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Old 20th April 2013, 12:44 AM   #1
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Default class D 1000 watts peak

My latest project 1000 watts class d amplifier.
1000 watts into 4 ohms with +/- 60 volt supply.

It uses basically the irs2092 datasheet circuit but with transistor gate drivers.

The only complication is the addition of a PIC microcontroller to control the shutdown pin.
If the VCC goes below 15 volts the 2092 is shutdown by the PIC.
I found with large power supply capacitors I got huge thumps or siren type noises on power down.
I notified IR of the problem and they said that I had done the right thing adding a simple PIC reset circuit.

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Last edited by nigelwright7557; 20th April 2013 at 12:53 AM.
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Old 20th April 2013, 04:56 AM   #2
paskal9 is offline paskal9  Malaysia
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an interesting project.

looks like it's not bridged. have you tried measuring voltage drop across the rails during high power? my current ir2110 seem to drop quite a lot. the rail stables after i bridged them.
and mind to ask how much inductance you're currently using?
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Old 20th April 2013, 01:15 PM   #3
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Quote:
The only complication is the addition of a PIC microcontroller to control the shutdown pin.
I'm more into microcontrollers then analog electronics..

What type of problems did you have?
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Old 20th April 2013, 08:12 PM   #4
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Originally Posted by paskal9 View Post
an interesting project.

looks like it's not bridged. have you tried measuring voltage drop across the rails during high power? my current ir2110 seem to drop quite a lot. the rail stables after i bridged them.
and mind to ask how much inductance you're currently using?
I cant measure the rails at high output current as I don't have a speaker large enough.
The inductance is around 22uH.
There is quite a bit of carrier left on the output so I might need to increase the inductance or capacitance a little.
It sounds Ok though.
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Old 20th April 2013, 08:14 PM   #5
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Originally Posted by Reactance View Post
I'm more into microcontrollers then analog electronics..

What type of problems did you have?
If you have very large capacitance on the 2092 supply rails as you switch off the reset circuit doesn't cut in in time and you get a huge thump or siren type noise through the speaker.
The PIC measures the 2092 VCC voltage and if it drops below 15 volts it holds the 2092 in reset.
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Old 21st April 2013, 01:21 AM   #6
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Originally Posted by nigelwright7557 View Post
If you have very large capacitance on the 2092 supply rails as you switch off the reset circuit doesn't cut in in time and you get a huge thump or siren type noise through the speaker.
The PIC measures the 2092 VCC voltage and if it drops below 15 volts it holds the 2092 in reset.
I think what happens the "rate of change" that the supply filter caps discharges is too slow for the ADC or what ever I/O you using on the PIC to detect logical "power off state"

You can use the PIC to measure power off immediately using a "loss of AC detector" detecting power down using a tap from the transformer or just don't use a PIC and use a relay with the same method i described.
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Old 21st April 2013, 01:46 AM   #7
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If I use 10,000uf per rail then there is no problem.
If I go up to 20,000uf per rail then the noises start on power down.

The problem is the 2092 not resetting properly on slow power downs.
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Old 21st April 2013, 04:14 PM   #8
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Originally Posted by paskal9 View Post
an interesting project.

looks like it's not bridged. have you tried measuring voltage drop across the rails during high power? my current ir2110 seem to drop quite a lot. the rail stables after i bridged them.
and mind to ask how much inductance you're currently using?
To test it I am just using a 2 amp transformer.
The rails do sag about 15 volts when driving it hard but that's to be expected with such a poor supply.
It really needs a 100VA transformer not a 200VA.
It is very loud even on the small transformer.

I found the VCC supply was dropping out at full power so I reduced the dropper resistors although this probably wont be needed on a 1000VA transformer.
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Old 22nd April 2013, 09:24 AM   #9
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by Reactance View Post
I think what happens the "rate of change" that the supply filter caps discharges is too slow for the ADC or what ever I/O you using on the PIC to detect logical "power off state"

You can use the PIC to measure power off immediately using a "loss of AC detector" detecting power down using a tap from the transformer or just don't use a PIC and use a relay with the same method i described.
using a relay does sound much simpler compared to PIC. i'm also using a simple AC detector drawn from the transformer tap to a diode and small filter cap to detect AC loss.

Quote:
Originally Posted by nigelwright7557 View Post
To test it I am just using a 2 amp transformer.
The rails do sag about 15 volts when driving it hard but that's to be expected with such a poor supply.
It really needs a 100VA transformer not a 200VA.
It is very loud even on the small transformer.

I found the VCC supply was dropping out at full power so I reduced the dropper resistors although this probably wont be needed on a 1000VA transformer.
i'm guessing it'll still sag with a large transformer. it's fundamental to all class d.
previously i'm using 500VA toroid and it still sag ~10V during heavy bass scene. adding more rail capacitance, rail decoupling caps and changing the layout doesn't improve much, until i bridge them.

now they hardly sag anymore. during intense bass scene they still go down 1-2V but that's it.
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