Winding Loss Analysis of PCB Winding Litz Wire

The concept of PCB Litz wire is proposed to mitigate the eddy loss of a PCB winding. PCB Litz wire emulates Litz wire by twisting copper traces on a PCB. However, to build a circular PCB Litz winding around a core, the pattern of a trace can be crucial to eddy loss. In this paper, some simple types of trace, which are track-shifting line, straight line and equidistant spiral, are evaluated. Then based on the geometry of the winding, some improved trace types are proposed for higher footprint usage. Windings with all the types of trace are implemented in finite element analysis (FEA) simulation. The result shows that dense spiral (DS) and filled equidistant spiral (FES) are the best trace types with lowest eddy loss. IES is better at lower frequency (< 250 kHz), while DS is better at higher frequency (250-400 kHz). At 200 kHz with the same footprint, PCB Litz wire windings with the 2 improved trace functions have a 15.1% lower winding loss compared to solid PCB winding.