Frequency-Dependent Resistance of Planar Coils in Printed Circuit Board With Litz Structure

Printed circuit board (PCB) windings are convenient for many applications given their ease of manufacture, high repeatability, and low profile. In many cases, the use of multistranded litz wires is appropriate due to the rated power, frequency range, and efficiency constraints. This paper proposes a manufacturing technique and a semianalytical loss model for PCB windings using planar litz structure to obtain a similar ac loss reduction to that of conventional windings of round wires with litz structure. Different coil prototypes have been tested in several configurations to validate the proposal.