Phone Charger Strange Noise

[Athosworld]

I have a Belkin phone charger and I have noticed that every time I disconnect the phone, It makes a series of strange noises, a high pitched one, a low pitched one and then it continues making a high pitched sound. I know that the transformer is making these sounds but, why does it make that series of sounds? Is it detecting that the phone has been unplugged and then it readjusts the duty cycle of the transformer driver transistor?

 

[Diver300]

Is it detecting that the phone has been unplugged and then it readjusts the duty cycle of the transformer driver transistor?

All the the phone chargers that I have seen have feedback to control the voltage. When little power is being taken, there will be periods of time when the output voltage remains high enough without any energy being fed to the transformer.

When the voltage has fallen enough, the transformer will be operated again.

The transformer operation can be single pulses, or bunches of pulses, which could account for the different sounds.

 

[Nigel Goodwin]

How old is it?, while it's absolutely true the charger will adjust itself to the load conditions, and noises will vary accordingly, if it's old it quite probably has sub-standard electrolytics inside, which have now gone high ESR. While it sounds like the feedback is 'just about' managing to control the supply (it's not gone BANG yet ) it may well be struggling, hence the much more audible noises than previously.

 

[Tony Stewart]

Possible sound sources are from Magnetostriction of ferrite triggered by repetitive cycles. When unloaded, there will be resonant power stored and dissipated at some cycle rate. The history or details of this unwanted symptom may give more clues.

 

[Athosworld]

How old is it?, while it's absolutely true the charger will adjust itself to the load conditions, and noises will vary accordingly, if it's old it quite probably has sub-standard electrolytics inside, which have now gone high ESR. While it sounds like the feedback is 'just about' managing to control the supply (it's not gone BANG yet ) it may well be struggling, hence the much more audible noises than previously.

I just purchased it. Im assuming it operates at an audible frquency.

 

[Nigel Goodwin]

I just purchased it. I'm assuming it operates at an audible frequency.

In which case it's probably fine - although if you're not happy with the noise, then you should return it.

 

[Dr_Doggy]

its a underrated cheap china trash capacitor that has failed, and will continue to destroy the circuits life and one of the reasons ima stop blowing my money on electronic doo dads just cos they twinkle