The current is the problem I need to reduce the current will the 0.2 ohm 15 w resistor in series be enough to drop the current 2 amps as I keep destroying the led lightes.
Thank you
Ok, hold on. I was under the impression you just needed to drop a bit of the 37V to below the led's rating of 36V and then vary the brightness from there. Although you did say vary current as well, but I assumed varying brightness is the end game.
Flyback, although a buckboost is probably a good idea, if it was me personally I wouldn't want to go that route, seems a little complex. So I'm not disagreeing, but I would personally do it differently. I do like the whole idea of using a transistor with negative feedback, although I think the OP needs to clarify a few things first.
Why do you want to drop the current by 2A, more specifically, how did you come up with that number? Previously you've just said 36V with a max 7A but you want to vary the current.
Can you answer the following for us to help you further:
1) What is the absolute max current you want?
2) Find out what voltage applied to the LED's gives you that current. This is critical.
3) Is your heatsinking adequate? Have you done any calcs? I know you said it'll be in water, however that may not be enough and thats why they're blowing, not due to overdriving them, but because you've assumed your heatsinking is enough, but haven't actually calculated anything.