Agro
(Agro)
25
We’re a bit off the topic, but…
I’ve seen one claim of a light making 200 lm/W. This was from Lux-RC.
Say that one wants to repeat this feat with a quad…
What are the losses? With a shallow MgF2 coated aluminum reflector and UCL2 lens you get 95% efficiency. Not including losses on bezel, washer, centring ring. So maybe real 93% is achievable. With cheap reflector that’s more like 88, with a clear TIR (and no protective lens) I would expect up to 90.
What kind of efficiency can you get with a buck driver? Let’s be optimistic and say 99. So to get 200 lm/W OTF you need 220-230 lm/W at the LED. Samsung LH351D can does 150 lm with 220 lm/W and 100 lm with 240 lm/W. So a quad TIR with 99 efficient buck driver could do about 500 lm with 200 lm/W.
If we drop driver efficiency to 95% which I think is realistic, that’s more like 430 lm.
With linear driver, efficiency wouldn’t be good, in the same setup it would be about 78% efficient because at such low currents Vf gets very low.
BTW 12V boost drivers can’t be so bad. It must be possible to make an efficient one. I say so because I observe that nothing gets close to Zebras for sustained output in their size class. Even multi-emitter lights.
And AFAIK Lux-RC does boost too. To 9V.