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 November 2012, 07:50 AM   #41
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Try FZT series also, you already have good ones with you, where is my diwali gift old man?
  Reply With Quote
Old 26th November 2012, 09:08 AM   #42
diyAudio Member
 
Ouroboros's Avatar
 
Join Date: Dec 2003
Location: Nottingham UK
Quote:
Originally Posted by pergo View Post
some DIP comparators with <30ns propagation delay
The first is the cheapest.

LM306
AD8561
LT1016
MAX903
TL3016 from TI. Works well for me and has slightly improved parameters over the LT1016 (with which it is pin compatible).
  Reply With Quote
Old 26th November 2012, 11:06 AM   #43
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Quote:
Originally Posted by Ouroboros View Post
TL3016 from TI. Works well for me and has slightly improved parameters over the LT1016 (with which it is pin compatible).
TL3116 is much better with common mode range extending to negative rail.
  Reply With Quote
Old 26th November 2012, 11:07 AM   #44
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
I have thought about some way to control the hysteresis: Markus and I were already in contact privately about this and I will try to sim it and if it "works" I will post details.
I don't know however, wheter soemeone else has already used the same principle already. One can never be sure nowadays - just make a patent search for class-d and you'll know what I mean.

Regards

Charles
  Reply With Quote
Old 26th November 2012, 11:47 AM   #45
diyAudio Member
 
Ouroboros's Avatar
 
Join Date: Dec 2003
Location: Nottingham UK
Quote:
Originally Posted by Workhorse View Post
TL3116 is much better with common mode range extending to negative rail.
Thanks Workhorse, I wasn't aware of that one. I use the TL3016 with +/-5V supplies so the c-m range isn't all that important, but the 3116 might be useful in the future.
  Reply With Quote
Old 26th November 2012, 04:47 PM   #46
diyAudio Member
 
Join Date: Dec 2003
Location: Munich
Great !
This sort of busy thread is making me feel better.
...ohps and is bringing me to the situation that I might not be able to handle all input properly....

@manojtm:
I am also wondering why a totem pole driver should cause noise.
Have a look to posting #27. The figures there are all derived with an amp design that uses a BJT totem pole gate drive.
Ok the MosFets there were just half as heavy as the IRFP4668, but still heavy.
IRFB4115 driven from FTZ853/953 and IRS20957.
IMHO the noise figures are far better than average.
Do you have even higher spec demands? I mean, I need a headphone plugged directly to the speaker output in order to hear the noise at all.

I don't think that totem pole drivers cause generally noise, but it would be interesting to dig for the very detailed trouble mechanism, which caused issues in your experience. Such know how avoids to get trapped by the same pit falls.
Could it be that the faster switching caused more HF-ringing and in consequence more NF-noise? I am seeing in your design from the 25-1200 thread, extremely slow gate drive, which most likely is good for EMI and will also calm down the HFjunk-to-NFnoise conversion of the comparator, but most likely such slow switching impacts THD.
With this thread here, I am not aiming for THD levels as in posting #27, but I don't want to worsen it more than 20db. And idle noise should not worsen more than 10db.
The downside of faster switching is that you cannot get away with mini snubbers. I am sure that I cannot go with such light snubbers as your design. I am expecting more that I need 1nF and something between 5-10 Ohms. ...and of course will have to live with about 1.5W snubber losses.
  Reply With Quote
Old 26th November 2012, 07:03 PM   #47
diyAudio Member
 
Join Date: Dec 2003
Location: Munich
LM306: PropDelay is 28ns. Stoneagedesign. I like it. Available in DIP8 at DigiKey.

AD8561: To much of high speed high end. But at least available at as DIP8 at DigiKey.

LT1016: Also faster than I love. Available as DIP8 at DigiKey, Bürklin and Reichelt.

Max903: Again pretty fast, TTL output, not available at any of my daily sources.

TL3016/3116: Again very fast, not available in DIP8 at all, SMD available at Digikey.


My favorites would be LM306 and LT1016. Unfortunately they have pretty different PIN connections.
Any comments on personal taste and availability in other parts of the world?
  Reply With Quote
Old 26th November 2012, 09:43 PM   #48
pergo is online now pergo  Italy
diyAudio Member
 
pergo's Avatar
 
Join Date: Dec 2008
i always use LT1016 (soon i will try the AD8561 as upgrade) with good results. No audible noise. But i never go over 350kHz switching frequency.

In my experience, it needs hard decoupling between rails and good layout.

All these comparator are sold by RS or Mouser.
  Reply With Quote
Old 26th November 2012, 09:49 PM   #49
diyAudio Member
 
Join Date: Dec 2003
Location: Munich
The floating input stage of the IRS20957 does not need to be connected to GND. It could also be bound to -8.25V in example.
This would allow an ultra simple discrete comparator as shown in the attached schematic. Not sure if this thing already deserves the name comparator, but basically it seems to work reasonably good even with standard components.
The low gain causes an additional delay. With the concerned signals it takes about 60ns until the differential input signal is large enough to generate a comparator output which crosses the flipping point of the IRS input (comp out ramps in approx 120ns).
Impact on idle frequency is still moderate (less than 10kHz).
I have to check for impacts on performance like distortion and frequency control by dynamic hysteresis....

Don't wonder about my strange voltages like 1.65V, 3.3V or 8.25V.
They can easily be derived from a chain of red LEDs ==> low noise zener substitute.

An upgrade with much more comparator gain could be the second schematic, still I am not convinced that the extra efforts are worth it. But it simulates nice. Sloping with the concerned input signals takes 30ns, delay just a few ns (hard to believe).
Please also note the inspiration from Workhorse combined with my improvement to move the mirror to a neg voltage and clamping which avoids saturation of the BJTs.
Attached Images
File Type: jpeg Simple_shrinked.jpeg (94.6 KB, 657 views)
File Type: jpeg Less_Simple.jpeg (169.8 KB, 651 views)
  Reply With Quote
Old 26th November 2012, 10:04 PM   #50
pergo is online now pergo  Italy
diyAudio Member
 
pergo's Avatar
 
Join Date: Dec 2008
i made something similar.
Which is your switching frequency with IRS in your schematic?
I cannot get over 315kHz.

I've replaced the input PNP with BSS84 p-mos
  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
O2 Front Panel INTEREST POLL your own design Llama16 Group Buys 1 12th September 2012 05:23 PM
Probing interest in My inrush limiting design nattawa Power Supplies 2 19th November 2011 01:08 PM
Custom open baffle 12" woofer - any interest? SimontY Group Buys 2 4th March 2009 01:53 PM
Open baffle design lawbadman Multi-Way 1 17th January 2008 12:15 AM
Open call for suggestions on Open Source DIY Audio Design gfergy Everything Else 1 15th April 2007 07:33 AM


New To Site? Need Help?

All times are GMT. The time now is 02:41 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