Systems and methods for low power excitation in high power wireless power systems

1. A system for low power excitation of a wireless power transmitter configured to transmit high power, the system comprising:

a controller;

an inverter including at least two transistors, the transistors configured to be controlled by the controller such that a phase shift angle associated with at least one transistor is adjustable during low power excitation;

at least one variable impedance component coupled to an output of the inverter and configured to be adjusted by the controller to obtain a minimum attainable impedance during low power excitation, wherein the at least one variable impedance component is configured to operate between the minimum attainable impedance and a maximum attainable impedance; and

a resonator coil of the transmitter configured to generate a magnetic flux density less than or equal to a field safety threshold during low power excitation.

2. The system of claim 1 , further comprising a power factor correction (PFC) circuit configured to drive the transmitter at a minimum bus voltage during low power excitation, wherein the PFC circuit is configured to output a bus voltage between the minimum bus voltage and a maximum bus voltage.

3. The system of claim 1 , further comprising a power factor correction (PFC) circuit and a low voltage source coupled to an output of the PFC circuit, the low voltage source being configured to drive the transmitter during low power excitation.

4. The system of claim 3 , wherein the PFC circuit is disabled during low power excitation.

5. The system of claim 3 , wherein the low voltage source is one of a variable low voltage source or a fixed low voltage source.

6. The system of claim 3 , wherein low voltage source is configured to drive the transmitter such that, during low power excitation, a current in the resonator coil is less than or equal to a current limit, wherein the current limit is based on the field safety threshold.

7. The system of claim 6 , further comprising:

a current sensor coupled to the resonator coil and configured to provide a signal representative of at least one characteristic of the current in the resonator coil to the controller.

8. The system of claim 7 , wherein the at least one characteristic includes a level, a phase, and/or a frequency of the current in the resonator coil.

9. The system of claim 1 wherein the wireless power transmitter is configured to output power at 50 W or less during low power excitation.

10. The system of claim 1 wherein the field safety threshold is between 10 μTesla and 15 μTesla.

11. A method for low power excitation of a wireless power transmitter configured to transmit high power, the transmitter including a controller, an inverter coupled to an input of an impedance network, and a transmitter resonator coil coupled to an output of the impedance network, the method comprising:

adjusting, by the controller, one or more variable impedance components of the impedance network to obtain a minimum attainable impedance, wherein the variable impedance components are configured to operate between the minimum attainable impedance and a maximum attainable impedance;

adjusting, by the controller, a phase shift angle associated with one or more transistors of the inverter; and

driving the transmitter such that the transmitter resonator coil generates a magnetic flux density less than or equal to a field safety threshold.

12. The method of claim 11 , wherein the transmitter includes a power factor correction (PFC) circuit configured to output a bus voltage between a minimum bus voltage and a maximum bus voltage.

13. The method of claim 12 , wherein driving the transmitter such that the transmitter resonator coil generates the magnetic flux density less than or equal to the field safety threshold includes driving the transmitter, via the PFC circuit, at the minimum bus voltage.

14. The method of claim 12 , wherein the transmitter further includes a low voltage source coupled to an output of the PFC circuit.

15. The method of claim 14 , wherein the low voltage source is one of a variable low voltage source or a fixed low voltage source.

16. The method of claim 14 , wherein driving the transmitter such that the transmitter resonator coil generates the magnetic flux density less than or equal to the field safety threshold includes driving the transmitter via the low voltage source.

17. The method of claim 16 , driving the transmitter via the low voltage source includes disabling the PFC circuit.

18. The method of claim 16 , wherein driving the transmitter via the low voltage source includes driving the transmitter such that, during low power excitation, a current in the resonator coil is less than or equal to a current limit, wherein the current limit is based on the field safety threshold.

19. The method of claim 18 , wherein the transmitter includes a current sensor coupled to the resonator coil.

20. The method of claim 19 , further comprising:

providing, via the current sensor, a signal representative of at least one characteristic of the current in the resonator coil to the controller, the at least one characteristic including a level, a phase, and/or a frequency of the current in the resonator coil.

21. The system of claim 1 , wherein the controller is operably coupled to at least one of: (i) the at least two transistors or (ii) the at least one variable impedance component.

22. The method of claim 11 , wherein the controller is operably coupled to at least one of: (i) the one or more transistors of the inverter or (ii) the one or more variable impedance components of the impedance network.