Switching power supply circuit does not oscillate
Maintenance of switching power supply does not vibrate, you can take the photocoupler as a demarcation point, first determine whether the photocoupler or photocoupler before the failure, and then step by step to narrow the scope of the investigation, the specific operation is as follows: first photocoupler direct short-circuit, the photocoupler short-circuit is very simple, direct a pile of tin weld can be, so that it is equivalent to reducing the photocoupler of the internal resistance, short-circuit photocoupler, and then we measure the voltage, if the measurement of the main voltage has not changed, the fault is in the photocoupler! After the circuit, on the contrary, before the optocoupler circuit. Here switching power supply with light load, some switching power supply no load does not vibrate.
If the fault is in front of the optocoupler, mainly check whether the AC power input is problematic, whether the capacitor circuit is open, with the management chip to check the chip power supply and the chip pins of the correct voltage to ground. Although we give the photocoupler short circuit, but also to rule out whether the photocoupler itself is faulty.
If the optocoupler, check whether the switching transformer has a turn-to-turn short circuit or open circuit, if the switching transformer has a short circuit, then it is necessary to doubt whether the spike absorption circuit is caused by a short circuit, to prevent a misjudgement, because the switching transformer is bad the chances are very small, the pulse-width modulation transistor short circuit will cause the circuit does not vibrate.
If the repair experience is not enough to determine whether the original online damage, it is a little more trouble, remove the measurement, so more accurate. If the removed original is not a problem, then you can troubleshoot its fault associated with the relevant small devices, and gradually narrow the scope of investigation to determine the problem, beard and eyebrows together, which can easily lead to the face of the failure of a blank, do not know where to start.
As for the said vibration, I also make a brief explanation here: AC in the process of becoming DC, AC mains first rectified and filtered into DC for electronic circuits, this circuit includes high-frequency oscillator circuit, that is, DC into a variable frequency or pulse width of the pulse, this part is very important in switching circuits, the input voltage changes or the load increases and decreases, the oscillator circuit will be adjusted through the frequency or pulse width to keep the output stable. Or pulse width to keep the output stable, this is its role, to think about this role of course, we must vibrate, do not vibrate on the switching power supply failure, which is equivalent to adjust the fire or not regulate.
