Led driver dilemma

NorthernHize said:

One thing I want to say from personal experience is that the 3070 has a vf of 38v. But I currently only drive it with 32v and it runs fine

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So looking at the graph its taking just over 300mA from your driver, which is being pulled up by the COB?

JavaCo said:

Should have added this , Forward voltage does change with the amount of current the COB is given. So a cob with a Vf of 36 @ 1000mA will have a higher Vf @ 1400mA and a lower Vf @ 600mA. Resistance changes with the amount of amps going to the COB.

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I made a green line on the graph at about 1000mA, ill base some scenarios on that

d1 rated - 1000mA @ 40V-(40W) -- COB: Runs no problem
d2 rated- 1000mA @ 34V-(34W)-- COB: Perhaps it runs.... because it's a constant current driver it will try to deliver 1000mA and as a result the voltage will be 'pulled up', but at the expense of its efficiency, because the driver is only rated up to 34W, but now its delivering 36W to the load and so i2r losses decrease efficiency?
d3 rated-1000mA @ 30V-(30W) -- COB: Does not run.

That chart is not set in stone so to speak. The actual COB you get could be up to a couple volts off. It is just the Vf of the average COB they produce. It would be interesting to know the amps the driver is putting out with his set up because a CXA3070 @ 1.750 amps should have a higher voltage then 32. But as Mechmike pointed out some drivers will compensate to run by lowering the AMP output. So driver doesnt really heat up it just lowers the current output to run.

So with my current setup a meanwell lpc 60-1750 driver and a cxa3070 I took voltage and amp readings. At 34v the driver puts out 1.47a, kinda in line with mechmike.