I think they only produce 10V maximum, not 15V, but yes it is possible. The only snag with any of those sorts of converter is the potential noise ont he supply. They are also usually unregulated so as the load increases the voltage drops. A regulated output DC-DC converter would be best but then they cost more and take up more board space. You can design your own DC-DC converter (inductive switching) with regulation. National Semiconductor's WebBench is one place to start.
Keith.