Charger Noise when unplugged

The reservoir capacitor discharging.

I think it might because there is still a lot of electricity in the capacitor of its internal circuit when you are unplug a charger, it will be released through the circuit components after the charger is powered off.

Nigel Goodwin said:

The reservoir capacitor discharging.

Click to expand...

The reservoir capacitor is used for momentary (milliseconds) mains outages, right?

But the capacitor is typically a low rating (my charger is a small mobile one) around 2 to 5 microfarads, how could it last too long?

Athosworld said:

The reservoir capacitor is used for momentary (milliseconds) mains outages, right?

Click to expand...

The input cap after the AC rectifier has to be more than large enough to maintain the working DC voltage in to the switched mode section, through AC half cycles, at full load.

If the device is not loaded, the power used internally could be eg. a hundredth or a thousandth of the maximum through power, and decreasing as the cap voltage falls, so they can take a while to fully discharge and shut down.

Athosworld said:

The reservoir capacitor is used for momentary (milliseconds) mains outages, right?

Click to expand...

No, it's to convert the rough DC to 'smooth' DC - it's size is dependent on the power requirements

Athosworld said:

But the capacitor is typically a low rating (my charger is a small mobile one) around 2 to 5 microfarads, how could it last too long?

Click to expand...

It has to be large enough to do it's job, it's only small because the power requirements of the charger are very small - hence when you unplug it, it slowly discharges, and as the voltage drops the switch-mode controller tries to maintain the output voltage, so the frequency changes as it does. Eventually the voltage is too low, and the switch-mode controller switches off.

Nigel Goodwin said:

No, it's to convert the rough DC to 'smooth' DC - it's size is dependent on the power requirements

Click to expand...

Yes, i know.
I meant that it has the second function of keeping the oscillator running if there’s a momentary outage of mains.

Athosworld said:

Yes, i know.
I meant that it has the second function of keeping the oscillator running if there’s a momentary outage of mains.

Click to expand...

Not really, that's just an 'unexpected' bonus of the way it works.