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Class D Switching Power Amplifiers and Power D/A conversion

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Old 8th April 2004, 06:06 AM   #11
TNT is offline TNT  Sweden
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Many other folks finds PWN amps and icepower in particular excellent for the rest of the frequency spectrum and are in good compant with e.g jeff rowland etc.

The "class d = subfoower" is really .... wrong!

Go for it, particulary for Your type of load !


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Quote:
Originally posted by subwo1
Many folks like PWM amps for subwoofer applications for several reasons. They are efficient, enabling more output power from the electrical service with less wasted heat to make the listening environment hot. Subwoofers tend to have higher distortion so any higher amount from class D amps is less likely to be a problem. They are smaller, capable of as much driver damping as a larger completely linear amp, depending on topology--self-oscillating types like UCD tend to be better at load damping than pre-oscillated types.
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Old 8th April 2004, 06:17 AM   #12
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Quote:
ICEpower very much includes the output filter in their design
Well,

they certainly don't do that in their self oscillating modulator design, only in multi feedback loop design which is usually based on fixed frequency carrier based PWM modulation. I have read all the Niels Karsten's articles and the patents, and nowhere is phase shift of output filter used to sustain oscillation.

Best regards,

Jaka Racman
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Old 8th April 2004, 06:26 AM   #13
Pabo is offline Pabo  Sweden
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Jaka Racman

Try WO98/19391

Read the claims and you will see.

I also agree that classd no longer is limited to low frequency applications. Most topologies though have problems with capacitive loads as their swtching frequency is affected by them. With the correct type of speaker it is possible to reach really low distorsion levels.

best regards / Patrik
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Old 8th April 2004, 07:05 AM   #14
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Hi Patrik,

WO98/19391 is the same as US6297692. Quote from the first and most important claim :
Quote:
Pulse modulating power amplifier... wherein a first negative feedback is introduced from the SWITCHING STAGE OUTPUT...
Just show me any picture from the ICEpower articles or patents that resembles UCD patent principle, and I will stand corrected.

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Jaka Racman
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File Type: gif ucdpat.gif (9.7 KB, 1476 views)
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Old 8th April 2004, 07:10 AM   #15
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Some thoughts:

The EDN modulator is nothing else than the standard circuit for AMVs using an op-amp! We used this circuit 20 years ago during lab training.

The ICE power amp uses feedback from the switching stage AND from the filter. The lowpass in the feedback path of the inner loop causes the inner loop to behave like a lead filter and therby compensationg for one pole of the output filter.

The patent as such is not that sensational.

I think that the UCD doesn't infringe B&O's patent, since doing the same thing in a simpler and better way is definitely a technical improvement and therfore be worth getting patented.

Regards

Charles
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Old 8th April 2004, 09:19 AM   #16
subwo1 is offline subwo1  United States
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The circuit Jaka Racman posted an image of seems so obvious and universal that it should not be patented whether anyone has tried and succeeded or not. I even feel that variations of it adding additional resistors and capacitors around the feedback node to modify the oscillation and loop properties also should not be patentable. That view is the one I have.:-). Sorry for ruffling feathers.
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Old 8th April 2004, 09:24 AM   #17
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You are right in principle. But you will sometimes find things that are more obvious that have been patented. Or even worse, things that are completely useless.

Regards

Charles
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Old 8th April 2004, 04:00 PM   #18
Pabo is offline Pabo  Sweden
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subwo1

The picture is from Putzeys ucd patent. Simon J Broadley has patented a similar topology but with a error amplifier comparing the input to the output before converting to PWM.

Jaka Racman

The circuit in which ICEpower uses the technique is VCOM (Voltage Controlled Oscillation Modulator). I think it was shown in fig13. in the patent mentioned earlier.
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Old 8th April 2004, 04:13 PM   #19
subwo1 is offline subwo1  United States
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Sorry Bruno, I did not mean to make light of your efforts. I have been using variations of that circuit for ages. I am remiss because I gave up spending lots of time searching for patents. Congratulations for your success in getting a patent on it. I wish you the best.
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Old 8th April 2004, 06:13 PM   #20
Pabo is offline Pabo  Sweden
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subwo1

Are you sure that you have used the same technique? Did you invent it yourself or where you influenced by other circuits? If you have seen any circuit (published or manufactured) from before 1998 or so that uses the technique it would be splended if you could come up with that reference. That way Philips cannot enjoy the advantages of owning the sole rights to a circuit that they haven't invented.
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