Power Supply

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

 

[Tim Wescott]

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