Power Supply

Hi,

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

I am using the following setup to test the supplies

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Questions:

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

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

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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 th e " Electric" and " Magnetic field" generated by this waveform.

I found the following device to measure the electric field of HBM

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But sure that this probe can work for this purpose.

How can I measure input and output impedance of a fly back transformer b ased switching power supply? I found the following paper
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I was unable to understand the whole paper but I think that a separate devi ce is required to measure the input and output impedance of the supply? Is it possible that I can buy one?

mel

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.

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?

VCP? Please don't use jargon.

Again, that's a search page and not a specific page.

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.

HBM? Jargon? Does it hurt to type things out?

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.

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.