Switching power supply how maintenance
Check whether the input, and then check the switch control circuit part, and finally the power drive sector.
Do not burn insurance, check the resistance and electrolysis of the starting circuit. Burned, the power tube is usually burned. To be fully checked. Otherwise energized and burned.
1, analysis circuit, draw a block diagram.
2, the use of external auxiliary power to detect the oscillation circuit.
3, detection of measurement output sampling circuit.
4, one by one detection, measurement of the various block diagram of the work situation.
5, with a load to detect a working point is normal.
6, remove the external auxiliary power supply, restore the normal power supply, check the work of all the work is normal.
7, with a load of 24 hours or 72 hours test is normal.
Above for the basic order, but also according to the specific appearance, and specific characteristics of the circuit analysis.
1. No output, the fuse is normal This phenomenon shows that the switching power supply is not working or into the protection state. First to measure the power control chip boot pin whether there is a starting voltage, if no start voltage or start voltage is too low, you have to check the starting resistor and start the foot of the external components of the leakage, this time if the power control chip is normal, then the above check You can quickly find the fault. If there is a starting voltage, then the output of the measurement control chip in the boot moment whether there is a high, low level of the jump, if no jump, indicating that the control chip is bad, peripheral oscillator circuit components or protection circuit problems, Chip, and then check the external components; if a jump, the switch is generally bad or damaged.
2. Insurance burn or fry the main inspection 300V on the large filter capacitor, rectifier bridge diodes and switch tubes and other parts, anti-jamming circuit problems can also lead to insurance burn, black. It should be noted that: due to the breakdown of the switch lead to insurance burns will generally be the current detection resistor and power control chip burned. Negative temperature coefficient thermistor is also easy to burn together with insurance.
3. There are output voltage, but the output voltage is too high This failure is generally from the regulator sampling and regulator control circuit. In the DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits together constitute a closed control loop, any problem will lead to an increase in output voltage.
4. Output voltage is too low In addition to the regulator control circuit will cause the output voltage is low.
