# US 2009/0276014 A1 · External power source, system and method for predicting heat loss of implantable medical device during inductive recharging by external primary coil > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0276014 A1 - Document ID: US20090276014A1 - Status: Published application - Kind: A1 - Application number: 12/112,394 - Filed: 2008-04-30 - Published: 2009-11-05 - Earliest claimed: 2008-04-30 - Assignees: Medtronic, Inc. - Inventors: Boysie R. Morgan; David P. Olson; Andrew L. Schmeling - Web page: https://patentgrep.com/patent/US20090276014A1 ## CPC - A61N 1/3787: {from an external energy source} - A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B) ## Abstract External power source, system for controlling and method for predicting heat loss of implantable medical device during inductive recharging by an external primary coil. A primary coil inductively couples energy to a secondary coil when energized and placed in proximity of the secondary coil. Control circuitry, operatively coupled to said primary coil, determines the energy absorbed in said tissue based on a total applied power by said external power source, power lost in said electronic circuitry, power lost in said electronic circuitry, power lost in said primary coil and power applied to said rechargeable power source and controlling said total applied power based upon said energy absorbed in said tissue. ## Claims ### Claim 1 An external power source for an implantable medical device having a secondary coil operatively coupled to a rechargeable power source, said implantable medical device being implanted in a patient having tissue, comprising: a primary coil inductively coupling energy to said secondary coil when energized and placed in proximity of said secondary coil; electronic circuitry driving said primary coil; and control circuitry, operatively coupled to said primary coil, determining energy absorbed in said tissue based on a total applied power by said external power source, power lost in said electronic circuitry, power lost in said primary coil and power applied to said rechargeable power source and controlling said total applied power based upon said energy absorbed in said tissue. ### Claim 2 An external power source for inductively charging of an implantable medical device in a patient, said implantable medical device having a rechargeable power source having a voltage and a secondary coil operatively coupled to said rechargeable power source, comprising: a primary coil; electronic circuitry driving said primary coil; and control circuitry, operatively coupled to said electronic circuitry, controlling energy absorbed in said patient during inductive charging of said rechargeable power source by: determining a total applied power by said external power source by measuring current applied by said external power source during said charging and an applied voltage of said external power source; determining power lost in said electronic circuitry; determining power lost in said primary coil by determining current in said primary coil during said recharging in view of a resistance of said primary coil; determining power applied to said rechargeable power source by measuring said voltage of said rechargeable power and current applied to said rechargeable power source during said inductive charging; calculating said energy absorbed in said body by subtracting said power lost in said electronic circuitry, said power lost in said primary coil and said power applied to said rechargeable power source from said total applied power; and adjusting said total applied power by said external power source as a function of said energy absorbed in said patient. ### Claim 3 (depends on 2) The external power source as in claim 2: wherein said power lost in said primary coil is calculated by multiplying a square of said current in said primary coil during said charging by said resistance of said primary coil; wherein said external power source supplies power, having a current and a voltage, to said electronic circuitry, wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said voltage supplied by said external power source; and wherein said power applied to said rechargeable power source is calculated by multiplying said current applied to said rechargeable power source during said charging by said voltage of said rechargeable power source. ### Claim 4 (depends on 3) The external power source as in claim 3 wherein said voltage supplied by said external power source comprises an RMS voltage, wherein said RMS voltage supplied by said external power source and said current supplied by said external power source have a phase difference and wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said RMS voltage supplied by said external power source and further multiplying by a power factor representative of said phase difference. ### Claim 5 (depends on 3) The external power source as in claim 3 wherein said power lost in said electronic circuitry is determined empirically. ### Claim 6 (depends on 5) The external power source as in claim 5 wherein said power lost in said electronic circuitry is approximately fifteen percent (15%) of said total applied power. ### Claim 7 A system for controlling energy absorbed in a patient during inductive charging, comprising; an implantable medical device, comprising; therapeutic componentry delivering a therapeutic output to said patient; a rechargeable power source operatively coupled to said therapeutic componentry; and a secondary coil operatively coupled to said rechargeable power source; and an external power source, comprising: a primary coil; electronic circuitry driving said primary coil; and control circuitry, operatively coupled to said electronic circuitry, controlling energy absorbed in said patient during inductive charging of said rechargeable power source by: determining a total applied power by said external power source by measuring current applied by said external power source during said charging and an applied voltage of said external power source; determining power lost in said electronic circuitry; determining power lost in said primary coil by determining current in said primary coil during said recharging in view of a resistance of said primary coil; determining power applied to said rechargeable power source by measuring said voltage of said rechargeable power source and current applied to said rechargeable power source during said inductive charging; calculating said energy absorbed in said body by subtracting said power lost in said electronic circuitry, said power lost in said primary coil and said power applied to said rechargeable power source from said total applied power; and adjusting said total applied power by said external power source as a function of said energy absorbed in said patient. ### Claim 8 (depends on 7) The system as in claim 7: wherein said power lost in primary coil is calculated by multiplying a square of said current in said primary coil during said charging by said resistance of said primary coil; wherein said external power source supplies power, having a current and a voltage, to said electronic circuitry, wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said voltage supplied by said external power source; and wherein said power applied to said rechargeable power source is calculated by multiplying said current applied to said rechargeable power source during said charging by said voltage of said rechargeable power source. ### Claim 9 (depends on 8) The system as in claim 8 wherein said voltage supplied by said external power source comprises an RMS voltage, wherein said RMS voltage supplied by said external power source and said current supplied by said external power source have a phase difference and wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said RMS voltage supplied by said external power source and further multiplying by a power factor representative of said phase difference. ### Claim 10 (depends on 7) The system as in claim 7 wherein said power lost in said electronic circuitry is determined empirically. ### Claim 11 (depends on 7) The system as in claim 7 wherein said power lost in said electronic circuitry is approximately fifteen percent (15%) of said total applied power. ### Claim 12 A method of determining energy absorbed in a body during inductive charging of an implantable medical device having a rechargeable power source having a voltage and a secondary coil operatively coupled to said rechargeable power source by an external power source having electronic circuitry driving a primary coil, comprising the steps of: determining a total applied power by said external power source by measuring current applied by said external power source during said charging and an applied voltage of said external power source; determining power lost in said electronic circuitry; determining power lost in said primary coil by determining current in said primary coil during said recharging in view of a resistance of said primary coil; determining power applied to said rechargeable power source by measuring said voltage of said rechargeable power source and current applied to said rechargeable power source during said inductive charging; and calculating said energy absorbed in said body by subtracting said power lost in said electronic circuitry, said power lost in said primary coil and said power applied to said rechargeable power source from said total applied power. ### Claim 13 (depends on 12) The method as in claim 12: wherein said determining power lost in said primary coil step comprises calculating said power lost in primary coil by multiplying a square of said current in said primary coil during said charging by said resistance of said primary coil; wherein said external power source supplies power, having a current and a voltage, to said electronic circuitry, wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said voltage supplied by said external power source; and wherein said determining said power applied to said rechargeable power source comprises calculating said power applied to said rechargeable power source by multiplying said current applied to said rechargeable power source during said charging by said voltage of said rechargeable power source. ### Claim 14 (depends on 13) The method as in claim 13 wherein said voltage supplied by said external power source comprises an RMS voltage, wherein said RMS voltage supplied by said external power source and said current supplied by said external power source have a phase difference and wherein said determining said total applied power comprises calculating said total applied power by multiplying said current supplied by said external power source during said charging by said RMS voltage supplied by said external power source and further multiplying by a power factor representative of said phase difference. ### Claim 15 (depends on 12) The method as in claim 12 wherein said power lost in said electronic circuitry is determined empirically. ### Claim 16 (depends on 12) The method as in claim 12 wherein said power lost in said electronic circuitry is approximately fifteen percent (15%) of said total applied power. ### Claim 17 A method for adjusting an amount of energy dissipated in a patient during inductive charging of an implantable medical device having a rechargeable power source having a voltage and a secondary coil operatively coupled to said rechargeable power source by an external power source having electronic circuitry driving a primary coil, comprising the steps of: determining a total applied power by said external power source by measuring current applied by said external power source during said charging and an applied voltage of said external power source; determining power lost in said electronic circuitry; determining power lost in said primary coil by determining current in said primary coil during said recharging in view of a resistance of said primary coil; determining power applied to said rechargeable power source by measuring said voltage of said rechargeable power and current applied to said rechargeable power source during said inductive charging; calculating said energy absorbed in said patient by subtracting said power lost in said electronic circuitry, said power lost in said primary coil and said power applied to said rechargeable power source from said total applied power; and adjusting said total applied power by said external power source as a function of said energy absorbed in said patient. ### Claim 18 (depends on 17) The method as in claim 17: wherein said power lost in said primary coil is calculated by multiplying a square of said current in said primary coil during said charging by said resistance of said primary coil; wherein said external power source supplies power, having a current and a voltage, to said electronic circuitry, wherein said total applied power is calculated by multiplying said current supplied by said external power source during said charging by said voltage supplied by said external power source; and wherein said power applied to said rechargeable power source is calculated by multiplying said current applied to said rechargeable power source during said charging by said voltage of said rechargeable power source. ### Claim 19 (depends on 18) The method as in claim 18 wherein said voltage supplied by said external power source comprises an RMS voltage, wherein said RMS voltage supplied by said external power source and said current supplied by said external power source have a phase difference and wherein said determining said total applied power comprises calculating said total applied power by multiplying said current supplied by said external power source during said charging by said RMS voltage supplied by said external power source and further multiplying by a power factor representative of said phase difference. ### Claim 20 (depends on 17) The method as in claim 17 wherein said power lost in said electronic circuitry is determined empirically. ### Claim 21 (depends on 17) The method as in claim 17 wherein said power lost in said electronic circuitry is approximately fifteen percent (15%) of said total applied power.