[sdiy] DC/DC and DC/AC conversion...

[Batz Goodfortune]

Y-ellow Rainer.

At 04:18 PM 8/20/02 +0200, Rainer Buchty wrote:
>Hi there,
>
>I got a bunch of VFDs which didn't come with one of those handy
>conversion devices allowing to completely drive it with 5VDC. Instead,
>they need 9VAC for the filament and 50VDC anode voltage.

Assuming you can derive your 9VAC from the PSU directly, you could do worse 
than having a poke round the PAIA site at their valve gear. It's a common 
enough technique it's just the first place I thought of.

Essentially it's a little CMOS driven oscillator using a bunch of buffer 
stages for current. Then this is run through a more-or-less standard 
tripler type circuit (Bunch of diodes and caps) which bumps the AC up. I 
think they use about 47/50 volts in those things so it would be about 
right. I won't get into issues of their starved-tube-topology but suffice 
it to say I'm with Eric on this one. As he put it. "A starved tube is not a 
happy tube."

But with a bit of mucking around, this should generate the 50 odd volts you 
need. The only thing I don't know is how finicky the VFDs are. Usually 
these things are for quantity not quality. But the technique is so well 
used these days that I wouldn't be surprised if there were a bunch of ICs 
already set up to do this job right out of the box. MAXIM springs to mind.

Hope this helps.

Be absolutely Icebox.

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