USB has a standardized voltage of 5V. The problem with using the Pi is the amperage (current) it can supply but your (Bluetooth?) dongle shouldn't draw enough to stress the Pi, it can provide for a 0.5A (500 mA) draw, you shouldn't need to replace the dongle
This article on connecting the DualShock seems good http://www.raspians.com/Knowledgebase/ps3-dualshock-controller-install-on-the-raspberry-pi/