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Power Supply

Started by Unknown September 12, 2015
Hi, 

I have been assigned to do some "switching power" ESD testing recently. I am a beginner engineer. So, please forgive me and do not be offended, if I ask dumb beginner's questions. 

I am using the following setup to test the supplies 

https://www.google.com/search?q=esd+test+table&rlz=1C1OPRB_enUS590US592&espv=2&biw=1360&bih=639&tbm=isch&imgil=3tz5_C44aehh8M%253A%253B8uqga2t8D7s3RM%253Bhttp%25253A%25252F%25252Fwww.noiseken.com%25252Fmodules%25252Fproducts%25252Findex.php%25252Fcontent0186.html&source=iu&pf=m&fir=3tz5_C44aehh8M%253A%252C8uqga2t8D7s3RM%252C_&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA%3D&ved=0CEAQyjdqFQoTCN3ey-3C8scCFcG3gAod1RYA6Q&ei=JaT0VZ24NcHvggTVrYDIDg#imgrc=3tz5_C44aehh8M%3A&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA%3D 


Questions: 

1. I found that that VCP is grounded to Ground Reference plane (GRP) via two resistors of value 470Kohm in series. Why 470k and two of them? 

2. The ESD gun air discharge looks like the following ( Human Body Model) 


https://www.google.com/search?q=esd+test+table&rlz=1C1OPRB_enUS590US592&espv=2&biw=1360&bih=639&tbm=isch&imgil=3tz5_C44aehh8M%253A%253B8uqga2t8D7s3RM%253Bhttp%25253A%25252F%25252Fwww.noiseken.com%25252Fmodules%25252Fproducts%25252Findex.php%25252Fcontent0186.html&source=iu&pf=m&fir=3tz5_C44aehh8M%253A%252C8uqga2t8D7s3RM%252C_&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA%3D&ved=0CEAQyjdqFQoTCN3ey-3C8scCFcG3gAod1RYA6Q&ei=JaT0VZ24NcHvggTVrYDIDg#tbm=isch&q=HBM+WAVEFORM&imgrc=PkbogCsYgLB8bM%3A 


How can I calculate how much charge this waveform has delivered? Plus if I charge the VCP and HCP plane with this waveform then how can I calculate the " Electric" and " Magnetic field" generated by this waveform. 

I found the following device to measure the electric field of HBM 
http://www.lessemf.com/probe.html#182 

But sure that this probe can work for this purpose. 


3. How can I measure input and output impedance of a fly back transformer based 
switching power supply? I found the following paper 
http://www.deltartp.com/dpel/dpelconferencepapers/33.3_10275.pdf 

I was unable to understand the whole paper but I think that a separate device is required to measure the input and output impedance of the supply? Is it possible that I can buy one? 

mel 


On Sat, 12 Sep 2015 18:19:34 -0700, erica.cross1989 wrote:

> Hi, > > I have been assigned to do some "switching power" ESD testing recently. > I am a beginner engineer. So, please forgive me and do not be offended, > if I ask dumb beginner's questions.
Oh, welcome to Dilbert-land. Effective ESD testing is something that should be taught, not done by grabbing some poor unsuspecting new hire (that's you) by the ankle and flinging them at it. I sincerely hope that you're just doing preliminary testing. Unless the environment at your work is seriously toxic, find out if anyone has done it before, and then go ask that person if they'll give you a run-through. If no one has, then find out what lab your company uses for certification and see if they'll let you witness a test -- some labs will be very territorial about this, but I suspect that most will want to help insure that your products have fewer run-throughs at their site, to encourage happy customers.
> > I am using the following setup to test the supplies > > https://www.google.com/search?q=esd+test
+table&rlz=1C1OPRB_enUS590US592&espv=2&biw=1360&bih=639&tbm=isch&imgil=3tz5_C44aehh8M %253A%253B8uqga2t8D7s3RM%253Bhttp%25253A%25252F%25252Fwww.noiseken.com% 25252Fmodules%25252Fproducts%25252Findex.php% 25252Fcontent0186.html&source=iu&pf=m&fir=3tz5_C44aehh8M%253A% 252C8uqga2t8D7s3RM%252C_&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA% 3D&ved=0CEAQyjdqFQoTCN3ey-3C8scCFcG3gAod1RYA6Q&ei=JaT0VZ24NcHvggTVrYDIDg#imgrc=3tz5_C44aehh8M %3A&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA%3D That is a search page that might change from day to day. Are you using one specific setup? Could you post the page for that?
> > Questions: > > 1. I found that that VCP is grounded to Ground Reference plane (GRP) via > two resistors of value 470Kohm in series. Why 470k and two of them?
VCP? Please don't use jargon.
> > 2. The ESD gun air discharge looks like the following ( Human Body > Model) > > https://www.google.com/search?q=esd+test
+table&rlz=1C1OPRB_enUS590US592&espv=2&biw=1360&bih=639&tbm=isch&imgil=3tz5_C44aehh8M %253A%253B8uqga2t8D7s3RM%253Bhttp%25253A%25252F%25252Fwww.noiseken.com% 25252Fmodules%25252Fproducts%25252Findex.php% 25252Fcontent0186.html&source=iu&pf=m&fir=3tz5_C44aehh8M%253A% 252C8uqga2t8D7s3RM%252C_&usg=__eA52lSfnuQGXwPtyAWj9d42PnxA% 3D&ved=0CEAQyjdqFQoTCN3ey-3C8scCFcG3gAod1RYA6Q&ei=JaT0VZ24NcHvggTVrYDIDg#tbm=isch&q=HBM +WAVEFORM&imgrc=PkbogCsYgLB8bM%3A Again, that's a search page and not a specific page.
> > How can I calculate how much charge this waveform has delivered? Plus if > I charge the VCP and HCP plane with this waveform then how can I > calculate the " Electric" and " Magnetic field" generated by this > waveform.
Electric fields come from charges that are sitting around, or as part of radiated energy (i.e., RF -- remember E&M?). Magnetic fields come from charges that are moving, or as part of radiated energy. I'm pretty sure that in ESD events you're mostly concerned with electric fields.
> I found the following device to measure the electric field of HBM > http://www.lessemf.com/probe.html#182
HBM? Jargon? Does it hurt to type things out?
> But sure that this probe can work for this purpose.
That appears to be a probe for measuring an AC electric field, not a static field. Moreover, the site offers personal EMF shielding products, which is a huge red flag. It means that they cater to the tinfoil hat brigade. If they do that, then they either are members and therefore they're wackos, or they aren't members and therefore have no compunctions about making money off of wackos. So you can take your pick about whether you should distrust their sanity, their technical competence, or their intentions -- but you should pick at least one of the three.
> 3. How can I measure input and output impedance of a fly back > transformer based switching power supply? I found the following paper > http://www.deltartp.com/dpel/dpelconferencepapers/33.3_10275.pdf > > I was unable to understand the whole paper but I think that a separate > device is required to measure the input and output impedance of the > supply? Is it possible that I can buy one?
That paper is written for an entirely different purpose, and doesn't really apply here. I suspect that any ESD event is going to be over long before anything in the power supply circuit has a chance to react to it aside from the input and output capacitors. So, from the perspective of ESD, you may as well measure the impedances with the supply turned off. Getting a measure of the voltage rise on the flyback diode itself when you zap the supply output might be a good CYA (cover your ass) measurement, though. -- www.wescottdesign.com