A modern ATX power supply unit (or PSU) is the component that supplies power to a computer. Most personal computers can be plugged into standard electrical outlets. The power supply then pulls the required amount of electricity and converts the 110 v AC current to DC current (. It also regulates the voltage to eliminate spikes and surges common in most electrical systems. Not all power supplies, however, do an adequate voltage-regulation job, so a computer is always susceptible to large voltage fluctuations.
Power supplies are rated in terms of the number of watts they generate. The more powerful the computer, the more watts it can provide to components.
