Power Supply Unit (PSU)

A Power Supply Unit (PSU) converts AC (alternating current) from the wall outlet into regulated DC (direct current) voltages required by computer components. It distributes power to the motherboard, CPU, GPU, drives, fans, and peripherals. The power supply unit (PSU) evolved with early electronic computers in the 1950s, standardized later with IBM PCs.

Key Functions

• Voltage Conversion: Converts 110V/220V AC to multiple DC rails (typically +12V, +5V, +3.3V).
• Power Distribution: Supplies power to CPU (EPS), GPU (PCIe), motherboard (ATX), and drives (SATA/Molex).
• Regulation & Protection: Includes over-voltage, under-voltage, over-current, short-circuit, and thermal protection.
• Efficiency Management: Reduces energy loss and heat via high-efficiency circuitry.

PSU Connectors

PSU Form Factors

Wattage & Efficiency

• Wattage Rating: Total power output (e.g., 550W, 750W, 1000W+); must match system needs.
• Efficiency Certification:
  • 80 PLUS ratings: Standard → Bronze → Silver → Gold → Platinum → Titanium
  • Higher ratings = less power wasted as heat

Choosing a PSU — What to Consider

• System Power Needs: Add up CPU, GPU, drives, fans, and headroom (~20–30% extra).
• Efficiency: Choose 80 PLUS Gold or better for lower heat and electricity cost.
• Modularity:
  • Non-modular: All cables fixed
  • Semi-modular: Some removable cables
  • Fully modular: All cables detachable — better for cable management
• ATX Version: ATX 3.0 supports PCIe Gen5 and 12VHPWR for modern GPUs.
• Brand & Reliability: Look for trusted brands (e.g., Seasonic, Corsair, EVGA, Super Flower).

PSU Trends (2025 and beyond)

• ATX 3.0 standard: Supports transient GPU loads and 12VHPWR connectors.
• Digital PSUs: Real-time monitoring via software (voltage, temperature, fan speed).
• Eco-friendly designs: Lower standby power, recyclable materials.
• AI-powered power management: Emerging in server and workstation platforms.