If LED lights bulbs are so efficient, then why do they have cooling fins?

Most of the LED bulbs now sold as incandescent replacements have cooling heat sinks on them. If they have such great efficiency, I would expect minimal waste heat with no heat sink needed. Do they get too hot to touch as well?

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They are very efficient, but they are also very small, so the waste heat they DO generate has to be dissipated carefully, hence the heatsink. Only the latest LEDs are actually more effiicient than the previous best tech, which used to be CFL.

Let's face it., modern LEDs are more efficient (lm/W) than light bulbs, but they still waste a good amount of energy as heat. Although less than a light bulb - that's what makes them more efficient.

But, the wolfram helix inside a light bulb has to be hot to produce light, so the heat is an accepted (and kind of needed) by-product. For LEDs that's different. An LED chip getting hotter than 150°C will just die (and degrade in efficiency before getting that hot). So LEDs have to be kept as cool as possible, hence the fins.
That's right. An incandescent gives about 15 lumen/Watt. State of art LEDs, over 50 lumen/watt. An incandescent dissipates 100W to deliver 1500 Lumen. A comparable LED cluster, 30 W. 30W will STILL MAKE THINGS HOT.
Jorsz6 years ago
They do have Colloing fins, because maximum junktion temp. of a LED is 185°C!
Chips are very small sized. High power/current on a small surface means high temperature.
The wolfram helix inside a bulb has to reach 2500°C to work properly. Plus, inside the Bulb is a vacuum, therefore no Oxigen.
The wire can't "burn" as easy as a LED does. Even if LEDs were more efficient, lets say 300lm/W, there would still be the problem of cooling down the chip.

So remember to cool down your LEDs :-)
iceng6 years ago
In the US an other reason is the manufacturers didn't want to populate
the full complement of then costly white LEDs ( 50 or so )
to balance US power lines.
So they put in a regulator to drop the voltage down to 25 or 30 LEDs.

Regulators dissipate heat.