On Tue, March 4, 2014 10:26 am, Carl Denk wrote:
> The application is an auto power (cigarette lighter) power outlet plug
> containing a 3.3 VDC switching regulator to power a handheld GPS. The
> regulator is a:
> http://www.dimensionengineering.com/products/de-sw033
> which fits nicely in the plug housing. Initial testing using a 12 VDC
> bench supply was good, but when powered from 13.7 volt car battery,
> overheat caused the thermal protection to drop things out until it could
> cool down.
>
> The regulator has a  78XX pin out and a nice little aluminum heat sink.
> My first thought is to fill the housing cavity (1" dia.) with an epoxy
> or silicone with a bond breaker to the aluminum heat sink. After cure
> use a heat sink compound where the bond breaker was for good heat
> transfer. For the filler I'm thinking JBweld, but open to suggestions.
> Something with a good heat conduction. Would need to be something
> readily available. I do have a thin epoxy that I could add a filler, and
> have fine ground milled glass filler for it.
>
>
> Any thoughts appreciated. :)

I've used JB Weld to affix some ceramic substrate high power LEDs to
aluminum (10W strips) (the strips only had holes for screws on the ends),
and they have held up well. The thermal qualities of JB weld aren't
particularly great- a good mechanical bond is also necessary, and the
heart of any heat sink connection.

The regulator you point to doesn't look to have need for a heatsink? It
looks like it is covered with plastic- if that is there, any sort of
heatsink you use won't really do much.

But, with this setup (the switcher), is a heatsink really necessary? How
much power are you actually dissipating?



Matt Bennett
Just outside of Austin, TX
30.51,-97.91

The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with.
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