Timeline for Getting LEDs brighter without drawing much more current
Current License: CC BY-SA 3.0
14 events
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| Apr 23, 2013 at 6:24 | history | edited | user17592 | CC BY-SA 3.0 |
Clarified title so that it doesn't look like a shopping question
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| Apr 23, 2013 at 6:20 | answer | added | Kurt E. Clothier | timeline score: 1 | |
| Apr 23, 2013 at 5:07 | comment | added | Kurt E. Clothier | @Johnny - I'm not going to dig through datasheets. Here is an Appnote I had saved from a while ago: 1stvision.com/lighting/Gardasoft/apps/… But the concept of luminous efficiency isn't always so straight forward. There is a difference in instantaneous brightness, average brightness, and perceived brightness. While the data sheet may not exactly specify what I am saying, my eyes have seen this to be true in numerous cases. | |
| Apr 23, 2013 at 2:40 | comment | added | Johnny | @Kurt: Sure, I can believe that PWM at higher peak current could make the LED more efficient, can you point me to one of those datasheets? I've looked at several and don't see any sign that luminous efficiency increases by overdriving the LED at less than 100% duty cycle. There are thousands of LEDs, so if you could point me to one that exhibits this behaviour, I'd appreciate it. | |
| Apr 23, 2013 at 1:33 | comment | added | Kurt E. Clothier | @Johnny - Different things are true for different cases and different LEDs. Many LEDs have two different ratings for current: constant and pulsed. One would have to compare the charts in the data sheet to determine which would be more efficient while providing maximum brightness. If only one brightness (max) is desired, it may well be the case that a constant current is best. | |
| Apr 23, 2013 at 1:04 | comment | added | Johnny | @Kurt: I understand how PWM is an efficient way to dim the LED below max brightness while maintaining high efficiency, but for an application that needs maximum brightness, I wasn't aware that you can pulse the LED for better luminous efficiency than just running it at 100% of its rated current. This article seems to dispute that PWM leads to greater efficiency than running it at max current: electronics.stackexchange.com/questions/17528/… | |
| Apr 23, 2013 at 0:51 | comment | added | skyler | i bet this is bright, 70 dollars for 1 led! digikey.com/product-detail/en/PT-121-R-C11-MPB/1214-1059-ND/… | |
| Apr 23, 2013 at 0:22 | comment | added | Kurt E. Clothier | @Johnny - Using PWM to control brightness is pretty common knowledge. In fact, at specific frequencies, the LED can appear brighter when pulsed at a lower current. Plus, the LED temperature stays lower than if it were on all of the time, so it has better characteristics and a longer life. | |
| Apr 22, 2013 at 23:47 | comment | added | Johnny | @Kaz: Do you have any references for that? I thought LEDs were most efficient at or near their maximum current. I can see how pulsing them would make them more efficient when running at less than full brightness, but does it really make them more efficient at full brightness? | |
| Apr 22, 2013 at 23:43 | comment | added | Kaz | Make a circuit which rapidly pulses the LEDs rather than keeping them on all the time. You can get nearly the same brightness at a fraction of the average current. | |
| Apr 22, 2013 at 23:21 | history | edited | Matt Young | CC BY-SA 3.0 |
removed signature
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| Apr 22, 2013 at 23:20 | review | Close votes | |||
| Apr 23, 2013 at 14:28 | |||||
| Apr 22, 2013 at 23:10 | review | First posts | |||
| Apr 22, 2013 at 23:21 | |||||
| Apr 22, 2013 at 22:52 | history | asked | Rob Decker | CC BY-SA 3.0 |