Do I need a choke for a ACDC 5V 10W external power supply?

[mfd]

Hi,

I need to design an ACDC 10W 5V EPS in a small PCB. The reference designs I find all use choke for EMI. Is the choke really necessary to pass EMI testing for FCC? Most of commercial 5W EPS do not use chokes, they only use common inductors and filter caps. At what power level do you need to start using chokes?

Thank you,

MFD

 

[IanP]

At what power level do you need to start using chokes?
MFD

It's not power level - it's noise level ..
Have a look at the attached picture and it's really up to noise measurements which components of the noise reduction configuration must be included and which can be omitted ..

IanP
:-D