2 Oct
2008
2 Oct
'08
12:41 p.m.
On 2 Oct 2008 at 18:29, Tony Duell wrote:
Alternatively, consider using a transformer 'back
to front'. Start of
taking in mains and stepping it down to, say, 12V AC using a normal
transformer in the conventional way. Yo ucan rectify/smooth/regulate that
for your logic supply. But then take another 220V-12V trasnformer and
connect the 12V winding to the secondary (12V) side of the first
transformer. You'll get around 230V from the other (original primary)
winding of that transformer.
If you happen to have one handy in the USA, of course. Although
"universal" 95-240v transformers can be found in the US, most of the
small ones (such as are found in wall warts) are 120vac primaries
only.
But if I had a 12vdc supply at sufficient current and needed to power
some nixies, I'd be sore tempted to work up a boost supply using any
of the currently available DC-DC converter ICs. EDN/Electronic
Design is full of such circuits (e.g. using the Maxim MAX1771). Much
more compact and not requiring much in the way of a DC filter
capacitor.
Where I'd draw the line is with any small signal application, such as
a receiver using tubes/valves. Those converter ICs can really
generate a lot of RF noise.
Cheers,
Chuck