AC Power Switching (was Electronic components sources)

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Wed Mar 24 20:14:02 2004

> My original comment was made specifically in reference to 2-wire
> (therefore single phase) power sources WITHOUT an independent ground.
> Note: This is ALWAYS the case with a device that uses an external
> power supply wich just supplys a low voltage to the actual device
> (e.g. Wall Warts).

I'm not so sure of that last. I have seen wall warts - not many, but a
few - that had three-pin plugs. Whether they actually did anything
right with the ground pin (like connecting it to the shield on the
low-voltage connector) is another issue, but they certainly had it.
(They also tended to be physically large; I'm counting them as
wall-warts because they had their mains plug rigidly fixed relative to
the body of the unit, rather than on the end of a wire.)

> The comment is totally in-applicable (IMHO) when there is a dedicated
> (non-switched) ground connection OR the power is multi-phase.

The devices I, at least, thought we were talking about were
desktop-style machines with an always-on mains cord, with a power
switch that breaks the two power leads but not the ground lead. So
either I misunderstood something from the get-go or most of the
discussion has been talking past one another. :-)

As someone pointed out, peecee ATX power supplies often use soft
power-off, which is a different sort of thing. Some ATX supplies also
have a real power switch; some don't - I can't see anything in this
discussion that's relevant to soft power switching.

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Received on Wed Mar 24 2004 - 20:14:02 GMT