Here is a 445nm build I did with an Ehgemus host. There is a separate thread for the driver in the drivers board.
A full write up and large images can be found at Chris's Electronics Page
This is very similar to what another member posted a few weeks ago. I built this driver and found it can do 2 A with 4 V input. It shuts off when the battery gets to 3 V. Mine is currently driving an M140 diode at 1.25 A and barely gets warm. I calculated the efficiency to be 82% into my diode...