Transformer:- AC input voltage is applied to step down transformer which reduces amplitude of ac voltage to required level .
Rectifier: Reduced ac voltage is applied to rectified which converts it into pulsating dc voltage.usually bridge wave rectifier is mostly used.
Filter: Pulsating dc voltage is applied to filter which eliminates ac ripples from signal and convert it into pure dc.
Types of fiter:- C fiter,L filter,LC Filter,CLC Filter.
Regulator: The combination transformer ,rectifier and filter makes unregulated power supply.which gives unregulated power supply to convert it into regulated an regulating element is used which keeps output voltage constant.