input output diferential in LM317 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th June 2004, 09:07 AM   #1
Pablo is offline Pablo  Spain
diyAudio Member
 
Join Date: May 2004
Location: Santander
Default input output diferential in LM317

Hi!
I want to make a power supply with a LM338, the Lm338 can give 5A but only when the input-output differential is less than 10V aprox, and I have 50V at the input fron the rectifier.. if I want output ranges less than 10 V...
Can somebody explain how can I do to make that the regulator sees only 10V betwenn input and output?
Thanks!
(eva si puedes escribeme al correo y me lo explicas en espańol que en ingles me cuesta.el correo es pl_minguez@hotmail.com
gracias!)
  Reply With Quote
Old 9th June 2004, 09:16 AM   #2
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
You can use a simple preregulator, like an emitter-follower, that lowers the input voltage to say 20V. But then that preregulator has to dissipate 30V at 5Amps = 150Watts!

This kind of application screams for a switching regulator, 48V in, 10V out.
Or maybe you can change the raw supply to something less than 50V?

Jan Didden
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!
  Reply With Quote
Old 9th June 2004, 09:37 AM   #3
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Pablo, take a look at National's "Simple switcher". I don't know if they have 5 A out but some of those regulators are very easy to get going... with a good pcb. I have used those at work but then it was only 500 mA or so.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 11th June 2004, 01:20 AM   #4
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
and I have 50V at the input fron the rectifier..
Quote:
Or maybe you can change the raw supply to something less than 50V?
If those 50V are coming from a ~ 35AC xfmr winding which is FWB rectified into a capacitive load you could use a FW C input rectifier instead.
This would give you ~ 25VDC at full xformer secondary current capacity and a lot easier to step down but at 5A this would still mean a whopping 75W of heat.

I'm just mentioning this alternative as it often seems to me as if everyone automatically thinks FWB and C input which in cases like this can work against you.

Cheers,
__________________
Frank
  Reply With Quote
Old 15th June 2004, 04:26 AM   #5
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
Default Transistorised Zener

Construct a zener (with transistors) of Vin max of LM338 and use it as a shunt preregulator, with a resistor in series, and use smaller filter C.

Gajanan Phadte
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LM317 max input voltage?? imperfectcircle Parts 11 10th March 2007 12:09 PM
aleph x CCS curent for diferential input elviukai Pass Labs 14 10th November 2006 08:05 PM
Need amp for DC input --> AC output chipco3434 Solid State 12 31st July 2005 08:51 PM
double vs diferential Praise! Solid State 11 7th November 2003 01:31 PM
Zen V4 PCB input and output vsr123 Pass Labs 2 25th April 2003 03:22 AM


New To Site? Need Help?

All times are GMT. The time now is 02:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2