700ma LED Buck Regulator PWM

I am testing a 700ma LED Buck Regulator from an Arduino using PWM.

Available on EBAY at 700ma LED Buck Regulator

The Buck Regulator is powered by a 36v DC Power Supply and a 20W COB LED CHIP is being used.

When I send an AnalogWrite(0) I notice that the led is still just lit. I assume it is just the Capacitator having some charge in it and the current draw is very low so a long time for it to pass all current.

It appears that the LED over a period of 30+ seconds fade to nothing but I would like it to be off when I provide AnalogWrite(0)

Is there something I could put inline to make this happen faster?

Post a link to the COB LED.

The COB could have 10 LEDs in series, with a total Vf of 33-36volt.
A buck driver needs at least 2-3volt overhead.
So you must use a ~40volt supply, assuming the COB is made with 10-strings.
Most buck LED drivers can't handle that voltage.
Try to find COB LEDs with 6-strings.