Spinal cord stimulator system
A wireless charger for automatically tuning an optimum frequency to inductively charge a rechargeable battery of an implantable pulse generator (IPG) that generates spinal cord stimulation signals for a human body is provided. The charging coil in the charger is wirelessly coupled to a receiving coil of the IPG to charge the rechargeable battery. An optimization circuit detects a reflected impedance of the charging coil through a reflected impedance sensor, and select an optimum frequency of a charging signal supplied to the charging coil based on the detected reflected impedances of a plurality of charging frequencies in a selected frequency range. Advantageously, the optimum charging frequency provides a more efficient way to charge the IPG's rechargeable battery.
1. A wireless charger for automatically tuning an optimum frequency to inductively charge a rechargeable battery of an implantable pulse generator (IPG) that generates spinal cord stimulation signals for a human body, the wireless charger comprising:
a processor;
a charging coil adapted to be wirelessly coupled to a receiving coil of the IPG to charge the rechargeable battery, the charging coil receiving a signal under a direction of the processor;
a reflected impedance sensor coupled to the charging coil to detect a reflected impedance of the charging coil;
an alignment circuit coupled to the reflected impedance sensor to detect a proper alignment of the charging coil and the receiving coil; and
an optimization circuit coupled to the reflected impedance sensor and adapted to select an optimum frequency of a charging signal supplied to the charging coil based on detected reflected impedances of a plurality of charging frequencies in a selected frequency range.
2. The wireless charger of claim 1 , wherein the optimization circuit includes the processor which is programmed to receive the detected reflected impedances of the plurality of charging frequencies.
3. The wireless charger of claim 1 , wherein the optimization circuit periodically repeats a selection of the optimum frequency at a selected time interval.
4. The wireless charger of claim 1 , wherein the optimization circuit sweeps the plurality of charging frequencies in the selected frequency range from one end to another end at a selected interval to obtain the detected reflected impedances.
5. The wireless charger of claim 1 , wherein the optimization circuit selects, as the optimum frequency, a charging frequency of the plurality of charging frequencies that results in the detected reflected impedance representing a highest peak-to-peak voltage of the charging coil.
6. The wireless charger of claim 1 , wherein the reflected impedance sensor includes a current sensor coupled in series with the charging coil.
7. The wireless charger of claim 1 , wherein the reflected impedance sensor includes a transformer having a primary winding coil coupled in series with the charging coil and a secondary coil coupled to the primary coil.
8. The wireless charger of claim 1 , wherein the reflected impedance sensor includes:
a current sensor coupled in series with the charging coil for detecting a voltage across the charging coil; and
a rectifier to rectify an output of the current sensor such that an output of the rectifier represents a rectified voltage level of the charging coil.
9. The wireless charger of claim 1 , further comprising:
a class-E amplifier adapted to generate the charging signal for the charging coil; and
a current limiter connected between a power supply and the class-E amplifier to limit a current supplied to the class-E amplifier below a threshold value.
10. A method, comprising:
wirelessly charging, via a charging coil of a wireless charger, a rechargeable battery of an implantable pulse generator (IPG), wherein the charging coil is wirelessly coupled to a receiving coil of the IPG during the wirelessly charging;
detecting, via a reflected impedance sensor, a reflected impedance of the charging coil;
detecting, via an alignment circuit, a proper alignment of the charging coil and the receiving coil; and
selecting, via an optimization circuit, an optimum frequency of a charging signal supplied to the charging coil based on detected reflected impedances of a plurality of charging frequencies in a selected frequency range.
11. The method of claim 10 , further comprising: receiving, via a processor of the optimization circuit, the detected reflected impedances of the plurality of charging frequencies.
12. The method of claim 10 , wherein the optimization circuit periodically repeats the selecting of the optimum frequency at a selected time interval.
13. The method of claim 10 , wherein the optimization circuit sweeps the plurality of charging frequencies in the selected frequency range from one end to another at a selected time interval to obtain the detected reflected impedances.
14. The method of claim 10 , wherein the selecting comprise: selecting, as the optimum frequency, a charging frequency of the plurality of charging frequencies that results in the detected reflected impedance representing a highest peak-to-peak voltage of the charging coil.
15. The method of claim 10 , wherein the detecting the reflected impedance is performed at least in part using a current sensor that is coupled in series with the charging coil.
16. The method of claim 15 , wherein the detecting the reflected impedance further comprises: detecting, via the current sensor, a voltage across the charging coil.
17. The method of claim 16 , wherein the detecting the reflected impedance further comprises: rectifying, via a rectifier, an output of the current sensor such that an output of the rectifier represents a rectified voltage level of the charging coil.
18. The method of claim 10 , wherein the detecting the reflected impedance is performed at least in part using a transformer having a primary coil coupled in series with the charging coil and a secondary coil coupled to the primary coil.
19. The method of claim 10 , further comprising:
generating, via a class-E amplifier, the charging signal for the charging coil; and
limiting, via a current limiter, a current supplied to the class-E amplifier below a threshold value.
20. A wireless charger, comprising:
a charging coil adapted to be wirelessly coupled to a receiving coil of an implantable pulse generator (IPG) to charge a rechargeable battery of the IPG;
a reflected impedance sensor coupled to the charging coil to detect a reflected impedance of the charging coil, wherein the reflected impedance sensor includes a current sensor coupled in series with the charging coil;
an alignment circuit coupled to the reflected impedance sensor to detect a proper alignment of the charging coil and the receiving coil;
an optimization circuit coupled to the reflected impedance sensor and adapted to select an optimum frequency of a charging signal supplied to the charging coil based on detected reflected impedances of a plurality of charging frequencies in a selected frequency range, wherein the optimization circuit periodically repeats a selection of the optimum frequency at a selected time interval; and
an amplifier configured to generate the charging signal for the charging coil.