DC-Protect Circuitry - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 2nd September 2006, 07:51 PM   #1
diyAudio Member
 
Join Date: Jul 2004
Location: Sweden
Default DC-Protect Circuitry

Hello! Been a while

I'm getting some more expensive speakers and if my homebuilt amplifier decides to breakdown at some point I don't wan't to burn the speaker. So I was thinking of adding a DC-protect circuit. I know there was some big thread about this a while ago, but I'm not intending to to the most perfection but just a simple protectcircuit that is reliable and deactivates the amp or the speaker when DC is at the output. I alredy have other protectioncircuits for overload etc.

It's the detection circuit I'm intrested in mostly. The breaking-circuit can be some in many ways. Breaking the output with a relay or with solid-state components, or cutting the PSU from the amp. The simplest way I believe is to break the output.
Anyway, I was googlin' some and found this:
http://www.amb.org/audio/epsilon12/epsilon12_sch.png

Any comment'? I'm having problems finding those big cap's for some reasonably price.. (100uF non pol) Would'nt it be possibly to increase the resistor and use a smaller capacitor instead?

Thanks.
Fritzell
  Reply With Quote
Old 2nd September 2006, 07:58 PM   #2
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Make a search in this forum or google for TA7317P (speaker protection IC from Toshiba). It has enough features in one chip. No longer in prudction, but you can still get them, e.g. from www.reichelt.de.

Patrick
  Reply With Quote
Old 2nd September 2006, 08:08 PM   #3
AKN is online now AKN  Sweden
No snake oil
diyAudio Member
 
AKN's Avatar
 
Join Date: Aug 2005
Location: In the middle of Sweden
Send a message via MSN to AKN
Or maybe this from Rod Elliott:
http://sound.westhost.com/project33.htm

Edit:
Quote:
I'm having problems finding those big cap's for some reasonably price.. (100uF non pol) Would'nt it be possibly to increase the resistor and use a smaller capacitor instead?
100F bipolar electrolytic does not cost much. Or use two 220F back to back instead of one bipolar.
__________________
/ Anders
  Reply With Quote
Old 2nd September 2006, 10:14 PM   #4
diyAudio Member
 
Join Date: Jul 2004
Location: Sweden
Aha thank's for your replies. I think I will build Rod Elliots design But instead of relay I will probarly design a Mosfet transistors circuitry instead.

Oh I didn't find the electrolytic bipolar capactitors on Elfa.se at first but now I found them. I was looking on the Mkt 100u before But these others are not very expensive so it's ok.

Thanks!

Btw: In the schematic: http://sound.westhost.com/p33-fig1.gif
Can 1N4002 be used for D1-D4?
  Reply With Quote
Old 2nd September 2006, 10:29 PM   #5
AKN is online now AKN  Sweden
No snake oil
diyAudio Member
 
AKN's Avatar
 
Join Date: Aug 2005
Location: In the middle of Sweden
Send a message via MSN to AKN
I hope that you won't intend to switch speaker output with some mosfet circuit instead of a relay.
You could use 1N4148 100mA diodes instead, so low current there so it's no danger.
__________________
/ Anders
  Reply With Quote
Old 2nd September 2006, 11:10 PM   #6
diyAudio Member
 
Join Date: Apr 2004
Location: ventimiglia
Hi to all
This is also a good solution for DC protection.
It is very reliable.
Attached Files
File Type: pdf protection.pdf (14.7 KB, 750 views)
  Reply With Quote
Old 3rd September 2006, 12:27 AM   #7
fab is offline fab  Canada
diyAudio Member
 
fab's Avatar
 
Join Date: Mar 2004
Location: Canada
Quote:
Originally posted by parsecaudio
Hi to all
This is also a good solution for DC protection.
It is very reliable.
one question: What will happen if you have full max DC on the output of audio amp...?
I think that the maximum DC voltage that X1 can take at its input is 2 X VC (or VE) since greater than taht X1 may latch up or could be damaged...
  Reply With Quote
Old 3rd September 2006, 12:38 AM   #8
diyAudio Member
 
Join Date: Apr 2004
Location: ventimiglia
Hi fab
I have tested this circuit for this.
The high value of the resistors in input stage limits the currents on the inverting and non inverting input of the op amp.
This high value protect the inverting input in case of DC voltage.
Also you must to use an I.C. without latch-up problems.
The test that i have made is for 85 V DC....
  Reply With Quote
Old 3rd September 2006, 07:51 AM   #9
diyAudio Member
 
Join Date: Jul 2004
Location: Sweden
Quote:
I hope that you won't intend to switch speaker output with some mosfet circuit instead of a relay.
I don't see this as a big problem out of Audio aspect, and a relay (10A+ DC) is expensive and takes a lot of space (which I don't have in my amp ) And Mosfets are alot faster, so a solid-state solution is good, maybe less practical though. Instead of breaking the output I think it feels better to cut the DC supply from the poweramp because it's not nice to have electronics on the output as you said...

The DC sensor:http://files.upl.silentwhisper.net/u..._DCprotect.pdf

The DC detect circuit looks like this. In normal mode, The last BC556 to the right will be open and send a "protect-voltage". When DC is applied to the circuit-input (from amp-output) the same transistor will cut off. Only minor changes from Rod Elliots design (A Led that indicates)

The PSU: http://files.upl.silentwhisper.net/upload6/Amp_PSU.pdf

Don't bother the circuit to the left, it's just a softstart and is longtime tested.

Anyway, when protect voltage (+33V in my case) comes to "Protect" it opens so that current goes between the rails through the zeners and opens the mosfets. When Protect-voltage is cut, the Mosfets will cut also. The mosfets should handle up to 10A without any problems. I think this design should work. But feel free to comment

//Fritzell
  Reply With Quote
Old 3rd September 2006, 08:47 AM   #10
Leolabs is offline Leolabs  Malaysia
diyAudio Member
 
Leolabs's Avatar
 
Join Date: Dec 2004
Location: Bukit Mertajam
Send a message via MSN to Leolabs
Quote:
Originally posted by parsecaudio
Hi to all
This is also a good solution for DC protection.
It is very reliable.
A little bit expensive but should be a nice one in term of response.
  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
LM3886 circuitry jmillerdoc Chip Amps 3 5th June 2009 01:25 PM
amp goes to protect, why? eeyore757 Subwoofers 6 22nd March 2007 12:29 AM
MCU controlled DC Protect for SKA gbyleveldt Solid State 3 12th October 2006 07:55 PM
About circuitry design, etc... J_Starner Parts 16 5th June 2006 02:30 AM
Using DC instead of Ac for some control circuitry filholder Chip Amps 3 2nd July 2005 04:53 PM


New To Site? Need Help?

All times are GMT. The time now is 08:28 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