[sdiy] Phantom Power Supply

[Czech Martin]

got me!
Abs max says max input 37V, and that is related to reference point, of course.
You can raise the reference point, but a short to gnd (no so unusual
during plug in or cable problems) then will not be catched by the SOA
circuit (I think).

I like the discrete circuit that was posted.

m.c.

> -----Original Message-----
> From: Theo [mailto:t.hogers at home.nl]
> Sent: Freitag, 29. August 2003 20:36
> To: Czech Martin; Dave Magnuson; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Phantom Power Supply
> 
> 
> Depends on the design actually.
> Its a maximum output of  35V or so against the reverence voltage.
> If the reverence has been raised to sufficient level the 317 
> may even output
> 400V.
> 
> Theo
> 
> 
> ----- Original Message -----
> From: Czech Martin <Martin.Czech at micronas.com>
> To: Dave Magnuson <resfreq at hoohahrecords.com>; 
> <synth-diy at dropmix.xs4all.nl>
> Sent: Friday, August 29, 2003 6:33 PM
> Subject: RE: [sdiy] Phantom Power Supply
> 
> 
> > Ok, if the datasheet tells you that the LM317 can not
> > have such high input, output voltage, then do not do it.
> > I do not have it in front of me, but this again this
> > recommended and abs. max. game.
> >
> > There is another thing: there is some limit for the
> > output short protection. The 317 seems to have a limit
> > for the output voltage, where the protection circuit
> > will not keep it in SOA.
> >
> > Some LT regulator has better performance in this case.
> >
> > All from my head, late now, time to go home.
> >
> > m.c.
> >
> >
> > > -----Original Message-----
> > > From: Dave Magnuson [mailto:resfreq at hoohahrecords.com]
> > > Sent: Freitag, 29. August 2003 18:09
> > > To: synth-diy at dropmix.xs4all.nl
> > > Subject: [sdiy] Phantom Power Supply
> > >
> > >
> > > Hi List,
> > >
> > > I was researching a simple 48V phantom power supply, and 
> I keep coming
> > > across designs using the LM317T regulator.  They typically
> > > use an 18-24VAC
> > > transformer and a voltage doubler, then rectify and 
> regulate to 48VDC.
> > >
> > > My question is this:  The LM317T is listed as being
> > > adjustable to 37VDC,
> > > yet all of these designs claim a 48VDC output.  Do you think
> > > it's unwise to
> > > use (abuse?) the 317T in this way?
> > >
> > > I don't want to build something that's going to burn out in a
> > > year, yet the
> > > sheer multitude of phantom supplies like this makes me think
> > > it must be
> > > ok...  Perhaps the very low current used in phantom power
> > > avoids stressing
> > > the part too much?
> > >
> > > If all else fails, I'll pick up a TL783 regulator... But
> > > unfortunately I
> > > can't get it locally (and I can get an LM317T down the street)
> > >
> > > Thanks for your input!
> > >
> > > Dave Magnuson
> > >
> > > Resonant Frequency:
> > > resfreq at hoohahrecords.com
> > > http://www.hoohahrecords.com/resfreq/index.html
> > >
> >
> >
> 
>