SMPS Buck Converter Controller Design and ICs

I am required to build a buck converter which would be able to convert 230V AC to 210V DC with 25mA load current. I am having significant trouble designing the controlling part for the converter.

1. I need to know some widely available and used controller ICs used for feedback control.

2. I also want to know how I can provide Vcc to the controller IC by converting the 230V AC to a voltage close to 5V DC.

3. For comparison purposes I think I would need to convert the 210V output voltage to a lower voltage that a controller IC can manage. I initially thought of using a voltage divider, but am worried that the accuracy of the output voltage would be lowered due to low tolerance values in the resistors.

Can I know what other methods are available for doing this (since it is hard for me to find good quality resistors in my country)?

Any help would be greatly appreciated. I am close to clueless at the moment.

The idea of a buck conv.. is to switch the transistor say 50% on/off this way u will not have the problem of having the series transistor holding across collector emiter about 70v dc and 25mamps .
so first rectify full wave getting about 300 volts to colector and apply 50khz to base the output emmiter needs a coil.
thats the general idea .
u will need ltspice to get all the calculations right.
Here is a example of buck boost supply u will need to adapt all comp to your voltages the hv transistor is added thru opto (not shown )

Hi my friends
You can not use an lm2576 , at this aim , simply . you should use a opto coupler , and a mosfet . you will ask , why ?!!
That IC can not tolerate that voltages . but you can use an opto coupler to give command from lm2576 to that , and thus , you can give the command to a mosfet , and thus you will have a High power buck regulator . and your feed back will be at the end of the filter , at the end of your mosfet.
Best Wishes
Goldsmith