USB Hub + Y cable = Powered Hub?

I have a notebook cooler that comes with an integrated USB hub that takes mini-USB for it's power supply. So I was wondering if getting a Y cable and plugging the auxiliary end to the mains through an adapter will allow me to use more high-power devices on it. Also, is it safe to do such a think? Is there a risk of the Y-cable pushing power to my mobo and possibly frying it?