Switching Power Supply Overhaul Tips
Switching power supply troubleshooting is easy and difficult, but as long as you grasp the core of things, that is, fully familiar with the basic structure and characteristics of the switching power supply, it will be able to quickly To troubleshoot switching power supply, to achieve twice the result with half the effort. The following electrician learning network for everyone to introduce the switching power supply overhaul skills.
1 for the insurance burn or fried faults mainly check the 300V on the large filter capacitors, rectifier bridge diodes and switching tubes and other parts of the anti-interference circuit problems can also lead to insurance burn, black. Problems with the anti-interference circuit can also lead to insurance burn, black. It should be noted that: due to the breakdown of the switching tube caused by the insurance burn will generally be the current detection resistor and power control chip burned out. Negative temperature coefficient thermistor is also easy to be burnt together with the fuse.
2. For no output, the fuse is normal, this phenomenon shows that the switching power supply does not work or enter the protection state. First of all, measure the power control chip start If there is no starting voltage or the starting voltage is too low, then we should check the starting resistor and start the external components of the foot leakage, at this time, if the power supply If the power control chip is normal, the above checks can quickly find the fault. If there is a starting voltage, then measure the output of the control chip in the boot moment whether there is a high and low level jump. If there is no jump, the control chip is bad, peripheral oscillation circuit components or protection circuit problems, can replace the control chip, and then check the peripheral components; if there is a jump, the control chip is bad, peripheral oscillation circuit components or protection circuit problems, can replace the control chip, and then check the peripheral components. If there is a jump, generally bad or damaged switching tube.
3. For the output voltage, but the output voltage is too high for this fault generally comes from the regulator sampling and regulator control circuit. In the DC output, sampling resistor, DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits together constitute a closed control loop, any one of the problems will lead to output voltage voltage rise.
4. Switching power supply load has a short-circuit fault (especially DC / DC converter short circuit or poor performance, etc.), at this time, you should disconnect all the switching power supply circuit load, in order to distinguish between the switching power supply circuit At this time, you should disconnect all negative loads of the switching power supply circuit to distinguish whether the switching power supply circuit or the load circuit is faulty. If you disconnect the load circuit voltage output is normal, indicating that the load is too heavy; or still not normal that the switching power supply circuit is faulty. The switching power supply circuit is faulty.
5. For the output voltage end of the rectifier diode, filter capacitor failure, you can judge by substitution method.
