Unregulated 12vac generated supply from moped. Solution on a chip for conversion to LED headlamp?

Looking at the TPS92560

http://www.ti.com/product/tps92560

Amateur level electronics.  Could I implement this or other into an unregulated generator electrical system that ranges from 6 to 18 vac depending on RPM?  Idea is to replace existing 20w halogen with 20w rated LED for higher lumen, lower wattage,  enhanced reliability.

This is only the starting point in a Google search.  What would be a better alternative IC or Board, with straightforward instructions for implementation, that might

serve my purpose?

Thanks for any help,

Brad Williamson