What is computer power supply?
A power supply unit (PSU) is the component that supplies power to a computer. It’s was designed to comvert 100-120 V (North America and Japan) or 220-240 V (Europe, Africa, Asia and Australia). Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.
POWER SUPPLY CONNECTOR
The below illustration is the typical female connector which would be used to connect to a device such as a CD-ROM or Hard Drive. This connector is refereed to as a large Molex connector. Additional to these types of connectors you may also find a small Molex which is generally used for the floppy disk drive.
| Pin | Wire Color | Signal |
| 1 | Yellow | +12v |
| 2 | Black | Ground |
| 3 | Black | Ground |
| 4 | Red | +5v |
POWER SUPPLY CONNECTIONS
| Pin Number | Color | Function | Connector |
| 1 | Orange | "Power Good" | P8 |
| 2 | Red (XT No Wire) | +5V DC | P8 |
| 3 | Yellow | +12V DC | P8 |
| 4 | Blue | -12V DC | P8 |
| 5 | Black | Ground | P8 |
| 6 | Black | Ground | P8 |
| 7 | Black | Ground | P9 |
| 8 | Black | Ground | P9 |
| 9 | Black | Ground | P9 |
| 10 | Yellow | -5V DC | P9 |
| 11 | Red | +5V DC | P9 |
| 12 | Red | +5V DC | P9 |
What is ATX?
ATX power supplies also are designed to turn on and off using a signal from the motherboard (PS-ON wire, which can be shorted to ground to turn on the PSU outside the computer), and provide support for modern functions such as the standby mode available in many computers.