Again, my numbers were just a general examination ("back of the napkin"
<g>) of the very basic issue of whether or not the LM-317HV, rated at 60
V, could be expected to handle a wide range of AC mains voltages in a
phantom power application. I would answer "maybe".
Bri
Matt Syson wrote:
Hi
I am not disputing Brian's calcs but have the ripple voltages been
allowed for in the calcs?
Regulation of the transformer (if small) can be quite high (10 - 15
percent). About 4 or 5 percent if it is part of a bigger transformer.
Mains surges and spikes (fridge going on and off) although filtered by
the res cap can be high.
Although more complicated, a 'pre regulator' (transistor, zener and
resistor) could be employed to prevent overvolting the regulator.
None are perfect!
Matt S
Brian Roth wrote:
I did a "back of the napkin" analysis....
Assuming a "raw" PSU voltage of 60 VDC at 130 VAC Mains (very much on
the high side for the USA), which would be RIGHT at "absolute max" for
the LM-317HV:
If the same circuit was fed from a 120 VAC mains, the "raw" DC voltage
would be a 120/130 ratio, or 0.923 x 60 VDC = 55.38 VDC....well
within the LM-317HV's "drop out" spec.
At 110 VAC mains, "raw" VDC would be 110/130, or 0.846 x 60 VDC =
50.77 VDC....now approaching the dropout V for the 317HV.
At 100 VAC mains, the ratio is 100/130, or 0.77 x 60 VDC = 46.15
VDC....oops!
In a separate email, Ike Z. pointed out the STUPIDLY high drop-out
voltage for the 783....but at currents far higher than required for
any reasonable phantom supply.
I am "torn"....neither the 317HV not the 783 are totally perfect. The
dropout behavior of the 317HV seems to be a familiar one, yet the 783
MIGHT be more bullet-proof, especially when using a 65V or higher
"raw" rail.
Siiigh....
Now checking prices....
Mouser has the 783 for $1.60. Digikey has the 317HV for $3.94.
Bri
Matt Syson wrote:
Hi
The HV variant is only just capable in this situation as you would
normally anticipate around 65 Volts when your 'designed' supply is
fed with mains on the high side of it's tolerance. It certainly
stands a better chance than the 'standard' 317. A useful 'dodge'
could be to put a 36 Volt 3 Watt Zener from in to out of the reg and
a resistor on the input to the reg (JLM show a 47 R but perhaps a bit
larger would be better, the normal volts drop across it will be
small). Then you could use a standard part.
Matt S
[email protected] wrote:
There is also a "HV' 317 variant rated for a 60V in/out differential:
http://www.national.com/ds/LM/LM317HV.pdf
Bri
---- Ike Zimbel <[email protected]> wrote:
I think what Matt was talking about was a TL-783
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-20687-5-ND.
best,
Ike
eliya gwetta wrote:
Hi Matt
Yes! I remembered the LM317 not being the right regulator for 48V,
a TL583 would be a drop in replacement or I would have to change
other components in the circuit as well?
On Sat, Jul 4, 2009 at 9:25 PM, Matt Syson
<[email protected]
<mailto:[email protected]>> wrote:
Hi
The JLM circuits are pretty much what you need so you could
either
'copy' the circuit and build it yourself or buy the kit.
I am not too impressed at using a LM317 for the phantom 48 rail,
they are only rated to 39 or 40 volt DIFFERENTIAL (input pin to
output pin) , meaning that if you short the output you stand a
good chance of 'blowing it up'. I presume the 47 Ohm resistor
is a
lame way of trying not to 'kill' it, hardly a good engineering
solution.
You should substitute it for a TL583 (sorry this number won't
come
to me, but there is a similarly packaged regulator that handles
125 Volts).
Matt S
Donald Put wrote:
If you're up to making your own, there are numerous PCBs/kits
available for this type of project. They're set up for dual
voltages and 48VDC for the phantom power. Check out JLM's
offerings on his website:
http://www.jlmaudio.com/JLM%20Power%20Supply.htm
Cheers,
--
Don
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] <mailto:[email protected]>
with "unsubscribe neotek" in the message body. If you have any
difficulties, or questions --please send an email to
mailto:[email protected] <mailto:[email protected]>.
The Neotek list is lovingly hosted by Catapult Web. Remember that
any message or reply sent to the list will be automatically
forwarded to all subscribers.
Vive Le Neotek!
Thanks.
--
Ike Zimbel
Zimbel Audio Productions Ltd.
Toronto
416-720-0887
"Studio House Calls" - Repairs and upgrades to analog audio
equipment including: Amek, Allen & Heath, Neve, Neotek, MCI,
Soundcraft and more.
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please
send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that
any message or reply sent to the list will be automatically
forwarded to all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please
send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that
any message or reply sent to the list will be automatically
forwarded to all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please
send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to
all subscribers.
Vive Le Neotek!
Thanks.
------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database:
270.13.5/2220 - Release Date: 07/05/09 17:54:00
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please send
an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to
all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at: http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the message
body. If you have any difficulties, or questions --please send an email
to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to all
subscribers.
Vive Le Neotek!
Thanks.
------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.375 / Virus Database: 270.13.8/2226 - Release Date: 07/08/09 21:51:00
------
View the list online at: http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to mailto:[email protected] with
"unsubscribe neotek" in the message body. If you have any difficulties, or
questions --please send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any message
or reply sent to the list will be automatically forwarded to all subscribers.
Vive Le Neotek!
Thanks.
