Dynamic multi-coil tuning
Systems, methods and apparatus for wireless charging are disclosed. A wireless charging device has a plurality of charging cells provided on a first surface and a processor configured to provide a charging current to a first charging coil in a surface of the wireless charging device, determine that an impedance of a resonant circuit has varied from a threshold or setpoint impedance, and restore the threshold or setpoint impedance by modifying frequency of the charging current. The resonant circuit may include the first charging coil. A method for operating the wireless charging device includes providing a charging current to a first charging coil in a surface of the wireless charging device, determining that an impedance of a resonant circuit has varied from a threshold or setpoint impedance, and restoring the threshold or setpoint impedance by modifying frequency of the charging current. The resonant circuit may include the charging coil.
1. A method for operating a wireless charging device, comprising:
providing a charging current at a first frequency to a resonant circuit when the resonant circuit includes a first transmitting coil of the wireless charging device;
coupling a second transmitting coil of the wireless charging device to the resonant circuit;
determining an impedance of the resonant circuit after coupling the second transmitting coil to the resonant circuit;
providing the charging current at a second frequency to the resonant circuit based on the impedance of the resonant circuit after the second transmitting coil is coupled to the resonant circuit; and using a lookup table to determine the second frequency.
2. The method of claim 1 , wherein the charging current is provided at the second frequency to restore a nominal impedance of the resonant circuit.
3. The method of claim 1 , wherein the first frequency corresponds to a first resonant frequency associated with the resonant circuit before the second transmitting coil is coupled to the resonant circuit.
4. The method of claim 1 , wherein the second frequency corresponds to a second resonant frequency associated with the resonant circuit after the second transmitting coil is coupled to the resonant circuit.
5. The method of claim 1 , wherein changes in impedance of the resonant circuit are tracked using a current sense feedback loop.
6. The method of claim 1 , wherein changes in impedance of the resonant circuit are tracked using proportional-integral-derivative (PID) tuning.
7. A non-transitory processor readable storage medium, comprising code for:
providing a charging current at a first frequency to a resonant circuit when the resonant circuit includes a first transmitting coil of a wireless charging device;
coupling a second transmitting coil of the wireless charging device to the resonant circuit;
determining an impedance of the resonant circuit after coupling the second transmitting coil to the resonant circuit;
providing the charging current at a second frequency to the resonant circuit based on the impedance of the resonant circuit after the second transmitting coil is coupled to the resonant circuit; and comprising code for: using a lookup table to determine the second frequency.
8. The storage medium of claim 7 , wherein the charging current is provided at the second frequency to restore a nominal impedance of the resonant circuit.
9. The storage medium of claim 7 , wherein the first frequency corresponds to a first resonant frequency associated with the resonant circuit before the second transmitting coil is coupled to the resonant circuit.
10. The storage medium of claim 7 , wherein the second frequency corresponds to a second resonant frequency associated with the resonant circuit after the second transmitting coil is coupled to the resonant circuit.
11. The storage medium of claim 7 , wherein changes in impedance of the resonant circuit are tracked using a current sense feedback loop.
12. The storage medium of claim 7 , wherein changes in impedance of the resonant circuit are tracked using proportional-integral-derivative (PID) tuning.
13. A wireless charging device, comprising:
a plurality of transmitting coils provided at a surface of the wireless charging device;
a resonant circuit that includes a first transmitting coil of the plurality of transmitting coils; and
a controller configured to:
cause a power source to provide a charging current at a first frequency to the resonant circuit;
cause a second transmitting coil of the wireless charging device to be coupled to the resonant circuit;
determine an impedance of the resonant circuit after coupling the second transmitting coil to the resonant circuit;
cause the power source to provide the charging current at a second frequency to the resonant circuit based on the impedance of the resonant circuit after the second transmitting coil is coupled to the resonant circuit; and the controller is further configured to: use a lookup table to determine the second frequency.
14. The wireless charging device of claim 13 , wherein the charging current is provided at the second frequency to restore a nominal impedance of the resonant circuit.
15. The wireless charging device of claim 13 , wherein the first frequency corresponds to a first resonant frequency associated with the resonant circuit before the second transmitting coil is coupled to the resonant circuit.
16. The wireless charging device of claim 13 , wherein the second frequency corresponds to a second resonant frequency associated with the resonant circuit after the second transmitting coil is coupled to the resonant circuit.
17. The wireless charging device of claim 13 , wherein changes in impedance of the resonant circuit are tracked using a current sense feedback loop.