Wireless charging magnetic parameter determination

1. A wireless-power receiver system comprising:

a power reception circuit coupled to an electrical load and configured to receive power wirelessly from a power transmit circuit to power the electrical load;

a memory; and

a processor, communicatively coupled to the memory and to the power reception circuit, configured to:

obtain a first frequency indication of a first resonant frequency of the power reception circuit corresponding to a combination of the power transmit circuit and the power reception circuit being in a first state having a first combined circuit configuration;

obtain a second frequency indication of a second resonant frequency of the power reception circuit corresponding to the combination of the power transmit circuit and the power reception circuit being in a second state having a second combined circuit configuration, the first combined circuit configuration differing from the second combined circuit configuration by at least one of component content or a value of at least one component; and

determine a value of a magnetic characteristic of the wireless-power receiver system using the first frequency indication and the second frequency indication.

2. The system of claim 1 , wherein the processor is further configured to cause an evaluation signal to be emitted by a power-coupling element, of the power reception circuit, that is configured to receive the power from the power transmit circuit, and wherein the processor is configured to obtain each of the first frequency indication and the second frequency indication by determining a frequency of the evaluation signal.

3. The system of claim 2 , wherein the power reception circuit comprises a self-resonant structure, and wherein the processor is communicatively coupled to the self-resonant structure and configured to cause the self-resonant structure to produce the evaluation signal.

4. The system of claim 2 , wherein the power reception circuit comprises a signal generator, and wherein the processor is communicatively coupled to the signal generator and configured to cause the signal generator to produce the evaluation signal with a plurality of different frequencies.

5. The system of claim 1 , wherein the processor is further configured to cause the combination of the power transmit circuit and the power reception circuit to change between the first state and the second state.

6. The system of claim 1 , wherein to determine the value of the magnetic characteristic of the wireless-power receiver system the processor is configured to:

determine a first leakage inductance of a transmit coil of the power transmit circuit;

determine a second leakage inductance of a receive coil of the power reception circuit; and

determine a mutual inductance between the transmit coil and the receive coil.

7. The system of claim 6 , wherein the processor is configured to:

obtain a first current indication of current in the transmit coil, and a second current indication of current in the receive coil;

obtain a first impedance indication of an impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the first state, and a second impedance indication of the impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the second state; and

use the first frequency indication, the second frequency indication, the first impedance indication, the second impedance indication, the first current indication, and the second current indication to determine the first leakage inductance, the second leakage inductance, and the mutual inductance.

8. The system of claim 1 , wherein the power reception circuit comprises a resonant structure including a capacitance and an inductance.

9. The system of claim 1 , wherein the power reception circuit comprises a self-resonant structure comprising a plurality of switches coupled between a power-coupling element of the power reception circuit and the electrical load.

10. The system of claim 1 , wherein the processor is further configured to send the first frequency indication and the second frequency indication to the power transmit circuit via the power reception circuit.

11. A method of determining a value of a magnetic characteristic of a wireless-power receiver system, the method comprising:

obtaining a first frequency indication of a first resonant frequency, the first resonant frequency being of a power reception circuit of the wireless-power receiver system and corresponding to a combination of a power transmit circuit and the power reception circuit being in a first state having a first combined circuit configuration;

obtaining a second frequency indication of a second resonant frequency of the power reception circuit corresponding to the combination of the power transmit circuit and the power reception circuit being in a second state having a second combined circuit configuration, the first combined circuit configuration differing from the second combined circuit configuration by at least one of component content or a value of at least one component; and

using the first frequency indication and the second frequency indication to determine the value of the magnetic characteristic of the wireless-power receiver system.

12. The method of claim 11 , further comprising emitting an evaluation signal from a power-coupling element of the power reception circuit, wherein obtaining each of the first frequency indication and the second frequency indication comprises determining a frequency of the evaluation signal.

13. The method of claim 12 , further comprising causing the power transmit circuit to change a content of a component set that receives energy from the evaluation signal between the first state and the second state.

14. The method of claim 13 , wherein causing the power transmit circuit to change the content of the component set comprises causing an inverter bridge to change between being open circuited and shorted between the first state and the second state.

15. The method of claim 12 , wherein emitting the evaluation signal comprises causing a self-resonant structure of the power reception circuit to provide the evaluation signal to the power-coupling element.

16. The method of claim 12 , wherein emitting the evaluation signal comprises causing a signal generator to induce current in the receive coil with a plurality of different frequencies.

17. The method of claim 11 , wherein determining the value of the magnetic characteristic of the wireless-power receiver system comprises:

determining a first leakage inductance of a transmit coil of the power transmit circuit;

determining a second leakage inductance of a receive coil of the power reception circuit; and

determining a mutual inductance between the transmit coil and the receive coil.

18. The method of claim 17 , further comprising:

obtaining a first current indication of current in the transmit coil;

obtaining a second current indication of current in the receive coil;

obtaining a first impedance indication of an impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the first state;

obtaining a second impedance indication of the impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the second state; and

using the first frequency indication, the second frequency indication, the first impedance indication, the second impedance indication, the first current indication, and the second current indication to determine the first leakage inductance, the second leakage inductance, and the mutual inductance.

19. The method of claim 11 , wherein obtaining the first frequency indication and the second frequency indication comprise receiving the first frequency indication and the second frequency indication at a power transmit circuit from a power reception circuit of a wireless-power receiver system.

20. A wireless-power receiver system comprising:

an electrical load;

power reception means for receiving power wirelessly from a power transmit circuit and for providing power to the electrical load;

first determining means, communicatively coupled to the power reception means, for determining:

a first frequency indication of a first resonant frequency of the power reception means corresponding to a combination of the power transmit circuit and the power reception means being in a first state having a first combined circuit configuration; and

a second frequency indication of a second resonant frequency of the power reception means corresponding to the combination of the power transmit circuit and the power reception means being in a second state having a second combined circuit configuration, the first combined circuit configuration differing from the second combined circuit configuration by at least one of component content or a value of at least one component; and

second determining means, communicatively coupled to the first determining means, for determining a value of a magnetic characteristic of the wireless-power receiver system using the first frequency indication and the second frequency indication.

21. The system of claim 20 , wherein the first determining means are for causing an evaluation signal to be emitted by a power-coupling element, of the power reception means, that is configured to receive the power from the power transmit circuit, and wherein the first determining means are configured to determine each of the first frequency indication and the second frequency indication by determining a frequency of the evaluation signal.

22. The system of claim 21 , wherein the power reception means comprise a self-resonant structure, and wherein the first determining means are for causing the self-resonant structure to produce the evaluation signal.

23. The system of claim 21 , wherein the first determining means are for causing the power reception means to produce the evaluation signal with a plurality of different frequencies.

24. The system of claim 20 , wherein the first determining means comprise means for causing the combination of the power transmit circuit and the power reception means to change between the first state and the second state.

25. The system of claim 20 , wherein the second determining means are for determining:

a first leakage inductance of a transmit coil of the power transmit circuit;

a second leakage inductance of a receive coil of the power reception means; and

a mutual inductance between the transmit coil and the receive coil.

26. The system of claim 25 , wherein:

the first determining means are further for determining:

a first current indication of current in the transmit coil;

a second current indication of current in the receive coil;

a first impedance indication of an impedance of the power reception means with the combination of the power transmit circuit and the power reception means in the first state; and

a second impedance indication of the impedance of the power reception means with the combination of the power transmit circuit and the power reception means in the second state; and

the second determining means are for using the first frequency, the second frequency, the first impedance indication, the second impedance indication, the first current indication, and the second current indication to determine the first leakage inductance, the second leakage inductance, and the mutual inductance.

27. The system of claim 20 , further comprising means for sending the first frequency indication and the second frequency indication to the power transmit circuit.

28. A wireless-power transmitter system comprising:

a power transmit circuit configured to transmit power wirelessly to a wireless-power receiver system;

a memory; and

a processor, communicatively coupled to the memory and to the power transmit circuit, configured to:

obtain a first frequency indication of a first resonant frequency of a power reception circuit of the wireless-power receiver system, the first resonant frequency corresponding to a combination of the power transmit circuit and the power reception circuit being in a first state having a first combined circuit configuration;

obtain a second frequency indication of a second resonant frequency of the power reception circuit corresponding to the combination of the power transmit circuit and the power reception circuit being in a second state having a second combined circuit configuration, the first combined circuit configuration differing from the second combined circuit configuration by at least one of component content or a value of at least one component; and

determine a value of a magnetic characteristic of the wireless-power receiver system using the first frequency indication and the second frequency indication.

29. The system of claim 28 , wherein to determine the value of the magnetic characteristic of the wireless-power receiver system the processor is configured to:

determine a first leakage inductance of a transmit coil of the power transmit circuit;

determine a second leakage inductance of a receive coil of the power reception circuit; and

determine a mutual inductance between the transmit coil and the receive coil.

30. The system of claim 29 , wherein the processor is configured to:

obtain a first current indication of current in the transmit coil, and a second current indication of current in the receive coil;

obtain a first impedance indication of an impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the first state, and a second impedance indication of the impedance of the power reception circuit with the combination of the power transmit circuit and the power reception circuit in the second state; and

use the first frequency indication, the second frequency indication, the first impedance indication, the second impedance indication, the first current indication, and the second current indication to determine the first leakage inductance, the second leakage inductance, and the mutual inductance.