This DC-switching LED driver-controller drives an external MOSFET and supports buck, boost, buck-boost, and single-ended primary-inductance converter (SEPIC) topologies for high-power LED lighting ...

I also have some discarded 1980s track-lighting fixtures, which used 12-volt incandescent bulbs. I swapped in some LED spotlights, then added a few more to bulb sockets screwed onto a 1x6 pine board.