SG3525 technology

[HJeon.2]

hi i use your product SG3525 for Solar inverter (input-dc 12v , out put -110v ac 60hz​

could you recommend me how to use transformer for step up tr(T1)

how to calculate core size, coil thickness and turns for primary, and secondary

also i hope to know inductance value

i make 250w solar inverter but i didnt get enough efficiency (above 90%)

i got only 89% efficiency of them , i attached our drawing for reference(refer to page 2)

i hope to get your information and recommend value

thanks my phine no [phone]