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Class D Switching Power Amplifiers and Power D/A conversion

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Old 7th July 2007, 05:07 PM   #11
Tim__x is offline Tim__x  Canada
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I'm fairly certain she didn't just take a UcD modulator, rip out the RC network that makes it a UcD modulator in the first place and then post the nonoptimal hysteric modulator that would result.

It appears to be an entirely different, perhaps somewhat novel, modulator.
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Old 8th July 2007, 05:27 AM   #12
RX5 is offline RX5  Philippines
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very true..
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Old 13th July 2007, 05:54 PM   #13
walkura is offline walkura  Poland
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very nice project you are making .
some time ago i tried to make something like this .
low power i managed to get a perfect sinus
(the aim was a inverter with a sinus output)
from the pictures i get you aim for higher frequency's then i did .
good luck mate i'm curious how the end result is
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Old 5th August 2007, 08:50 AM   #14
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it's similar to UCD but I suppose it's not covered by the patent because there is no damn RC network or any other thing in parallel with the feedback resistor...
Dear Eva

I hope you didn't go through a lot of effort to dodge that patent. He tried to scare me into not using the RC network thing last year, but then it turned out there were tonnes of prior art. So they (Philips) can't enforce any patent rights on it. I doubt they are that keen anyway.
Well it turned out, it was quite easy to find another solution, with the same stability, but without the bandwidth limiting problems of Bruno's basic solution as described in the UcD patent.
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Old 5th August 2007, 09:31 AM   #15
TOINO is offline TOINO  Portugal
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http://www.pat2pdf.org/patents/pat4507619.pdf
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Old 5th August 2007, 01:14 PM   #16
Eva is offline Eva  Spain
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Wow, that's quite an advanced patent for 1985 alhough the phase shift oscillator was already invented for a long time when we all were born.

Concerning my circuit, it's not complex at all and it didn't took me a lot of effort to figure out, and on the other hand, it allowed for simple current limiting as a bonus

Concerning the low oscillating frequency, It has been set intentionally that way because my current application only requires 5Khz bandwidth, and because of the +/-208V supply rails which represent a challenge by themselves... Has anybody tried 400Khz with such high voltages??
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Old 5th August 2007, 01:30 PM   #17
djQUAN is offline djQUAN  Philippines
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I like to see pictures of the prototype. eye candy.
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Old 5th August 2007, 02:04 PM   #18
TOINO is offline TOINO  Portugal
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Eva

Sometimes I suspect that you are making a locomotive controller… but you have a problem with music by mycrophonie effect on the motor coils...
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Old 5th August 2007, 04:08 PM   #19
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I have done +/-200V on 400 kHz, worked with much fewer challenges, than i had expected.
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Old 5th August 2007, 06:16 PM   #20
Eva is offline Eva  Spain
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Shall I jump off a cliff, would you jump too?
Just kidding...

At such higher voltages, dealing with 400.000 body diode reverse recovery events per second is not an easy task. For voltages below 150V there are nice MOSFETs with body diodes whose reverse recovery charge is below 100nC (typ), but the best 600V devices exhibit 1.5uC (typ) and the most straightforward ones 5uC (typ). Switching losses may be reduced dramatically with the help of SiC diodes and Schottkys, but at higher currents conduction losses increase resulting in almost no efficiency advantage (not to mention the cost of SiC stuff). On the other hand, magnetic snubbers are the key for low-loss soft switching but they have their own internal losses...

Also, losses due to internal switching transistor capacitances become significative and a lot of stress is put on the core and the magnet wire of the output inductor.

BTW: Go on, why not a +/-200V NewClassD module?
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