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Class D Switching Power Amplifiers and Power D/A conversion

Class D Design Issues
Class D Design Issues
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Old 15th May 2017, 10:27 AM   #111
irribeo is offline irribeo  Netherlands
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You also have the noise peak at same frequencies with NAD M3, only less high ? Seems to have nothing to do with amplifier then ?

I guess the 100uH 220nF outputfilter does behave overdamped when load is below 32 ohm around 30kHz. Removing the outputfilter inductor: running a 400/800/3000 watt class D amplifier filterless could be considered.......... at least a bad idea.
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Old 15th May 2017, 10:50 AM   #112
Dimonis is offline Dimonis  Russian Federation
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Quote:
Originally Posted by irribeo View Post

I guess the 100uH 220nF outputfilter
It' s not a filter for the working frequency , it's a common mode choke.The strait inductance for a two pole winding is not 100uH , it's not more than 1-3uH.Class D Design Issues

https://en.m.wikipedia.org/wiki/Chok...on-mode_chokes

Last edited by Dimonis; 15th May 2017 at 10:53 AM.
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Old 15th May 2017, 12:06 PM   #113
irribeo is offline irribeo  Netherlands
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OK so probably not entire outputfilter in that pic.
Ribbon (near flat and low impedance) frequency respons is only relevant if you want to use that ribbon as speaker.

Fixing noise that shows up in class A(B) ? NAD M3 output too, by modding the Behringer seems wrong to me.
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Old 15th May 2017, 04:13 PM   #114
JonasKarud is offline JonasKarud  Sweden
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Quote:
Originally Posted by Dimonis View Post
It' s not a filter for the working frequency , it's a common mode choke.The strait inductance for a two pole winding is not 100uH , it's not more than 1-3uH.Class D Design Issues

https://en.m.wikipedia.org/wiki/Chok...on-mode_chokes
That's correct, there are only a few turns of each winding, cannot be 100uH.

I do not get consistent results, shall lend a another NU3000 from the music store.

There's definitely something wrong with my NU3000 phase wise.
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Old 15th May 2017, 05:12 PM   #115
Dimonis is offline Dimonis  Russian Federation
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Quote:
Originally Posted by JonasKarud View Post
cannot be 100uH.
It can , that small ring is ferrite with high permability , something about mu=6000-10000.
The main inductor is wound on a T130-2 core , it's an ironpowder material with a permability of only 10 !!!!! And it has around 45turns making 22uH.



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Old 14th December 2017, 01:05 PM   #116
kees52 is offline kees52  Netherlands
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Hmm I saw this tread, so I am go asking something I get it not right, yes it is because class d is quite new for me and learning is always nice.

I have try these ones, however despite I have plus and minus 5 volts so ref is 0 volts the swing of the audio is only on negative side, This is what I want to ask why, because I see it is not as simple as it looks this D technology, I manage to get low HD, I do try get low HD without feedback and a full bridge.

It,s output voltage is not well, I did try a ucd feedbacked one who did work, so fellows, is there a teacher here for me Normally we need to put the audio 180 degree for full bridge d amp, but is it also needed to flip the square output of the power mosfets? to prevent cancel them out..

In last pic you see single ended amp, strange it does only swing in negative part, while I have symmetrical supply everywhere.

regards
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Last edited by kees52; 14th December 2017 at 01:14 PM.
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Old 1st January 2018, 09:07 PM   #117
Electrone is offline Electrone  United States
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I'm not sure what is going on there, yet a hunch is there might be duplication of more circuitry than should be done. I would use only one set of analog audio circuitry and then once the signal is level shifted down, use fast switching to produce the inverted and noninverted signals for both totem pole MOSFET drives. Something like CMOS logic chips to derive the inverted signals. I've done a circuit a bit how you are doing it, but with only one set of analog audio components, and it simulated well. It was a long time ago, so my memory is only general.

Something I just noticed is that your UcD version worked. It turns out that is all I have been using, even for years before I became aware of Bruno's patent, 100% post filter feedback, for as long as I can remember. It turned out that I was simulating almost identical circuit to the one in his patent artwork. I attribute it to lucky? chance and perseverance in my obsession for high power bass production almost twenty years ago.

Last edited by Electrone; 1st January 2018 at 09:19 PM.
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Old 2nd January 2018, 12:24 PM   #118
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by Electrone View Post
I'm not sure what is going on there, yet a hunch is there might be duplication of more circuitry than should be done. I would use only one set of analog audio circuitry and then once the signal is level shifted down, use fast switching to produce the inverted and noninverted signals for both totem pole MOSFET drives. Something like CMOS logic chips to derive the inverted signals. I've done a circuit a bit how you are doing it, but with only one set of analog audio components, and it simulated well. It was a long time ago, so my memory is only general.

Something I just noticed is that your UcD version worked. It turns out that is all I have been using, even for years before I became aware of Bruno's patent, 100% post filter feedback, for as long as I can remember. It turned out that I was simulating almost identical circuit to the one in his patent artwork. I attribute it to lucky? chance and perseverance in my obsession for high power bass production almost twenty years ago.

I am moved to a thread of mine own, there I do post in future, not all over diyaudio, it get's a mess.

Here I am, last post 116 very low distortion hysteric ucd, output 16 amps in 4 ohms.

what D amp give best sound.

I have solved the problems here mentioned, just a learning proces.

regards

Last edited by kees52; 2nd January 2018 at 12:28 PM.
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Old 24th June 2018, 07:37 AM   #119
steveu is offline steveu  United States
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Quote:
Check the power supply for the high side switch. It may be dropping too low if it is normally refreshed by bootstrapping.
Ya, I noticed this problem simulating variations on the UCD circuit. Best idea I have is a buck converter for the lower bias that is also capacitor coupled to a diode above the +rail. Issue then becomes limiting that bias to follow the output, and cut it off when the output goes negative, and keep the diode that dumps the lower bias into the upper bias.
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Old 24th June 2018, 11:28 AM   #120
kees52 is offline kees52  Netherlands
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I have done this class d, it has very low distortions, but because it is a fase shifted one, in full bridge, I have the dead times done as in picture, I did see in simulation that the dead time through the mosfets do go cross each other on zero voltage, where afcouse is no shoot through, but di I have it right?, can someone explaine more from schematic, Maybe something is wrong but sim do well..

I have with post-prefeedback very low distortion on 20 amps 4 ohm output signal, the amp stays stable also with open output and full power, afcourse in simulation, not in real yet..

Thanks,
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