TPA3122 not working with 24V Switching PS

[aviatorbja]

My amp works fine with a 15V Linear DC power supply. When I use a 24V switching supply, 24VDC 3.75A POWER SUPPLY | AllElectronics.com

The amp does not work. It appears to be going into some type of shutdown mode.

My amp and board are on this post.
http://www.diyaudio.com/forums/class-d/186399-tpa3122-not-working-nothing-2.html see very last post for latest PCB which I am using.

Does anyone have an idea on what may be causing this?

 

[killerbobjr]

Most likely going into thermal shutdown. That DIP package can only dissipate a watt or two in free air. You need to mount some sort of decent sized heat sink on it (not the little DIP types).

 

[aviatorbja]

Thanks killerbobjr. So should I try a 18V switching supply?
I can't seem to find a heat sink which is compatible with this chip.

 

[killerbobjr]

This is why I recommend that the TPA3122D2 be mounted underneath the PCB so you can easily attach a heatsink or mount the PCB onto the large plate included with many project boxes (which will heatsink the DIP package).

That said, I've one TPA3122D2 board that's conventionally designed with no heatsink, running with an 18V supply. That's about the limits of the chip thermal envelope (6W channel output, 85% efficiency, 0.9W per channel dissipation, 1.8W total for the chip).

If you didn't make room for a heatsink on your PCB, you'll have to ghetto-attach whatever size heatsink you can fit over it to use your 24V supply. If other components are in the way, stick a chunk of aluminum block (with thermal compound) on the DIP that will rise higher than the surrounding components, and attach your heatsink to that.

 

[aviatorbja]

I'll try the ghetto-attach method. I'm pretty good at that. I have some copper and aluminum scrap; I should be able to fabricate a heat sink. Actually attaching it to the chip may be a challenge. Thanks.