Power supply

 POWER SUPPLY

What is a Power Supply?

The Power Supply Unit (PSU) is the component responsible for converting alternating current (AC) from the electrical outlet (110V or 220V) into direct current (DC) that the computer’s internal components need to operate.

Without it, no component (motherboard, CPU, GPU, drives, etc.) can function.

Main Functions

1. Power conversion:

   • Converts AC (alternating current) → DC (direct current).

   • Typically provides +12V, +5V, +3.3V (and sometimes −12V and +5VSB).

2. Voltage distribution:
   Delivers power through different voltage rails to the motherboard, CPU, GPU, storage devices, and peripherals.

3. Electrical protection:
   Includes built-in protection systems such as:

   • OCP (Over Current Protection)

   • OVP (Over Voltage Protection)

   • UVP (Under Voltage Protection)

   • OTP (Over Temperature Protection)

   • SCP (Short Circuit Protection)

Internal Components

A PSU contains several electronic modules:

1. EMI Filter: Removes electrical interference at the input and output.

2. Rectifier and PFC (Power Factor Correction): Improve electrical efficiency and stabilize input current.

3. Transformer: Converts high-voltage AC into lower-level DC.

4. Secondary Rectifiers: Convert the transformed signal into clean DC.

5. Regulators and Filters: Smooth out voltage to maintain stability.

6. Fan and Thermal Sensors: Regulate internal temperature.

Types of Power Supplies

1. ATX (current desktop standard)

• The most common physical format.

• Versions: ATX 2.3, 2.4, 3.0, and the newer ATX 3.1, which supports 12VHPWR connectors for modern GPUs.

2. SFX / SFX-L

• Smaller units used in compact PCs (Small Form Factor).

3. Flex-ATX, TFX, etc.

• Designed for specific case formats or server environments.

Energy Efficiency (80 PLUS Certification)

PSUs are rated by 80 PLUS efficiency certifications, indicating how efficiently they convert power:

Certification	Approx. Efficiency
80 PLUS White	80%
80 PLUS Bronze	82–85%
80 PLUS Silver	85–88%
80 PLUS Gold	87–90%
80 PLUS Platinum	90–92%
80 PLUS Titanium	92–94%

Power Output (Wattage)

The wattage determines how much power the PSU can deliver.

• Basic PCs: 400–550 W

• Mid-range gaming: 600–750 W

• High-end gaming / workstations: 850–1200 W

• Servers or multi-GPU setups: >1200 W

The most important factor is not just total wattage, but the quality and stability of the 12V rail, which powers the CPU and GPU.