I have noticed that some buck boost converters say "led driver", some have step down/up control and what looks like a display voltameter and ammeter, they are adjustable to 5 Amps/32v. Obviously these devices are not stand-alone LED drivers as they need a constant current, so how are boost/step down with adjustable control incorporated into powering a high powered LED?. Do they act as the driver when powered by a power supply?, or can they be used alongside a constant current or constant voltage driver?.
The goal is to convert the wrong DC voltage into the desired DC current for a limited voltage range of an array of LED's.
They are connected in series and loading must be satisfied on both sides.
Some topologies include Cepic, buck/boost, flyback.
That being said, you will find many obsolete CV power supplies with bad ripple being sold as LED drivers cheap on Ebay. Since they have a simple pot to adjust the voltage over a small range, they can work OK with some high power LED arrays, but you have to measure the current yourself.
Here is one you will find on Ebay with specs in Mouser for 10 cents per watt.
All I can say is Buyer Beware...