Functions of each block:
1) Transformer: It Converts an AC input source to AC required output without changing frequency. The transformer is step up or step down transformer.
2) Rectifier: It is a circuit which is used to convert AC into pulsating DC. A rectifying diode is used.
3) Filter: It is a circuit used to convert pulsating DC into pure DC. A inductor and capacitors are used as filter
4) Voltage regulator: An unregulated DC voltage is converted into regulated DC voltage. IC 78XX & 79XX series are used as regulator.