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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th September 2011, 08:23 PM   #1
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Lightbulb Has anyone written a decent book on class d amp design?

Just wondering if anyone knows of a decent book containing any useful information regarding class d amplifier design.

i need to build something for my university project and thought a power amplifier would be good, its an excuse to build some more bass bins too

I've got Audio Power Amplifier Design Handbook, which is a great book but has little information on class D other than the basic principles.
I've never built a class D amp and want to build something pretty powerful too probably about 600w per channel or 1200w bridged in to 4ohms, (though i'm sure i'll knock up something smaller as an educational project along the way). I know class D is can be very challenging but that's the point, I've built an amp for my last qualification so it stands to reason that i ought to build a more complex one this time

I know you hear this all the time on here, "can someone please post a nice easy diy class d 2000w amp schematic please" etc etc. I know such a thing is practically impossible and that building a decent class d amp has a lot to do with circuit layout/design.
I build design circuits at work so have access to multilayer board fabrication but its mostly logic stuff so little experience with hf switching. I've built amps before (class A and class AB) but class D seems a very different world. If someone could point me in the direction of suitable books / information / threads etc that may help it would be appreciated.

P.S
this is going to be my university project so will be fully documented during build and i will happily upload build documentation to this wonderful website.

P.P.S
If you've actually read to this point then Respect
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Old 6th September 2011, 08:29 PM   #2
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There are loads of designs on the internet.
Look up International Rectifier for their designs IRS2092.

Experience of class d problems can be found on this forum again and again.

You can make discrete class d amps but some of these have problems.
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Old 6th September 2011, 08:54 PM   #3
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Yeah i was thinking probably going for one of the IR chips rather than my own discrete design.

I have had a peek through the threads but theres just so much stuff about little modules and low power amps, I shall delve deeper.
and maybe go find myself some service manuals for current high end PA class D amps
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Old 6th September 2011, 08:57 PM   #4
trevmar is offline trevmar  United States
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Quote:
Originally Posted by soundbadger View Post
this is going to be my university project
The problem you are going to have is that the majority of designs you will find here on the Internet are not soundly based from a University engineering-design perspective. You can use a simulator, I used SPICE for my masters thesis on Class E design, but that was 1978, there are better tools out there now. Or you can use stepwise approximation and adapt the tried and true analog analyses to the digital domain. It really isn't too hard. The delta-sigma design methodologies date back to ca. 1974 (I know that date, 'cos it was one of my own papers ) and you will find plenty of mathematical treatises if that is what your supervisors want. If they just want something that works, then your task will be a lot easier
.
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Old 7th September 2011, 10:06 AM   #5
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not a book, but might be helpfull anyway

http://www.ti.com/lit/an/sloa031/sloa031.pdf

http://www.nxp.com/documents/user_manual/UM10155.pdf

Design and analysis of a basic class D amplifier
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Old 7th September 2011, 10:52 AM   #6
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I suggest you look at all of the IRAUDamp application notes from IR, as well as making sure you understand how their IRS20124 and IRS20955 gate driver chips work.

Also Bruno Putzey's various technical documents are very helpful if you want to make a self-oscillating design with the NFb taken directly from the amplifer output.
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Old 7th September 2011, 11:32 AM   #7
dewardh is offline dewardh  United States
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Quote:
Originally Posted by soundbadger View Post
useful information regarding class d amplifier design.
Here's another vote for the IRS2092 designs, and the IR app notes for them.

Regarding 2000 Watt (or even 600 Watt) amps the question has to be "why?". At those power levels (for audio, anyway, maybe not if you're running a shaker table for earthquake sims) you will be running multiple drivers . . . it's far easier to just put one amp per driver (at $20-30 each why not?) and parallel the inputs. There aren't many drivers that you won't slag rather quickly at even 600 Watts . . .
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Old 7th September 2011, 11:40 AM   #8
marce is offline marce  United Kingdom
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There is a thread with links to the EMC aspects of switching circuit design, which is a critical side of these sort of designs and so gives some good information on layout etc, layout being one of the most (if not THE MOST) critical aspect.

Switcher EMC design

Last edited by marce; 7th September 2011 at 11:40 AM. Reason: Forgot the link!
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Old 7th September 2011, 01:03 PM   #9
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"Regarding 2000 Watt (or even 600 Watt) amps the question has to be "why?""

dewardh, I have single speakers that will hand more than 600W, there not for my living room its PA

cheers marce, Thats the sort of info i need.
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Old 7th September 2011, 03:46 PM   #10
dewardh is offline dewardh  United States
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Originally Posted by soundbadger View Post
I have single speakers that will hand more than 600W,
Just out of curiosity . . . what drivers are those? That is a lot of heat to dissipate in a voice coil . . .
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