I need to make a low cost power supply for 3V.?

Question

I want to make a low cost power supply to run a few LED's. My input voltage will be 12V storage batteries, or perhaps 24V. Power consumption should be around 30W. I would like it to be as efficient as possible, so a simple resistor is out.

Thanks for any input you may have, or any research direction you may know about.

Answer 1

How many LED's are you powering? 30W is 2.5 A @ 12 VDC, and since most LED's take max of 20 mA, that's about 125 LED's. You will always need a current-limiting resistor for the LED's so they don't fry, so why not make it the only component other than the LED's? That's truly efficient...

If you know the forward voltage of the diodes, you can use that in the design. For instance, if each diode dropped 1.2V across it, you could put 9 in series and use a resistor for current limiting to 20 mA.

(1.2V/20mA) = 60 ohms for a 12V system

You can use a combination of series and parallel diodes to create your circuit and then use a single resistor for current limiting.