Creating positive phase shift?

[Kenshin]

And,how about UcD's patent? connecting a NFB from output and make the system self-oscillate, will this touch their patents?

[Pabo]

Kenshin

I am not sure what you are referring to specifically but the ucd-patent and the ICEpower-patent are different in the way that ICEpower uses a separate 2nd order filter before the output filter to create the phase modulation while ucd uses the existing 2nd order filter itself.

None of these patents claim a zero in the feedback loop.

[classd4sure]

Hi Pabo,

It is because of what Charles said I believe:

"...Because the feedback thingie is not restricted to polyphase PWM in B&O's patent it does cover almost any PWM topology where the phase-lead is generated by a lowpass around an inner feedback loop.

It does however not cover any other topology that generates a phase-lead.

Regards

Charles
"

How many other ways can you create a phase lead? UCD uses lead compensation... you're right though I don't think it is one of their claims.

Ooooooooooohhhhhhh look.... tripath owns that patent

http://www.acutechnology.com/ClassD/...05909153__.pdf

You know .... IMHO, there's far too much concern here over who's got what patented, use what works best!

[phase_accurate]

I was aware of that patent but it 1.) mentions the old-fashioned method with the parallel feedback capacicor as prior art (i.e. the patent claims don't cover this) and 2.) the proposed topology is a little complicated IMO. AFAIK they don't use it for their own audio amps. I somehow remember that they wanted to use this principle for RF applications rather than audio but have to think where I got this from.

I just saw that my statement about the feedback around the inner loop was a little unprecise. No one could say anything if you use lowpass-filtered NFB around maybe an OP-AMP for making a phase-lead, even if it is the part of an inner loop of a switching amp. What is claimed is the lowpass-filtered NFB around a modulator stage.

Regards

Charles

[Kenshin]

I found the UcD patent WO03090343 at
http://l2.espacenet.com/espacenet/ab...B=EPD&DRDB=EP1

and the feedback do include a zero.

http://l2.espacenet.com/espacenet/bn...+03090343A2+I+

Originally posted by Pabo
Kenshin

I am not sure what you are referring to specifically but the ucd-patent and the ICEpower-patent are different in the way that ICEpower uses a separate 2nd order filter before the output filter to create the phase modulation while ucd uses the existing 2nd order filter itself.

None of these patents claim a zero in the feedback loop.

[Kenshin]

Rf//Cf...UcD has it,Tripath has it...and SODA has it....

is it still a valid patent?
if somebody use it commercially,what would happen?

nothing? or be charged of BOTH UcD & Tripath?

Originally posted by classd4sure

Ooooooooooohhhhhhh look.... tripath owns that patent

http://www.acutechnology.com/ClassD/...05909153__.pdf

You know .... IMHO, there's far too much concern here over who's got what patented, use what works best!

[phase_accurate]

A diifferentiating feedback branch as such is a well-known feedback control topology. That part alone would not be enforceable IMO.

Regards

Charles

[Kenshin]

what about use 180 deg of phase lag to oscillate?

Originally posted by phase_accurate
A diifferentiating feedback branch as such is a well-known feedback control topology. That part alone would not be enforceable IMO.

Regards

Charles

[phase_accurate]

what about use 180 deg of phase lag to oscillate?

Then you would definitely have to think about a topology that isn't covered by either UcD or ICE. It may be possible but I don't have any usable idea in this direction at the moment.

Regards

Charles

[Kenshin]

Originally posted by phase_accurate


Then you would definitely have to think about a topology that isn't covered by either UcD or ICE. It may be possible but I don't have any usable idea in this direction at the moment.

Regards

Charles

But any feedback from the filtered output implies a possibility of phase shift exceeding 180 deg and oscillate--at a frequency of 500KHz, parastical paramters such as delay of the opamp could cause unexpected oscillation easily.

A namely(topologicly) "hysteresis" or "carrier-driven" D-amp (even a namely class AB amplifier)may well be a "180 deg of phase-shift" one in fact. Boundaries between tham are clear theoreticly, ambiguous in schematic (can you tell me how SODA oscillate at a glance on its schemetic?) and almost impossible to recognize in real-world systems.

This means that "180 deg of phase-shift" modulator is rather a combine of parameters than a topology.

So it's probably that enforcing the "180 deg of phase-shift" patent really means patent the feedback from output filter and enforce it.