Measurement and analysis of voltage transfer ratio (VTR) of package-level WPT considering PDN conditions

In this study, a three dimensional multi-helix inductor design with a size smaller than 10mm×10mm is proposed for package-level wireless power transfer (WPT) using magnetic resonance, and the performance of an inductor-to-inductor voltage transfer ratio (VTR) of 70.1 % is presented. The effect of the power distribution network (PDN) load impedance on the VTR is studied and verified through measurement of the fabricated package-level WPT system. The PDN conditions consist of a power/ground (P/G) plane and various decoupling capacitors with different capacitances (10 nF, 100 nF, and 1 μF). The PDN impedance of the receiver package exhibits resonant frequencies that depend on the stack-up and dimension of the power/ground planes and also the capacitances and the locations of the decoupling capacitors. As the resonance frequency of the WPT system approaches the resonance frequency of the PDN connected to the end of the WPT system as a load, the VTR efficiency rapidly decreases. In addition, the VTR performance of the package-level WPT system can be further improved to a maximum of 18.84 % with the insertion of ferrite sheets.