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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th January 2005, 02:46 PM   #11
SudFab is offline SudFab  France
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Any people which has an interrest in digital class D will conclude than loopback is the key point.

Actually, here is the same case for analog class D.

For fun, I saw on internet an IEEE article written by Bruno Putzeys saying the same

So, because I'm working on a class D digital design, for my personnal use and technical skill improvment, I decided to add a loopback in my original design.

Some existing articles confirm again than a good approach may be to use an adaptive filter, due to the delay introduced by the PCM to PWM chain and the delay introduced bu the A/N loopback chain.

Does anybody already try to work in that direction and does anyone has a ... feedback ?

Fabien
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Old 6th January 2005, 03:00 PM   #12
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Hi,

B&O site is back on line so search for articles containing PEDEC. You can also search this forum for the same term. John_W also posting on this forum has far the best impementation seen so far, and it seems that eventually it will be comercially available.

Best regards,

Jaka Racman
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Old 6th January 2005, 05:25 PM   #13
SudFab is offline SudFab  France
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Hi Jaka,

Thanks a lot for the link and PEDEC naming.

This approach in very interresting but it has been patented, so even if I reuse it for myself only, I will be unsatisfactory by this fact. May be I will try it, to see if performances are really here.
I guess yes in fact !

But I'm trying to work in a different approach, i.e. using an complete digital loopback, between the load and the modulator, through AN conversion.

The idea, not mine : found in an article in the web, is to use an adaptive filter in the feedback loop, associated with an image of the input delayed by, at least, the sum of the global modulator delay plus AN converter delay.

Designing such a kind of filter is quite challenging, but that's why I have an interrested to do it
For sure, the goal is to improve PSRR, non-linearity of power stage and load variation.

If you have any feedback, according to your own analysis, they are welcome.

At least, do you think it does make sense to work on this algorithm ?

Fabien
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Old 6th January 2005, 06:11 PM   #14
ingrast is offline ingrast  Uruguay
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Quote:
Originally posted by SudFab
.....The idea, not mine : found in an article in the web, is to use an adaptive filter in the feedback loop, associated with an image of the input delayed by, at least, the sum of the global modulator delay plus AN converter delay.
....Fabien

Have you analyzed this idea in depth?

I mention it for I was thinking on similar lines and have the purpose to explore it in the near future, but am not quite sure the effects of this so introduced pole has in stability.

I currently believe (not working at it yet) that a predictive strategy could be inherently more stable though less accurate, but this is only speculation on my part right now.

Rodolfo
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Old 6th January 2005, 06:30 PM   #15
SudFab is offline SudFab  France
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Quote:
I currently believe (not working at it yet) that a predictive strategy could be inherently more stable though less accurate, but this is only speculation on my part right now.
It meets my first idea, but to be honnest, I didn't already perform a real depth analysis.

I'm working on a model which includes perturbation sources, like power supply variation, loud speaker model and power stage distorsion.

After that, I have to look for the better adaptive algorithm and implementation and next run some Mathlab simulations.

Because I do it during my free time, I prefer to not give a target date to publish my first results

Some papers on web let's suppose a amelioration by a factor of 10 on the full bandwidth THD at nominal power, versus open-loop architecture...

Fabien
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