Computer Power Supply Knowledge

A Computer Power Supply (PSU) is vital to the operation of a computer. The Power Supply converts AC current to DC current and then sends power to all of the internal components in the computer system so they can function.

A Computer Power Supply is a metal box usually located inside the top backside of the computer case. The power supply is visible from the back of the computer.

It is easily identified by the presence of a port for the power cable. There are three typical voltages used in a power supply: 3.3 volts, 5 volts, and 12 volts. The 3.3 and 5 volt supplies are usually used by digital circuits, while the 12 volt supplies are more typically used to supply power to fans, motors, and disk drives.

The main specification of a power supply is in watts. Most PC’s today use a push button switch on the front of the computer case to power up the computer. This push button sends a 5 volt signal to the power supply letting it know it is time to send power to all of the internal computer components. To shut the computer down most computers have a “shut down” option located in a menu bar. When this is used the operating system sends a signal to shut the computer down. The Power supply also has a 5 volt circuit of “standby voltage”, known as VSB. This circuit is used so even when the computer is turned off, the push button to start up the computer will still work (enabling the computer to turn on). There are different types and styles of power supplies on the market today. Three of the basic types of desktop PC power supplies are AT, ATX and ATX-2.

AT Power Supply – Typically used in older PC’s

ATX Power Supply – Commonly used in PC’s today

ATX-2 Power Supply – New standard for power supplies today

Power supplies are easily changed and are generally cost effective. If you are going to change a power supply make sure you get one with room for expansion so you are prepared for the future.