Explanation of Self Oscillating Class D

Genomerics · 1st October 2006, 06:01 PM

http://www.genomerics.org/selfosc/selfosc.html

I got bored but I'm getting better apart from it throwing up other questions so I may get worse.

Anyway, if it floats your boat there may be more to be added.

Cheers

DNA

IVX · 1st October 2006, 08:37 PM

Wrong link? Check this out.

Baldin · 1st October 2006, 08:38 PM

Great work. I can only encourage you to dig deeper

What would also be very interesting is a reliable model in the frequency domain, that would enable the design of the right feedback loop (phase compensation etc.)

Have tried to make some models in Mathcad .... but I'm not sure at all if it's correct

Keep it up

Genomerics · 2nd October 2006, 04:06 PM

Quote:

Originally posted by IVX
Wrong link? Check this out.

Yes, sorry, I went to bed early and switched it off. Sort of between 8AM and 10PM GMT would be good.

I suppose I could claim I need my beauty sleep because I am pug ugly but then, since I am so ugly beauty sleep won't help too much.

It's up at the moment.

I'll drink lots of cider and leave it on overnight.

DNA

raintalk · 2nd October 2006, 06:42 PM

Great job. Cleared a few things up in my mind.
Very entertaining

Your whole site is great. Keep it up.

BWRX · 2nd October 2006, 07:18 PM

That's a nice spice model to start experimenting with. Simply add a cap (say 0.68uF) in parallel to the load and a cap (say 100pF) in parallel to the feedback resistor (reduce it to something like 30k) and you've got something going.

fokker · 3rd October 2006, 01:30 AM

it didn't work for me, displaying "this page cannot be displayed".

maybe it is off again?

classd4sure · 3rd October 2006, 01:43 AM

seems to be.

DNA, any chance of hosting that stuff where it's up all the time? I think it'd be worth it.

Genomerics · 3rd October 2006, 03:41 PM

Quote:

Originally posted by Baldin

What would also be very interesting is a reliable model in the frequency domain, that would enable the design of the right feedback loop (phase compensation etc.)

Keep it up

Just got on to that bit, thought I knew a little. The result is almost alarming, I didn't expect it. Probably done something wrong but it certainly looks cute....

DNA

analogspiceman · 3rd October 2006, 04:44 PM

Self-oscillating class-d amplifiers always have enough loop gain to saturate the output stage such that effective gain forward through the amplifier and back again around the feedback loop self-adjusts to drop to unity (i.e., zero dB) exactly at the frequency where phase shift around the entire loop just reaches 360 degrees (positive feedback, unity gain).  The frequency of oscillation is controlled entirely by phase loss - gain plays no roll.  In this regard, a self-oscillating class-d amplifier is nothing more than a high level, high power phase-shift oscillator.  Setting operating frequency (and limiting its smear when producing large signal audio) is all about designing and controlling the phase shift around the loop.

An earlier diyAudio thread covered most of the pertinent details: Non clocked (e.g. free running, self oscillating) class d

Regards -- analogspiceman

1st October 2006, 06:01 PM	#1
Genomerics Account Disabled Join Date: Oct 2004	Explanation of Self Oscillating Class D http://www.genomerics.org/selfosc/selfosc.html I got bored but I'm getting better apart from it throwing up other questions so I may get worse. Anyway, if it floats your boat there may be more to be added. Cheers DNA

1st October 2006, 08:37 PM	#2
IVX diyAudio Member Join Date: Jul 2003 Location: Everywhere (Buddhist's context)	Wrong link? Check this out. __________________ Best regards, E1.

1st October 2006, 08:38 PM	#3
Baldin diyAudio Member Join Date: Jan 2005 Location: Copenhagen	Great work. I can only encourage you to dig deeper What would also be very interesting is a reliable model in the frequency domain, that would enable the design of the right feedback loop (phase compensation etc.) Have tried to make some models in Mathcad .... but I'm not sure at all if it's correct Keep it up __________________ Visit www.sensibleaudio.dk or read latest news on Baldin's Blog

2nd October 2006, 07:18 PM	#6
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	That's a nice spice model to start experimenting with. Simply add a cap (say 0.68uF) in parallel to the load and a cap (say 100pF) in parallel to the feedback resistor (reduce it to something like 30k) and you've got something going. __________________ Brian

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2nd October 2006, 06:42 PM	#5
raintalk diyAudio Member Join Date: Jul 2004 Location: Seattle USA	Great job. Cleared a few things up in my mind. Very entertaining Your whole site is great. Keep it up.

3rd October 2006, 01:30 AM	#7
fokker diyAudio Member Join Date: Jul 2006	it didn't work for me, displaying "this page cannot be displayed". maybe it is off again?

3rd October 2006, 01:43 AM	#8
classd4sure Account Disabled Join Date: Feb 2004	seems to be. DNA, any chance of hosting that stuff where it's up all the time? I think it'd be worth it.

3rd October 2006, 04:44 PM	#10
analogspiceman diyAudio Member Join Date: Sep 2004 Location: Yahoo, USA	Self-oscillating class-d amplifiers always have enough loop gain to saturate the output stage such that effective gain forward through the amplifier and back again around the feedback loop self-adjusts to drop to unity (i.e., zero dB) exactly at the frequency where phase shift around the entire loop just reaches 360 degrees (positive feedback, unity gain).  The frequency of oscillation is controlled entirely by phase loss - gain plays no roll.  In this regard, a self-oscillating class-d amplifier is nothing more than a high level, high power phase-shift oscillator.  Setting operating frequency (and limiting its smear when producing large signal audio) is all about designing and controlling the phase shift around the loop. An earlier diyAudio thread covered most of the pertinent details: Non clocked (e.g. free running, self oscillating) class d Regards -- analogspiceman

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