Elements of a Power Supply:

When dealing with electronic circuits, we have to meet the basic requirement of providing electrical power for them to work. The basic purpose of a power supply is to provide one or more fixed voltages to the working circuit, with sufficient current-handling capacity to maintain the operating conditions of the circuit. The power source doesn't have to be fancy; the typical hand-held transistor radio uses a 9-volt battery as its power source. A flashlight uses cells that are physically much larger, but provide a lower voltage. Major electronic appliances such as television sets, VCRs, and microwave ovens have electronic circuits built in that take power from a wall socket and convert it to the form and voltages required by the other internal circuits of the appliance.
A basic power supply consists of four main sections, as shown in the block diagram below. Depending on the requirements for a given power supply, the sections can be very simple or extremely complex, or even left out altogether in certain circumstances. Each of the sections serves one or more specific purposes, one or more specific purposes, as follows:
DC
OUTPUT->RECTIFIER->REGULATOR->TRANSFORMER->AC INPUT -> FILTER