hi!
Actually i do not know what you meant by topology, if it is a method of regulation then i think i will use PWM, but uptill now i didnot reach at that level because even a simple non-regulated circuit is not working properly.
The operating frequency can be any thing between 10khz to 100khz but i don't know optimal frequency value and how it interact with the SMPS principle.
I am very careful in experimenting the circuit but still i got two blown and burned circuits. I will be more careful next time.
Thanks!