On Polish and Russian sites i found a few nice schematics .
Both Schema's are welding inverters .
The Polish schema is a fullbridge based on the 3525 .
For this schema you will have to calculate your main transformer though .http://www.ep.com.pl/pobierz.php?id=12162
The Russian schema is a mix of Flyback ,Forward and 2 transistor forward
(Now this is creative use of parts)http://imajr.com/Original.aspx?Id=spawark1100_393678
There are several variations on this one on the web .
Mostly on Russian sites