Output characteristics modeling and experimental verification of secondary-uncompensated inductive power delivery link operating without feedback

Series-none compensated induction wireless power delivery link (SN-IPDL) was recently shown to be capable of achieving minimal complexity receiver with reduced losses in case of strong coupling, typical for applications such as power delivery into enclosed compartments such as industrial glove boxes and close-range inductive heating. Common practical applications often feature power delivery to varying loads which require a stable operational voltage. Operation at LIVO frequency allows establishing potentially feedback-free wireless power delivery with constant output voltage for varying loads. The paper reveals that due to nonzero equivalent series resistances and invalidity of the first-harmonic-approximation (FHA) based equivalent circuit, the output voltage remains affected by the load despite operation at LIVO frequency, residing within a certain range of values, lower and upper bounds of which correspond to rated and zero loading, respectively. This must be considered during SN-IPDL system design in order to assure that output voltage stays within allowed bounds for relevant loading conditions. This paper derives analytical expressions for output voltage bounds of a power-loaded series-to SN-IPDL, functioning at load-independent-voltage-output (LIVO) frequency. Time domain differential equations (DE)-based analysis is applied to derive the two bounds and allows (as a by-product) establishing an alternative FHA-based equivalent circuit of SN-IPDL operating in continuous conduction mode. Simulations and experiments based on 380V, 1.2 kW-rated prototype demonstrate excellent matching with analytical outcomes, validating the proposed analysis.