Questions Regarding Transformer Design in AN2794 for Push-Pull Converter

[Nafi-Can]

Hello,

I’m designing a 1 kW converter using a push-pull topology with 24 V input and 400 V output. While doing so, I referred to the transformer design guidelines in your document AN2794. Unfortunately, I believe there are some inconsistencies or errors in a few of the equations. I would appreciate your assistance on the following points:

• The “RMS Input Current” value shown in Table 3 seems to be derived from Equation 9. However, shouldn’t the value be derived from Equations 6 or 8 instead?
• Regarding Equation 32, is it correct to assume that if the calculated Kg value in this equation is greater than the one calculated in Equation 31, then the selected core is suitable for the application? Additionally, I believe the unit in Equation 32 should be cm⁵ instead of cm².
• In Equation 33, does the number of primary turns represent a single winding on the primary side of the push-pull transformer, or the total primary turns? If it refers to a single winding, then the total would be 4 turns (2+2), considering the center-tap.

• Also, in Equation 33, what does T stand for? What is the definition of ΔB? Can you please tell me their values used in calculation of Equation 33.

I would be very grateful to receive answers to these questions. Thank you very much in advance for your support!

Best regards,
Nafi Can

[Peter BENSCH]

Welcome @Nafi-Can, to the community!

The application note AN2794 refers to the discontinued evaluation kit STEVAL-ISV001V1 and can therefore no longer be supported by STMicroelectronics. But perhaps a community member can comment on this?

Regards
/Peter

[Nafi-Can]

Well, I wish someone, like community member, can help but I do not think anyone here will hear my voice.. I am seriously struggling with transformer design in my project. Each solution gives me different results. Therefore, I am not sure which solution, method I should use. When I saw your application note AN2794, I had a little hope, but ..

Thanks.