I am trying to wire up 24 - 3W LEDs ((VF): 2.2V~2.6V (IF): 800mA). I was thinking about wiring up two sets of 12 LEDs in series and connecting both of those sets in parallel to an LED driver rated at 1300mA. I was thinking about running them at around 600mA. Wired this way the current would be 1200mA wouldn't it? A 1300mA driver would be enough to power it wouldn't it?

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  • \$\begingroup\$ Schematic/block diagram or it didn’t happen. \$\endgroup\$
    – winny
    Apr 15 '18 at 20:48
  • \$\begingroup\$ If you're using a 1300mA driver, I would expect the current to be 1300mA. It would split roughly equally, provided that all the LEDs are identical. \$\endgroup\$
    – Simon B
    Apr 15 '18 at 22:14
  • \$\begingroup\$ I added a schematic. If a LED goes out in one series would the other series be overloaded if the driver provides constant current? Would it be better if all the LEDs were in series? \$\endgroup\$ Apr 16 '18 at 16:53
  • \$\begingroup\$ @Brian: When you use the CircuitLab tool it saves an editable schematic inline with your post. No need for screengrabs. By the way, you missed the LED symbol right beside the diode symbol. We get the idea though. \$\endgroup\$
    – Transistor
    Apr 16 '18 at 16:54
  • \$\begingroup\$ @Transistor: This is from an online tool (digikey.com). Good catch on the LED symbol. \$\endgroup\$ Apr 16 '18 at 17:19

That's too many LEDs to be running parallel strings.

I ran some experiments on two parallel strips of 16 Lumiled Rebel ES LXML-PWC2 white LEDs.

One experiment the strips had a Vf of 43.29V and 43.85V

When driven with 375 mA the currents were 240 mA and 135 mA.
When driven with 770 mA the currents were 450 mA and 320 mA.

In another similar experiment with strips from the same LED reel the strips when in to thermal runaway after about 12 hours.

I used three sets of Bridgelux off the shelf EB-Series Gen2 strips with Vf's of 37.94, 37.86, and 37.77 @ 500 mA.
Each set was two strips wired in series and the three sets in parallel. When connected in parallel the Vf was 39.06V. When driven with 4173 mA the current in each set were 1515, 1430, and 1228 mA.

When I tried two 35V (34.9 measured) CoBs in parallel driven with 1227 mA the currents in each CoB were 764 mA and 463 mA.


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