Voltage Regulators Sharing Heatsink?

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Siegfried Meier

Well-known member
Joined
Jul 2, 2004
Messages
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Location
Ontario, Canada
Can 3 voltage regulators in a small PSU (+18, -18 & 48V phantom) share one large heatsink?  I was under the impression that they couldn't touch together or something would short out.  Specifically, I'm referring to Keith's 9k PSU, but I guess the question could be related to all PSU's in general.  The usual problem is that smaller heatsinks on each reg don't do enough to dissipate the heat, and putting larger ones on each doesn't really work because of space restraints.

Thanks,
Sig
 
There are thermal mounting kits available around the web that will isolate the tab electrically but still conduct thermally. I know radio shack has them but they're overpriced.
 
Does anyone have any part numbers for some good solid heatsinks that can attach 3 regulators that are so tight together?  I've been looking around and am not seeing anything that won't require some fabrication or custom work.

I guess the other way is to mount them all on the chassis with flying leads, and decouple them from the chassis - thinking back now, I'm not sure why I didn't think of this before asking the original question about a solid heatsink - it's essentially the exact same thing.

Since most of my cases are steel construction, and nearly all heatsinks are aluminum, is steel really that good to use as a heatsink over aluminum?

Thanks!
Sig
 
Steel doesn't disperse heat across it's mass like aluminum does, it tends to localize it at the source for quite a while. In lower power situations, a steel chassis can work fine though.
 
Hi Sig

here is a photo of a 'mock-up' using a single aluminum heatsink and 3 teflon insulator's, no drilling required. You can trim the heatsink of course.

If this will work for you, I can send it to you as an Xmas present.
 

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Hey!  Very cool, nice work.  My question is, how are you going to get that cap behind the +48v to go in there...?  It's such a tight little PSU!

I have decided to go a little bit more drastic, and pull all the regs offboard and give each of them their own massive heatsink, all isolated.  I'm testing now, but if it's a go I'll mount the sinks to the chassis.

Regs.jpg


Thanks for the offer though!  Much appreciated!
Sig
 
I checked that C11 fits with the mock up(pic attached), but your solution is better. nice work
 

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Question - is there any glue/goop type stuff that I can affix the heatsinks to the chassis?  I was thinking epoxy, but this might get too warm and melt?  The sinks really don't get hot at all now, been running since this morning to test.  I suppose I could tap a thread into the bottom of them and drill through the chassis and mount, but just wondering what other options there are.

Thanks!
Sig
 
If they do end up getting warm, they may expand more than the epoxy would allow, breaking the bond, or worse, breaking the regulator. They're pretty cheap though, so maybe try some 2 part epoxy, although I don't know what kind would be best for electrical insulation.
 
Well, I don't see how anything could break the regulator - I'm talking just a tiny goop of stuff on the bottom of the heat sink to hold it in place inside the chassis.  But ya, I don't know what would work best either.  I saw this crazy sh*t in Rona the other day, bonds ANYTHING to ANYTHING, no matter what temperature, wetness, whatever.  White looking stuff.  They had a demo set up where a brick was attached to some PVC piping.  It always stays a little flexible, so it'll never dry out, but the stuff sticks like sh*t to a bear!  Wish I could remember the name...
 
use some RTV silicone, electrical grade for not harming leads and other important metal.

obviously you do not want to glue the chassis case to the heat sink, who wants to rip the leads out of the pc board anyway?
 
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