SEPIC Shock

[SuzyC]

I am now studying how to design SEPIC convertors and have encountered two conflicting datasheet reference designs that seem to contradict each other regarding the polarity of the switching inductors (transformer).  Which is correct? (They both are, according to the dots!)


Since both inductors are identical and share the same core, a bifilar winding would be the easiest way to construct the transformer and the dots always match up in this case.

[Buk]

Are you being confused by the fact that the polarity of the secondary coil is different in the two diagrams?

In both cases the dotted secondary terminal is grounded.