Help with current limiting device - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 23rd November 2009, 05:40 AM   #1
diyAudio Member
 
Rob11966's Avatar
 
Join Date: Jun 2007
Location: Australia
Default Help with current limiting device

Hi Folks,

I am usually found around the tubes forum but I am currently building a benchtop power supply and I am struggling with a problem at the moment.

The power supply is a variable 0-28 V supply capable of 6A at 12V. The power supply works fine, no problems but I am trying to add on a varible current limiting device. This is the one that I have chosen

Variable (Adjustable) Current Limiter Circuit | Free Circuit Diagram

Trouble is that it does not seem to work. When the current limiting 'module' is place in the circuit, all that happens is that the output voltage seems to get reduced and is only variable between 0 and about 3v (using a 10 ohm/10w resistor as load). I think that the schematic may be wrong. The authors refer to shorting the base of Q4 to ground but there is no ground on the original schematic?

I have attached an original schematic and also my idea of what it should like. Is anyone able to comment?

Thanks in advance,

Rob
Attached Images
File Type: gif Original Schematic.gif (7.3 KB, 108 views)
File Type: gif Modified schematic.GIF (7.8 KB, 101 views)
  Reply With Quote
Old 23rd November 2009, 06:44 AM   #2
diyAudio Member
 
Join Date: Apr 2006
Location: Minnesota
The circuit on the left should work fine. The one on the right will not work, because the sense transistor will always be on.
  Reply With Quote
Old 23rd November 2009, 06:47 PM   #3
diyAudio Member
 
Rob11966's Avatar
 
Join Date: Jun 2007
Location: Australia
Quote:
Originally Posted by sawreyrw View Post
The circuit on the left should work fine. The one on the right will not work, because the sense transistor will always be on.
Thanks - The one on the right was the one that I have bread boarded. Armed with your information, I replaced all of the parts sequentially. It was a bad BD139.

It's now working fine.

Thanks again,

Rob
  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
12V DC/DC for amplifier. Current limiting? Pierre Power Supplies 22 1st May 2007 11:46 AM
Does any power amp have a current limiting device? beppe61 Solid State 44 22nd December 2005 11:47 PM
Current limiting by the PCB coil, why not? IVX Class D 3 18th December 2005 09:08 AM
Load Current limiting k1jroth Solid State 2 20th November 2004 06:20 AM


New To Site? Need Help?

All times are GMT. The time now is 09:27 PM.


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