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Power Supply (PSU – Power Supply Unit)

A Power Supply Unit (PSU) is a hardware component that converts electrical power from a wall outlet into usable energy for a computer.

It provides stable and regulated power to all internal components.

What the PSU does

The PSU:

  • Converts AC (alternating current) from the outlet into DC (direct current)
  • Distributes power to the motherboard, CPU, GPU, storage, and other components
  • Protects the system from electrical issues

Without a PSU, the computer cannot operate.

How it works

  1. Electricity enters the PSU from the wall socket.
  2. The PSU converts AC power into DC power.
  3. Voltage is regulated to safe levels (e.g., 12V, 5V, 3.3V).
  4. Power is delivered through cables to components.

The PSU must provide stable voltage to prevent hardware damage.

Wattage

PSUs are rated by wattage (W), which indicates how much power they can supply. Higher-performance systems (with powerful GPU and CPU) require higher wattage.

Typical ranges:

  • Office PC: 400–500W
  • Gaming PC: 600–850W
  • High-end systems: 1000W+

Choosing the correct wattage is important for stability.

Efficiency Rating (80 PLUS)

PSUs have efficiency certifications such as:

  • 80 PLUS Bronze
  • 80 PLUS Silver
  • 80 PLUS Gold
  • 80 PLUS Platinum

Higher efficiency means:

  • Less energy waste
  • Less heat
  • Less heat

Modular vs Non-Modular

Non-Modular PSU

All cables are permanently attached.

 

Semi-Modular PSU

Some cables are removable.

 

Fully Modular PSU

All cables are detachable.

 

Modular designs improve cable management and airflow.

Why it is important

  • Ensures stable system operation
  • Protects components from power surges
  • Affects system reliability and lifespan
  • Supports hardware upgrades

A low-quality PSU can cause crashes or hardware failure.

A simple example

Think of the PSU as the heart of the computer. It pumps energy to every component, just like the heart pumps blood through the body.

Related terms

  • What is Motherboard?
  • What is CPU?
  • What is GPU?

Source

Information simplified from the Wikipedia article “Power supply unit (computer)”.

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