Methods and systems for frequency adjustment to optimize charging of implantable neurostimulator

1. A charger for coupling with an implantable neurostimulator for delivering one or more electrical pulses to a target region within a patient's body, the charger comprising:

a memory;

a power source for storing electrical energy;

a resonant circuit, wherein the resonant circuit is configurable to a plurality of natural frequencies;

a driver coupled to the power source and the resonant circuit, wherein the driver is configured to power the resonant circuit; and

a processor coupled to the resonant circuit to control the natural frequency of the resonant circuit, wherein the processor is configured to control the natural frequency of the resonant circuit according to data associated with the implantable neurostimulator and stored in the memory, wherein controlling the natural frequency of the resonant circuit according to data associated with the implantable neurostimulator comprises:

receiving identifying data from the implantable neurostimulator; and

retrieving characterization data, wherein the characterization data identifies a natural frequency of a resonant circuit of the implantable neurostimulator.

2. The charger of claim 1 , wherein controlling the natural frequency of the resonant circuit according to data associated with the implantable neurostimulator comprises:

detecting a first natural frequency of the resonant circuit of the charger;

comparing the first natural frequency of the resonant circuit of the charger to the characterization data; and

changing the natural frequency of the resonant circuit of the charger from the first natural frequency to a second natural frequency.

3. The charger of claim 2 , wherein detecting the first natural frequency of the resonant circuit of the charger comprises at least one of: determining a driving frequency of the driver; or detecting ringing of the resonant circuit.

4. The charger of claim 2 , wherein the second natural frequency corresponds to the characterization data.

5. The charger of claim 4 , wherein the resonant circuit comprises:

an inductor;

a first capacitor coupled in series to the inductor; and

a plurality of capacitors switchably coupleable to the inductor, wherein the plurality of capacitors are each configured to be in parallel with the first capacitor when switchably coupled to the inductor.

6. The charger of claim 5 , wherein the plurality of capacitors comprises three capacitors.

7. The charger of claim 6 , wherein each of the plurality of capacitors is switchably coupleable to the inductor via a transistor.

8. The charger of claim 7 , wherein the transistor is a field effect transistor.

9. The charger of claim 5 , wherein changing the natural frequency of the resonant circuit of the charger from the first natural frequency to a second natural frequency comprises:

identifying a first switch configuration of the resonant circuit resulting in the first natural frequency;

identifying a second switch configuration of the resonant circuit resulting in the second natural frequency; and

generating a control signal to control at least one of: opening of at least one switch in the resonant circuit to disconnect at least one of the plurality of capacitors from the inductor; or closing of at least one switch in the resonant circuit to connect at least one of the plurality of capacitors from the inductor.

10. The charger of claim 4 , wherein changing the natural frequency of the resonant circuit of the charger from the first natural frequency to a second natural frequency comprises:

identifying a first inductance of an inductor in the resonant circuit resulting in the first natural frequency;

identifying a second inductance of the inductor in the resonant circuit resulting in the second natural frequency; and

generating a control signal to change the inductance of the inductor from the first inductance to the second inductance.

11. The charger of claim 10 , wherein changing the inductance of the inductor from the first inductance to the second inductance comprises changing a saturation level of a core of the inductor from a first saturation level to a second saturation level.

12. The charger of claim 11 , wherein changing the saturation level of the core of the inductor from the first saturation level to the second saturation level comprises changing a voltage applied to the core of the inductor from a first voltage to a second voltage.

13. The charger of claim 4 , wherein the first natural frequency is repeatedly detected.

14. The charger of claim 4 , wherein the first natural frequency is periodically detected.

15. The charger of claim 4 , wherein the natural frequency of the resonant circuit can be adjusted within a range of 20 Hz.

16. The charger of claim 4 , wherein the natural frequency of the resonant circuit can be adjusted within a range of 10 Hz.

17. The charger of claim 4 , wherein the natural frequency of the resonant circuit can be adjusted between approximately 119 Hz and 130 Hz.

18. The charger of claim 1 , wherein the driver comprises a class-E driver.

19. A charger for coupling with an implantable neurostimulator for delivering one or more electrical pulses to a target region within a patient's body, the charger comprising:

a memory;

a power source for storing electrical energy;

a resonant circuit, wherein the resonant circuit is configurable to a plurality of natural frequencies;

a driver coupled to the power source and the resonant circuit, wherein the driver is configured to power the resonant circuit; and

a processor coupled to the resonant circuit to control the natural frequency of the resonant circuit, wherein the processor is configured to control the natural frequency of the resonant circuit according to data associated with the implantable neurostimulator and stored in the memory wherein the data associated with the implantable neurostimulator identifies the implantable neurostimulator and identifies a previously determined natural frequency of the implantable neurostimulator.