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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th October 2004, 06:25 AM   #11
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Location: Switzerland
What you want to do can be accomplished by using ONE triangle signal and TWO comparators that are switching at different levels. I did this to achieve adjustable dead-time control within this circuit:

http://www.diyaudio.com/forums/showt...684#post194684


Regards

Charles
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Old 6th October 2004, 06:30 AM   #12
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Join Date: Dec 2002
Location: Slovenia
Hi Felix,

I see two possible problems with your approach. First, there is added mosfet capacitance and inductance (in effect a resonant tank) to your schottkys, so switching waveforms might be less clean than in BCA. Second, at light modulation filter inductors will be running in discontinious conduction mode. Vin/Vout vs duty cycle D transfer function becomes severely nonlinear in that case, beeing also dependant on some factor K=2L/Rload*fswitching. If you are interested you might take a look in the following article: Slobodan Cuk and R.D. Middlebrook "A General Unified Approach to modelling Switching DC-to-DC Converters in Discontinious Conduction Mode" IEEE Pesc 1977.
Your modulation approach is also possible with one ramp and shifted treshold of comparators. Look at old Silicon General SG1731 data sheet.

Best regards,

Jaka Racman
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Old 6th October 2004, 07:02 AM   #13
JohnW is offline JohnW  Hong Kong
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Location: Discovery Bay, Prague, Paris...
Well I braved searching though old papers and found these possibly interesting patents, some are directly relevant, others just food for thought

4,992,751 Audio Amplifier with Phase Modulated Pulse Width Modulation
4,600,891 Digital Audio Amplifier Having a High Power Output Level & Low Distortion
4,479,175 Phase Modulated Switch mode Power Amplifier & Waveform Generator
5,657,219 Opposed Current Power Converter (Crown BCA)

Jaka,

My uncle was a quite famous political dissident in the CZ, this made life very difficult for the family – which meant my mother (we) was not able to return to visit CZ even when her farther died. As a child I grew up in the West, but when we did visit the “East”, even at my young age I was struck how creative the engineers in the East where. When we visited CZ, I also remember my farther smuggling across the boarder well hidden box’s of “High Frequency” power transistor (in the ties of our Austin 1100) which where used to construct “Ultra sound” machines for the main hospital in Bruno (which until they built there own, hadn’t even seen / heard of an ultra sound machine before). I can still remember almost 30 years on, the Doctor / professor almost having a heart attack when my farther presented them to him.

John
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