Different types of buck regulators

[Dalistro]

A bit of a stupid question, Tried using search but not entirely sure what to type down.

Ive noticed nobody uses these types of regulators and I'm wondering why?

Can this particular board be used?, assuming the voltage in meets the requirements
http://www.elecfreaks.com/store/lm2596-dcdc-stepdown-module-p-292.html

 

[Th232]

A bit more info on what you're powering and with what would be helpful.

That looks like a voltage regulator, which means that it'll output a set voltage. LEDs are current based devices and have a very steep V-I curve, so a slight change in the voltage will result in a massive change in the current delivered, which may cook the LED. Given the Vf variation in an LED, if you just rely on the datasheet to figure out the voltage to set it at you may end up with a nasty surprise. Also, if the Vf changes due to temperature or something else, the current delivered will also change.

 

[Dalistro]

Sorry, should have mentioned it.
It will be powering a Cree XML with 2 lithium ion batteries in series.

But you answered my question nicely anyway. :D