LED's are about to distribute the light bulbs in many applications. While for a simple control LED is usually a simple resistor is sufficient, modern high-power usually need a special driver circuit, a constant current to ensure and to use the lifetime and brightness optimal.
Frequently used here for then switching regulator (step up / step down), just to make Gerig losses.
Here links to LED driver circuits

Here you may find Circuit, Basics, Schematic Diagram and DIY Kit components for LED Drivers