An LED I'm looking at has various specs listed that I can't make heads nor tails of. It is listed as a "3W LED" supporting a 2.5V minimum and 3.6V voltage. However, "Forward voltage" is listed as 3.4V-3.6V. Which makes me wonder what the 2.5V minimum means.

Also, it lists "Forward current" as "350mA@1W 700mA@3W". Now, if I take those values I get respectively 1W/0.35A = 2.85V and 3W/0,7A = 4.28V - totally different ranges than listed under the supported voltages. Besides, I would imagine that a 3W LED running at 3.6V would have a forward current of 833mA. Why are they listing two of them?

Is this just a mistake on the seller's specifications or am I missing something?

  • 2
    \$\begingroup\$ As always, please link to the datasheet. \$\endgroup\$
    – Transistor
    Mar 30 at 15:53
  • \$\begingroup\$ That parameters are not accurate, mostly from unknown manufacturers. Similar devices from known manufacturers with datasheet has another values, like 2W, etc. \$\endgroup\$
    – user263983
    Mar 30 at 16:01
  • \$\begingroup\$ @Transistor There is no datasheet, this is the data available to me. \$\endgroup\$
    – Bas
    Mar 30 at 16:12
  • \$\begingroup\$ "No datasheet? No sale!" You might find LEDs and binning relevant. \$\endgroup\$
    – Transistor
    Mar 30 at 16:32
  • \$\begingroup\$ I mean, that "always get a datasheet" rule is great if you're not on a budget but sometimes components like these are the only affordable ones available. Too bad, I'll have to look further or just take a chance on them I guess. \$\endgroup\$
    – Bas
    Mar 30 at 17:51

As others suggest - a LED without a datasheet is a black box.

That said, you might cull some information from a decently specified 3W LED made by Broadcom on its data sheet: Their device: ASM3-SxDx-xxxxH-DS100

Figure 7 below shows voltage and current relationship for a few different colour LEDs. The royal blue or cool white LEDs are somewhat similar to your meager specs. Figure 7 would be pulse-measured so that ambient temperature remains at 25 degrees C.
Figure 12 shows how temperature modifies forward voltage. It is very likely that your LED will need a heat sink to keep cool - since you have no specs, how much cooling you need is unknown. Your LED might do for just foolin' around, or for running much less than the limits shown here.
Most LEDs are best driven with a current source, rather than a voltage source. Broadcom 3W LED current/voltage/temperature graphs


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