[sdiy] Phantom Power Supply

[Czech Martin]

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
>