Also of interest is this teardown of the Koppla USB power supply: https://www.youtube.com/watch?v=uRe9w5PKmsE https://www.youtube.com/watch?v=uRe9w5PKmsE It's

Also of interest is this teardown of the Koppla USB power supply: https://www.youtube.com/watch?v=uRe9w5PKmsE https://www.youtube.com/watch?v=uRe9w5PKmsE It's also a pretty darn good piece of kit.