Typical power supply will need to pass Radiated Immunity test. So you really need to address this problem.

You can basically addressed radiated immunity by

1. Layout - reducing area of switching loops

2. Damp the diode current waveforms or used diodes with low trr. Output diode and primary clamp diode current waveforms should have minimum ringing to addresses radiated problem.

You can refer to the appnote (snubber section and minimizing loop area on this appnote)

http://www.powerint.com/sites/default/files/product-docs/an44.pdf

Good transformer design/construction is a big factor to minimize these parasitics that causes undamped oscillations resulting to poor emi performance. Pls refer to the appnote for some design tips in designing transformer

Rgds

Ok. In our circuit output diode damp circuit is not included we will use the damp circuit across the output diode but across primary clamp circuit we used damp circuit...  

We appreciate your suggestions and help.

regards,

Mohan