LED Heat Calculations

[LEDQA]

I'm trying to get a good handle on how to estimate the heat created from different LEDs. Not really sure how better to describe the question but it's kind of hard to design a proper heat transfer system when I don't know what's coming in.

I've checked around and haven't found much more than calculations on voltage, current and resistors to use.

Thanks in advance.

 

[dpc]

If you know the voltage and current, then V times I will be very close to the heat loss in an LED circuit. The LED requires a resistor somewhere to limit the current. The heat loss is divided mainly between this resistor and LED itself with most of the loss in the resistor.



"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[VEBill]

If you know the Vf of the LED under the operating conditions, then you can more-exactly calculate the power at the LED (I times Vf = watts).

You could even adjust for the energy emitted as light (as opposed to heat) by reference to the efficiency. Or leave this added margin as an intentionally-overlooked added safety factor.

 

[MacGyverS2000]

If you know the Vf of the LED under the operating conditions, then you can more-exactly calculate the power at the LED (I times Vf = watts).

You could even adjust for the energy emitted as light (as opposed to heat) by reference to the efficiency. Or leave this added margin as an intentionally-overlooked added safety factor.

This is the safest method and the one I use, except when projects require very narrow specs.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[lumenharold]

Perhaps you came upon this one but perhaps not so I thought I would post it:

http://www.diodes.com/_files/calculators/zxld1350calcv2.xls

Harold
SW2009 SP2.0 OPW2009 SP0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com