Today almost every electronic device needs a dc supply for its smooth operation and they need to be operated within certain power supply limits. This required dc voltage or dc supply is derived from single phase ac mains. A DC regulated power supply can convert unregulated an ac (alternating current or voltage) to a constant dc (direct current or voltage). A DC regulated power supply is used to ensure that the output remains constant even if the input changes. A regulated DC power supply is also called as a linear power supply, it is an embedded circuit and consists of various blocks. The regulated power supply will accept an ac input and give a constant dc output. Figure below shows the block diagram of a typical regulated dc power supply.