After playing with my new HLG-100H-36A constant voltage driver for awhile, I conducted a little experiment this weekend to see if I could get either of my Vero 18 COBs to go into thermal runaway. Thermal runaway can happen in constant voltage systems where the current is allowed to vary, while the voltage is held steady. As the COB LEDs heat up, their properties change, and this causes them to draw more current, thereby heating them up further and drawing even more current. Eventually, the LED can destroy itself due to this cycle of drawing more current and heating.
Quite often, you’ll see recommendations to add a resistor in series with your LED if you’re using a constant voltage driver. I wanted to see if I could get away with skipping these resistors and simply running my COBs hooked up directly to the driver.