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 26th May 2004, 06:02 AM   #11
IVX is offline IVX  Russian Federation
diyAudio Member
 
IVX's Avatar
 
Join Date: Jul 2003
Location: Everywhere (Buddhist's context)
Quote:
U cant synchronise multiple Self-Oscillating Class-D amps
Why do you think that ZeroTHD can't do it? Candid camera again is ON?
__________________
Best regards,
E1.
  Reply With Quote
Old 26th May 2004, 09:38 AM   #12
ZeroTHD is offline ZeroTHD  Sweden
diyAudio Member
 
Join Date: May 2004
Location: Gothenburg
Quote:
The reason is simple , U cant synchronise multiple Self-Oscillating Class-D amps to a common SWitching frequency.
"Can not" is a strong combination of words...
As I told you before- I'm new to this business, but do I really need to synchronise the switching frequencies? I guess you mean that i.e. the left and the right channel wouldn't oscillate at the same frequency. Do they have to? Can you notice if they differ a few percent?
Regards,
Anders
  Reply With Quote
Old 26th May 2004, 11:09 AM   #13
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Quote:
Can you notice if they differ a few percent?
A few percent could indeed be even worse than a large difference ! This is because they might cause intermodulation products. This all depends on construction, PSU decoupling etc.

Regards

Charles
  Reply With Quote
Old 26th May 2004, 12:26 PM   #14
ZeroTHD is offline ZeroTHD  Sweden
diyAudio Member
 
Join Date: May 2004
Location: Gothenburg
Quote:
A few percent could indeed be even worse than a large difference ! This is because they might cause intermodulation products. This all depends on construction, PSU decoupling etc.
I guess this would be a problem even in non-self-oscillating designs as long as it runs from separate tri-wave generators. The problem should be solved by minimzing the coupling between the two channels (by distance and by proper PSU design).
Right now I'm having problmens with shoot through. I'm not sure if this is because of imbalance in the circuit, or if I need to incorporate some dead time circuitry.
This is getting interesting!
Thanks,
Anders
  Reply With Quote
Old 26th May 2004, 02:49 PM   #15
diyAudio Member
 
Join Date: Sep 2003
Location: -
Hi Anders,

The routing of the PCB is very importend to avoid coupling of between multichannel Class-D.

Please post your schematic perhaps the forum can give you some idees for decreasing the shoot through problems.

Regards,

Jan-Peter

www.hypex.nl
  Reply With Quote
Old 26th May 2004, 04:27 PM   #16
ZeroTHD is offline ZeroTHD  Sweden
diyAudio Member
 
Join Date: May 2004
Location: Gothenburg
Remember, I'm new to this, so don't be too hard on me.
Regarding choice of components. I picked components I have on the shelf for easy and cheap prototyping.
Thanks,
Anders
Attached Images
File Type: gif draft1.gif (47.6 KB, 635 views)
  Reply With Quote
Old 26th May 2004, 06:34 PM   #17
IVX is offline IVX  Russian Federation
diyAudio Member
 
IVX's Avatar
 
Join Date: Jul 2003
Location: Everywhere (Buddhist's context)
hmm, i haven't problems with shoot through in this simulation (MC7), but with si4480 (haven't 4484 model).
Jan-Peter,
BTW, in UcD 180 sync. input doesn't exist???
__________________
Best regards,
E1.
  Reply With Quote
Old 26th May 2004, 07:03 PM   #18
Pabo is offline Pabo  Sweden
diyAudio Member
 
Join Date: Feb 2003
Location: Helsingborg, southern sweden
ZeroTHD

You cannot measure THD in the simulation program without lowpassfiltering extremely hard because of the same reason that you lowpass filter a signal before A/D conversion. My own classD amplifier measures 0,0008% at 1kHz 1W with AP but shows 20% or so in a simulation. Even with third order low pass filter after the second order output filter the simulation shows about 0,5% or so. Donīt really kno why.

In order to reduce shoot through, make sure that the turn off transistor that you use is a high beta type with large bandwidth. If the bandwidth is too low the beta will drop, maybe down to unity, at the switching speeds you are trying to obtain. You will allways have some shoot through though, otherwise the distorsion will increase.
__________________
If something that measures good doesnīt sound good, measure again!
  Reply With Quote
Old 26th May 2004, 07:05 PM   #19
Pabo is offline Pabo  Sweden
diyAudio Member
 
Join Date: Feb 2003
Location: Helsingborg, southern sweden
A good choice by the way is BCX-56 or something like that??
__________________
If something that measures good doesnīt sound good, measure again!
  Reply With Quote
Old 26th May 2004, 07:15 PM   #20
diyAudio Member
 
Join Date: Sep 2003
Location: -
IVX,

No there is no seperate sync input on the UcD180.

I don't have experience with synchronisation but I guess you can try to mix the HF signal together with the input. As far as I understand the UcD will then synchronize to this HF signal.

We use a NE5532 as symmetrical gainstage with a gain of 5x. So the HF signal must pass also the NE5532.

I don't know if this work, anyway I haven't tried it yet.

ZeroTHD,

Did you actually build a physical module for testing?

Regards,

Jan-Peter

www.hypex.nl
  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
simple se success! newtube Tubes / Valves 3 24th May 2009 09:23 PM
TDA7560 car amp, second try, success! Redshift187 Chip Amps 6 22nd September 2008 11:48 AM
First Re-Cap Success ! ! 65blkbkgt Car Audio 9 11th July 2007 07:47 AM


New To Site? Need Help?

All times are GMT. The time now is 06:27 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2