US 12609234 B2 / Apr 21, 2026

Planar transformer

A planar transformer including first and second parts of a core with least one of the first and second parts having a center post that resides in an aperture of a PWB. The PWB includes primary windings and secondary windings that surround the center post, are magnetically coupled by the core, and are electrically independent. Separating an uppermost winding from the first part of the core is a first prepreg structure and separating a lowermost winding from the second part of the core is a second prepreg structure. There being no windings disposed between the first and second prepreg structures and the core. This planar transformer structure inhibits the windings from electrically shorting through the core when the planar transformer is subjected to shock or vibration. One variant includes the use of pre-form adhesives sheets located between the solder mask layers of the PWB and the core that further inhibit the windings from shorting through the core.