> -----Original Message-----
> From: Roman Black [SMTP:fastvid@EZY.NET.AU]
> Sent: Tuesday, March 04, 2003 12:35 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: High Voltage Controler
>
> Michael Rigby-Jones wrote:
> >
> > > -----Original Message-----
> > > From: Roman Black [SMTP:fastvid@EZY.NET.AU]
> > > Sent: Monday, March 03, 2003 2:38 PM
> > > To:   PICLIST@MITVMA.MIT.EDU
> > > Subject:      Re: [EE]: High Voltage Controler
> > >
> > > Hi, why try to control the 2000v side??
> > > Since he only needs 40Hz updates, it might be easier
> > > (and more reliable) to generate the HV from a LV
> > > PWM supply via flyback transformers and HV diodes.
> > > HV diodes can be bought quite cheap and you can
> > > get small HV flyback transformers dirt cheap from
> > > many sources, usually sold as "flash or strobe
> > > transformers".
> > >
> > Because the OP needs 60-200 outputs independantly adjustable, and
> presumably
> > just one high voltage supply rather than 60-200 individual supplies.
>
>
> And that's why I suggested it. :o)
> I've got plenty of 2.5kV power transistors here,
> special purpose rugged units from TV repair stock.
> They are NOT cheap and i'll tell you now that 200 of
> them linearly controlling a 2kV DC supply is NOT
> going to be cheap or even close to reliable.
>
> Considering these transistors cost $4 or more each,
> and will still need snubbers, heatsinking etc I think
> a cheaper and definitely *more reliable* result will
> come from 200x HV diodes and 200x flash transformers
> driven by cheap rugged transistors.
> -Roman
>
You don't have to use transistors with that high a voltage rating, it's
entirely possible to use 2 (or more) lower voltage transistors to spread the
voltage drop.

Mike


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