Patent ID: 7496404

Claim:
A spinal cord stimulation system comprising: an implantable pulse generator (IPG) including at least one integrated circuit (IC) that when powered allows the IPG to generate electrical stimuli, the IPG having a housing; a replenishable power source contained within the IPG housing; an implantable electrode array detachably connected to the IPG, the electrode array having at least two electrodes thereon; wherein the electrical stimuli generated by the IPG are selectively delivered to at least one of the electrodes on the electrode array as controlled, at least in part, by electrical circuitry contained within the IC; an implantable secondary coil coupled electrically to the replenishable power source; an external power source charger including: a primary coil; an external power source contained in the charger, electrically coupled to the primary coil; and a power amplifier that applies alternating current derived from the external power source to the primary coil, whereby the alternating current in the primary coil induces a magnetic field that is transcutaneously coupled to the implantable secondary coil, thereby inducing a corresponding alternating current in the secondary coil, which alternating current in the secondary coil initiates a power-up sequence for a powered-down IPG and recharges the replenishable power source contained in the IPG; a power source replenishing system housed within the IPG, including: a rectifier circuit that converts the alternating current induced in the secondary coil to a dc current that is applied to the replenishable power source; power source protection circuitry for controlling electrical connection and disconnection between the replenishable power source and the at least one IC included within the IPG; whereby the power source protection circuitry allows connection between the replenishable power source and the at least one IC upon transcutaneous transfer of power from the external power source to the replenishable power source; alignment circuitry for detecting alignment between the primary and secondary coils, the alignment circuitry including a back telemetry receiver for monitoring the magnitude of an ac voltage at the primary coil as applied by the power amplifier, wherein reflected impedance associated with energy magnetically coupled through the primary coil is monitored; and an alarm generator that generates an audible alarm signal in response to a sensed change in the reflected impedance monitored by the back telemetry receiver.