Protection and control of wireless power systems
Methods, systems, and devices for protecting a wireless power transfer system. One aspect features a sensor network for a wireless power transfer system. The sensor network includes a differential voltage sensing circuit and a current sensing circuit. The differential voltage sensing circuit is arranged within a wireless power transfer system to measure a rate of change of a voltage difference between portions of an impedance matching network and generate a first signal representing the rate of change of the voltage difference. The current sensing circuit is coupled to the differential voltage sensing circuit and configured to calculate, based on the first signal, a current through a resonator coil coupled to the wireless power transfer system.
1. A protection system for a wireless power transfer system, the protection system comprising:
a differential voltage sensing circuit arranged within a wireless power transfer system to measure a rate of change of a voltage difference between portions of a tunable impedance matching network (TMN) and generate a first signal representing the rate of change of the voltage difference;
a first current sensing circuit arranged to measure a first current and generate a second signal representing the first current, the first current being through the TMN;
a second current sensing circuit coupled to the differential voltage sensing circuit and to the first current sensing circuit, the second current sensing circuit configured to calculate, based on the first signal and the second signal, a second current and generate a third signal representing the second current, the second current being through a resonator coil coupled to the wireless power transfer system; and
fault protection circuitry coupled to respective output terminals of the first current sensing circuit and the second current sensing circuit, the fault protection circuitry configured to bypass the TMN in response to a magnitude of the second signal or a magnitude of the third signal exceeding a respective threshold value.
2. The protection system of claim 1 , wherein the differential voltage sensing circuit is coupled to the first current sensing circuit, and wherein the differential voltage sensing circuit is configured to scale the first signal in response to the second signal.
3. The protection system of claim 1 , wherein the differential voltage sensing circuit comprises an amplification stage comprising a unity gain amplifier.
4. The protection system of claim 3 , wherein the unity gain amplifier is configured to provide the first signal as a single-ended voltage signal.
5. The protection system of claim 3 , wherein the differential voltage sensing circuit is coupled to the first current sensing circuit, and wherein the differential voltage sensing circuit is arranged to apply the second signal to the unity gain amplifier to scale the first signal in response to the second signal.
6. The protection system of claim 1 , wherein the differential voltage sensing circuit comprises a differentiator circuit.
7. The protection system of claim 1 , wherein the second current sensing circuit comprises a differential circuit configured to generate the third signal by subtracting the first signal from the second signal.
8. The protection system of claim 1 , wherein the fault protection circuitry is further configured to bypass the TMN by latching a control signal for a TMN bypass transistor in an asserted state.
9. The protection system of claim 8 , wherein the fault protection circuitry is further configured to delay latching the control signal until a voltage across the TMN is below a TMN voltage threshold value.
10. The protection system of claim 1 , wherein the fault protection circuitry is configured to shutdown an inverter-rectifier in response to a magnitude of the second signal or a magnitude of the third signal exceeding a respective threshold value.
11. A wireless power transfer system comprising:
a resonator coil;
a tunable impedance matching network (TMN) coupled to the resonator coil; and
a sensor network comprising:
a differential voltage sensing circuit arranged to measure a rate of change of a voltage difference between portions of the TMN and generate a first signal representing the rate of change of the voltage difference,
a first current sensing circuit arranged to measure a first current and generate a second signal representing the first current, the first current being through the TMN,
a second current sensing circuit coupled to the differential voltage sensing circuit and to the first current sensing circuit, the second current sensing circuit configured to calculate, based on the first signal and the second signal, a second current and generate a third signal representing the second current through the resonator coil, the second current being through the resonator coil, and
fault protection circuitry coupled to an output terminal of the first current sensing circuit and the second current sensing circuit, the fault protection circuitry configured to bypass the TMN in response to a magnitude of the second signal or a magnitude of the third signal exceeding a threshold value.
12. The wireless power transfer system of claim 11 , wherein the fault protection circuitry is further configured to bypass the TMN by latching a control signal for a TMN bypass transistor in an asserted state.
13. The wireless power transfer system of claim 12 , wherein the fault protection circuitry is further configured to delay latching the control signal until a voltage across the TMN is below a TMN voltage threshold value.
14. The wireless power transfer system of claim 11 , wherein the differential voltage sensing circuit is coupled to the first current sensing circuit, and wherein the differential voltage sensing circuit is configured to scale the first signal in response to the second signal.
15. The wireless power transfer system of claim 11 , wherein the differential voltage sensing circuit comprises an amplification stage comprising a unity gain amplifier.
16. The wireless power transfer system of claim 15 , wherein the unity gain amplifier is configured to provide the first signal as a single-ended voltage signal.
17. The wireless power transfer system of claim 15 , wherein the differential voltage sensing circuit is coupled to the first current sensing circuit, and wherein the differential voltage sensing circuit is arranged to apply the second signal to the unity gain amplifier to scale the first signal in response to the second signal.
18. The wireless power transfer system of claim 11 , wherein the differential voltage sensing circuit comprises a differentiator circuit.
19. The wireless power transfer system of claim 11 , wherein the second current sensing circuit comprises a differential circuit configured to generate the third signal by subtracting the first signal from the second signal.
20. The wireless power transfer system of claim 11 , wherein the fault protection circuitry is configured to shutdown an inverter-rectifier in response to a magnitude of the second signal or a magnitude of the third signal exceeding a respective threshold value.