DD> I have a "portable" DVD unit which runs on a (switch mode)
DD> mains power pack. The power pack produces 6.3v DC at 3A. How
DD> hard would it be to produce a switch mode supply to produce
DD> that output, but from a (nominal) 12V DC supply? 

 Shit easy.... but why not use a series regulator? It's only 20
watts extra loss.

 You can buy switch mode regulator ICs, but you have to wind your own
switching coil and stuff around with fast diodes. If you're not
worried about battery life, I'd use a simple series regulator with a
nice big transistor on a nice big heatsink. If you need a dropping
resistor, use a 12V light bulb across the regulator.

Regards,
Bob


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