Solve problem 15.3 of book Fundamentals of Power Electronics - Robert W. Erickson.Flyback/SEPIC transformer design. The "transformer" of the flyback and SEPIC converters is an energy storage device, which might be more accurately described as a multiple-winding inductor. The magnetizing inductance functions as an energy-transferring inductor of the converter, and therefore the "transformer" normally contains an air gap. The converter may be designed to operate in either the continuous or discontinuous conduction mode. Core loss may be significant. It is also important to ensure that the peak current in the magnetizing inductance does not cause saturation.