Class D amplifier help

yellowblue1909 · 7th July 2009, 09:50 PM

Hi all,

I am building a class D audio amplifier using the following parts:

LM311 - comparator
IR2010 - gate driver for the mosfet pair

This is the data sheet for the IR2010
http://www.irf.com/product-info/data...ata/ir2010.pdf

I am unsure what the input for the IR2010 would be..

Thanks

Iain McNeill · 7th July 2009, 09:54 PM

Do you have a schematic?

The 2010 is basically just a level shifter so you can switch the gate of the high side FET.

How are you generating the 2 PWM streams?

yellowblue1909 · 7th July 2009, 11:21 PM

as i can see from the data sheet, there are 2 inputs - LIN , HIN for the IR2010. However, I just have one pwm stream. I am generating this stream by comparing my input signal (i.e. audio) with a saw-tooth waveform using the LM311 comparator chip.

I did not know that there were 2 PWM inputs required... how do I get the second PWM input and why is it required.

Iain McNeill · 7th July 2009, 11:43 PM

usually, there's a dead time at each transition so that the on FET turns off before the off FET turns on. It takes longer to turn the on FET off than the off FET on. This means that at low level (input to driver) the PWM stream is almost identical except for dead time gaps.

Hence upper stream is different from lower stream.

Oh, and the high side is inverted. Does the driver do that for you?

yellowblue1909 · 8th July 2009, 02:54 AM

hmmm .. thats interesting .. i was not aware of this ..

how would i generate the other PWM stream (with the dead times)?

I noticed that some comparators like the LM361 yield two outputs... so if i decide to switch my comparator from the LM311 to the LM361 can I just feed in one of the outputs into the HIN and the other into the LIN without actually having to generate another PWM stream?

sawreyrw · 8th July 2009, 03:29 AM

yellow,

Given your questions you need to do your homework on Class D, before you try to build anything.

Rick

Iain McNeill · 8th July 2009, 04:03 AM

Yes, read a book or two.

Can anyone recommend an authoritative text?

I'd be interested myself.

darkfenriz · 8th July 2009, 08:35 AM

One of possible solution for dead time generator and symmetrizer with some intentional time delay.
Input at transistor's base, 2 complementary outputs with adjustable dead time.
http://www.diyaudio.com/forums/attac...amp=1208267656

P.S. There are gate drivers with just one PWM input, like IR2104, but for class D amplifier you should have much lower dead time, possibly adjustable.

yellowblue1909 · 8th July 2009, 02:21 PM

Yeah I will refer to books.

I am an EE undergrad student and took this project upon myself for educational purposes. My goal is to get a functional class D amplifier and in the process realize how the various components work with each other.

sawreyrw · 8th July 2009, 02:33 PM

I don't know of a good book, but you should look for application notes from companies that make class D control ICs.

7th July 2009, 09:50 PM	#1
yellowblue1909 diyAudio Member Join Date: Jul 2009	Class D amplifier help Hi all, I am building a class D audio amplifier using the following parts: LM311 - comparator IR2010 - gate driver for the mosfet pair This is the data sheet for the IR2010 http://www.irf.com/product-info/data...ata/ir2010.pdf I am unsure what the input for the IR2010 would be.. Thanks

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7th July 2009, 09:54 PM	#2
Iain McNeill diyAudio Moderator Emeritus Join Date: Oct 2007 Location: Santa Cruz, California	Do you have a schematic? The 2010 is basically just a level shifter so you can switch the gate of the high side FET. How are you generating the 2 PWM streams?

7th July 2009, 11:21 PM	#3
yellowblue1909 diyAudio Member Join Date: Jul 2009	as i can see from the data sheet, there are 2 inputs - LIN , HIN for the IR2010. However, I just have one pwm stream. I am generating this stream by comparing my input signal (i.e. audio) with a saw-tooth waveform using the LM311 comparator chip. I did not know that there were 2 PWM inputs required... how do I get the second PWM input and why is it required.

7th July 2009, 11:43 PM	#4
Iain McNeill diyAudio Moderator Emeritus Join Date: Oct 2007 Location: Santa Cruz, California	usually, there's a dead time at each transition so that the on FET turns off before the off FET turns on. It takes longer to turn the on FET off than the off FET on. This means that at low level (input to driver) the PWM stream is almost identical except for dead time gaps. Hence upper stream is different from lower stream. Oh, and the high side is inverted. Does the driver do that for you?

8th July 2009, 02:54 AM	#5
yellowblue1909 diyAudio Member Join Date: Jul 2009	hmmm .. thats interesting .. i was not aware of this .. how would i generate the other PWM stream (with the dead times)? I noticed that some comparators like the LM361 yield two outputs... so if i decide to switch my comparator from the LM311 to the LM361 can I just feed in one of the outputs into the HIN and the other into the LIN without actually having to generate another PWM stream?

8th July 2009, 03:29 AM	#6
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	yellow, Given your questions you need to do your homework on Class D, before you try to build anything. Rick

8th July 2009, 04:03 AM	#7
Iain McNeill diyAudio Moderator Emeritus Join Date: Oct 2007 Location: Santa Cruz, California	Yes, read a book or two. Can anyone recommend an authoritative text? I'd be interested myself.

8th July 2009, 08:35 AM	#8
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	One of possible solution for dead time generator and symmetrizer with some intentional time delay. Input at transistor's base, 2 complementary outputs with adjustable dead time. http://www.diyaudio.com/forums/attac...amp=1208267656 P.S. There are gate drivers with just one PWM input, like IR2104, but for class D amplifier you should have much lower dead time, possibly adjustable.

8th July 2009, 02:21 PM	#9
yellowblue1909 diyAudio Member Join Date: Jul 2009	Yeah I will refer to books. I am an EE undergrad student and took this project upon myself for educational purposes. My goal is to get a functional class D amplifier and in the process realize how the various components work with each other.

8th July 2009, 02:33 PM	#10
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	I don't know of a good book, but you should look for application notes from companies that make class D control ICs.