buck converter for high current LED
I can see where you are going with this but the circuit won't oscillate. I did a quick simulation and came up with this diagram: -


Be aware that your LEDs I modelled with a 20R resistor and that this circuit needs refining for it to work correctly with your requirements.

V2 is the demand voltage and it's currently set at 0.05V meaning the demand is very low i.e. the 20R load takes about 20mA. With V2 at 1V there is 200mA in the load. Like I say this will need refining for your circuits but it should give you a good idea how to get it oscillating. The trick is R5 and C1 and taking R4 from the current sense resistor R1. It then should work but it needs refining - did I mention that!!!