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I have matched an led driver (constant current power supply) to a circuit of leds such that no resistors are needed to limit the current by taking advantage of the leds "near" linear voltage current relationship. By dividing the supply voltage by the number of LED's i know how many volts each will get and thus how many amps the will pass through the LED.

Here is an example circuit:

enter image description here

Im quite confident this will work well, but if one LED goes out, the whole row will go out.

Here is a proposed circuit: enter image description here First off, is there a name for this wiring? I could not find any information on it.

Is this proposed circuit a safer and more reliable method of wiring than the prior?

Also, if one of the leds failed and broke the circuit somewhere what would be the relevant behaviour of the other leds - Assuming the current the now broken LED was carrying could be safely divided amoung the remaining two leds, such that their current is still under their max rating?

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  • \$\begingroup\$ "... but if one LED goes out, the whole row will go out." The whole column will go out. \$\endgroup\$ – Transistor Jul 13 at 19:08
  • \$\begingroup\$ You must use a batch of very closely matched LEDs to make this work. \$\endgroup\$ – Elliot Alderson Jul 13 at 23:34
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I'm quite confident this will work well, but if one LED goes out, the whole row will go out.

If you mean an open-circuit with "go out" then I'd ask "what if one LED gets shorted instead?". Of course, things get worse for the remaining LEDs.

You should always consider a possible short-circuit of at least one LED as well because a damaged LED does not always get open-circuit.

Is this proposed circuit a safer and more reliable method of wiring than the prior?

To me, yes it is.

The latter one can tolerate any short- or open-circuit LED better:

  • If one LED gets short-circuited then the other paralleled LEDs don't light up. And the remaining LEDs will still be driven with the same current. The light output may decrease a little bit. Shouldn't be a problem.

  • If one LED gets open-circuited then the other two parallel LEDs will share the drive current equally, which results in an increase of %50 more drive current. This may or may not harm those two LEDs depending on the drive current and the tech specs of the LED.

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  • \$\begingroup\$ The obvious disadvantage of the second one is that the best-case scenario of randomized Vf allow for better current distribution, but worst case scenario is still the same. \$\endgroup\$ – winny Jul 13 at 18:39

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