I have a portable lithium battery-powered speaker which takes auxiliary sound input from a single AAA-battery powered pocket radio. The speaker includes a USB port for charging source devices:
I would like to build/buy a circuit which could be used to efficiently transform the 5V DC output source of the USB to operate the AAA-battery powered portable radio, to save me from having to buy batteries.
However, I'm no electronics expert! What can you suggest? I'm handy with a soldering iron, but don't know how to design what is needed. I'm at least aware that I probably want to:
- Transform the 5V DC source down to 1.5V in an efficient way (so, not with a linear regulator, but with something like a "Buck converter"). I don't want unnecessary drain on the portable speaker battery, so want the transformation to be as efficient as possible).
- Support an output current of at least 1A, but it's likely that the radio will require much less (perhaps 50mA?).
After more reading/searching, I found the LM317 linear regulator might do the trick. A linear regulator, while inefficient, has the advantage of not generating RF noise which may interfere with the radio reception (as suggested by @BrianDrummond, below).