Building a TPA3132 amp board - 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 25th February 2014, 11:35 AM   #1
rosvall is offline rosvall  Denmark
diyAudio Member
 
Join Date: Dec 2009
Default Building a TPA3132 amp board

I want a tiny, efficient, cheap class-D amp for active speakers. Both for hifi and for a portable battery powered setup.
I've read the thread about the chinese tpa3116 boards. While they are cheap, they look like they all suffer from bad board layout and worse components.
I'd like to build one that satisfies these requirements:
- High efficiency both at no output and when playing music with low crest factor at full power into 8Ohm.
- Low distortion.
- Doesn't radiate like a WWII radio jammer.
- Is cheap to build.

This is what i've got so far: https://github.com/rosvall/tpa3132-amp

This is my first SMD layout, so i'd like to know if it looks reasonable. Routing high frequency, high current stuff through 0.2mm traces makes me feel dirty.

I really don't know what i'm doing with the EMI related stuff - the output snubber circuits, ferrite beads and stitching ground planes. A little help would be appreciated.

Feel free to clone it and start hacking.
  Reply With Quote
Old 25th February 2014, 01:06 PM   #2
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
You'll need a pull down resistor between Vcc and SDZ or the amp won't turn on at all.
  Reply With Quote
Old 25th February 2014, 01:29 PM   #3
rosvall is offline rosvall  Denmark
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by Saturnus View Post
You'll need a pull down resistor between Vcc and SDZ or the amp won't turn on at all.
Thanks. I've fixed that now.
  Reply With Quote
Old 25th February 2014, 03:21 PM   #4
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
For active speakers it would probably be a good idea to have signal sensing turn on/off with timer output. For example a NJU7181 chip have everything you need integrated at an extremely low power consumption. Drive the SDZ (and FAULT) pin directly with the output, ie. no connection directly to Vcc. There are other similar chips but this one provides everything that is needed in one simple package and it costs about $0.50 each.

http://semicon.njr.co.jp/eng/PDF/NJU7181_E.pdf

Note that there's probably no need for sensing 2hz signals so the 10F input capacitor could just as easily be 220nF instead.

Also note you need a voltage divider or some other voltage regulator to supply the chip.

Last edited by Saturnus; 25th February 2014 at 03:30 PM.
  Reply With Quote
Old 25th February 2014, 03:42 PM   #5
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
On another issue. Drop the LC output filter and have just a ferrite bead plus CRC output snubber. The main culprit of RF noise is long cables and the output inductors. Active speakers by definition have short speaker cables.
  Reply With Quote
Old 25th February 2014, 04:03 PM   #6
rosvall is offline rosvall  Denmark
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by Saturnus View Post
For active speakers it would probably be a good idea to have signal sensing turn on/off with timer output. For example a NJU7181 chip have everything you need integrated at an extremely low power consumption. Drive the SDZ (and FAULT) pin directly with the output, ie. no connection directly to Vcc. There are other similar chips but this one provides everything that is needed in one simple package and it costs about $0.50 each.

http://semicon.njr.co.jp/eng/PDF/NJU7181_E.pdf

Note that there's probably no need for sensing 2hz signals so the 10F input capacitor could just as easily be 220nF instead.

Also note you need a voltage divider or some other voltage regulator to supply the chip.
That is a good idea. I'll see if can squeeze that in.

WRT the output LC filters, I definitely wouldn't mind getting rid of the inductors. I just fear the efficiency would suffer from using the speaker as filter. I can't find any numbers though. Also, what about the harmonics and stuff from 400kHz up to where the ferrite starts working?
  Reply With Quote
Old 25th February 2014, 04:26 PM   #7
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
Quote:
Originally Posted by rosvall View Post
WRT the output LC filters, I definitely wouldn't mind getting rid of the inductors. I just fear the efficiency would suffer from using the speaker as filter. I can't find any numbers though. Also, what about the harmonics and stuff from 400kHz up to where the ferrite starts working?
You mean the AM frequency band? That's what the modulation is specifically designed to suppress so no problems there, it's higher order harmonics that can cause problems so a ferrite bead is used to suppress that.

Efficiency penalty of a ferrite bead is in the range of 0.3% to 2.1% depending on the speaker inductance.
  Reply With Quote
Old 25th February 2014, 04:36 PM   #8
rosvall is offline rosvall  Denmark
diyAudio Member
 
Join Date: Dec 2009
Quote:
You mean the AM frequency band?
The ferrite beads i've looked at really don't do much up to about 30MHz with any sort of DC bias. That makes me slightly uncomfortable.

Quote:
Efficiency penalty of a ferrite bead is in the range of 0.3% to 2.1% depending on the speaker inductance.
That is energy wasted in the ferrite bead or the speaker?
  Reply With Quote
Old 25th February 2014, 05:21 PM   #9
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
Quote:
Originally Posted by rosvall View Post
The ferrite beads i've looked at really don't do much up to about 30MHz with any sort of DC bias. That makes me slightly uncomfortable.

That is energy wasted in the ferrite bead or the speaker?
They don't need to. The FM radio band is 100MHz +-10%, so the ferrite beads needs to have their impedance maximum there. Fortunately, that's also what the vast majority of ferrite beads is designed for.

I cannot stress enough that in my opinion the audio quality is a lot better with ferrite beads instead of LC output filter. The bass and lower midrange is a lot better detailed and controlled but it's the very high range that really stands apart. In that regard it's like the difference between a (high quality) .mp3 and a .wav file.

Lower efficiency means a higher percentage is lost in the amp heat sink but you have almost zero loss in the ferrite beads themselves due to the high frequency impedance resonance and the ultra low series resistance. They do not get even remotely warm. Output inductors on the other hand can get burning hot with added loss and even lower audio quality as a consequence due to thermally variable resistance and inductance as well as saturation in some cases.

Last edited by Saturnus; 25th February 2014 at 05:26 PM.
  Reply With Quote
Old 26th February 2014, 07:05 PM   #10
rosvall is offline rosvall  Denmark
diyAudio Member
 
Join Date: Dec 2009
https://github.com/rosvall/tpa3132-amp/tree/filterless

I've removed the LC filters and replaced it with some beefier ferrite beads. Then i took a look at the eval board and realized that it was much nicer than what i was doing, so i changed the output routing completely. And i copied their RC-snubbers.

Any idea if it's going to behave?

I'm not really sure what i'm looking for with the ferrite beads, apart from a DC bias of up to 5A. The ones i've found ( http://datasheet.octopart.com/HI3312...heet-65586.pdf ) look kind of large.
I'm pretty sure i've overdone it with the vias.
I'm feeling a bit out of my depth with this stuff.

Anyway, this layout did free up a lot of space for power management and whatnot. So there's that.
  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
HIFI 700W Subwoofer Mono Amplifier Board By 10 Pairs 1943/5200 Amp Board For Subwoofe nelnar Solid State 2 21st July 2014 06:35 PM
How to connect PSU board to amp board? emerth Power Supplies 6 17th June 2012 01:35 PM
Building the TSE board upside down Alan Hope Tubelab 8 22nd September 2011 02:34 AM
FS- Twisted Pear Buffalo 32S Board & System New & Unused secretriches Swap Meet 1 10th August 2009 02:17 PM
SMPS & tube pre-amp development board. ianl Tubes / Valves 2 10th April 2006 06:05 PM


New To Site? Need Help?

All times are GMT. The time now is 07:05 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