Electrical – LED Power vs current and voltage

ledled stripled-driverlow-power

I have 6 parallel connected led "strips" each having 4 leds in series connection (see image below).

Those leds should be 3W each (2.4V and 700mA max each)
I have a LED drive as power supply (should be 12V and 6A max)

I tried measure the voltage and the current and I found out, that there is only 1/6A = 0.16A running through each LED with the voltage 12/4 = 3V each (rounded) thus having 0.16*3 = 0.48W.

I can't find what is wrong with my observations and/or calculations or if those leds are not really a 3W LED. I guess there is something wrong with my calculations or observations because the LEDs in this setup are bright enough and based on my original calculation it should work this way.

Thanks for help


Best Answer

LEDs have no internal current regulation & require a series resistor to keep them from overcurrent that can cause them to melt/explode/die horribly.

Also, the listed "voltage" of an LED is the "knee" voltage of the diode...more of a "no light comes out below this voltage" than an ideal operating point.

Try running a series of 3 LEDs, with a 7.5ohm series resistor to see if you get the LEDs to react closer to "datasheet specs."

Something like this:


simulate this circuit – Schematic created using CircuitLab

NOTE: After testing it with a 7.5ohm resistor, you can check the current flowing through each strand, then use more/less resistance to get closer to your "goal" 700mA.