Wireless power transmission system

1. Wireless power transmission system comprising:

a base unit including:

multiple magnetic field generator circuits; and

a controller, configured to determine a transmission circuit from said generator circuits to transfer power to a device when a receiving inductor of said device is in proximity to said transmission circuit, whereupon the controller is configured to operate said transmission circuit to generate a first magnetic field, having a first phase, to induce a current in said receiving inductor; and

said controller is further configured to operate at least first and second ones of the remaining generator circuits as a compensation circuit to generate a second magnetic field, having an opposite phase to said first phase, wherein said controller is further configured to compensate a magnetic far-field of said first magnetic field by controlling a sum of magnetic fluxes generated in the second magnetic field to be substantially equal in magnitude and opposite in direction to a magnetic flux generated in the first magnetic field.

2. The system according to claim 1 , wherein said generator circuits each comprise a coil with multiple windings for generating said magnetic fields.

3. The system according to claim 2 , wherein the number of windings of the transmission circuit corresponds to the number of windings of the compensation circuit.

4. The system according to claim 1 , wherein each generator circuit has an associated detector, connected to the controller, for detecting the proximity of the receiving inductor to the corresponding generator circuit.

5. The system according to claim 4 , wherein said detectors are RFID detectors and said device comprises an RFID tag.

6. The system according to claim 1 , wherein said generator circuits are arranged in a plane, forming a transmission area.

7. The system according to claim 6 , wherein said compensation circuit comprises at least one conductor winding, arranged on a periphery of said transmission area to generate said second magnetic field.

8. The system according to claim 1 , wherein the controller is configured to determine said compensation circuit from said multiple generator circuits, so that said transmission circuit and the remaining generator circuits comprising said compensation circuit are adjacent to each other.

9. The system according to claim 1 , wherein said base unit comprises a sensor, connected to the controller for sensing far-field effects of the magnetic field, so that said compensation circuit is operated to minimise the magnetic far-field of said transmission circuit in response to a measurement from said sensor.

10. The system according to claim 1 , wherein the system further includes said device, which includes said receiving inductor.

11. Method for operating a wireless power transmission system, comprising a base unit, having multiple magnetic field generator circuits, and a device, separable from said base unit having a receiving inductor, adapted to receive power inductively when said device is in proximity to one of said generator circuits, wherein the method comprises:

determining the proximity of the receiving inductor to a transmission circuit of said generator circuits;

determining a transmission circuit from said generator circuits to transfer power to a device when a receiving inductor of said device is in proximity to said transmission circuit;

operating said transmission circuit to generate a first magnetic field, having a first phase, to induce a current in said receiving inductor;

operating at least first and second ones of the remaining generator circuits as a compensation circuit to generate a second magnetic field, having an opposite phase to said first phase of said first magnetic field; and

compensating a magnetic far-field of said first magnetic field by controlling a sum of magnetic fluxes generated in the second magnetic field to be substantially equal in magnitude and opposite in direction to a magnetic flux for the first magnetic field.

12. A non-transitory computer-readable medium having one or more executable instructions stored thereon, which when executed by a processor cause the processor to perform a method for operating a wireless power transmission system, the system comprising a base unit having multiple magnetic field generator circuits, and a device, which is separable from said base unit and includes a receiving inductor that is adapted to receive power inductively when said device is in proximity to one of said generator circuits, the method comprising:

determining the proximity of the receiving inductor to a transmission circuit of said generator circuits;

determining a transmission circuit from said generator circuits to transfer power to a device when a receiving inductor of said device is in proximity to said transmission circuit;

operating said transmission circuit to generate a first magnetic field, having a first phase, to induce a current in said receiving inductor;

operating at least first and second ones of the remaining generator circuits as a compensation circuit to generate a second magnetic field, having an opposite phase to said first phase of said first magnetic field; and

compensating a magnetic far-field of said first magnetic field by controlling a sum of magnetic fluxes generated in the second magnetic field to be substantially equal in magnitude and opposite in direction to a magnetic flux for the first magnetic field.