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From: Kevin McMurtrie
Subject: Re: Strange failure mode in switchmode power supplies: Followup
User-Agent: MT-NewsWatcher/3.2 (PPC Mac OS X)
Date: Tue, 24 Sep 2002 09:58:20 GMT
NNTP-Posting-Date: Tue, 24 Sep 2002 02:58:20 PDT
In article <3D8F74CA.9DC367D8@usa.net>, w_tom wrote:
> Summarizing important points as I understand them:
>1) High frequency noise in SMPS is only when powered in your
>house and not in any other house; both powered by same utility
>transformer (and phase).
>2) Using an oscilloscope in differential mode, electrical
>source of that noise cannot be observed / detected.
>3) Noise source is believed so strong as to damage every power
>Point 1 says the source of electrical noise is only in your
>Microwaves, et al as the noise source in point 3 is not
>reasonable. To damage electrical components, the noise energy
>would not just damage resilient SM power supplies and not less
>resilient dimmer switches, GFCI, electronic clocks, etc. To
>have noise that high, another important household component
>would also suffer damage - the human.
It's true that most circuits can't see microwaves but even a few generic
semiconductors can rectify in the GHz range. Radar is especially bad.
The RMS power may be very low but the peak power is extremely high. I
live near an airport and a few military bases. Radar interference with
electronics isn't unusual. It sometimes hits my TV and completely jams
it momemtarily. My previous car CD player skipped and blanked out
frequently near airports.
Microwaves entering a SMPS could bias the voltage feedback loop so it's
no longer properly compensated. I would expect that modern motherboards
would also contain microwave sensitive semiconductors and that exposed
computers would crash more frequently. How reliable is your system,
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