PIExpert V7.1 doesn't work well

You cannot change the converter topology or device family of an existing design. The design equations, options and GUI maybe different for different families and topologies. You can only change the package type, current limit programming, optimization routine (cost or efficiency) and switching frequency (if applicable) through the options dialog
You will have to create a new design for designing with different topology or family.

tks for your reply.
In my project,I need a full range input, full bridge rectifier and VO=15v/200mA,non-isolation,I choose LNK305P ,Is this OK?

aaron mu

Either LNK305 or LNK306 will work. I would recommend that you use the LK306 and keep the design Mostly discontinuos. With LNK305 your design will be mostly continuous and so you will need a faster freewheeling diode. (like the spreadsheet will recommend)