hi.
a flyback converter design for multiple output(5) +ve & -ve 5v and 12v, -180v.  having input voltage 40V, 700mA..
could u please help me out whether start with design of transformer or any other approach.

The biggest problem that I have faced when there are a large number of outputs is finding a bobbin with enough pins. Tight coupling of the windings is important especially for the low voltages. Winding capacitance is more of an issue for the high voltage winding. I believe the Unitrode (TI) seminar books have good guidance on flyback transformer design.

Hi Sangamesh,
Number of good literature & documents are available in websites. Even step by step design for flyback based transformer SMPS is also available.
You can also search good help from industry websites like fairchild for their FPS ( fairchild power switch), TOP switch etc. Online software simulation model is also available for quick design of converter.

hi raja saha

thank you for the valuable information.