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Computer power supply1. Short for power supply and sometimes abbreviated as PSU, which is short for Power Supply Unit. A power supply is an internal hardware component that supplies components in a computer with power. The power supply converts a 110-115 or 220-230 volt alternating current (AC) into a steady low-voltage direct current (DC) usable by the computer and rated by the number of watts it generates. For example, the image to the right is an Antec True 330, a 330 Watt power supply and an example of a computer power supply.

Caution: Do not open the power supply, it contains capacitors that can hold electricity even if the computer is off and unplugged for a week.

Tip: You can protect your power supply and your computer from a surge and voltage drops by investing in a UPS. If you cannot afford a UPS, you should at the very least have the computer plugged into a surge protector.

Parts found on the back of a power supply

Below is a list of parts you may find on the back of the power supply.

  • A connection for the power cord to the computer.
  • A fan opening to draw air out of the power supply.
  • A red switch to change the power supply voltage.
  • A rocker switch to turn the power supply on and off.

On the front-end, which is not visible unless the computer is opened are several cables that connect the power supply to each of the devices and the computer motherboard. A power supply connects to the motherboard using an ATX style connector and uses other connectors include an auxiliary connector, Berg connector, Molex connector, and P4 connector to power other devices.

What items are powered by the computer PSU?

Everything contained within the computer chassis is powered by the computer. For example, your motherboard, ram, CPU, hard drive, and disc drive are all drawing power from the power supply. Any other external devices and peripherals such as the computer monitor and printer have their own power source.

Note: If the computer is a laptop or an all-in-one computer the display may also be powered by the computer power supply.

2. With Linux, ps is a command, see the ps command page for further information.

3. PS is short for PowerShell.

4. On a keyboard the Ps or Ps/SR key is short for the print screen key.

Also see: AC adapter, Power cord, Power terms, Power switch, Redundant power supply, SMPS