Configuration of 3V led filaments ? - Page 1
Forum section: electronics / beginners

author: Jaunedeau
author_rank: Regular Contributor
timestamp: November 22, 2022, 09:51:59 pm
content: Hi,according to the video linked at the end, the short 100mA 3V led filaments use 20 leds, and some aliex listing indeed state 5mA per led.I wonder what is the configuration: are they just all in parallel?I remember playing with the first "super bright" leds about 20 years ago (:s) and is was definitively not possible to run 20 in parallel (too much difference in voltage drop).Do the small tracks act as serie resistors? (I doubt so because according to the video, you need 2.7V to get 5mA per led, which is already a bit low when compared to most datasheet for white smd led I've found)Are nowadays LEDs more consistant, allowing to run 20 of them with the same voltage?Are those led filaments just designed to randomly explode?thanks,John.Edit : there are also the flexible filament, some of them apparently having 100 led in parallel... thought they seems to be driven at about 1mA each... is it part of the answer ?

author: Manul
author_rank: Super Contributor
timestamp: November 22, 2022, 10:38:07 pm
content: Must be parallel then. It is not ideal, but might be ok. If they are all tightly thermally coupled it makes matters better. Some small resistance in the tracks and bonding wires too. It is what it is. But I would run such parallel configurations with slight current derating if longevity is to be expected.

author: tooki
author_rank: Super Contributor
timestamp: November 23, 2022, 12:26:34 am
content: My guess is that they carefully bin the dice before assembling them into filaments.

author: EPAIII
author_rank: Super Contributor
timestamp: November 23, 2022, 10:25:37 am
content: With today's miniaturization, each one of the LEDs could have it's own, built in current regulator.

author: Psi
author_rank: Super Contributor
timestamp: November 23, 2022, 10:36:08 am
content: Originally led filaments were all in series and needed like 70V.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 23, 2022, 11:21:03 am
content: Quote from: EPAIII on November 23, 2022, 10:25:37 amWatch the video. Do you still want to suggest that?

author: RJSV
author_rank: Super Contributor
timestamp: November 24, 2022, 08:49:47 pm
content: Not persposed-to run LEDs by way of voltage, but can get away with it, having that particular power supply, maybe current limiting was already in place. With today's bright LEDs you have no clear way of knowing, if you were 'burnin' some, at '3 V'. (I'm still cringing, only a little, after watching the Voltage get adjusted, with current limit setting as a 'maybe do that, too'.First thing, set your current, to where you want to run.LED set-up is as a current precise, voltage don't care, although a run at some current will have some voltage, kind of like a 'reaction' to the current.I had the good luck, to get corrected, when I did that...setting the LED voltage.Course, it's good to glance at the voltage, that happens after you've set the current and stepped back, it might read 2.94 or something nominal, for a '3V'.You could argue, nothing bad happened. I think battery charging, Nimh, has similar procedure, based on charging current, not voltage.

author: Zero999
author_rank: Super Contributor
timestamp: November 24, 2022, 10:45:49 pm
content: They're connected in parallel. That's the only way to do it. LEDs work fine in parallel, just keep the current well below the maximum rating, that way, if some use more current they won't burn out. The dies are the same as those used in 5mm though hole LEDs, which are designed to take 20mA, so at 5mA they'll be fine in parallel.