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Class D Switching Power Amplifiers and Power D/A conversion

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Old 23rd November 2013, 09:50 AM   #101
Acca is offline Acca  Serbia
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You must use high speed opto or use level shifter.
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Old 23rd November 2013, 04:25 PM   #102
PetruV is offline PetruV  Romania
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Amp with totem pole shows signs of life,but high side with optocoupler does not work and there is huge power consumption,indicating the side with the optocoupler is stuck on and causing cross conduction.
Surely learned a lot about class d from this,but i will try layout with ir2110
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Old 23rd November 2013, 04:28 PM   #103
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Your opto is too slow,if you use any like PC817 or similar.Best will be with ir2184 but you can use ir2111 too.
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Old 23rd November 2013, 04:34 PM   #104
PetruV is offline PetruV  Romania
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My opto is p627,maybe i have hooked it up backwards
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Old 25th November 2013, 11:30 AM   #105
iperv is offline iperv  Italy
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Quote:
Originally Posted by Acca View Post
Hello iperv

Yes,very simple and very good.No sub,I use it on full range,with 150kHz osc. freq.
This means that all sounds up to 15kHz will have same audio quality as input (not same but very close).For me 150kHz is best freq.Easy to drive fet's,but sound good.Yes,you can easy change RT/CT.Go with smaller CT and larger RT.
You can increase to 450kHz but i don't recommend this. 300kHz is enough to reproduce all sounds up to 30kHz clearly.20Khz is max. frequency that people can hear.So 200kHz is best choice betwen gate drive and sound quality.Try first with 150kHz.If don't sound's good to you,increase freq.
My choice is to build it,not give up.You will learn many things.It is more efficient than UcD one.

Regards

Ok, I'll build it.

But...I'll need some tips and tricks on how to build and set an amplifier like this one.
I'm not a newbie, but I'm an analogic builder, and my experience on class D is only Tripath 'plug'n play' chips.

So, can you please tell me a little more about the working operation?
In particular, how can I modify Rt/Ct ratio?
I don't see any Ct nor Rt on the main schematic...
Which power fet should I choose?
Is +90V DC smps ok, or maybe better??

Txia for spending your time here.

p.s: is this a classic Class D amp? (so I can study in deep Class D operation...)
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Old 25th November 2013, 11:53 AM   #106
PetruV is offline PetruV  Romania
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You want irfb4229 for 90v,this is a classic class d amp,i recomend building it as is and if it works modify it after research and asking,so you dont break anithing
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Old 25th November 2013, 12:48 PM   #107
iperv is offline iperv  Italy
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Yes,

I agree with you.
So this means I can modify switching frequency later too.
Very good.
I said +90V, but I don't know which is the best voltage to choose for the best audio quality.
Anyway, can I go with something like this?

It's only an example.
Can I choose 50V/60V/70V ?
Only single ended psu is needed?
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Old 25th November 2013, 02:00 PM   #108
iperv is offline iperv  Italy
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Edit:
I don't understand:
the main schematic on the first post seems to have a single power supply (+V/ground);
the PCB has dual power supply (+V/-V/ground).
And also the fact that 12V external supply is referred to -V (and not to ground) let me think there is a dual power supply, but the schematic shows only a single power supply.

Where's the truth?
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Old 25th November 2013, 03:08 PM   #109
iperv is offline iperv  Italy
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Ok,
I saw datasheets and learned something more about class D.

So, before I start to collect the stuff, I would like to know if this project is ok for hifi, or only PA.
My goal is a very hi fidelity and hi quality ampli, 100Wrms is good enough.
Don't know if this is the right way...
I would like to start a diy class D hi quality full range ampli, but first is better to start with a collaudate design.
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Old 25th November 2013, 03:29 PM   #110
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This is pure class D.It can be described as synchronous buck converter.
It uses single psu,and any voltage from 0V to 200V can be used.Only power and output volume depends of power supply.You can chenge volume with changing power supply voltage without any modification,and changing volume at input.This is because fer example when duty cycle is say 60%,on 5V it will be 3V at out,but on 50V it will be 30V.12V is referenced to negative supply.You can use center taped,but center tap of transformer can't be connected with speaker because SG IC maybe have temp drift or another thing,but you can try.Set voltage at 0V and play music about 10 min's.Monitor voltage at output in any 2 minutes without signal.If voltage after 10min's remain max. +/-100mV you can use dual psu.
Download SG IC datasheet and see what's CT and RT pin's.
If you have another Q's post here,I will respond as fast as I can.

Cheers
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