So i find this circuit (flyback power supply 24 V 1 A) which use the ic top255yn from top-switch HX and the transformer MYRRA 74030 so i would to change it with the ic top245yn from top-switch GX,i know for that i need to change R3,R4 and R5 (R6 and R7 i know how to change them) so how i can calculate the values of R3,R4 and R5 to get the same features (Vout,Iout,Pmax).
either read the datasheet , do ctrl F search, or do a design in PI Expert from Power integrations.
If you post the datasheet link i will help you search.
thank you verry much for your replay ,i know how to use PI Expert from Power integrations but this version dont supprt topswitch gx it supports only HX and Jx
there are the links of topswitch gx and topswitch hx
Suggest you upgrade the bridge rectifiers to 1N4007. With 265V AC at the input they only have 50V PIV rating overhead and could easily be damaged by relatively small transients on the AC.