🚀 go-pugleaf

Gordon.Newell@C031.aone.net.au (Gordon Newell) contributed the
following:

>In message <32b22fb2.14926704@news.mel.aone.net.au> -
>dcstar@acslink.aone.net.au (David Clayton)Sun, 15 Dec 1996 21:16:35 GMT
>writes:
>
>[edit]
>
>:>>I would like to know your background for making such statement. We are
>:>>The switched mode power supply is one of the safest I can think of.
>:>>From the very start in Colour TV some 25-30 years ago, you find very
>:>>little wrong with these supplies. They very rarely have a disasterous
>:>>burn out as had the standard supplies. 
>:>>
>:>Except that there is no physical isolation from the mains supply - as
>:>there would be with a double insulated transformer.
>
>The low voltage side of a switching power supply is isolated from the mains by
>a large area of PCB and the switching transformer. The only connection between
>the two is the feedback loop, usually through an opto-coupler. Seems pretty
>well isolated to me.
>
The point I was making is that the "older" power supplies had double
insulated transformers with the primary and secondary windings
seperated by whatever was required to satisfy the local Australian
power authorities. Compared to the switched mode supplies that I know
about, this should provide a greater level of isolation that occurs
now.

If this *greater* level of isolation is actually required is a moot
point, (it looks like we are living without it quite well at the
moment), but it seems to me that the switched mode supplies can be
made with varying level of isolation, and therefore safety, and we
should be using the ones with the appropriate U.L. or whatever
compliance, not dogey ones that the original post was warning us
about.

I don't know about you, but the blanket statements from another poster
about all switch mode power supplies being safe, (and if they aren't,
the company that makes them will go out of business, so be quiet!),
just cause me to shake my head in amazement.

Regards, David.
-------------------------------------------------
David Clayton, e-mail: dcstar@acslink.aone.net.au
Melbourne, Victoria, Australia.

"Virtual Reality - Give it a rest, Actual Reality has me stressed enough as it is."