SMPS

In a PC, the computer power supply is the metal box usually located in the corner of the computer case. In many systems the power supply is visible from the back of the case because it contains the power-cord receptacle and the cooling fan.

The main purpose of the power supply is to convert AC power from the mains to usable low-voltage DC power for the internal components of the computer.

The power supply gives out three different DC voltages to your computer, 12VDC, 5VCD, and 3VDC. These three voltages are used for different components in your system. For example, the 5VDC voltage powers the motherboard, voltage regulators, serial and parallel ports, and PCI and AGP ports.

How Much Power Do You Need?

Each power supply has a certain wattage based on their maximum output power. Common wattages range from 300W to 500W, although for a high-end gaming power supply wattages of 500W to 800W are common. Some units even go up to 1 kW of wattage, but this amount of power isn't necessary for normal users.