On Thu, 03 Oct 2019 17:03:55 +0100, Max Demian wrote:

On 03/10/2019 15:16, Commander Kinsey wrote:
On Thu, 03 Oct 2019 15:08:43 +0100, Martin Brown
wrote:

White LEDs rely on a yellow phosphor absorbing and re-emitting blue
photons to make a perceived white light. Coloured LEDs typically have a
forward voltage related to the energy of photon that they emit.

There is a hit for doing that that limits ultimate efficiency to
something like 40% of power consumed out as useful light.

I didn't realise that, I thought white LEDs were designed to directly
emit a handful of different visible light wavelengths to make white. Is
there a reason this can't be done? An LED can make anything in the
visible light spectrum, so surely a mixture of them would be more
efficient than using phosphors? There could even be seperate LEDs
within the housing, like growlamps which have visible, IR, and UV LEDs.

You can have red, green and blue LEDs to make up white, but it's less
efficient and usually not worth doing unless you want to vary the hue.

I see. So for some reason blue LEDs are more efficient? (Even after wasting energy converting it with phosphors?) Do you know why?