Power Supply TO220 vs TO3?

Jim Patchell patchell at silcom.com
Wed Aug 30 23:58:07 CEST 2000


    NO!  While I prefer TO3's myself, there is nothing wrong with TO220's.
Whether they catch on fire or not is determined by how much voltage drop you
have accross the regulators and the size of the heat sinks.  Generally, most
people just don't put enough heatsink on the TO220's.  If you are going to be
dropping about 5 volts at 1 amp, you need a heat sink that will radiate that 5
watts into space with a reasonble temperature rise.  Now I realize, it is going
to be difficult to pick a heat sink to do this because information on this is
difficult to find (does anybody know a good place to get this?).  A good rule of
thumb is the bigger the heat sink, the more heat it will get rid of, but also
remember, that the poor little TO220 has a maximum disipation that you cannot
exceet (should be on the data sheet for the device).

    -Jim

Dave Wilke wrote:

> Design and planning continues for my modular (mostly based on EFM's stuff).
>
> An engineer friend dropped by and said my +/-12v PS design would simply
> catch fire because I'd used TO220 7812 & 7912 regulators instead of going
> with TO3 packages.
>
> Should I be concerned?  What would the expected current draw be from (let's
> say) 18 modules of the VCA5b and deg2a sort?  Can I get away with TO220's or
> do I need to do a (third) redesign using TO3's?
>
> dave
>
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