Hi,

If you look at the circuit carefully you''' see the inductor and the
schottky blocking diode.  For your example a simple FET like a VND10 or
so and a much smaller inductor and 1N5817 diode would be more than
adequate.  The high value inductor is used to generate the high voltage
and you don't need nearly that size.  I didn't either but I had it in
_my_ junk box.  8-)

John


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Jinx
> Sent: Friday, April 05, 2002 8:09 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]:Dual voltage rails from PIC
>
>
> > http://www.pacificsun.ca/john/www/pdf-files/UVPower.pdf
>
> Thanks for the circuit. A little more than what I expected, and
> although I don't think I can use it for the current job, it'll be a
> handy starting place for an EL backlighting project on hold
>
> >  I'll see if I can find it and post the pertinant info.
>
> That would be absolutely chipper if you could
>
> > A switching supply will be far more efficent and use less
> > components. I'm not sure that the capacitor multiplier circuit
> > would have any less noise but perhaps some other expert
> > can voice an opinion
>
> Was thinking more along the lines of cheap "junk box" parts,
> hence trialling a Cockroft-Walton type first. Efficiency isn't a
> great concern, not so much as using a PIC and 5V for the
> whole deal if possible
>
> > that to make the voltage more stable
>
> Using 317s for two reasons - (1) variable V outputs and
> (2) able to use as current limiters. The voltages themselves
> are pretty quiet, no 20kHz left that I can see. BTW, the "50us
> TMR0 interrupt" was an error. It's of course 25us, 50us for
> the whole cycle
>
> > You could use the PIC isntead of the 555 to create the PWM signal
>
> I've found the CW is very forgiving of mark:space ratio. Seems
> anything greater than 25:75 will give the full output, even right
> up to 99:1. Seems to be pretty good with square waves too,
> although they are knocked out of shape a bit
>
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