The AC/DC power supply converts an alternating current power input into a direct current output. It is a necessary component of the modern automation system such as PLC, sensor, network devices to name a few. This chapter discusses fundamental topics including the idea of a power supply, characteristics and functions of AC and DC power supplies, and the construction and operation of AC/DC power sources. A power supply is a device or circuit that translates electricity from the mains or different sources. What is a Power Supply? A power supply is an electrical device that converts the electric current that comes in from a power source, such as the power mains, to the voltage and current values necessary for powering a load, such as a motor or electronic device. AC/DC. , and reliability of power converters.