I am having an issue with the above circuit when LED DRIVER B has 0 PWM and LED driver A is being driven by a signal driver B is supposed to be off but the leds from BANK B are still lit dim. I checked with a scope and have 0 PWM on LED DRIVER B. One LED from BANK A is enclosed with one LED from BANK B. Bank A is white LEDs and BANK B is Green LEDs. The same issue happens in reverse. When LED driver B has a PWM and LED driver A does not, all LEDs are on. I was not involved with the design and need to find a way to fix this. The LED's are very difficult to get to and it is a last resort to modify the boards they are on by separating the grounds. The banks are never supposed to be on at the same time. When one turns off the other turns on and both are supposed to dim up or down at the same time. The drivers for this circuit are LDD-1500L https://www.meanwell.com/Upload/PDF/LDD-L/LDD-L-SPEC.PDF. I am hoping someone can provide a solution to this without modifying the boards they are on.
We did try adding a diode at the - outputs of the driver to block any possible feedback into the driver but this did not work.