lnk419 problem on wattage ratings at different input voltage.

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the expected output wattage at 100-230Vac range should be 18W but I am getting 23W at 100Vac and 33W at 220Vac. I am using the design example der298 application, where I attached here.

Please,help me with this problem.I am using the same PCB size and layout as the application suggested.

Thanks in advance..

Please attach your schematic and inductor designs.

What is your output voltage ?

thanks for your reply.

this is the same as the DER298 design sample of LNK419.

using the same values on components I am getting 24Watts on 110vac and 31Watts on 220Vac.

according to the documents I should get 18Watts on both 110 and 220Vac.

what might be the problem? 

If there is switching noise on the feedback pin or reference pin, the output current might not be well regulated.

It might be better to copy the DER298 layout, and the gerber file of DER298 is available in the PI website.

what would be the solution for regulation issue. I had been try to make the capacitors value more on the line before the LNK419 but still I get large difference of wattage at minimum and maximum AC input .

Please help me......I need to send this project to mass production as soon as possible.