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Class D Switching Power Amplifiers and Power D/A conversion

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Old 30th April 2005, 03:34 PM   #1
Ging is offline Ging  United Kingdom
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Default 20kw amp, are u sure?

i found this website claiming to be a 20kw class D amp design
http://www.geocities.com/pa_schematics/schematics.html
i came accross this design i think it came from a link somewhere in this forum actuly so maybe someone here has made one or maybe it's thier design
i'm just wondering is it for real? would it work?
i did a course last term at uni about amplifiers but we didnt go as far as learning too much about class D, more how the concept worked than the actuly circuits so this kind of thing is a bit over my head still.

i'm thinking of making my own amp but i guess that's possible a little bit ambitious for first amp
anyone know a good book(ideally a picture book) or a good starter project for someone with no money and lots of time over the summer? i'm specificly intrested in class D because i want to be able to make my own car amps and these are aprently the best type of amps to use in a car because of thier efficency.
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Old 30th April 2005, 05:07 PM   #2
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It is NOT a class D amplifier. And it can only produce around 700 W in 8 Ohms.

However it would be fully possible to build a Class D amplifier with 20.000 W power. Also in 8 Ohms.
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Old 30th April 2005, 06:29 PM   #3
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With the current state of MOSFET technology, amplifiers above 5kW are best built using a multiphase power stage. If the control system is well planned you could actually make a redundant system. I've built a small multiphase amplifier in the past (8 phases). It put out over 300W at an efficiency of over 97%. All SMD power stage.
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Old 30th April 2005, 06:53 PM   #4
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Question Lars

How do you calculate the 700W into 8 Ohms on +/-78VDC rails ???
I only get around 400W..............
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Old 30th April 2005, 06:54 PM   #5
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Jan: The rightmost supply is 115 V DC (minus a bit of rail loss etc ....)
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Old 30th April 2005, 07:05 PM   #6
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Lars:
You're absolutely right !! My fault...... I was looking at the 2000W schematic
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Old 30th April 2005, 07:07 PM   #7
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Bruno: How do you propose the implementation of a multiphase output stage?
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Old 1st May 2005, 06:48 AM   #8
Alme is offline Alme  Ukraine
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With given rails, an amplifier can only pump 20,000W into load of 0.25ohm. So peak current is going to be 400A
Probably too high for given 25 parallel output pairs, assuming secondary breakdown (and maybe heat dissipation)...
For such design more real data can be 5,000W into 1ohm.
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Old 2nd May 2005, 07:19 AM   #9
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I once found a web-page of a manufacturer making switching amps in the range of several tens of kW.
Those are mainly used for shaker tables or those large field coils like they are used on subs and minesweepers in order to compensate ships influence on the earth's magnetic field (to avoid detection or triggering of mines).
when I stumble upon it I will post the link here. Maybe they give a hint on topology as well.

Regards

Charles
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Old 2nd May 2005, 08:00 AM   #10
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Quote:
Originally posted by Lars Clausen
Bruno: How do you propose the implementation of a multiphase output stage?
Have a look at pat US6803816. For practical reasons there'll always be a bit of logic required to drive the output stages but you can feed that from a flash ADC and put an analogue loop around the thing.
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