Function, structure of ATX power supply unit of Desktop

This post is lesson 13 of 42 in the subject Computer Hardware

Power supply unit (PSU) is a component that provides power to the entire computer. If the power supply unit is failure, the computer cannot work.

1. Function of power supply unit (PSU)

PSU used to convert AC current into DC voltage for supplying components on mainboard.

Power supply unit (PSU)

2. Types of power supply unit (PSU)

The power supply unit has many design standards such as AT, ATX, BTX corresponding to each type of motherboard.

AT power supply unit

Intel introduced in 1984, used in old computers with weak power. Can only be turned off by pressing the power switch.

ATX power supply unit

  • Allows power off by software.
  • Intel introduced in 1996. It has 20 pins.
  • ATX12V has 20 pins + 4 pins.

In addition, there is BTX power supply unit, which is a type to replace ATX.

3. Structure of power supply unit

(1) Cooling fan

(2) Types of power connector

(3) Power on and power off switch

(4) AC power connector

Structure of power supply unit

Power supply unit specifications: see the back of the power supply unit

  • Voltage
  • Amperage
  • Wattage
Power supply unit specifications

Commonly used power supply unit such as ACBEL 450W, Cooler Master 500W, Corsair 550W.

Commonly power supply units 

4. Types of connector of PSU

Connector of ATX12V power supply unit: ATX12V power supply unit has connectors such as main power, cpu power, molex power, SATA power, etc.

ATX connectors

Main connector of ATX power supply unit

  • Orange wire: 3.3V
  • Red wire: 5V
  • Yellow wire: 12V
  • Blue wire: -12V
  • White wire: -5V
  • Purple wire: 5VSB
  • Black wire: ground
  • Green wire: open main power
  • Gray wire: indicates good power on the ATX power supply unit
Main power connectors pins of ATX

Connector of CPU power

  • Supply power for CPU regulation circuit
  • Black wire: ground
  • Yellow wire: 12V
CPU power pins on mainboard

Connector of hard disk drive power

There are 2 types: connector ATA and SATA.

HDD connectors

5. How to check the power supply unit ATX?

To check the power supply unit, we use a metal conductor to connect pin 14 (green) to pin 16 (or any black pin) on the main connector of power supply unit ATX. Then, supply AC power to the power supply unit. If the power supply unit’s cooling fan rotates, the power supply is still working and vice versa.

How to check the power supply unit ATX?
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Posted by Vinh Le

Composer at ITLearningCorner.

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