Control Circuit of Buck Converter ???

Look at National Semiconductors website...they have loads of good SMPS stuff including the 'simple switcher' series with software that does a lot of the design for you.

A word of warning, this sort of thing is not ideal for amateurs... because of the tricky wound components, and they can easilly go bang!

Del

There are lots of IC for you use to the goal, such as

3524, 494 etc very classical IC. hundreds of new IC come to market for selection. such as from Ti,Linear,NT,MT, Irt etc, countless.

But if you hope to design a good control parameter, seems not too easy.

if you like tell me how much math knowledge do yuou hve? I may give you relative suggestion to your knowledge.

voltage loop, current loop and double loop have different method. and trasnformer design. brtw, can you make up a transformer?

mean high frequency transformer

Have a look at the power control section of texas instruments (ti.com) or linear technologies (linear.com). They have excellent documentations about basics and full circuits as much as you cant read in a month.
Good luck, regards Uwe