Various diagram

In recent years, the use of switch mode power supply (SMPS) has become more comon as more applications demand for greater power eficiency. It makes use of semiconductor (mostly MOSFET) fast switches to switch DC input that has been rectified at high frequency. The advantages of high frequency switching are that it reduces the size of inductor, capacitors & transformer used. Other advantages of switching power supply over linear power supply are :

1) High Efficiency (up to 90% and above for nice design).

2) Output can be higher than input.
3) Able to operate over a variety of input power supply.
4) Able to have over output.

The setback of using SMPS compared to linear power supply is that it generates electrical noise which contributes to electromagnetic compatibility design issues & more part count.

Buck Converter SMPS

The SMPS schema below from Power Integration makes use of LNK304 as its high frequency switch. Take note that this schema is non isolated type which means that the output is not electrically isolated from the input & all testing ought to be completed using an isolation transformer to provide the AC line input to the board.

Make positive that you have electrical safety knowledge & experience before you embark on doing this project.