Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Cause of conducted common mode noise in an smps?

Status
Not open for further replies.

grizedale

Advanced Member level 3
Joined
Jun 13, 2011
Messages
838
Helped
17
Reputation
34
Reaction score
17
Trophy points
1,298
Activity points
8,804
Hello,

In an offline SMPS, please can you confirm that conducted common mode noise is ONLY caused by signals which radiate out of the switching stage and return to the neutral wire at a point outside of the mains input connector.?

So, for common mode noise to occur, some signal must actually *radiate* out from the smps.?

...this must be the case, because current ALWAYS travels in loops, and so any noise that doesnt radiate will simply loop back and go back down the neutral wire....and thus NOT produce common mode noise.?
 

Loop current ought to result in differential mode noise, but
not all current returns, some goes out the output, and the
imbalance might appear to have some common mode
component.

To the extent that AC ground current and input current
are in phase (likelier during edges than the quasi-DC
settled conduction periods) the noise will be put to
"common mode" category.

If input ground is your reference point and VIN has
a perturbation, is common mode noise then just half
the differential noise?
 

any electronic device has Johnson–Nyquist noise .....
Johnson
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top