Re:Transcend (YC S15) Launches an Extra-Efficient LED Light ...
by nkurz on Wednesday July 08, 2015 @07:52PM
(#9855391)
I'm still surprised at the level of efficiency, but glad to hear that you can back it up. I wasn't doubting that an underdriven LED would last that long, rather I was surprised that the remote phosphors would last that long without decrease in output. But reading more elsewhere, I now see that the lifespan of the remote phosphors can be excellent: http://www.digikey.com/en/articles/techzone/2014/apr/develop...
For others who are interested, here's another interesting link on the remote phosphor approach:
http://www.ledsmagazine.com/articles/print/volume-9/issue-7/...
And a nice overview of the efficiencies of white LED's, and where the losses usually are: http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf
The exact figure in the last are already somewhat out of date, but if you plug in the specs for the newer LED's, presumably the underlying physics hasn't changed.
The Royal Blue LEDs we use have a ~55% EQE (external quantum efficiency). This gives a μmoles per joule a fair amount above 2.0. We lose a few photons during the conversion process and that drops us down to about 2.0.
We have a ~30% efficiency improvement over standard white LEDs because the phosphor is remote. The gain is 100% due to to the recycling cavity and omnidirectional nature of phosphors.