IRS2092 Amp Design Review

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brent113

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Joined 2009
Hello all,

I've been working on a design for a Class D Amp using the IRS2092 to drive a 1Ohm Subwoofer load. I was hoping I could get some feedback on it from some people that know more than me, as this is my first design. Thanks a ton to Eva, Mag, and all the others that I've benefited from while reading through these forums.

Currently I'm laying out the PCB. Wish PADS had an auto-place for some of the small resistors :p

More information on the project can be found here: http://beaversource.oregonstate.edu/projects/44x200914/wiki
The goal is to eventually get this amp above 500W.

Thanks!

Brent Scrivner
 

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brent113

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Thanks for the optimism. I just ordered the pcb about 15 hours ago. Good catch on the 47R, made me check my parts list. I actually ordered a 4r7, that was just a typo.

I'm not looking forward to testing the protections. Thinking of putting the protection signal connecting diode on headers for easy removal :D
 
kASD

kASD

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Joined 2004
brent113 said:
Hmm. Don't know enough about this to tell if that is going to be a show stopper. How badly do traces that long affect the output. If I dropped the carrier frequency down lower could that help mitigate that problem?
Click to expand...

Why you guys never CARE TO READ application notes related with that driver chip and a basic understanding of RF and switching electronics is must prior to any adventure of this much calibre.


The forum is FILLED with numerous examples, seems you havent done your homework.:)
 
kASD

kASD

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Joined 2004
brent113 said:
I have read all of the related application notes. Care to make any suggestions for improvements? I do not have a fundamental understanding of RF and switching electronics as they are not currently in my major. I will be studying those in years to come.
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Minimise gate/source trace length
Minimise the switching node area between mosfets also
and a solid grounplane is a must

besides this there are many key factors which fall under basic switching electronics fundamentals. I am surprised how you took class-d as your project without knowing these.
 
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brent113

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Thanks for the feedback. It's brutal, but I knew it was coming :p

Workhorse said:
Minimise the switching node area between mosfets also
Click to expand...
One problem I was having with the layout of the FETs was since I was using single TO-220 heatsinks I valued not overlapping the footprints of those. If I had access to a solid custom drilled heatsink I probably could have done a lot better. Was there a way I missed that I could move the FETs closer together without screwing up the cooling?

Workhorse said:
and a solid grounplane is a must
Click to expand...
Is trying to do this on a 2-layer board pointless? I've heard "use a 4 layer board" before but that wasn't an option. Or, did I just lay it out that poorly and could have gotten away with 2 layers but didn't.

Workhorse said:
I am surprised how you took class-d as your project without knowing these.
Click to expand...
I'm ambitious? :p This subject really interests me, and I figured I'd go for it. Go big or go home, right? Unfortunately, I've been studying computer networks and IC design, not power electronics, so I've missed a lot of the RF subject matter.
 
kASD

kASD

Member
Joined 2004
brent113 said:
Thanks for the feedback. It's brutal, but I knew it was coming :p


One problem I was having with the layout of the FETs was since I was using single TO-220 heatsinks I valued not overlapping the footprints of those. If I had access to a solid custom drilled heatsink I probably could have done a lot better. Was there a way I missed that I could move the FETs closer together without screwing up the cooling?


Is trying to do this on a 2-layer board pointless? I've heard "use a 4 layer board" before but that wasn't an option. Or, did I just lay it out that poorly and could have gotten away with 2 layers but didn't.


I'm ambitious? :p This subject really interests me, and I figured I'd go for it. Go big or go home, right? Unfortunately, I've been studying computer networks and IC design, not power electronics, so I've missed a lot of the RF subject matter.
Click to expand...

At least read IR app notes on class-d amps on www.irf.com under audio section, you will learn a great deal as a beginner.
 
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brent113

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Joined 2009
I have read those, and specifically in AN-1135 a star ground is recommended instead of a ground plane. Most reference designs I've seen though use a ground plane.

I guess a couple revisions I would make now are make the bottom middle plane at -B and the top at +B instead of both at the same reference and break up the ground plane a bit around the input circuitry.

Not sure how I could move the FETs in and shorten the gate traces without finding a better heatsink solution. Getting the FETs in D-FET packaging would've allowed me to shorten the traces to within an inch but I don't have any sinks for those. That was my logic at least, not trying to defend it.
 
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