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Old 15th May 2004, 02:43 AM   #1
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Question How This Circuit Works

Where is a oscillator on this circuit?
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Old 15th May 2004, 03:35 PM   #2
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Post class-d 200w@4ohm /osc 400K

this original pdf
http://www.irf.com/product-info/audi...sdtutorial.pdf




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Old 15th May 2004, 04:59 PM   #3
bellx is offline bellx  South Africa
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Yes I'd like to know too. And pin 1 vcc does it look right, connected to 50V?
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Old 15th May 2004, 08:10 PM   #4
Steven is offline Steven  Netherlands
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The whole amp is an oscillator. This is an example of a self oscillating class D amplifier. Other examples are UcD, Mueta and ICE-power. Do a search on these to learn the difference between open loop class D amplifiers that use a fixed frequency sawtooth or triangle wave, that is compared to the input signal, and the self oscillating amplifiers that use a hysteresis controller to determine the approximate oscillating frequency.

It is explained also here: http://hem.passagen.se/johanps/audio...iption_0_5.htm

Or even better: read the book 'High efficiency audio power amplifiers; design and practical use' from Ronan van der Zee, you can get the pdf for free! http://doc.utwente.nl/fid/1351
It is on page 48.

Steven
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The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973
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Old 16th May 2004, 02:57 PM   #5
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thanks,steven

anyone build self oscillating class-d amplifier,how good is the sound,it is better than class-AB.i thing want to build one class-d
amplifier with switching power supply, +/- 130V.so anyone can
advise me,now i have some ic AD8561/LM311/IR2106/IR2110&
IR2153.
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Old 16th May 2004, 09:38 PM   #6
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I have built a self-oscillating Class D, that is to say, one without
a clock, and it worked fine. I have no reason to think it would
suffer from other than the ordinary limitations of Class D
amplifiers, which is to say switching speed, comparator
sensitivity, and output filtering.
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Old 17th May 2004, 07:24 AM   #7
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Quote:
Do a search on these to learn the difference between open loop class D amplifiers that use a fixed frequency sawtooth or triangle wave, that is compared to the input signal, and the self oscillating amplifiers that use a hysteresis controller to determine the approximate oscillating frequency.
You forgot the third principle: Those self-oscillating ones that use phase-shift for stable oscillation.

Regards

Charles
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Old 19th May 2004, 04:14 PM   #8
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Hi Charles

Is compare self-oscillating & fix oscillating which circuits is batter and more stable.
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Old 20th May 2004, 10:15 PM   #9
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Given the latest incarnations of self-oscillating designs like Philips UCD it looks as if the performance/complexity ratio is definitley better for the self-oscillating designs.
One advantage of the carrier based designs is that they can be accurately run at a specific frequency. This has advantages when the input signal is coming from a D/A converter using only marginal output filtering. The other advantage is the possible use of notch filters in order to get rid of the output ripple.
I once designed a carrier-based class-d amp that had a carrier suppression of more than 80 dB that way.

Regards

Charles
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Old 20th May 2004, 10:41 PM   #10
Steven is offline Steven  Netherlands
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Default Interference

Another advantage of the carrier based designs is that they might be used in (AM) tuner-amplifier combinations if the carrier has been chosen carefully. Most designs will interfere.

Steven
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