dlloyd:
Thanks Paul__B, wow - so difficult trying to explain something while using the wrong picture
Ah well, that would explain it!
Chagrin:
Never understood how those "COB" (chip on board) LEDs work with the LEDs in parallel like that. Maybe the fact that they're all sitting on the same heatsink ensures they share current more closely?
Ol' Mike persistently disagrees with me on this one, but it seems to me that the fact is that like most other IC technologies, LEDs fabricated from the same die will have closely matching characteristics, and obviously these higher power array LEDs would each use chips from the same die. Certainly, being thermally synchronised will cancel the problem of negative temperature coefficient.