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Class D Switching Power Amplifiers and Power D/A conversion

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Old 2nd April 2014, 07:32 PM   #321
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Default Post #275 LTSpice file

Ok, here is the Spice file from schematic at post #275.

Look at current spikes thru diodes D2 and D3 (D4 and D5 in Acca's posted schematic)

Are those diodes going to fail?
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File Type: asc DiscreteSimple.asc (5.1 KB, 42 views)
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Old 2nd April 2014, 07:59 PM   #322
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Here is a screenshot of the high current thru diodes (output unclipped, 40v P-P)

Surprisingly, there is very little cross- conduction on the output MOSFETS though
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File Type: png class d.png (46.4 KB, 519 views)
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Old 5th April 2014, 06:30 PM   #323
PetruV is offline PetruV  Romania
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mine has just 3.5 a on diodes, which seems fine, since peaks are short
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Old 5th April 2014, 09:45 PM   #324
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Will you post your spice file?

I removed D5 (the one that connects directly to the output) and that solved the problem, with no apparent problems from removing it. I don't think it was needed.
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Old 7th April 2014, 08:45 AM   #325
PetruV is offline PetruV  Romania
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The peaks look like simulation errors,they are very short and they look much different on different fets
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Old 8th April 2014, 01:04 AM   #326
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What is the purpose of the diode that connects to the output (D5)? I took it out and my circuit simulates better, and no more current spikes!
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Old 15th June 2014, 07:48 AM   #327
Acca is offline Acca  Serbia
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Few new (better) designs from me
All schematics is tested.(second schematic tried directly on 310V line,with IRF740)

Answer to Q about D5:
It's used to remove negative voltage on upper fet.
Attached Images
File Type: gif Klas D4_4.GIF (19.6 KB, 243 views)
File Type: gif Klas d1.5k_494.GIF (33.0 KB, 239 views)
File Type: gif Klas D3.GIF (16.6 KB, 230 views)
File Type: gif Klas d7k.GIF (19.2 KB, 232 views)
File Type: gif Klas D 12V.GIF (15.6 KB, 137 views)

Last edited by Acca; 15th June 2014 at 08:08 AM.
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Old 15th June 2014, 07:53 AM   #328
Acca is offline Acca  Serbia
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Quote:
Originally Posted by spare_parts View Post
Here is a screenshot of the high current thru diodes (output unclipped, 40v P-P)

Surprisingly, there is very little cross- conduction on the output MOSFETS though
Yes,there is short current peaks because lower fet have small delay (in order to form dead time)
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Old 15th June 2014, 07:54 AM   #329
Acca is offline Acca  Serbia
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Quote:
Originally Posted by Mondan View Post
I can say what I thought,
For a 'correct' dead time, you need need a digital circuit, as they did here with gates A1,A2 :
http://geekcircuits.com/wp-content/u...power-amp1.png
Because the signal is too weak, after these gates, you need a MOSFET driver (IR2010).

The price of IR2010 plus the remaining components It's almost as the price of IRS2092.(SMD version of IRS is cheaper). (Using this IRS, your risk of error is less)
I already ordered the IRS.


Still looking for very cheap variant class D amplifier (price of TL494 is less than SG3525)
For "correct" dead time we can use RD network too.
Before I try,I think same as you.
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Old 15th June 2014, 07:59 AM   #330
Acca is offline Acca  Serbia
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Quote:
Originally Posted by MrPerform View Post
-And irfz48 it will serve?
-I will use it for listen some music at home not hi-fi.
-Is this possible with a smps at 56Vcc made from a ATX power supply conversion?
-Thank you and have a good weekend.
-Yes
-You are my man
-Why not?
-You too
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