D4 is 8A. Or maybe you mean 8A/LED?….

Would be an interesting test.

Now… that’s a really good question. Now I also have my doubts about maukka’s result. Some people who are more knowledgable than myself have validated them so I still view them as “rather true than not” but I’m no longer sure about them.
Therefore my statements that Lux-RC was incorrent in saying that FETs always run LEDs at full power are also questionable.
I’d love to some more people who know to chime in….

Also I’d like to clarify one thing. I’m not claiming that FET based drivers are particularly good.
I think that when used correctly they are a fair compromise between price and quality. Heavily leaning to the “price” side.
When used incorrectly they are terrible, I surely think so.

FET drivers are a quite polarizing topic. Many despise them. Many love them, some don’t even want to read about regulation. Myself I’m between.

On many occations I reject some statements from the first camp:

  • that PWM means flickering
  • that they are super-inefficient
    • yes, I will stop using one argument until I see more evidence on the topic
    • but people speaking about inefficiency tend to ignore FET+1 and FET+N+1 which are significantly better than FET alone. And often better than PWMing 7135s.
  • that FETs kill LEDs
    • they do…but only when used wrong

I reject claims from the other group as well:

  • that this is the only option with good power density
    • Led4Power shows this is wrong
  • that nothing else will drive LED X strong enough
    • same as above
  • that this is the only cheap-and-powerful option
    • OK, I don’t straight reject it - but I question it. FET-based linear drivers shouldn’t cost much more if not for the lack of competition.

ADDED:
And I’d like to also note that I’m a big fan of buck and boost drivers. Because efficiency tends to matter to me a lot. And I’m a big fan of FET-based linear drivers. Because they offer superb power density and regulation. And I kinda like FET+1 and FET+N+1 drivers. Because they are cheap, powerful and available. I don’t think that there’s only 1 driver type that makes sense. I dislike PWM*7135 drivers but I see uses for them as well. Primarily - I think that different lights call for different designs.