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I need to drive and dim 4 parallel LED strings.

Each color (see below) dims separately. Another constraint is minimising the number of wires running from the light to the driver.

Here are my options as I see them.

Option A is the baseline, each string is driven separately. It's not physically reasonable in my case as the LEDs and the driver are on different PCBs and that would create a lot of wires.

enter image description here

Option B is how I do it currently. Each color is connected to a separate CC driver (LDD-300H). Although it works fine now and the brigthness seems pretty even, I know there are concerns around current imbalance between strings. I could probably connect the positive ends also?

Option C is to use a multi-channel CC LED driver like LP8860. Presumably I could connect the positive ends, which would leave me with 5 (1 positive, 4 negative) wires going from the light to the driver.

The space on the light PCB is pretty limited, so putting anything other than resistors on it would be difficult.

Am I missing any options? Am I wrong in my assumptions?

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Am I missing any options?

I'd measure the voltage drop across the strings, if it's vastly different (like more than say 5%) then use different CC drivers. If not then it's fine to parallel them. Separating out the strings will allow for better control of the current, but if your not calibrating the LED's or have any requirements, then the configuration probably isn't that important.

If I were doing this myself I would probably choose A, because it would reduce PCB trace size requirements, allow for easier routing/placement of the CC drivers on the PCB and give better control on each string.

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  • \$\begingroup\$ Yeah, A is not an options because the driver and the LEDs are on separate PCBs and that would create a lot of wires. \$\endgroup\$
    – andrey
    Oct 8 '19 at 18:53
  • \$\begingroup\$ I'm confused, why is it even list that as an option, with no description that it can't be used as an option? \$\endgroup\$
    – Voltage Spike
    Oct 8 '19 at 18:56
  • \$\begingroup\$ My bad, added that to the OP. BTW I've measured the voltage differences between the LEDs across the current range and the worst I'm seeing is 2%. \$\endgroup\$
    – andrey
    Oct 8 '19 at 19:13
  • \$\begingroup\$ So? Is this site about harvesting votes? Or generating good questions and good answers? \$\endgroup\$
    – Huisman
    Oct 8 '19 at 19:25
  • \$\begingroup\$ I can't write a good answer if they don't ask a good question \$\endgroup\$
    – Voltage Spike
    Oct 8 '19 at 19:27

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