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LM5155: Quickstart Calculator for Flyback, Efficiency

Christian Riesch
Intellectual 710 points
Part Number: LM5155

Hi,

I calculated a Flyback with the LM5155 Flyback Controller Quick Start Calculator. The efficiency results are shown below:

At Pout=2W the diode losses are 0.15W, MOSFET and RS losses are very small, maybe 0.01W each. With total losses of 0.17W, I would expect an efficiency of 2W / (2W + 0.17W) = 92%. However, the diagram shows around 88% for Pout=2W. What additional power losses are used in the calculation here? Thank you!

Christian

  • 0
    TI__Genius 11215 points

    Hello Christian, 

    Thanks for reaching out. I cannot unlock this document, but in general, additional source of losses in a flyback converter are for example the transformer and the ESR of the caps. 

    Kind regards,

    Elisabetta