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Old 20th April 2010, 06:17 PM   #1
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Default My first Class D plans (schematics)

Before I start making the schematic I want something to ask. Some questions might be noob but that's why I am asking them.

I want to build Class D amplifier with oscillator LM566. The input signal will be passed throe TL072 Op Amp. Then this signal will be amplified little and send to LM319 or LM311 comparator.
Now I don't know what IC to use for separating High and Low signals.
I don't want to use any of IR or IRS components. Can someone help me? I want to make half bridge amp.

And the last question what is all about that feedback? Do I need feedback with separate oscillator like LM566 or this feedback is only for self oscillating circuits that don't have separate oscillator.
And what is all about that dead time? How should I implement that dead time? I was reading about this but I can't get it So I would be happy if someone can explain these questions to me.

Thanks.
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Old 21st April 2010, 06:05 PM   #2
jej is offline jej  France
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Hi RealForce,
Why don't use IR products ?
My first class D amplifier used separates components. One for sawtooth generator, one high speed comparator and one driver. But layout is very sensitive! You can trust me
Poor result
With IRS2092, the only one problem is the requirement of many supply but we obtain very good results
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Old 21st April 2010, 08:26 PM   #3
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Quote:
Originally Posted by jej View Post
Hi RealForce,
Why don't use IR products ?
My first class D amplifier used separates components. One for sawtooth generator, one high speed comparator and one driver. But layout is very sensitive! You can trust me
Poor result
With IRS2092, the only one problem is the requirement of many supply but we obtain very good results
So you are telling me that there is no way to make good class D amp with discrete components?
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Old 21st April 2010, 10:19 PM   #4
jej is offline jej  France
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I simply say It's easier with appropriate IC! Your layout is more elaborate with several components. Don't forget you work at high frequency. Leakage inductance, parasitic capacitances become prevailling factors. With only one component including dead time, feedback, driver... you reduce length of connections and then don't use RC networks to reduce this effects.
Of course you can perform a amp with dicrete components but (it's my opinion and my experience) unlike class AB Amp you will have several designs before obtaining good amplifier
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Old 21st April 2010, 11:52 PM   #5
savu is offline savu  Romania
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Quote:
Originally Posted by jej View Post
Hi RealForce,
Why don't use IR products ?
My first class D amplifier used separates components. One for sawtooth generator, one high speed comparator and one driver. But layout is very sensitive! You can trust me
Poor result
With IRS2092, the only one problem is the requirement of many supply but we obtain very good results
hello Jet,

stupid question:

what did you mean to say by:"With IRS2092, the only one problem is the requirement of many supply but we obtain very good results "

regards,
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Old 22nd April 2010, 10:46 AM   #6
jej is offline jej  France
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Hello Savu,
IRS2092 need 5 supplies: 5V for digital part, 15V for analog part and 50V for power.
For better results this supplies must be separated. This is more expensive,It's the only one problem!
regards
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Old 22nd April 2010, 10:00 PM   #7
savu is offline savu  Romania
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Quote:
Originally Posted by jej View Post
Hello Savu,
IRS2092 need 5 supplies: 5V for digital part, 15V for analog part and 50V for power.
For better results this supplies must be separated. This is more expensive,It's the only one problem!
regards
Ok ...

I understand the part with the +15V and the +/-50V, but where exactly do you use +/-5V on it?

From my point of view it's not that hard concidering that you have to add 3 more windings on your SMPS or trafo, and some rectifiers, stabilizers, etc

Take in concideration that the multi voltage part doesn't interfeer with the audio comutation.

An UCD type amp is prone to generate more parasitics if you don't understand PCB importance. But in this case you get a nice tight and low parts count PCB for the audio part witch gets you out of the woods.

The SMPS or trafo is more easy to modify and it won't damage the audio quality and amp randament.

best regards,
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Old 23rd April 2010, 12:43 AM   #8
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Personally I really dislike "ONE CHIP CLASS D AMPLIFIERS".
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Old 23rd April 2010, 01:38 AM   #9
savu is offline savu  Romania
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Quote:
Originally Posted by RealForce View Post
Personally I really dislike "ONE CHIP CLASS D AMPLIFIERS".
Hello ...

any particular reason for the above ?

regards,
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Old 23rd April 2010, 05:20 PM   #10
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Originally Posted by RealForce View Post
So you are telling me that there is no way to make good class D amp with discrete components?
Well, there in posting #50 I had posted a schematic with discrete level shifter.
1kW Gen2
Of course you can also do the gate drivers in discrete....

You may also dig for the older UcD circuits, their discrete level shifters and gate drivers are proven circuit parts, which can basically be adopted for any class D amp.

The drawback with lower integration:
Resulting mess is an overproportional function of the component count.
- optical
- signal integrity
- human errors & debugging

And of course you will also find a negative impact when calculating your mtbf or fit rate.
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