EM Noise fields in offline 2kW SMPS?

[cupoftea]

Doing a offline SMPS prototype…high power (2kW) so lots of EM noise fields all over the place. Primary and sec bias power is by way of wired_in cheap, isolated, 12v, offline , isolated wall-warts. Would you bother adding ferrite beads to the points on the PCB where these wall-warts wire in to?…to prevent possible noise issues messing up signals and control etc?

 

[scopeprobe]

Doing a offline SMPS prototype…high power (2kW) so lots of EM noise fields all over the place. Primary and sec bias power is by way of wired_in cheap, isolated, 12v, offline , isolated wall-warts. Would you bother adding ferrite beads to the points on the PCB where these wall-warts wire in to?…to prevent possible noise issues messing up signals and control etc?

No, Ferrite beads won't do anything useful unless you identify a very specific issue. If EM is an issue you'll want proper filters as opposed to ferrites. If your doing a 2kW supply its probably worth factoring in you auxilaries before you start and do away with the wall warts

 

[cupoftea]

Thanks, though do you agree that adding a ferrite bead will provide some impedance to high frequency noise?...which cant be a bad thing? AYK, the trouble with LC filters , is the real "bad-news" high frequency EM just goes right through the interwinding capacitance and reaks havoc thereafter.

 

[scopeprobe]

Thanks, though do you agree that adding a ferrite bead will provide some impedance to high frequency noise?...which cant be a bad thing? AYK, the trouble with LC filters , is the real "bad-news" high frequency EM just goes right through the interwinding capacitance and reaks havoc thereafter.

Depends on what noise your filtering, is some impedance enough? A ferrite will turn differential high frequencies (usually 10’s to 100’s Mhz) into heat and also provide some differential filtering when formed as an LC filter yes but will provide very little benefit at switching frequencies of most PSU’s and won’t really help with any common mode so adding ferrite for the sake of it won't provide much benefit unless you know what your issue is. Most filters will filter well above 100Mhz so whilst the SRF of the inductor has an influence on its performance it still filters