# What am I doing wrong? COB LED with LED Driver

I am relatively new to electronics and I am trying to turn on a Bridgelux BXRC-50C2001-D-74COB LED (Digikey listing, Datasheet ) using a 500mA Mean Well DC-DC LED Driver (LDD-500LW). The LED Driver is powered by a Mean Well 24V AC-DC power supply (IRM-60-24ST).

I've hooked up the LED Driver control wire to an Arduion's PWM output, added a heatsink to the back of the LED, and grounded myself when handling the LED.

I can't figure out why this setup is failing to turn the LED on. I shouldn't need a resistor in line with a constant current power supply, right? I read 24V across the other input pads of the LED, so I know power is being delivered.

Am I burning it out somehow?

• You can use an LDB-500L buck-boost ($8.71 at Mouser) with your 24V supply or switch the LDD-500L supply to an LVP-60-36 ($16.45 at Mouser). FYI Buck-boost does both step up and step down. If you are not using the 24V supply for any other devices then you could use an AC-DC constant current driver. Mean Well has plenty of choices for AC-DC CC supplies. HGL is my choice with a 7 year warranty. EGL is cheaper. There is also IDL, ODL, PDL, PCD, PWM. NPF, LPF, LCM. PLM, HLN, GSC, OWA, PLM, PLC, HVG, HBG, FDL, CEN, CLG, LDC, HSG, and ULP I like Mean Well. – Misunderstood Dec 28 '18 at 8:57
• IDLV-25 -36, LCM-40Um, or IDLC-45-500 look like good replacements for the IRM. The HBG-60 is made for CoB fixtures. The HBG-60-P is a simple wired open frame. – Misunderstood Dec 28 '18 at 9:26

You have a buck converter that can output a maximum of 32V with 36V supply, but your LED needs 31V typical, the particular sample you have might need more, the data sheet link is broken.

Anyway, the key thing is that a buck converter can only output less than the supply, so it will not light with a 24V supply, and only maybe marginally supply enough even with a 36V supply to regulate well.

The output voltage limit is 30V and see also note 4 (maximum output voltage is input -3V).

• Possibly the correct driver would be the LDB-500L which can boost the 24V to as high as 32V. While the datasheet on page 8 says 30.9V for the BXRC-50C2001-D-7x stabilized at 85° C. The Vf on page 4 is 31.8V at Tc=25° C. I have found Vero CoBs to operate below the published Vf. But as they heat up the Vf will drop. I would expect the Tc to be higher than 85° C unless significant forced convection thermal management is used. Even if the Vf of the CoB is higher than 32V at start up. it will strill warm up and drop the Vf to within the range of the LDB-500L. – Misunderstood Dec 28 '18 at 8:24

INSUFFICIENT VOLTAGE!