Power Supply Unit (PSU) is an essential component in electronic devices, especially computers. Its primary function is to convert electricity from a wall outlet (typically AC or alternating current) into a form that can be used by the device's internal components, usually DC (direct current).

PSUs come in various sizes and power ratings, depending on the needs of the device. For example, in a desktop computer, the PSU provides the necessary power for the motherboard, CPU, hard drives, graphics cards, and other peripherals. It ensures that the correct voltage and current are supplied to each component while maintaining system stability.

In addition to power conversion, PSUs are equipped with safety features like surge protection, short-circuit protection, and overvoltage protection, which help safeguard both the PSU and the device it powers. PSUs also play a role in energy efficiency, with modern units featuring ratings like 80 Plus (certification indicating high efficiency), which means they convert a higher percentage of power into usable energy rather than wasting it as heat.