A Compact Planar Transformer With an Improved Winding Configuration

A compact planar transformer with an improved winding configuration has been designed and fabricated. Meander-type design was engraved over the surface of a planar ferrite core, so that the primary and secondary windings can fit into the engraved design. The planar core, with the primary and secondary windings fit into it, was covered with another ferrite core, thus forming a compact planar transformer. Apical type AV polyimide film of 0.025 mm thickness is used between the windings to prevent short circuit. A coupling coefficient of >0.93 was achieved, while the primary and secondary inductance was ~1600 nH. A coupling coefficient for air core transformer with the windings of identical geometry was >0.35 and the inductance of the windings near 160 nH. Fabricated transformer prototype has significantly higher coupling coefficient and inductance of the windings in comparison with the previously developed planar transformer of the similar design.