Laptop power supply torroid filter

Jon Danniken wrote: ===================

A bit of RF noise will not affect a computer but will of course get into the front ends of a radio or TV set.

..... Phil

I probably helps pass FCC or CE radiated EMI limits.

Correct

Typically the toroid reduced radiated emission from the device in the 100MHz range

Thanks Phil. I am re-purposing a laptop power brick for another device because the voltage and ampere ratings are in line with what I need. I don't know if the surgery adapting it to a GX12-2 connector will permit me to keep the toroid on the end of the cable, so I am glad to know I can safely have the option of removing it.

Jon

Thanks John, I appreciate it.

Jon

If you remove it, it is not compliant any more. The manufacturer did not add it for fun ;-)

If it is at the laptop end of the cable, then it is likely to have been needed to make the *laptop* pass EMC testing (by preventing the long cable from acting as a transmitting antenna for the laptop), and so the power supply may well have been compliant without the laptop. (If the ferrite core had instead been placed at the power supply end of the cable then I would suspect that the power supply was the noisy bit.)

I have an Epson scanner which has such a huge ferrite core on the cable of its power supply that it is only slightly smaller in size and weight than the rest of the power supply. It has made feel a bit sorry for whoever it was that had a very bad day at the EMC lab.

It is mainly to stop the RF noise escaping from the laptop. The PSU lead would act like an aerial without the choke on it to block the RF.

Hence the position of the choke. The PSU should be relatively quiet although some bricks are much worse than others. Nasty cheap Chinese ones that skimp on the filtering components and sometimes also the proper electrical isolation - fit only to be used on US mains.

I can only use a Wifi dongle on my own fast laptop in combination with a USB extender cable. The local interference field near the case probably from adjacent USB sockets is enough to jam mobile phone signals.