Hi
You need to use boost converter circuit . you can use lm25xx series ic 's . or you can use step up fly back or forward converter. (with changing the ratio of turn )( out put higher than input) forexample : uc3844 or uc3845
Best lucks
Goldsmith
any current mode ic , almost, will do....what about ucc28c43?
With sepic over a couple of watts you MUST use a coupled inductor and not two separate inductors...or else you will get horrific resonant oscillations between the two sepic inductors and the sepic capacitor.