How This Circuit Works

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GEORGE HO

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Where is a oscillator on this circuit?
 

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Steven

Steven

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Joined 2003
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/audioexperiment/Amp0_5/DesignDescription_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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GEORGE HO

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Joined 2003
:rolleyes:

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.
 
Nelson Pass

Nelson Pass

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Joined 2001
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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.
 
P

phase_accurate

Member
Joined 2002
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.
Click to expand...

You forgot the third principle: Those self-oscillating ones that use phase-shift for stable oscillation.

Regards

Charles
 
P

phase_accurate

Member
Joined 2002
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
 
G

GEORGE HO

Member
Joined 2003
HI bellx
I think you confused with class-AB & class-D amplifier,Is you
need more power you must increased voltage, one pair mosfet is
enough to drive up to 1 kw on half bridge configuration,so now I just
strat my class-D amplifier project,voltage +/- 130-150v ,mosfet use
irf450 ,power supply user ETD 49 CORE with ir2153 self oscillation
driver can up to 400W /4 ohm,but power supply design is not completed:rolleyes:
 
C

classd4sure

Disabled Account
Joined 2004
diyaudio.com
GEORGE HO said:
HI bellx
I think you confused with class-AB & class-D amplifier,Is you
need more power you must increased voltage, one pair mosfet is
enough to drive up to 1 kw on half bridge configuration,so now I just
strat my class-D amplifier project,voltage +/- 130-150v ,mosfet use
irf450 ,power supply user ETD 49 CORE with ir2153 self oscillation
driver can up to 400W /4 ohm,but power supply design is not completed:rolleyes:
Click to expand...

Hi,

IRF450.....500V, 13 amps? RdsOnb .4ohms....seems kind of high..if you doubled them up...you could have 26 amps.... 0.2ohms...which still seems high, but there is at least a reason for doing it.

Bit harder to drive though.

I think the prefered solution seems to be, find a better mosfet, which can be a real pain, but in the end the payoff is large.

Your amp sounds interesting...I'd like to know how that controller works for you.

Good luck,

Chris
 
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