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Class D Switching Power Amplifiers and Power D/A conversion

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Old 29th June 2004, 09:44 AM   #21
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Hi,

We could use the components side as a pure ground plane, so it wouldn't cause much trouble for diying double sided boards (having to align the 2 sides...)


Nice! Should have no need to worry about vias either.

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Chris
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Old 29th June 2004, 09:50 AM   #22
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Quote:
3 minutes too late
Being a slow and bad typist this happens to me quite often.

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Charles
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Old 29th June 2004, 10:12 AM   #23
Bricolo is offline Bricolo  France
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Quote:
Originally posted by classd4sure
Nice! Should have no need to worry about vias either.

Yes but only if we use through hole components
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Old 29th June 2004, 10:28 AM   #24
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Quote:
Originally posted by Bricolo



Yes but only if we use through hole components
Yeh or it's off to the board house huh. Should we limit ourselves to through hole? SMD seems to have alot of advantages in this area, might be worth getting the board done, since it looks like we're going for quality over quick and easy.

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Chris
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Old 29th June 2004, 10:28 AM   #25
johanps is offline johanps  Sweden
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Quote:
Originally posted by phase_accurate
The better an amp performs open loop, the better it will perform when the feedback loop is closed.
Quote:
Originally posted by Bricolo
As for UcD and non-linearity. See it as feedback on a linear amp.
Try to correct a heavilly non linear amp (or stage) with some feedback: it will work, but won't be as good as a much more linear stage corrected with the same amount of feedback
In general, these are accurate statements. But the open loop performance of a comparator followed by a switching power stage is pretty awful by itself . But thanks to feedback and noise shaping we can get good fidelity in the audio range anyway.
That's why I was wondering how much difference the filter coil makes in the end, when feedback is taken from the filter output...
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Old 29th June 2004, 10:32 AM   #26
Bricolo is offline Bricolo  France
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Do we have a starting point schematic for the UcD amp? (even if there's no components references and values)
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Old 29th June 2004, 10:43 AM   #27
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Hi,

Quote:
That's why I was wondering how much difference the filter coil makes in the end, when feedback is taken from the filter output...

Makes a huge difference in a UCD type of design..

but feedback wise ...having the filter inductor included in the loop is key to the high performance as noise generated within it/picked up by it is now compensated for.....that was the holy grail we were all wanting a little while back right?

Non linearity wise of the core....hmmm well that's included in the feedback loop as well, and so more easily minimised over the EMI radiating all over the rest of the circuit as it seems an air core would be. It should never saturate anyway right?

Given the major advantage by having it inside the feedback loop, simplicity of said loop, when compared to noise shaping schemes, lower output impedance..part count..load independance...just far too many huge advantages to not want to include it, I think anyway. Before we had that class d was "good for sub woofer applications".

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Chris
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Old 29th June 2004, 10:52 AM   #28
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Quote:
Originally posted by Bricolo
Do we have a starting point schematic for the UcD amp? (even if there's no components references and values)

Well so far, what do we want?

100W?
High quality...

No compromise?
Yet simple as can be..

All we really need to use from UCD is the feedback loop.

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Chris
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Old 29th June 2004, 11:02 AM   #29
Bricolo is offline Bricolo  France
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In fact I asked for a basic schematic. No power/THD defined in it.

BTW, could we define here what UcD is?
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Old 29th June 2004, 11:07 AM   #30
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Quote:
Originally posted by classd4sure
All we really need to use from UCD is the feedback loop.
Quite precisely. That's why I think the most important thing is getting the comp/PS/filter done right. The control loop can be saved for last. You could even consider not placing the modulator on the same PCB with the power stage so you have a Universal Test Mule to try anything you like.
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