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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th October 2009, 04:42 AM   #11
Electrons are yellow and more is better!
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I'm sure Mr. Bruno can explain what this is all about.
/Per-Anders (my first name) or P-A as my friends call me
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Old 6th October 2009, 06:00 AM   #12
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To me it seems to be targeted at cheap boom boxes. The title 25 times more efficient than class-d is just marketing ** used as eyecatcher. What they do is achieving less IDLE losses than class-d. Which can not be neglected in battery powered applications that are just used for background listening.
On the circuit board pictured one doesn't see an output filter. Maybe it is a linear amp with a highly efficient PSU. Maybe it is a filterless class-d amp - in this case it is definitley targeted at cheap crappy products.


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Old 6th October 2009, 08:48 AM   #13
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I think it's a mix of several technologies. Feed forward switching supply, filterless output, probably also some sound processing to filter out less dominant frequncies and emphasize dominant frequencies.

Definitely targeted at ultra-low end sound (think integrated speakers in mobile phones here). But still "20 times more effecient than class-D"? Load of **! The Tripath 2020 uses ~55mA in idle, or about twice as much a normal power LED, so if you include one you have raised the power consumption by 50%.

Last edited by Saturnus; 6th October 2009 at 09:14 AM.
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Old 6th October 2009, 12:02 PM   #14
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For something that is (almost) idle more than 98% of the time there are definitley solutions that offer additional reduction of wasted power than ordinary class-d.

I don't think this chip is targeted at lowest-power applications like mobile phone but at boom boxes.

BTW: Really LOW power applications like mobile-phones and hearing aids are the areas that are mainly class-d nowadays. I was attending a class-d conference recently. A lot of topics covered small integrated class-d amps for mobile phones etc.


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Old 6th October 2009, 02:33 PM   #15
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Defineatly cheap aps. Maybe integrated on board PC sound, iPods, etc.
Rather interesting claims, though, and I agree that it is probably some
combinations of various technologies and may be indeed a bit more
efficient than Class D (but nowhere near the claims). I don't want to
buy any yet. But if somebody else wants to experiment in small amps,
it would be nice to have them give us results.
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Old 7th October 2009, 04:12 AM   #16
star882 is offline star882  United States
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I'm not going to believe it at all until I can get the datasheets. And I won't fully believe it until I actually have one to play with. I'll power it with some supercaps and solar cells for the ultimate smug experience.
Actually, I'll power it with some CoolChips ( ) running in reverse. (Unlike solar cells, a custom machined copper rod thermal collector will work indoors in total darkness, but would be very awkward to use outdoors. So solar cells for outdoors, thermal collector for indoors.)
"Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!
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Old 7th October 2009, 05:07 AM   #17
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That could be the perfect application. If you can charge some VERY LOW ESR caps with solar cells, and do a good job with the power device PCB layout you could have a winner.

Very interesting.
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Old 7th October 2009, 06:50 AM   #18
MOER is offline MOER  United States
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Default Class D efficiency

Class D amplifiers are NOT 70% efficient or anything close.

A class D amplifier at idle is 0% efficient.

A class d amplifier at clip into a load which does not push the RDs on to its limits is 90%+ efficient BUT with a sine wave....last time I looked nobody was actually listening to sine waves.

So the typical efficiency of a class D amplifier with average music into a reasonable load with the musical peaks just at clipping is well below 70%

Drive your class D with pink noise at 1/8 of rated power = typical program material with occasional clipping and then measure the efficiency and post that result
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Old 7th October 2009, 07:16 AM   #19
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agreed, the efficiency spec is pure bunkum.
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Old 7th October 2009, 09:45 AM   #20
Hurtig is offline Hurtig  Denmark
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Originally Posted by DSP_Geek View Post
20 times more efficient? Gee, worst-case class-D is 70% efficient, so this thing must be 1400% efficient! Call the Nobel Prize committee, we've discovered the secret of endless power!

That's what happens when you let the marketing pukes put out a press release before the engineers fact-check it.
Read all the info, before trashing the chip. The 20 times more efficient is at low levels.
I do NOT know any class-D with 70% efficiency at low levels, since the "household-consumption" in the amp typiclly consumes some watt's. And at ex 0,1 watt output, the efficiency is very low.
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