Discrepancy in designs between PI Expert and PIxl spread sheet

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We designed a 72V/950mA LED driver with LNK420 first with PI Expert and second by PIxl spread sheet. Please see the attached copies. The designs dont tally at all. Please throw light on this and clarify where we are going wrong? Please also confirm which on is correct and why?





You cannot see your designs so I took the liberty of doing one design in PIXls and in PIExpert. As you can see for yourself they seem to match pretty well.


PIXls is not an automatic design tool. Even though it will try to get a mosfet and a transformer for you it will not necessarily be the most optimum design. It requires manual inputs from the user in terms of Kp, VOR, etc. I suggest you use this document as guideline if you are new to the tool and


PIExpert will try to find a full schematic that will work within the transformer library it posesses. To get a design you need only to enter input and ouptut variables.

Dear Mr.Wesley, Thanks for the clarification. The attachments you sent are garbled, May be some software issue so I could not see your sample designs. Please forward the attachments again.

We will add the Customs cores and Bobbins to PI expert library and try out the designs again.Please however clarify the parameter 'BW' in the Core input data. It says 'Bobbin winding width'. Is it the total window space width on the Bobbin?.How do we define this for a round Bobbin for the PQ series cores?  Again the 'Effective winding width' increases in multiplesof the Primary winding layers selected! How is this explained?

As for Bobbins we are able to enter Vertical or Horizontal in the box provided. There are no boxes for other specs of the Bobbin except some'Generic no'. How do we enter the details of the Bobbin we propose to use?