3 Oct
2008
3 Oct
'08
11:27 a.m.
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
I really do find iron more reliable than silicon :-)
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.
Totally OT, but if you're trying to run one of those valved portable
radios that used a 90V HT supply, it's worth noting that a 30V
transformer (the ends of a 15-0-15 winding, for example), voltage
doubled, gives about 84V. That's run all the radios I've tried, including
an AM/FM (yes, a valved FM portable radio) Vidor set.
-tony