Patent ID: 11896838
Assignee: MEDTRONIC, INC.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC A  H | IPC A  H

Claim 17:
18. A system comprising:
an implantable neurostimulator device comprising a housing containing a rechargeable power source; and
an external charging device comprising:
a primary coil configured to provide recharge power to the rechargeable power source of the implantable neurostimulator device through transcutaneous charging;
a ferrite material adjacent to the primary coil and spanning an aperture defined by the primary coil; and
processing circuitry configured to:
determine a power being delivered to the primary coil of the external charging device for recharging the implantable neurostimulator device;
determine an estimated power delivered stored by the rechargeable power source during charging of the implantable neurostimulator device;
calculate an estimated heat generated by the primary coil based on a resistance of the primary coil, wherein the resistance of the primary coil is determined as a function of at least one of a recharge frequency, a temperature of the primary coil, and a current supplied to the primary coil, the resistance of the primary coil determined as a variable to account for the presence of the ferrite material in the external charging device;
calculate an estimated heat generated by the implantable neurostimulator device by subtracting the estimated heat generated by the primary coil and the estimated power delivered stored by the rechargeable power source from the power being delivered to the primary coil; and
control, based on the heat generated by the implantable neurostimulator device, the power being delivered by the primary coil of the external charging device,
wherein the estimated heat generated by the primary coil is determined at least in part by empirically derived values for a given recharge frequency based on a regression analysis fitting a curve to a measured coil resistance for the primary coil as a function of frequency for a given temperature of the primary coil.