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 29th April 2009, 12:59 PM   #1
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Default Ripple steering?

Hi all

Please have a look:
http://www.extron.com/download/files..._d_ampl_wp.pdf

Interesting read on how to make class D without any output ripple, however I've got a gut feeling something's wrong in it. Cannot figure out what for now, maybe I am wrong and missing something elementary...
Need your opinions!
  Reply With Quote
Old 29th April 2009, 06:09 PM   #2
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Hi, Darkfenriz,

You can look at US patent #7167048. But it won't work for UCD style, the ripple is needed for UCD amp to work.
  Reply With Quote
Old 30th April 2009, 07:01 AM   #3
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Yes, that's the patent.
The whole idea is new to me. What's the nature of filtering?
Brickwall filters don't exist and if they do to some extent, they are not for free.
Do you know the crossover frequency between main and auxiliary output and probably the current ripple through the auxiliary output?
BTW, scope shots donn't look very nice at the paper...
  Reply With Quote
Old 30th April 2009, 10:04 AM   #4
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
I am not sure whether zero current ripple in the output inductor is desirable at all. And how "zero" voltage ripple in the load can be achieved is old hats IMO.

Regards

Charles
  Reply With Quote
Old 30th April 2009, 05:20 PM   #5
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
I'm also not very clear about the inverted current direction in output filter. It makes larger current. It seems they wanted to get rid of mosfet's body diode reverse Qrr spikes, but in compliated way. Why don't choose a better mosfet instead?
Maybe EVA could give insight about this?
  Reply With Quote
Old 4th May 2009, 01:55 PM   #6
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Well, I believe it is more about being a steep crossover passing audio current into load and everything above to a secondary circuit. No circuit can have such jump in impedance from nearly nothing at 20kHz to very high at 130kHz (switching freq,) and above (harmonics).
So probably there is still some ripple current, just passing into the other coil.
Please correct me if I am wrong.
  Reply With Quote
Old 5th May 2009, 05:21 AM   #7
MOER is offline MOER  United States
diyAudio Member
 
Join Date: Aug 2003
Location: SIMI VALLEY CA
Default Ripple steering

We have tried this in the class D amplifiers using both pre and post coil feedback. It does nothing.

However in switching power supplies especially power factor correctors it sure does help

Stephen Mantz
Zed Audio Corporation
  Reply With Quote
Old 5th May 2009, 02:28 PM   #8
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
It could help that the amp's output signal looks more like that of a conventional linear amp - which can be a sales argument.

This could however be achieved with other filter topologies as well - which don't necessarily remove the ripple (which assists switching at low amplitudes) from the main filter coil.

Regards

Charles
  Reply With Quote
Old 6th May 2009, 02:07 AM   #9
JohnG is offline JohnG  United States
diyAudio Member
 
Join Date: Mar 2002
Location: Upstate NY
Nothing really new here. There is a Bloom and Severns article in the proceedings of the IEEE Power Electronics Specialists Conference (mid-80's, don't have it with me) covering the details.

There is no magic here. A complete analysis will show that you can add two extra poles to the file. In practical, there will always be a couple of parasitic zeros, not all of which are bad in practice; sometimes a little damping is a good thing.

Note that the benefit may be found in that the extra inductor need only carry the ripple and no DC, which can reduce size in some cases over a more conventional series inductor.

John
  Reply With Quote
Old 11th May 2009, 06:14 AM   #10
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Thanks for opinions.
Does anyone have any experience with series resonant LC tank instead of just C for the output filter?
Is that worth to have several LC tanks for e.g. 1st, 2nd and 3rd harmonic?
  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
Stock HU with steering audio controls needs upgrade colo Car Audio 1 25th April 2009 10:34 PM
too much ripple steevo Solid State 11 5th July 2007 07:27 PM
steering volume control? Bad silver Car Audio 3 26th June 2007 03:47 PM
Steering stalk adapter. leekirlew Car Audio 0 20th April 2006 05:54 PM
How much ripple?? JDeV Tubes / Valves 23 2nd April 2003 11:05 PM


New To Site? Need Help?

All times are GMT. The time now is 08:45 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