Commander Kinsey wrote
Rod Speed wrote
Commander Kinsey wrote
Rod Speed wrote
Fredxx wrote
Brian Gaff (Sofa) wrote

OK what do they use then, All I remember from my brief experience
trying to dim leds was that the most successful way of doing that was
by duty cycle, ie on to off times with them driven by some kind of
oscillator with variable mark space ratios. However it is obvious
that even the briefest of ons and the longest offs tends to still be
visible in most cases, and not terribly accurate if many leds are
used as the load, there being a spread of linearity in any given
number.

PWM is the cheapest way as it needs no other component.

For a small improvement in efficiency then a constant current source
would be best but obviously costs more.

Doesnt necessarily cost anything more at all with leds. Same price as
voltage regulators.

But if I buy a "dimmable LED" lightbulb, I can dim it with a dimmer
that's on the wall, at 240V AC. Is there electronics inside the bulb
sensing the PWM from the dimmer and using that to control its internal
current limiter?

I was talking about led bulbs that dim without a dimmer thats on the
wall. The dimmer is internal and just has a current regulator instead of
a voltage regulator that costs the same. No PWM involved.

And now you must talk of the other kind.

Nope, because dimmers on the wall are dinosaur technology. Much
better to have the dimmer in the bulb itself so it can be automatically
controlled as a scene etc so that when you indicate that you are
watching TV it sets the lights to the level that you have decided is
best for that, turns the TV on and plays what you have indicated
you want to watch when you select what you want to watch.

Stupid to have to fart around adjusting the lights with the dimmer
on the wall etc.