I have a 20VDC input with a buck CC LED driver, driving 48 LED strings of 6 x 3V LEDs in series.

I am underdriving the LEDs at 60% of rated power. Each LED string consumes ~33mA.
The LEDs are thermally coupled on the same PCB. The LEDs will be binned by Vf.

I want to add current balancing but the idea of the reference string failing and causing the other 47 strings to fail puts me off.

I have enough strings that if even 2 fail the other strings will just share the increased current which is not much, but in this approach, the LEDs are essentially fighting each other, correct?

Would a current mirror be necessary in this scenario, or would it be better to use a single current source per string? Such as 3 x LED1642GW (16 channel LED driver.)

Edit:The total Vf of each string @33ma is 17.2v. Regarding the Headroom, I've build the PCB and it does work fine with the CC source (AL8863).

Also, the resistors on the cathode side of LEDs are not really doing anything, correct? I added them to try and equalize current.

![schematic](https://i.stack.imgur.com/Nuoxd.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fNuoxd.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)