Galaxy S4 charger buzzing after unplug

[Stonent]

Just wondering if it is normal for a smps to oscillate for about 30 seconds after being unplugged?  It also buzzes just like this when plugged in and is somewhat annoying if I don't have the ceiling fan on as I hear it constantly.

The charger is only a month or so old and came with a new phone.

[Jeroen3]

Cheap smps might have coil whine for as long as the main filter cap has some juice.
The only way to get rid of the coil whine is to change the load or the smps.

[robimarko]

Yeah it simply coil,because there is no load and current draw.
It will whine until main filter cap is not discharged

[wraper]

It might be a bad specimen as well. It doesn't mean that it is less reliable than usual, just may be that transformer coil or core is not fixed good enough. Worth to compare with another same model charger. As I understand Samsung provides 1 year warranty on chargers.

[robimarko]

It does not affect performance of charger,it is just annoying.
Mostly they fix it by adding a lot of glue and strongly fixing it to the pcb.

[amyk]

By "buzzing" do you mean mains hum or a high-pitched whine (sometimes with a bit of tick-tick-tick mixed in)? The former shouldn't occur with an SMPS, the latter is normal when unloaded since many of them will go into discontinuous mode.

[Stonent]

To me it sounds about 60hz, but I could be wrong. It makes the same noise when plugged in. If I have time, I might try to capture the sound.

It is possible it is higher than 60hz but the same note in a different octave.

[tautech]

To me it sounds about 60hz, but I could be wrong. It makes the same noise when plugged in. If I have time, I might try to capture the sound.

It is possible it is higher than 60hz but the same note in a different octave.

You could try winding a few turns on a piece of ferrite and connecting to your scope and read off the frequency counter.
That should give clues to it's origin.

[Stonent]

Yeah I was thinking about that. I don't have a frequency counter but can figure it out. 

[Shredhead]

I just got a galaxy note 3 and the charger cord is defective.  My power supply for it makes no noise though.  The only switching supplies I have that whine like that are the cheapest garbage on the planet.  Send the piece of crap back while you still can for a new one.