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Class D Switching Power Amplifiers and Power D/A conversion

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Old 15th September 2011, 11:34 PM   #1321
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Originally Posted by lorylaci View Post
Could you send the exact schematic and pcb layout you have? And if you can the photo of the test setup! I am sure i can give lots of ideas.

What type of core do you use? Gapped toroid in my opinion is worse then a gapped EE, ETD or RM ferrite. Iron powder (micrometals material -2) toroids are usually good, and has the pro that magnetic field is same all around. In a gapped toroid the B function has a shift around the gap, leaking radiation.

For example try some of the Coilcraft shielded flat-wire wound inductors. They are extremely good, two of VER2923-103K connected series will give you 20uH 5mOhm, and >30A saturation current.



Use one big ground plane! If you can, use a two-sided board, even if you have no wire on top, use top layer as a big ground plane! See Bruno's ideas about star-ground vs ground plane.
Only if necessary separate ground planes as told in IR's manual (analog input, V- the common of IR2110, and power otuput ground)
My experiments have shown much reduced noise and EMI with one big ground plane.

Are you still useing the old IRF540 (no N no Z)? Even with the schottkys, it will produce EMI.
Hy lorylaci.

I am still on test board.

Diferent ground setups and diferent feeback wire placements give diferent distorsion paterns.I made a ground place with aluminium foil.Now i use t106-2 thanks to savu.I also use irf540z.Heat has decreased alot..and noise by a small margin..

Even if i wanted to do a pcb and give it to someone else to etch it(printer still broken) i have no ideea how to design it corectly since all my eforts have been invested into test board manipulations with no result..

First i will give a diagram of curent ground setup...

Last edited by CPX; 15th September 2011 at 11:38 PM.
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Old 15th September 2011, 11:35 PM   #1322
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so the core made a small improvement...
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Old 15th September 2011, 11:40 PM   #1323
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so the core made a small improvement...
I found a t106-2 Amidon core worked very well. I made the mistake of using power inductors start with and they got seriously hot 120 degrees C !

Making your own class d pcb is fun, keep connections as short as possible and decouple really close to devices. Keep outputs away from inputs.
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Old 16th September 2011, 12:07 AM   #1324
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Originally Posted by Dzony988 View Post
what is percent of THD 10V befere clip? What is supplay voltage and what is imedance of load?

What bridge do you use? If you use fast diodes, you will never kill 50Hz noise ( some of harmonics will pass accros diode). for main bridge you have to use slowest diode because the most slowest diode on the world is stll very fast to distroy 50Hz noise. You have to slow your bridge with 4x 100nF in parallel with all 4 diodes in bridge
Heareable..so >5-10 %.I do not have distorsion analizer.Load impedance 2 ohm.I will pun 100 nf capacitors on bridge.Thanks.
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Old 16th September 2011, 05:39 AM   #1325
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Quote:
Originally Posted by CPX View Post
Hy lorylaci.

I am still on test board.

Diferent ground setups and diferent feeback wire placements give diferent distorsion paterns.I made a ground place with aluminium foil.Now i use t106-2 thanks to savu.I also use irf540z.Heat has decreased alot..and noise by a small margin..

Even if i wanted to do a pcb and give it to someone else to etch it(printer still broken) i have no ideea how to design it corectly since all my eforts have been invested into test board manipulations with no result..

First i will give a diagram of curent ground setup...
FORGET THE TEST BOARD!
As i said previously, you most of your problems will simply dissappear when you switch to PCB layout!
Nigel said it short and right: keep connections, especially critical connections short. These incluede FET et driving path, FET dupply path from nearest cap.
Start developing a PCB layout, if you search this tread, there are lot of tries, some are bad but some are quite good.

This amp normally is able to kill the 50Hz hum, due to supply rejection of the a feeadback. The hum is because of long ground paths and the test board. Most of the noise and distortion is also becuase of test board.

And at the end: use one big ground plane, as Bruno reccomended for UcD.
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Old 16th September 2011, 03:14 PM   #1326
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Ok..i will start designing a pcb..
I kept conections as short as posible..but i was forced by the heat sink to keep mosfets apart by 4 cm....
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Old 16th September 2011, 03:22 PM   #1327
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Quote:
Originally Posted by CPX View Post
Ok..i will start designing a pcb..
I kept conections as short as posible..but i was forced by the heat sink to keep mosfets apart by 4 cm....
This is not a good choice of priorities. It's better to change the heatsink arrangement than to allow 4cm between output MOSFET.

Doing good real-world PCB layouts is about prioritizing the right things over the not so important ones.
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Old 16th September 2011, 03:50 PM   #1328
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Quote:
Originally Posted by CPX View Post
Ok..i will start designing a pcb..
I kept conections as short as posible..but i was forced by the heat sink to keep mosfets apart by 4 cm....
EVA is right!
Easy heatsinking should not be the first priority. A medium power (1-200W) system with proper FETs can even run without heatsink with music signal...
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Old 16th September 2011, 03:58 PM   #1329
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I also had output filter between them..
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Old 18th September 2011, 08:19 PM   #1330
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After reading over 100 pages of the topic have not come to a conclusion ...

Many say they are bad, others say it is very good
Unfortunately I do not have time to "try to mount, keep making changes, measuring, simulating, etc. .." so much that I read these 100 pages today, a Sunday ..

After all, if I mount the original circuit, the original board, as the toroid correct, it works well?

Has anyone actually got to 1000 W of power?
Someone uses it continually? at parties for example: 5,6,7 hours of continuous use at full power?

thanks
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