the Power Supply Unit

/ Hardware

The power supply unit in a computer converts the power from the wall outlet to the type of power needed by the computer. It sends power through cables to the motherboard and other components.

The power supply unit in a computer converts the power from the wall outlet to the type of power needed by the computer. It sends power through cables to the motherboard and other components.

 

 

1. Function

The Power Supply Unit (PSU) converts the alternating current (AC) from the wall socket into direct current (DC), which is required by internal computer components such as the motherboard, CPU, GPU, hard drives, and more. It also distributes the correct voltage levels (typically +12V, +5V, and +3.3V) to these components.

 

 

2. How It Works 

  1. AC Input: AC power enters from the wall socket.
  2. Rectifier: Converts AC to unregulated DC.
  3. Filter: Smooths the DC signal.
  4. Transformer: Steps voltages up/down (depending on output needs).
  5. Regulator: Produces stable output voltages (+12V, +5V, +3.3V).

Output to Components: Power is sent via connectors to the motherboard, CPU, drives, GPU, fans, etc.

3. Types of Power Supply Unit

Type

Description

Example Use

ATX PSU

Most common for desktops. Large and powerful.

Gaming and standard PCs

SFX PSU

Smaller than ATX; used in compact builds.

Mini-PCs, HTPCs

TFX PSU

Slim and long.

Low-profile desktops

Flex ATX

Very small and narrow.

Mini-server cases

Modular PSU

Detachable cables. Clean setup.

High-end/gaming PCs

Semi-Modular PSU

Some fixed cables, rest detachable.

Mid-range builds

Non-Modular PSU

All cables are attached.

Budget systems

PSU Size / Form Factors

Form Factor

Dimensions (mm)

Use Case

ATX

~150×86×140

Standard desktop PC

SFX

~125×63.5×100

Small Form Factor builds

TFX

~85×65×175

Slim desktops

Flex ATX

~81.5×40.5×150

Mini PCs & servers

PSU Connector Types:

Image: Various PSU connectors – 24-pin ATX, 4/8-pin CPU, SATA, PCIe, Molex.

Quick Summary Table

Feature

Details

Function

Converts AC to DC, supplies stable power

Main Voltages

+12V, +5V, +3.3V

Common Types

ATX, SFX, Modular, Non-modular

Sizes

ATX (standard), SFX, TFX, Flex ATX

Efficiency Rating

Look for 80 PLUS Bronze, Silver, Gold, etc.

Protection

Over-voltage, over-current, short-circuit protections