operation, integrating the information obtained at points 1 and 2 and focusing on questions; 4) according to the preliminary judgments obtained in the first 3 steps, further operation of the power supply to confirm the fault, such as borrowing a multimeter to detect the output voltage across the capacitor when the power supply is not powered, Check whether the switching power supply is vibrating.
The specific repair process of common faults of adjustable switching power supply:
The fuse is burnt out: the fuse of the power supply fuse needs to focus on checking the diodes of the rectifier bridge circuit, the high-voltage filter electrolytic capacitor and the power switch tube. The breakdown of the rectifier bridge circuit diode and high-voltage filter electrolytic capacitor or damage to the power switch tube will cause the fuse to burn out. (Note: The breakdown of the switch tube will cause the fuse to burn out, and the current detection resistor and power control chip will also be burned out.)
No output: This situation may be caused by the oscillation of the adjustable switching power supply, and the switch tube should be inspected intensively. If the collector of the switch tube does not get enough working voltage, the base electrode of the switch tube does not get the starting voltage, and the failure of the positive feedback circuit component of the switch tube will cause the phenomenon that the power supply has no output.
The output voltage is too high or too low: the failure of the power supply to output voltage is generally due to the failure of the voltage regulation sampling and voltage regulation control circuit. It is necessary to focus on this part of the circuit during maintenance.
Poor load capacity: after a long service life or long working hours, various components will have aging, switching tubes work unstable, stabilizing diode heat leakage, rectifier diode damage, etc., making the adjustable switching power supply have poor load capacity failure.
Failure of rectifier diode and filter capacitor at output voltage: Failure of rectifier diode and filter capacitor at output voltage is generally judged by the replacement method.
The structure of the adjustable switching power supply is complicated, and it needs to be carefully investigated when a fault occurs. The above is not absolute and needs to be combined with the actual situation.
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