Analysis of the Coupling Effect in Different Meander-Type Winding Planar Transformers

In this paper, planar printed-circuit board (PCB) transformers with different winding arrangements are presented. Three different arrangements of the primary and the secondary meander-type windings are designed and fabricated. The electrical parameters of the transformers for all three designs are analyzed and compared. A significant increase of inductance of the primary and the secondary winding is achieved with an appropriate meander-type winding arrangement. In the frequency range of interest, the inductance is approximately 145 nH for the first design, whereas the inductance is approximately 1250 nH for the second and the third design. The coupling coefficient is 0.14 for the first design, whereas it is around 0.9 for the second and the third design. The transformer of the proposed design is to be used in low-power DC/DC converters; therefore, the core with high permeability Ferroxcube 3C90 was chosen. In addition, the transformers of the same winding arrangements were tested with Ferroxcube 3F3 core.