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A Computer Power Supply Unit (PSU) converts the high-voltage alternating current (AC) from a wall outlet into the lower-voltage direct current (DC) that a computer's components need to operate. It is a critical component located inside the computer case, responsible for supplying stable power to the motherboard, CPU, storage drives, and other internal hardware, and often includes built-in protection features against power surges.

Key Functions

AC to DC Conversion: Converts the high-voltage AC power from the wall into the specific low-voltage DC power required by internal computer components.

Power Distribution: Delivers the correct voltage and current to all connected components, ensuring they receive the precise power they need to function.

Voltage Regulation: Maintains a stable and consistent power output to prevent damage from power fluctuations.

Protection: Incorporates safety features like overvoltage, undervoltage, short-circuit, and overcurrent protection to safeguard hardware from electrical faults.

How It Works

Input: The PSU connects to the wall outlet via a power cord and receives AC power.

Conversion: Inside the PSU, switching power supply technology converts the high-voltage AC to multiple lower-voltage DC rails (typically +3.3V, +5V, and +12V).

Distribution: Cables with various connectors distribute these DC voltages to different components:

Motherboard Connectors: A 24-pin (or 20+4 pin) connector provides primary power to the motherboard.

CPU Power Connectors: 4-pin or 8-pin EPS connectors supply power directly to the CPU. Peripheral Connectors: Connectors for hard drives, SSDs, and GPUs.