# Power LED without driver

I purchased a number of 50W 5B10C high power leds. Link at end. These need at least 25V to turn on and I am using a setup with a 21V LIPO battery and a 150W boost converter stepping this up to 30V. I fully expect the battery and boost converter to be able to deliver 150W if short circuited.

Having no constant current driver, I took a chance on blinking one of the leds by connecting it directly to the 30V, and it worked fine, as expected for very short blinks.

Eventually I extended the duration, and in the end I just kept power on, and the led did not burn out, or even get overly hot.

The question here, since I am apparently missing something, is how I am getting away with this? Assuming the boost converter is actually able to deliver 150W, as per data sheet, would it not be expected that the led burned out in short order, driven as directly as this?

edit: In the end, it probably comes down to a balance of internal battery resistance and resistance in the led, so with the right voltage, it can reach a balance.. by luck.

https://www.ebay.com/itm/Xmas-SMD-LED-Driver-Chip-Bulbs-Waterproof-High-Power-Supply-10W-20W-30W-50W-100W/113172342934?ssPageName=STRK%3AMEBIDX%3AIT&var=413476810397&_trksid=p2060353.m2749.l2649

• Try to add capacitor or RC-filter like 1.2.4 learnabout-electronics.org/PSU/psu12.php Sep 4, 2020 at 13:34
• What is the voltage and current going to the LED, while it is running? Actual measured values. Sep 4, 2020 at 14:29
• The voltage is 30V and the current is initially 0.8A and rising, as I keep the LED running. I let it run to the point where the current was 2A, which would be 60W. Sep 4, 2020 at 16:14
• Since $P =V I$ and V = 0 in a short-circuit the power delivered in a short-circuit is zero, not 150 W. Sep 4, 2020 at 20:43
• Looks like parasitic resistance is saving your bacon. But why would you risk damaging the LEDs in the first place? Get a constant current driver! Sep 4, 2020 at 21:44