Hi guys

i have a problem in my car.
when i charge my phone (SAMSUNG GALAXY S2) in my car , i'm getting noise when i listen to the radio , it's sounds like there is a weak reception.
when i unplug the charger , there is no noise.

any idea what should i do ?
what may cause the interference ?
and how can i fix this ? maby some kind of a filter?

thanks!

 

I had this before , its the rf osc causing spurious radiation , i fitted a ferrite ring, it just moved the rf to a different band, maybe it may work for you.

 

thanks for the information , ill try to fit a ring

but i have a question for you , where is the rf osc ? you mean the osc from the phone ?

 

no oscillator on the charger, it will be a mini smps so it will be giving out rf all over the place, try the ferrite ring or it may be that wrapping the circuit in tin foil ( Faraday cage) without shorting out the pcb, and connecting the foil to the supply negative may cure the problem.

Try and use the charger on an external battery and see if its radiating, if it works ok on a seperate battery , then its feeding back down the supply.

 

I agree it's most likely radiated emissions from your charger being a 12V to 5V (probably) switch mode power supply. A harmonic of the switching frequency of the SMPS is probably getting back onto some length of cable, and it's a high enough frequency on a long enough cable that it makes a good antenna that interferes with your local AM or FM bands (or both).