LEDs / Wake-up Light, 2

The high power LEDs are there 🙂
5 pieces rated at 3W, which is roughly equivalent to a 40W light bulb.

But unfortunately I didn’t do my homework; they are not running with 12V, but with much less.
I could regulate the excess voltage by just turning it into heat with a resistor, but this seems a) highly inefficient, and b) every LED will get hot and needs at least a passive heatsink — with even more heat I surely need active cooling, which i would like to avoid.
The other possibility is a constant voltage / current source, which regulates the voltage (and current) more efficiently. Without much cons, in contrast to possibility heat.

Now waiting for the delivery.