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I need to connect half a dozen COB LEDs (36V, 300mA). I can only connect them in parallel, not in series, because of wiring considerations.

For them to all be at the same brightness, my understanding is that I need one constant current LED driver for each. But could I use instead one Constant Voltage driver at 36V, 2A and one resistor of 120Ohms / 12W for each COB?

Will the system be prone to thermal runaway and will I get different brightnesses due to slight manufacturing differences of the COBs?

Also, if I want to dim all LEDs at once, will it work if I put a PWM dimmer between the constant voltage driver and the LEDs?

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You have good idea but values are way off.

With 120 Ohm resistors you would need 72V supply to get 36v@300mA across LED's, and you would waste 50% of energy on heat.

Reduce resistors to 6-12 Ohms 1W, and get power supply that can be adjusted to 39V(most aliexpress cheap ones are adjustable +-10%).

Brightness differences,if any, will be unnoticeable.

PWM dimming will work.

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