There is this socket for a light bulb, and it says LED only.
Why is it like that?
Is it just for power limitation (not to exceed power,) because LEDs take less power, or is there another reason?
Electronic – Lighting socket for LED only
ledlighting
Related Solutions
Better is coming.
Better costs money.
Present white LEDs usually use a single phosphor so you get two broad spectrum peaks - one from the direct light from the blue LED itself and the other from the yellowish phosphor.
In their recent PAR60 alternative LED bulbs (60 Watt mains replacements) people like Philips are placing the phosphor on a "globe" outside the LED and are using multiple phosphors to get several overlapping emission peaks and a better overall spectrum.
The standard measure of the "goodness" of the white from a light source is "CRI" = colour rendering index. This is essentially a measure of how well a range of test colours appear when illuminated with the test light compared to illumination with "white" light.
A CRI of 100 is "perfect".
CRI of >= 90 is very good.
CRI of 80 - 90 is bearable for many purposes.
CRI of 70 - 80 is definitely getting poor in most cases*.
CRI < 70 - they usually won't tell you.
- I say "in most cases" as I have some LEds with a CRI in the 70-80 range but most people (and me) find the light very nice indeed
Spectral peaks in multiphosphor LED. Usually you get blue plus one other.
Multiphosphor LED chromaticity diagram.
Excellent multiphosphor overview paper
There are several circuits on the internet from noatable sources that show how LEDs can be powered directly from an AC supply without a transformer. Here's one from ON semi: -
And here is the document it came from. The document is entitled "High Current LED - capacitive drop drive application note".
Here is another interesting article, this time from EDN. It shows the following diagram, again transformerless: -
And another article and circuit here: -
Best Answer
Yes it is a power limitation. Many light fixtures with just regular lamp sockets may have rating like 10W and it is quite clear that heat from regular incandescent bulbs would melt the material. It also might allow for cables with smaller wire diameter.