I have not breadboarded this yet due to lack of large LEDs, but it looks quite simple.
N Channel MOSFET
2N3904
0.75 = 1W (for 10W LED)
100K & 3.3k resistors = 1/4W
TTL level PWM signal to drive ckt.
Necessary to play with input voltage depending on LED requirements. Adjust 0.75 W value accordingly.
Shamelessly stolen ideas (with only slight modification) from instructables dot com
