PTs just do the voltage they are provided with directly, they are simply a connector. This is 5 volts out of the USB port or the mains adapter. You could get a variable voltage supply from an electronics store and adapt the PT cable of course. It would need to supply at least 3 amps to be on the safe side - although 'safe' is not the best way to describe it.
I don't advise it as you are getting into territory best left to people who understand all the risks. It's a non-standard hack so you are going outside the safe envelope and into the danger zone.