I resolved a similar problem by putting a resistor before the regulator.
This allows the resistor to dissipate most of the heat. You may need a
capacitor between the resistor and regulator.

Allen

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of
> Carl Denk
> Sent: Tuesday, March 4, 2014 11:26 AM
> To: PICLIST
> Subject: [EE] Heat sinking a 3.3 VDC switching regulator
>=20
> 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.
>=20
> 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.
>=20
>=20
> Any thoughts appreciated. :)
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--=20
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