Planar transformer with integrated shielding against differential to common mode conversion and capacitive currents

A passively driven shielding configuration for a planar transformer for high frequency switched mode applications is presented. The shielding configuration actively counteracts the problematic conversion of differential mode signals to common mode. This leads to very low levels of primary to secondary capacitive coupling, which is normally difficult to avoid in a planar transformer. The shielding configuration is described, analysed and shown to operate effectively in an experimental system.