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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th March 2008, 04:49 AM   #81
walkura is offline walkura  Poland
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I can't agree more Tim__x .
If Eva chooses to give schematics or not is her own choice .
The comments she writes are very educative for me and a lot of others .
I'm not going to ask for schematics but i am gratefull for what i learn from her (and others) .
Its a beautyfull piece of work she's making there and you should be happy you can follow those projects .

Pozdrawiam Walkura .
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Old 6th March 2008, 06:56 AM   #82
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I'm thinking at some point to do a self-oscillating switching amp for my subwoofer. I'll start first with a fairly Neanderthal approach to get the power train worked out. I may try asking Eva nicely what she did as far as block diagram functional elements to clear up some of the grittier aspects of a self-oscillating design (such as low load high frequency oscillation), but I prefer to work out the intimate schematic details myself. It's DIY, after all. Just the concept of a self-oscillating design working at the power levels described here is interesting. I'll probably be only shooting for 100 watts or so, as my subwoofer will rattle pictures on the walls with a 20W amplifier.
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Old 6th March 2008, 02:27 PM   #83
Pafi is offline Pafi  Hungary
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Some info:
http://www.irf.com/product-info/audi...sdtutorial.pdf

A pre-filter feedback, phase-shift self oscillating amp modell:
http://users.hszk.bme.hu/~sp215/PWM_...ing_theory.gif
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Old 23rd October 2008, 04:40 PM   #84
Eva is offline Eva  Spain
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New version 2.0 prototype

Main board:
Click the image to open in full size.

PFC control daughter board:
Click the image to open in full size.

Modulator, gate drive and input isolation daughter board:
Click the image to open in full size.

Magnetic snubber, main supply snubber, and output capacitor daughter boards:
Click the image to open in full size.

Housekeeping supply and active clamp daughter board:
Click the image to open in full size.



Improvements over previous version:

- A much better PCB layout with SMD parts as required.
- A new magnetic snubber concept featuring much lower losses and no longer having to deal with voltages over 600V (this is for loss-less soft switching of body diodes).
- A "snubberized" ringing-free main supply rail (99.9% of people using this word don't know how to implement it properly).
- The magnetic components are now placed further from the modulator.
- A "non-inductive" output capacitor featuring a clean carrier residual free of glitches or ringing.
- A balanced modulator scheme featuring both active and passive poles and balanced feedback (I had to give up on the RC-less design and use RC lead networks directly from the output to the comparator, as this gives the best performance).
- Hysteretic self-oscillating current limiting (set to approx 35A).
- A 560ns minimum pulse width limiter at the output of the comparator to prevent short destructive glitches (this was causing the previous version to fail).
- Input signal opto-isolation is now built in and powered with +/-13V through a DC-DC converter (a SG3525A and a tiny toroid with triple insulated primary).

Pictures will be posted soon.
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Old 24th October 2008, 12:25 PM   #85
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Evita, Nice design..........and very informative >>full of break through innovations.....


One question : Why the outpur inductor is vertically mounted, isnt this increases EMI?

I like the way you have mounted the output shunt CAP PCB.


and which mosfets you are using now?
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Old 29th October 2008, 02:19 PM   #86
ArthurG is offline ArthurG  France
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Wow impressive work
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Old 13th November 2008, 10:21 AM   #87
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mounting toroids specially the output inductors are worst in class-d, they produce lot of disturbance to nearby control circuits and also radiate emi.
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Old 13th November 2008, 12:03 PM   #88
luka is offline luka  Slovenia
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And this is not a problem if you do it righr
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Old 16th November 2008, 06:13 PM   #89
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Quote:
Originally posted by EnvisionAudio


Find another job - and don't share what you do for a living on a DIY site.
I am here because audio is a hobby for me. I have a VERY SMALL side business selling a power supply that I developed by myself with no outside "questions" to any forums. I read books, white papers and datasheets. I can do math. I just think it's nice to permit followers of a thread to see what you're working on. OR GET OUT. It bugs me.
Go post in the commercial listings. I don't ask Fumac to tell me how he builds his MCD amplifier - if I want it, I'll buy it (or license). If I want to sell it as my own, I'll develop my own.I'm not on anyone's side when it comes to stealing IP - ever.

/rant over. Thanks.
...if the DIY-Forums would not get any information from people, who spend most of their time on this stuff, then DIY-Forums would miss a lot of impulses.
You can see this with my postings & threads. It takes ages until things go on - simply because I have to spend most of my time with other topics.
So I prefer to get some info rather than nothing.
Of course I would also love to see Eva's schematics, but honestly speaking - with her layouts she is also showing her schematics for everyone, who is willing to spend some time and energy on this topic.
...yes, I am also to lazzy to draw a schematic from her layouts... But that's my own fault, not hers.
Furtheron, in class D the layout is one of the keys for success. Layout , HF-resonances, supply ringing... this is usually killing the success of class D beginners.

I also was struggling with that. First I could not see it at all, but JohnW was guessing that I might struggle with HF-resonances and gave me faster scope. Then I saw it and Eva gave me the key hints to handle this topic and she did this open visible for everybody in this forum.

So take the chance and learn from her PCB.
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Old 16th November 2008, 08:25 PM   #90
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Had you researched it for five minutes you'd have had the same answers just as easily.

You're not going to learn layout from looking at a picture and never thinking about anything.

If parasitic resonances causing EMI aren't an obvious pitfall in a high speed power switching circuit, what is.
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