Over Driving LED's

Over Driving LED\'s

I have noticed that a lot of you like to overdrive your LS's. I was wondering if overdriving hurts the LS, or is it the heat build up that hurts them. I.E. if they are properly heatsinked they can be overdriven, and it will not hurt them? /ubbthreads/images/graemlins/cool.gif

Re: Over Driving LED\'s

I suppose if you had one dipped into liquid nitro, you can probably pump a 5Wer up to maybe 20 watts.. /ubbthreads/images/graemlins/crazy.gif

But the main enemy is heat... Mr Bulk's been DDing his above specs for awhile, and all it takes is a good sinking.

Re: Over Driving LED\'s

If you look at manufacturer's specs, Lumiled or Nichia for that matter, you will see that a LED's presumed life is reduced as both a function of heat and current. In some cases, a significant reduction of luminous output can be seen in hundreds or hours and even less. These specs are typically based on operation of the LED's within the max allowed current and temperature parameters. /ubbthreads/images/graemlins/grin.gif

WHO knows what happens when the stops are pulled and it's peddle to the metal?

- Don

Re: Over Driving LED\'s

If the symptom of too much overdrive is gradually decreasing output rather than a sudden "pop!" at the end, maybe the solution is just make the LED replaceable. A 40-dollar 5W Luxeon lasting 300 hours is still a better deal than a couple of 20-dollar Surfire lamps lasting 30 hours each.

Re: Over Driving LED\'s

I'm curious if anyone has actually tested the effects of overdriving a Nichia white LED to its maximum rating (30 mA) on its overall brightness and life. Nichia has released graphs projecting brightness over 100-1000 hours at 10 mA and 20 mA, but not at 30 mA.

I'm *guessing* that it would reduce the overall life of the LED, but it's not clear by how much. If heat is the primary issue, Nichia LED's don't put out that much ...

Anyway, if anyone can point me in the direction of hard data on this, let me know.

-XCN-

Re: Over Driving LED\'s

I wonder how much of the decrease in brightness is due to the phosphor "aging". Don't phosphors loose their brillance over time? I may be wrong, but following this line of thought, the harder you excite a phosphor the faster the light output should decay.

Any comments?

Re: Over Driving LED\'s

[ QUOTE ]
trailstoride said:
I wonder how much of the decrease in brightness is due to the phosphor "aging". Don't phosphors loose their brillance over time? I may be wrong, but following this line of thought, the harder you excite a phosphor the faster the light output should decay.

Any comments?

[/ QUOTE ]

I don't know but my informed conjecture [guess] is that it is not a major factor. It *is* a major factor in degradation of fluorescent tubes but the mechanism there is not present in LEDs. In the case of fluorescent tubes, the thermionic emitter material gets sputtered off of the filaments and contaminates the phosphors in the tube. This is the cause of the blackening seen near the ends of well used fluorescent tubes

Re: Over Driving LED\'s

I suspect that not only damaging the LED, but "boiling off" the phosphor

I accidently ran a White Star/O at more than twice its rated current for a length of time, and the yellow phosphor appears "bumpy"

Heat is the enemy