Residual light comming from LED Driver

[lmagalhaes]

Hi there,

I've designed a LED board with multiple colors (true green, deep blue, white 5000k, etc) and am using individual LED drivers for each color. The LEDs are "sprinkled" around the PCB, which uses aluminum as the dielectric for better dissipation. I'm using DALI to control the dimming of the various drivers, but some of them, when turned OFF, leave some of the LEDs glowing. Only after removing the phase connection the leds stop glowing. Either that or disconnecting both outputs (LED+ and LED-). Leaving the phase connected with the neutral disconnected, the LEDs keep glowing, leaving both the phase and neutral connected and just disconnecting LED+ leaves the LEDs glowing too. I don't think it's a case of a faulty LED driver since I've switched the drivers between themselves and the problem keeps happening. The heatsink where the PCBs are screwed down to is connected to Earth, but I have also tried disconnecting the earth wire and nothing changed. I am going to try and add some capacitors to the input, but don't think it's going to help much.

Any ideas?

[FlyingDutch]

Hello,

if you have LED of high brightness than can be glowing with liitle current (even fractions of microamperes). Your LED drivet IC might to produce such small currents on it's outputs - hence the behavior of the circuit.You can try use diodes conected in parallel to LEDs and resistors (serially and parallel). You have to experiment with your circuit to get best behavior of it.

Best Regards

[Siwastaja]

Try a resistor in parallel with LED. Assuming the leakage current is really small, huge value like 100-470kOhm will solve the issue without causing any meaningful extra power consumption.

The tiny leakage current will then flow through that resistor, creating a small enough voltage drop so that the LED does not light up.

If the LEDs are brightly on, or a say 100kOhm resistor in parallel does nothing to it, then there is probably something more seriously wrong.

[lmagalhaes]

I added a 249k ohm resistor in parallel with the output of the LED Driver, still the LEDs keep glowing ... If I disconnect the LED+ of the driver, the LEDs glow even brighter, just like they are on. Any ideas?

[FlyingDutch]

Hello,

you can try adding diodes (normal not Schotky) in paralel to LEDs. You can also try resistor in series with LED.

Best Regards