Author Topic: EMC PCB simulation  (Read 4020 times)

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Offline mattkoTopic starter

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EMC PCB simulation
« on: October 29, 2018, 10:08:47 am »
Hello!

I would like your input about simulating a PCB for EMC. The applications I'm most interested in is power electronics, so DC-DC and similar (with some communication). It should include conducted and radiated emissions.

I have a few questions:
-Which software is on the market (price does not matter)? (I found 3DS SIMULIA and Ansys Siwave).
-Do these kind of programs support importing Altium PCB file?
-How accurate are these kind of simulations and are they useful? I would like to hear your experience.
-How long does it take to prepare and run a simulation like this to get useful results?

I did not find a lot of info online about this topic, so I would be very happy to hear your experience :)

Thanks!

 

Online Berni

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Re: EMC PCB simulation
« Reply #1 on: October 29, 2018, 10:16:55 am »
Usually this sort of software is used for simulating RF circuits and antennas where the PCB itself is used as capacitors, inductors and delay lines.

But i would like to hear if anyone is using it for things like switchmode converters.
 

Offline T3sl4co1l

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Re: EMC PCB simulation
« Reply #2 on: October 29, 2018, 06:56:00 pm »
Heard of a couple things, ANSYS comes to mind.  If you can't budget five digits... just do it the old fashioned way.

It is possible to design a layout in such a way that it's relatively easy to analyze, and this can be hand-waved into a ballpark EMC assessment as well.  I can do this, but it's much too involved to describe here unfortunately.

Tim
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Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline mattkoTopic starter

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Re: EMC PCB simulation
« Reply #3 on: October 30, 2018, 01:52:23 pm »
It is possible to design a layout in such a way that it's relatively easy to analyze, and this can be hand-waved into a ballpark EMC assessment as well.  I can do this, but it's much too involved to describe here unfortunately.
Would u mind share some resources where this is described?

I saw that u can do some conducted EMC even in LT Spice if u know what u are doing :)
 

Offline T3sl4co1l

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Re: EMC PCB simulation
« Reply #4 on: October 30, 2018, 03:36:06 pm »
Not that I know of; my approach is synthesized from physics principles, not from any particular source.

There's always Henry W. Ott, Electromagnetic Compatibility Engineering, I forget if he goes into much detail as far as design-for-EMC-analysis, but many of the principles apply in general as part of signal quality and EMC control in the first place.

Principles like using reference planes, so that -- in my case -- a trace can always be analyzed as a transmission line over that reference plane, and its in-circuit equivalent is fairly obvious, and its consequences as far as EMC should be fairly straightforward.

Comparing between a well-grounded board and something a beginner would route (traces going every which way, and no ground pour, or a poorly connected pour), the intent is to reduce trace-to-trace coupling, so that instead of a random network of all fairly significant coupling factors (between pairs of traces), traces are reasonably well shielded from each other so they can be analyzed on a one-by-one basis.  Consider all the couplings between all traces on a PCB, as the coupling matrix: in a naive layout, a lot of terms will have significant magnitudes; in a well-grounded layout, the matrix will be nearly sparse (i.e., most of the terms have magnitudes small enough to ignore).

The less heavy-weight things to work with, as far as conducted emissions goes, is to consider the supernodes in the system.  Don't look at, e.g., the mains input as line and neutral; look at line and neutral together, with respect to ground.  Effectively, the common-mode analysis shorts H+N together -- justified by the large value X1 capacitor bridging them at RF.  Do the same for internal nodes, and any groups leaving the board (e.g., DC+/-, output +/-, cables..).  Note any unbalanced sources (e.g., switching transistor tab screwed to heatsink: a capacitor from switch node (lots of RF voltage) to ground; similarly between windings in the transformer, for isolated SMPS), and reduce the circuit to its common mode equivalent.  Now you have a topology with known (approximately) noise voltages and branch impedances, and you have something to build a filter around.

So, yeah, I'm dancing around E&M fields, network theory, linear algebra, circuit analysis theory and more here.  It's... not easy to explain in a post. :scared:

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 
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Offline ddavidebor

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Re: EMC PCB simulation
« Reply #5 on: November 03, 2018, 02:22:14 pm »

-Do this kind of programs support importing Altium PCB file?


They often support importing ODB++ which altium can export
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Offline johnharold

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Re: EMC PCB simulation
« Reply #6 on: February 24, 2019, 03:50:50 am »
 



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