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Class D Switching Power Amplifiers and Power D/A conversion

New half bridge driver IC with GND!! referenced input
New half bridge driver IC with GND!! referenced input
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Old 28th July 2006, 10:26 PM   #1
analogspiceman is offline analogspiceman  United States
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Default New half bridge driver IC with GND!! referenced input

Hi DIYers -

IR has recently released a very interesting new class-d audio half-bridge driver IC, the IRS20954 (data sheet).  It is fabricated with their latest process, and has programmable dead-time and under-voltage and over-current protection available for both MOSFETs (latching or auto-recovering with adjustable hiccough mode delay), but perhaps most interesting of all is that its input is referenced to ground rather than the negative rail.  No more level shifting!  Just front it with a low noise comparator and the drive train is done.

... in theory, anyway.

PS: Not sure if these parts are actually available yet (single piece price seems to be about five US dollars).
 
Hmmm... if they only had an LTspice model.
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Old 28th July 2006, 10:35 PM   #2
Lars Clausen is offline Lars Clausen  Denmark
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analogspiceman: Thanks for bringing this chip about. It can make the amplifier slightly simper, because you don't need the PNP transistor for level conversion. A part from that, it is quite similar to earlier IR drivers.

It still doesn't have 'ultralow distortion' but might be ok for less critical applications.
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Old 28th July 2006, 10:54 PM   #3
analogspiceman is offline analogspiceman  United States
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Quote:
Originally posted by Lars Clausen
[...] It can make the amplifier slightly simper, because you don't need the PNP transistor for level conversion.  Apart from that, it is quite similar to earlier IR drivers.

It still doesn't have 'ultra-low distortion' but might be ok for less critical applications.
Are you sure (about the distortion part)?  All of the classical linear class-d parts would be outside of the IR driver IC - and it is capable of minimal dead-time and has seemingly constant delay.  What more could be required?

Maybe I'm missing something, but it would be interesting to get some feedback from a knowledgeable someone who has recent hands-on experience with one of these latest generation ICs from IR.

Regards -- analogspiceman
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Old 28th July 2006, 11:05 PM   #4
Lars Clausen is offline Lars Clausen  Denmark
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The rather bold stepping of the dead time, will never get you below 0.02% THD.
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Old 28th July 2006, 11:29 PM   #5
fokker is offline fokker  China
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it probably has internal level shifters: the fact that it is still com'd to the negative rail and requires a supply rail vs.t he negative rail is a giveaway.
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Old 28th July 2006, 11:40 PM   #6
Tim__x is offline Tim__x  Canada
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But of course. The difference is that they are incredibly fast, buffered, integrated level shifters instead of slow(er), bulky, harder to drive discrete level shifters.
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Old 28th July 2006, 11:52 PM   #7
fokker is offline fokker  China
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I do agree with Tim. This simplifies the design of a class D amp greatly, and takes out one more reason to go discrete.
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Old 29th July 2006, 12:00 AM   #8
analogspiceman is offline analogspiceman  United States
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Quote:
Originally posted by fokker
it probably has internal level shifters: the fact that it is still com'd to the negative rail and requires a supply rail vs.t he negative rail is a giveaway.
Of course it has internal level shifters - that's the point - it has them built-in so that the non-engineer DIYer doesn't have to deal with designing them him or herself.  This IC, although not quite the Holy Grail, is a big step forward in user convenience (sort of like what happened with switcher ICs for laptops).

Regards -- analogspiceman
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Old 29th July 2006, 12:17 AM   #9
analogspiceman is offline analogspiceman  United States
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Quote:
Originally posted by Lars Clausen
The rather bold stepping of the dead time, will never get you below 0.02% THD.
I suppose you are thinking of your fav open loop designs with that 0.02% remark, but the dead-time granularity certainly seems undesirable (don't know why IR didn't opt for a continuous analog adjustment scheme of DT).  One could always fine tune the dead-time elsewhere (but if it's no longer a straightforward cookbook design, then it kind of defeats the point of simplicity, doesn't it).

I'd like to see a solution with parametric "on-the-fly" adjustment of dead-time via some sort of feedback or feedforward.

Regards -- analogspiceman
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Old 29th July 2006, 01:27 AM   #10
powerbecker is offline powerbecker  Germany
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analogspiceman:
Hmmm... if they only had an LTspice model.

Indeed, thatīs not nice
BUT: I know there is a helpfully guy ... ...
lets hope he will find some time to do it for us

Regards
Heinz!
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