mulu:
It works but I can't dim it very low.I hooked it up to an old scope and realized that the fall time measured at D (between the LED strip and the NDP6020P) is very slow (upper curve on the scope).
How low. 1/256 of max brightness might not be that dim for the human eye.
Use at least 12-bit dimming if you want it to dim low.
That marked knee-point is probably Vf of the three LEDs in series (~9.5-10volt).
The LED strip is basically an open circuit below that voltage. Like a zener diode.
Drain of the mosfet is basically only pulled down to 0volt with the internal resistance of the scope probe (1Megohm).
Leo..