On Sun, 7 Nov 2004, Jan-Erik Soderholm wrote:

> Hi !
> I'm currently looking at a particular setup that will have a number
> (5-20) of small units/PCBs (mostly a 10F and a LED) all powered
> from a central power box connected to the mains using a wall wart.
>
> Now, 5V wall warts are a bit rare (not?), so I think I need some
> kind of regulator in this power box. A common linear regulator
> commes to mind, but in a closed box (some simple cheap plastic
> thing), heat would/could soon be a problem, right ?

Dig a little in phone accessories and such. Several minidisc players and 
at least a phone (mine) use 5V wall warts.

> Have anyone seen a simple switcher curcuit capable of
> supplying 5V from the usual 9-12 V (DC) wall warts ?
> Let's say from 500 mA up to 1A.

LM25xx simple switcher.

> Microchip has something called the TC105.
> Input max 10V, output 5 V @ 1A. 92% efficiency.
> Looks OK at a quick glance. Needs a few
> extra components but doesn't look to bad.
> But it would have been nice if it could take an input
> voltage up to at least 12V...

The LM is well established. If you want to use a mchip part, do it, the 
efficiency is higher (the LM does 85% real (measured) with a good shottky 
diode and low Rdc coil).

Peter
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