PC Power Supply
The power supply unit, or PSU, provides the electrical power that runs a personal computer. Mains electricity is supplied as alternating current at a relatively high voltage, but the components inside a computer need direct current at several lower, tightly regulated voltages. The power supply’s job is to convert the incoming mains supply into these steady direct-current outputs and to deliver enough current for the processor, drives, fans and other parts.
Modern PC power supplies are switching power supplies, a design that is efficient and compact compared with older linear approaches. In a switching supply, the incoming power is first converted to direct current, then switched on and off at a high frequency through a transformer, and finally rectified and smoothed to produce the required output voltages. The high switching frequency allows a smaller transformer and less wasted heat, which is why this approach is used in almost all computer power supplies.
A typical PC supply provides several output voltages over standardised connectors, including separate feeds for the motherboard, processor and storage drives. The ATX standard defines the common form factor, connectors and signalling used in desktop computers, so a compliant supply fits a matching case and motherboard. Power supplies are rated by the total wattage they can deliver, and a unit must provide enough capacity for all the components in the system, with some margin, to run reliably.
Frequently asked questions
- What does a PC power supply do?
- It converts high-voltage alternating current from the mains into the lower, regulated direct-current voltages that the computer’s components require.
- What is a switching power supply?
- It is an efficient design that switches the power on and off at high frequency through a transformer, allowing a smaller, cooler unit than older linear supplies.
- What does the ATX standard define?
- ATX specifies the form factor, connectors and signals for desktop power supplies, ensuring a compliant unit fits a matching case and motherboard.
