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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 24th June 2018, 12:31 PM   #121
nigelwright7557 is offline nigelwright7557  United Kingdom
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With gate driver circuits they usually have the mosfet switch off faster than the other mosfet switches on.
So your diode in the gate circuit should be the other way around.
Also I don't think you need the 470pf caps.
The gates already have high capacitance.
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Old 10th September 2018, 01:04 PM   #122
bogdan2011 is offline bogdan2011
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Quick question about IR2184 drivers. I can see that they have two versions of the chip, one has a common ground and the other seems to have a floating supply. Can I use Vss as the low signal ground (for the comparator, oscillator and audio) and COM as the separate, high voltage negative supply (say +-40V DC). I know I need level shifting for that, so does 21844 include them?Screenshot_Adobe_Acrobat_20180910-150002.jpeg
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Old 10th September 2018, 01:43 PM   #123
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by nigelwright7557 View Post
With gate driver circuits they usually have the mosfet switch off faster than the other mosfet switches on.
So your diode in the gate circuit should be the other way around.
Also I don't think you need the 470pf caps.
The gates already have high capacitance.
I did switch it that way yes, and it did well.

thanks.
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Old 28th October 2018, 05:44 PM   #124
dipolar is offline dipolar  India
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Default AC wave in class D output.

I tried the below given schematic from Apex (I guess.)
Amp is working and no heating but one issue.

Output have AC voltage swing of almost 1 volt all time even when input is grounded.

Power supply is 27-0-27 volt.

I am using 50uH inductor T106 -2 core and 2.2uF capacitor at output.
Earlier the LC was as mentioned in the schematic 0,47uF /30uH but the AC swing was even greater.

What is the cause of such a sine wave even after reasonably good LC filter.
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Old 28th October 2018, 05:48 PM   #125
nigelwright7557 is offline nigelwright7557  United Kingdom
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115KHz is quite low.
IRS2092 usually uses at least 250KHz.

I use 10uH and 470nF and get a little residual carrier but it doesn't cause a problem.
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Old 28th October 2018, 05:52 PM   #126
dipolar is offline dipolar  India
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Quote:
Originally Posted by nigelwright7557 View Post
What is the oscillation frequency of the amp ?
Aproximately 100-120 khz ,corresponding to that same AC wave.

Output Mosfets are IRF640.
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Old 28th October 2018, 05:54 PM   #127
nigelwright7557 is offline nigelwright7557  United Kingdom
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Originally Posted by dipolar View Post
Aproximately 100-120 khz ,corresponding to that same AC wave.

Output Mosfets are IRF640.
I would double that.
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Old 28th October 2018, 06:00 PM   #128
dipolar is offline dipolar  India
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Quote:
Originally Posted by nigelwright7557 View Post
115KHz is quite low.
IRS2092 usually uses at least 250KHz.

I use 10uH and 470nF and get a little residual carrier but it doesn't cause a problem.
Core is heating up with higher frequency and less than 35uH inductance. (T106-2 core)

After trial and error I reached to this frequency by changing 56pf to 100pf in feedback after this change nothing heats.
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Old 28th October 2018, 06:08 PM   #129
dipolar is offline dipolar  India
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I hope I haven't posted in wrong thread ?
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Old 28th October 2018, 06:10 PM   #130
nigelwright7557 is offline nigelwright7557  United Kingdom
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I use a T106-2 10uH with 470nF at 250KHz and it barely gets warm.

I know on mine I got a little residual carrier but I don't think its anything to worry about. The speaker wont reproduce 100KHz.
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