T106-2 core vs.??? core Amplifier problem - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

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 8th January 2008, 03:16 PM   #1
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
Arrow T106-2 core vs.??? core Amplifier problem

Ok...I think that I might have very interesting issue here.

I have build two 200W /4ohm amplifier modules (using LM311+IR2010+IRF540Z) using core I found localy in store(unknown type but I think is ferrite) with success.
Amplifier carrier is on 300khZ,self-oscillating..tested on full power for hours (on speakers-3 way proffesional boxes) and worked great (great sound-bass,mid and highs were great).Carrier level was just 150mV.
I decided to get some samples of T106-2 core (which is a lot smaller then my core(4 inch diam.)) and try it.
I got it 2 days ago and finally tried it.
Results were not that good as I expected.
I used 2 x 20 gauge wire to make core (44 turns ) to get 40-50uH inductor....After I installed it I got ripple (carrier level) on output of 4Vp-p(old core was just 150mVp-p),offset voltage of 0.450Vmeasured using DMM (old core was 0.001V).
I found out that big offset voltage has something to do with amount of FB feeded back to comparator (I guess 3Vp-p vs. 150mVp-p) so I tried to reduce feedback but it did not work well.
Basically everything looks ok when you turn amplifier on but once you apply anything to input of LM311(even you do finger touch) it offsets Vout to 0.4V.Very strange....

Do you have any suggestion???

Regards....
  Reply With Quote
Old 8th January 2008, 04:02 PM   #2
zkaiser is offline zkaiser  Yugoslavia
diyAudio Member
 
zkaiser's Avatar
 
Join Date: Feb 2005
Location: _
You cannot just switch core (dimensions and type) and remain the same number of turns. As far as offset consurned you must be able to add some dc counter component to cancel it. When I was build iraudio2 amp opamps needed to be trimed for zero offset at out of the amplifier.

Anyway you should post your sch. also to get more accurate answer.

PS.

BTW it seems that you got 26uH not 40-50 as you thought so this is the problem.
Click the image to open in full size.
  Reply With Quote
Old 8th January 2008, 04:31 PM   #3
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
OK...here is working schematic for you guys:
Attached Files
File Type: pdf ir2010 rev1.pdf (62.4 KB, 234 views)
  Reply With Quote
Old 8th January 2008, 04:54 PM   #4
zkaiser is offline zkaiser  Yugoslavia
diyAudio Member
 
zkaiser's Avatar
 
Join Date: Feb 2005
Location: _
Have you tried this ?

Click the image to open in full size.
  Reply With Quote
Old 8th January 2008, 05:10 PM   #5
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
No I have not.....Is that how you did yours?

Can you post how did you fix your DC offset....

regards
  Reply With Quote
Old 8th January 2008, 05:11 PM   #6
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
It is interesting that on startup dc offset is 0V and then when you even just touch input pin it jumps to 0.45V and stays there....
  Reply With Quote
Old 8th January 2008, 05:26 PM   #7
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
One leg of the comparator is seeing 1K at DC, the other is seeing 22k. The offset of the comparator (including switching time asymmetry) is being amplified by overall gain (23). This is basic amplifier design. You can find a fix in most schematics of class AB amplifiers.

You have zero offset upon power up because the circuit is not yet oscillating, it does not start until it gets some input signal. I though this was quite obvious too.

If you were getting 150mV ripple with the old inductor, the value was way too high. If you are getting 4V now, the value is way too low. I though that RF engineers knew the values of their inductors
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 8th January 2008, 07:03 PM   #8
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
Eva,

Thanks for reply....As far as value of inductor...I was doing this whole experiment over this past weekend so i did not have L meter at home...BTW...even at work if I need to measure inductance (BTW a lot smaller value then this inductor is-(range of up to 100nH max) I use Network Analyzer.RF HF design are a lot more sensitive and less tollerant on values then this amplifier inductor design.

But, thanks on all this informations regarding class D.You are very helpfull person in this field.I am wondering where do you live(secret location?).If you live at place I think you do then we might be originally from same location....

As far as DC offset----with other-original core I did not have a offset issue (with same part values).

So what is your recommendation to fix that problem?
What is "normal" ripple value?

Regards
  Reply With Quote
Old 8th January 2008, 08:16 PM   #9
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Fix no. 1: Put 100uF or so (preferably non polar) in series with the 1K resistor from pin 2 of LM311 to ground to bring gain to unity at DC. This should divide offset by 20 or so. Next time use differential inputs to the comparator.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 8th January 2008, 08:19 PM   #10
zox2003 is offline zox2003  United States
diyAudio Member
 
Join Date: Nov 2004
Location: usa
What about inductor on T106-2 core and wire size(200W) for 300khz?
  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
Which, Foil Air Core or Iron Core Inductors slhijb Multi-Way 16 20th November 2009 03:12 AM
inductor/choke/air core/ferrite core. . . same thing? poolorpond Pass Labs 24 29th March 2008 10:55 PM
Solen Air core inductors, Hammond Iron core. gnomus Swap Meet 0 30th July 2004 01:28 AM
Any website reference for diy choke ,siliver R-core, C-core, EI and power transformer bmpa Parts 2 22nd April 2004 04:15 AM
AIR-Core Vs Ferrite-Core Inductor in Class-D amplifiers Workhorse Solid State 13 23rd January 2004 09:14 AM


New To Site? Need Help?

All times are GMT. The time now is 12:34 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