Conducted Mode EMC Emissions Demo

Electronics in the UK and Julia Moses from worth Electronics Australia uh to showcase the Emi debugging demo uh based on both uh uh EMC demo boards uh F supplies from roaden shorts and our latest mx4 osilloscope so yeah uh to begin the demo I would like to invite Glen to brief about the experimental setup for the demo setup so what we have here is a uh good design bad design of a boost converter so it's normally running about 300 khz switching frequency so we got an input voltage of 19 volts and we're boosting up to 24 volts that we go through to our electronic load so I'll be drawing around about 420 milliamps off of that what we're doing is actually hooking the uh our demo board up to a sispa 25 lizen so this has been developed in partnership with worth electronics and Roden Schwarz so what makes this lizen slightly different compared to what's on typically on the market is it has dual output so basically we can measure both in like live and neutral line or positive and zero volt line the benefit with this coupled with things like the mx4 is that what we can actually separate out uh is both conduct is from a conducted emission plot both the comma mode noise and differential mode noise so by using this Lim we can help identify when when types of solutions are are applicable and this is partly what we're going to be doing do today so what we'll start off is our bad design so I'll switch on hopefully if I'm can do this right switch on the power supply and I'll Now set the load to draw the 420 milliamps what we can now see on the screen so we basically got in time domain so we're actually measuring the noise coming being conducted through the power supply into the lient being extracted off channel uh let's have a look probably Channel a we can now see in the time domain and the reciprocal in the frequency domain so we look at things like conductor emissions so from 9 khz to 30 MHz so yeah if I was a design engineer I might not be keeping my job too well because I've got all these harmonic noise running through so this is basically now my noise source and what I want to do is now Implement a in effect what a good design looks like so what we what do we mean by a good design so we got a second uh second circuit on the board that I'll now switch in and this will have uh improvements of things like common mode chokes differential mode filtering better layout and what we can now see it will be the end result so let me just power this down switch it over to a good design power back up and set my emissions so if you now look on the screen we can actually see in the time domain we have virtually suppressed all that noise that was coming off the Bad design and say this is implementation of things like com choke better layout out we can see the resultant conducted emissions has significantly dropped we probably dropped it down by about 20 to 30 DBS in in certain frequencies so that's that what I can now also do is go a step further and introduce a secondary commo choke and differential mode filter on on its input so let me just power this down okay so I've switched it back onto the bad design and my output is on so what we can actually see is we got a reference versus are current at the moment so basically what we have is this particular new board that we've now introduced has a main rated commo choke so it's made of manganese in cor material so this will typically operate around about s 9 khz up to probably about 1 to 2 MHz in frequency along with a x capacitor so this will be be doing some more low frequency filtering whereas when I now if I now power it down and switch in the the good design as well as so in fact I've now got two stage Emi filter what we've got is the reference trace and now we've got the real time measurement along with both the filters and we can see that we have now significantly attenuated any of the Emi noise that's now being conducted from that bad design through to the lizen and then being measured on the mx4 so once again we're just trying to show a very practical demonstration here couple with Roden schwarz's equipment how you can do at a bench level DC power supply filtering on a noisy Source thank you

Channel: EEVblog2

Views: 3,893

Keywords: eevblog, electronex, conducted mode, electromagnetic compatibility, conducted emissions, spectrum analyzer, electromagnetic interference, emi testing, emc testing, electromagnetic compatibility (emc), emi compliance, electromagnetic compatibility testing, wurth electronics, rohde and schwarz

Id: oVkrc3gF7ns

Length: 5min 3sec (303 seconds)

Published: Sat Jun 22 2024