In the context of personal computers, the term PSU (Power Supply Unit) refers to the device which regulates and distributes the power to the components inside your PC. It converts the AC (Alternating Current) power supply into specific DC (Direct Current) voltages which can be used to power the internal components.

The PSU of a desktop computer will have a certain power output capability, which is stated in Watts. The amount of power required by any one individual PC will depend on its internal components and any external peripherals which are to be powered by the PC, for example USB-powered devices.

The current standard for power supply units is the ATX form factor. This standard provides voltages of +3.3V, +5V, +12V and -12V. Later revisions of the standard also provide a standby voltage which, depending on the computers other hardware, can be used to remotely power-up the computer via a network (Wake-on-LAN/Wake-on-ring).

The PSU can also be accessed by the system to enable the PSU to be "put to sleep", conserve energy or shut down.

For more see our guide to Power Supply Basics inc ATX Pinouts.

Back to Computer Dictionary