A power supply, also known as a power supply unit or PSU, is a device that generally converts the alternating current (AC) into low-voltage regulated direct current (DC) power (AC/DC), or converts the direct current (DC) into low-voltage regulated direct current (DC) power (DC/DC) to ensure the electronic components can work properly. Each internal component of an electronic device needs a particular voltage; hence, the PSU can usually provide more than one DC voltage at the same time.