Great job 👍

Quoting the results of your near field top emission measurements (see time 2:55), the solid plane has -36 dbm emissions while the other configurations have -40 dbm emissions. It is my understanding that a more negative value means less emissions - which is better in terms of EMC. Based on this, the solid plane emits more power (-36 dbm) compared to the other configurations (-40 dbm). Does that make sense?

Informative demo. Thanks

Thank you !

Very helpful!

subscribed because of the demo!!! Thanks

Hi, Thanks for the useful demonstration - I expected those results. In my opinion, the cutouts are always tricky and should be avoided. The copper serves as a return path for switching edges/peaks and if you remove it, the noise will travel somewhere else - its power does not disappear.

Great

too much theoratical

This video started slow with the basics, but ended up making some good points about common mode vs differential mode noise, and pcb track design. Thanks

Does the Scan Phone show the conducted emissions or radiated emissions?

It would be great to see the effect of having a shield removed in an RF board

This has got to be the best application of AR I've seen. Such a great idea. I'm scared to ask the price... As they say, 'if you have to ask you can't afford it'. But are you able to share a ball-park cost?

Great video 👍 It would be interesting to see if there is any measurable increase in ripple/noise in the power supply output too. I.e. is additional noise present on the output (via ground plane) instead of being radiated.

Another thing I've been doing in my designs is not using a filled polygon for the switching net. It's just a small length of trace so current carrying capabilities are typically not a problem but reducing the capacitance seems to help keeping ringing down

This is very helpful, thanks. Strangely I was searching for this answer just yesterday evening and I see this video in my LinkedIn feed today ! Questions I have are - is what you have shown, applicable to all dc-dc converters or do you think it could vary from board to board ? for e.g., switching frequency? How does the result change for a multi layer board where the ground plane is not immediately below the power plane (This question might not be too relevant since designers usually place the GND plane of DC-DCs right below the power plane ? Lastly, does this observation apply to even a flyback inductor(transformer). In a flyback converter I designed long back, I was advised to remove copper under the transformer.

I've laid out hundreds of boards with switching supplies going back to the early 90's. I examine each circuit to see where the current is going and design around that. I usually use as much plane as possible, sometimes making a "moat" 3/4 of the way around the switcher so that any wild currents stay within a limited area, especially if the supply is near analog parts. For the most part, more copper is better. Also removing the copper under an inductor seems like a good idea in some cases, as PS performance can be affected for some inductor types.

Hi Andy, nice video again! But I'm a little puzzled when you say "clear the ground plane". Do you mean "make sure the ground plane is clear of interruptions" (ie: it's continuous), or do you mean "clear the ground plane away" (ie: remove it, as in having a cutout)?

Thank you sir

This is amazing work. So well explained. Thank you!

Hey I found you in my e-mail, you wanted to connect? I haven't logged into Linkedin in years

Reducing BW works only if the signal is always narrowband. Be careful with an RE measurement outside a shielded chamber that the preamp is not overloaded in or out-of-band.

6:30 "pretty decent loop antenna structure for efficiently converting conducted noise into a magnetic field but by moving the sense resistor to the other side of the inductor the rate of change of voltage and current is now much slower which limits the ability of the resistor to radiate" - I'm a bit puzzled by this remark. The inductor and resistor are in series, so surely the rate of change of current is the same in both components, and also the same in both design "A" and "B"? I do realize that with the resistor before the choke it will see a higher AC voltage than if it's after the choke (in which case quite low VAC). Do you think that actually the contrast in VAC makes the significant radiation difference? I suggest a couple of alternative rationales for moving the resistor loop: In the "A" position: In version "A", the large VAC meant significant parasitic capacitive loading when attaching a current clamp at that location (or a differential probe for that matter), which might have made a noticeable change in the behavior of the switching circuit -- it's tantamount to adding a snubber at that location. Having noticed that in the A version, they were motivated to swap the component order for the "B" version, so as to be able to take the same measurement, but without disturbing the switching operation. Or it could be just that using a differential probe across the resistor in the "A" design subjected the probe to relatively high AC voltages, in which, aside from possible probe damage, most of the AC voltage is common mode and not the voltage drop corresponding to the desired current measurement, in turn requiring a high CMRR in the probes for an accurate current reading. Whereas that's not a concern in the "B" design, where the VAC is far smaller, but the different voltage reflecting current is the same as before, so a far higher signal to CM ratio. (And is also simpler to deal with as a teaching tool.) Or maybe "all of the above". Hahaha. Thoughts? Also I concur with other viewers that it's great to see videos that dig into topics like this in some depth! Very much appreciated!

This is really interesting info Andie! Really enjoyed it especially the demo :)

thanks for the tutorial

Thanks

WOW... this is trully gold in terms of information on this top. this was very helpful to me as an electronics systems designer!

This is great but why would you want to use one of those VERY EMI noisy bench supplies too ?? Those are awful. Just saying :)

This is gold! Thanks Andie!

Hello, could you please very briefly let me know what equipment I need to perform precompliance testing for a wired mouse? Thank you

Worth watching,

9:30 simple and deep meaning, help to look at EMI issues.

wow tysm

Hi so nice video, Andy. keep going.

great product !

Very cool, Andy!

Nice Explaination with practical things

Hi, nice video. I have a doubt.Why are there two push-button switches on the Demo Board? One is for connecting the GROUND and what is the other switch for?

Thanks as always!

Much of the > 100 MHz noise is from the switching rectifier, where the snubber helps a lot. The better solution for these types of low power (2-3 A) designs is a Buck regulator with a Synchronous rectifier, available from TI, MPS, and many others. Also from 0.5 to 2 MHz are the AM broadcast bands. A switching supply operating near or at these frequencies is a real problem. Both the Vendors mentioned have ICs operating at or above 2 MHz, which mostly solve this issue. Most vehicle manufacturers specify CISPR 25, Level 5, with their own lowered limits, often less than 25 uV. For conducted emissions below 0.5 MHZ for vehicles, the only real solution is a large input inductor filter. I used to design audio power amplifiers > 400 W into 2 Ohms for OEM vehicle manufacturers which could draw >40 A from 12V. If it doesn't pass conducted emissions, it wont pass radiated emissions.

I found interesting how the low frequency performance made worse by the improvement. :-) I suspect the increased switching current caused by the snubber is responsible for it.

good work! looking forward for more!

Hi Andy, Where’d you get that TEM cell?

Great to see an actual demo not just theoretical.

Excellent video, thank you

nice information. thank you.

Thanks Andy :-) Very nice overview, looking forward to seeing more. Cheers

Hi, very instructive video! To compliment a bit the explanation take a look on this video kzbin.info/www/bejne/Z6nMlI18bsyffpI where you can actually see the effects of bypass capacitors and return currents/return current paths in a "real" (ie non simulated) environment. Cheers,

Excellent video. Unfortunately I could see no obvious difference in spectrum in the final experiment.

Very nice video. Subscribing. There is a confusion I have however. How is that the return current is exactly underneath the track (that is following the path of least inductance) at only 1kHz of the signal in 5:30. I though this effect happens only at higher frequencies which are above 100 kHz. Isn't 1kHz too low for the current to choose the path of least inductance? Thanks