there are two major designes .
1)chopper transformer based
2)transformer based.
chopper transformer based invertor is low losses designe as compare to transformer designe .
but transformer based designe is simple for beginners.
sg3525, sg3524 and tl494 are famous ic which have internal oscillator and pwm controll circuites.
tl494 is only famous for chopper designe but sg3525 is for booth designes but sg3524 is only suitable
for transformer designe.
sg3525 is recomended for you.
first you shuld decide about option 1 or 2.