Johnnycannaseed1
Well-Known Member
Bonjour
You said that driving our cob too low will decrease efficiency at some point...I always heard the contrary...lower we run them higher Is efficiency!
I have cxb 3590(137w) @1400mA (half nominal current...50w)...some use it @700mA (23w) some even [email protected] when it will become less efficient...not according to datasheet!!!
CU
Bonjour Jacob,
In response to your post yes it is definitely better to under-drive, but there is a sweet spot range on all semiconductors. And as with all current semiconductors if you start driving them too high the efficiency will drop off and this is known as efficiency droop. But all LED’s require a minimum voltage, which is called the threshold voltage or turn on voltage, to be applied across the junction before enough current flows in order to generate light. Each semiconductor will have a relative efficiency curve and a range where max efficiency vs drive current is achieved, this is what I mean about knowing where the sweet spot range is regarding the chip set you are running.
I went to the CREE datasheet for the model you mentioned and interestingly they do not supply the minimum forward voltage, they only supply some typical data and some maximum data for voltage and current. And if I am honest some of their data seems counter-intuitive and contradictory to the way LEDs work like their relative luminous flux graph vs drive current vs Tc for one droop is actually negated by a higher Tj albeit at the expense of shortening the LEDs life, yet their data seems to be saying the opposite.
Having not played around with the CREE chips and this being the first time I have properly looked at their datasheets I have to say I am somewhat puzzled and confused by them in certain area, maybe I am missing something and if so please feel free to point it out.