Patent ID: 8332040

Claim:
A stimulation system, comprising: (i) an implantable pulse generator (IPG) that comprises: a first rechargeable battery for powering the IPG; pulse generating circuitry; a first coil for receiving RF power; a rectifier coupled to the coil; and first control circuitry for controlling RF power conversion, wherein the first control circuitry prevents the coil from absorbing RF power for conversion by the rectifier when a power conversion voltage exceeds a predefined level; and (ii) an external charging device for recharging the IPG, comprising: a second rechargeable battery for powering the external charging device; a second coil for radiating RF power; drive circuitry for driving the second coil according to a duty cycle; circuitry for generating a signal that is indicative of an amount of current flowing through the second coil; and second control circuitry for controlling the drive circuitry, wherein the second control circuitry is operable to process the signal from the circuitry for generating to detect when the first coil temporarily ceases absorbing RF power, the second control circuitry modifying the duty cycle in response to detection of the first coil temporarily ceasing absorbing RF power.