I’ve been asking myself a question: what makes efficient thrower LED?
High cd/mm² together with high cd/mm²W?
In a way that’s a good metric. If you want a lot of throw in a thermally limited host, that’s what you need. But a smaller emitter always wins. When your thermal limits are more relaxed that may not be so good….
I wanted to abstract away LED size.
What is “efficient LED”? Here I say it’s one with high efficacy.
What is a “thrower LED”? One with high surface luminosity.
What I call efficient thrower LED? One that can achieve high surface luminosity without becoming inefficient.
So I charted lm/W against cd/mm² using koef3 data. That’s what I got:
Conclusions?
- It seems size abstraction works like expected - compare Blackie HWQP with Ostar Q8WP - their behaviour at high intensity is about the same.
- XHP35 HI really looks very nice here as well….until it reaches (probably thermal) limits.
- Looks like if someone reinforced SST-40 bond wires it could go for longer.
Note that alone this chart says nothing about “what LED should I use in host X”. Size is a critical factor here and I explicitly ignore it. But I think it’s an interesting secondary metric.
ADDED:
Domed emitters are more efficient than flat ones?
It’s not strictly false, but from now on I will call it a misconception - because that’s not so simple and often straight incorrect.
If you take a LED in domed and dedomed variant, the former is more efficient, regardless if it was domeless from factory or dedomed later.
But unless you want to have your LEDs severely underdriven, a flat LED with larger die will offer same throwiness (i.e. cd/lm) with better efficacy. Obviously there are often market related reasons why a domed emitter might be preferred. F.e. there is no larger one in the footprint and price point that you’re targetting. But in general I think that (outside of lanterns and other lights targetting extreme efficiency) flat LEDs are just better.
And thank you koef3 for enabling me to draw these charts as well as these conclusion.
Your intensity measurements are what makes your tests special.