my eyes percieve the average. except when we were using it for Strobe light at lower rates.
there is no doubt that PWM is not as efficent as running the Led at Lower total currents , and therfore at higher efficency levels.
but i would rather have PWM then no level adjustment. no mater how inneficient PWM is, if you only light up the led for 1% of the time, you Still get the longer runtimes.
also it SEEMS that temperature is a major factor, while being higher efficency with current control is more light & less heat, at LEAST with PWM the heat is reduced, not at the actual silicon gate, but it can passivly move away from that gate.
so while PWM is garbage compared to full control, it still has uses, because you can get more runtime and less heat , NOT that current control wouldnt do that better, its just that PWM can get that done.
See i might have said it right this time, instead of arguing with Newbie about it being "BETTER" or "OF NO VALUE AT ALL".
Then if you OVERDRIVE the led in pulses, then PWM is still overdriving the led, there does not HAVE TO BE overdrive to have PWM.
i know of no book on PWM that says you cant do PWM at well below spec within the (more) higher efficency levels of the led.
you try and explain that, without getting into a 50 page diatribe about how current control is better than PWM, it IS nobody doubts that, but PWM can functionally run the led, heat, and the visable light lower, and increase runtime.
the METHOD of current control, then becomes important, if your going to just TOSS out the extra power, using a resistive current control, you would have to balace that out with your efficency of the PWM and the power required to run the pwm controller itself.
and the better efficency of the current control with losses that occur due to the current control curcuit.
what it probably comes down to is the total package that is created and implemented not what one sees on a bench power supply. 20% loss here 50% loss there , 30% losses at the led, percentage of losses due to overheating, lifetime of the curcuit, and the teeney package they make it.
PWM based devices can be made to act in similarity to current control devices by just averaging the pulses out into one more hunk of lossy electronics, before it goes to the led itself.
lest we leave out one factor too in PHOPSHOR leds, is phospher persistance, the phosphers used would effect the persistance of the phospors. people would say that 60htz CRT monitors would drive them buggy , but there was huge variations in phosphor persistance used in monitors. what one person saw the other one did not, the claim was the refresh rate differance 60-200 say fed to the monitor, but the lines were still being drawn on the monitor in little pieces, it was only the phosphors that kept the light to percived levels. Phosphor persistance was why some percieved 60 to not be enough, and some 100 not enough. then turn around they get LCD monitors which have a light valve persistance , and they think they can run the light valve at at 200 refresh rate.
led manufactures really like thier on time and off time specs , .5ms turn on time, why dont they put in higher persistance phosphors ever in led item? what would be the ramifications? ever see a led with more or less phosphor persistance?
which brings up "gate triggering" at some current level some of the "organic" gates will not triger at all, i call it organic because the etching and doping process is a very rough process done with organic acids and baths and such. (at the molecular level)
Question: are all gates in a led die triggering when there is not enough current for a electon jump of the gate? ahh see you didnt think about that
if at low currents only close gates are triggering, what is the life of the low gates, vrses the high jumping gate. (something like that) only way to tell is very long term testing.
Dont we basically know that? lets see, the wavelength of the emitted light has something to do with the distance right? and PWM maintains the color of the light the same, but current control doesnt, hmmmmm . could it be that with current control shorter length waves are produced because shorter jumping locations are still operating, at the lower voltages
ya see at the molecular level as seen in other silicon devices, there is this rough molecular surface, not some magic perfection, that means that some jumps are longer and some are shorter to get across to the other side. the more "precise" they make the led gate, the more efficent and the more singular wavelenght would be produced from it.
the reason i bring that up, is because (sloppy) multiseries parellel leds wont have all the gates (or even whole emitters) triggered on low current control, short gates will invariably age faster? PWM has a jump occuring on every gate in the die., which is probably why it eventually kills every gate in the die, and every phospher it emitted to.
so if any of that ^ was true. Why does the voltage required to the led change over time, to LESS for the same current, why does the color change over time? something died inside, something changed in resistance. hmmm, wrack brains, less voltage same current, the resistance went down?? right?
2 ways leds die, one if you smack it hard it breaks to an open curcuit , resistance up. if you drive it hard, or just over time it does the opposite, resistance increases. in tests this gets so bad, it goes from Diode to Resister completly.
so
little broken gates are passing power through, and probably not putting out any light? then my logical estimation is that any led that had dropped in Vf over time has less light, more fried gates are just passing current through. and they would be the gates that are most likly to go from short jumping to charred remains, not the higher voltage gates?
so if i can wrap my brain around the cause of Vf lowering, and color change, would it be dead, short jumping, low power, high frequency, gates in the emitter are fried? so the color should shift to lower frequency light.
SOOO
if you use current control, you will fry less short gates , preserve the long and short gates for high powered operation, are less likly to have a change in the Vf over time, and are more likly to have more light and less useless resistance in the led.
or
they could just make the leds better
wouldnt that mean
that over the 100 hours where the led voltage (for the same current) drops , that in reality in 100 hours the item is basically burning parts of itself up, leetel teeney parts . and any lumens efficency over time, so a Led that did NOT decrease in resistance, or change in Vf , or change in color, would still be in very good shape. In this TIME situation, the low Vf led is NOT more efficent, its lower in Vf for the current because parts of it are going from diode to resister.
if they tighten up the gate, and precision up the gate, then the lower VF there would represent efficency for the single color output. that would explain how they can get High efficency leds in low quantites, perfection that doesnt translate to mass production.
even in-spec operation fries the weakest link in the led, the one being pushed the hardest for the power going in.