I made the stabilised power unit which used the switching regulator.
AC100 V is used for the input of the power unit. The output voltage can be changed from 5 V to 30 V. The output current can pour a maximum of 4 A. I made this power unit as the power unit of the electronic circuits making for the experiment.
I am posting the making example of the switching regulator in "Electronic Circuit Beans Collection". The one who want to know more about the switching regulator, please refer to it.