In message
<afedb093295d402bbfe7dfafe02fb...@blupr02mb116.namprd02.prod.outlook.com>
, dated Wed, 5 Nov 2014, Brian Oconnell <[email protected]>
writes:
My usual caveat - am an EMC amateur. If the transient is propagated in
serial fashion then 're-emitted' (as theorized by Mr Woodgate)
I didn't really theorize: I paraphrased to original description as I
understood it:
QUOTE
I was able to create the same effect using EFT (electrical fast
transient) pulses. Some power supplies can take a single EFT pulse and a
microsecond to several microseconds later generate one or more EFT
pulses, some larger that the stimulus one, embedded in corona
discharges!
ENDQUOTE
with similar characteristics as test pulse, do not see how the typical
control loop would see the disturbance, other than a resultant OV
lock-out. Oscillations on the PFC FET could result if the transient
energy were coupled to a hi-z gate drive circuit, but, at least
logically, it would seem that the main controller would just lock or
skip pulses until the disturbance energy is gone.
The implication of 'corona' is that radio frequencies are being
generated at high voltage. That suggest something knocked into a 'Tesla
coil' mode. Could it be? I'm by no means an SMPS expert, but the
necessary bits seem to be there.
Observed this 10 years past during variations of EFT and surge test
configurations while playing with floating and ground-referenced mains
on an open-frame SMPS, where the chassis could be ground pin-reference
or floated. Observed again last year while testing another factory's
class II p/s where my GRP was not correctly placed.
Including the corona? Or was the lighting too bright to see it?
Response of given model SMPS to ESD/EFT/Surge can vary somewhat, where
the difference is the end-use installation. EMC testing of an COMPONENT
p/s is problematic and mfr's test data may not be representative of
performance in your box. This may become a recurring and noticeable
problem as SMPS go to higher switching frequencies to increase
efficiency and decrease size per industry demands.
It's already responsible for a lot of grief.
Perhaps TC108 can consider looking at this for the glorious coming of
IEC62368-1, as there are power supplies being developed now that
operate up to 30MHz.
PLEASE do not involve TC108. Those guys are lovely but the vast majority
know in depth only about safety. Faced with an unexplained high-voltage
generation, things could very quickly go into disadvantageous orbits.
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
Quid faciamus nisi sit?
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
-
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