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From: Roy McCammon
Subject: Re: Strange failure mode in switchmode power supplies: Followup
Date: Mon, 23 Sep 2002 11:38:13 -0500
X-Mailer: Mozilla 4.5 [en]C-CCK-MCD 3M/NCP 4.5 (WinNT; I)
To: Peter Gutmann
Peter Gutmann wrote:
> The immediately obvious symptoms are that any SMPS plugged into the power in
> my house starts producing large amounts of high-frequency (ultrasonic)
> switching noise, both audibly and in its DC output. At 50W it's mostly
> inaudible (but enough to cause the usual unpleasant effects of ultrasonics
> if you sit next to it for awhile), at 100W you can sense it easily (although
> not necessarily directly hear it), and at 200W it's so bad you can't stand
> being in the room for more than a few minutes without feeling ill.
> What's bad for humans is even worse for any elecronics sitting downstream,
> so far this problem has caused about $2K of damage in assorted computers,
> routers, etc etc (the damage is pretty spectacular, one device which failed
> was an online UPS which I'd been using to protect the PC downstream, every
> high-speed switching component in it had been fried).
Have you considered that you may have two unrelated effects?
1. Some high frequency sound source that beats with the
SMPS frequency that you hear but which causes no problem.
2. An occasional transient that kills your electronics.
Thank you for reading and or replying
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