The present invention provides a multi-coil inductive power transfer primary comprising a plurality of coil. A power transfer regime is selected based on a determined load on each of the plurality of coils.

The present invention provides a multi-coil inductive power transfer primary comprising a plurality of coil. A power transfer regime is selected based on a determined load on each of the plurality of coils.

The present invention suppresses leakage magnetic field. A power transfer coil configured to transmit or receive power includes: an inner coil; a first outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and the other end connected to one end of the inner coil; and a second outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second outer coil, the second outer coil having one end connected to a second terminal and the other end connected to the other end of the inner coil.

The present invention suppresses leakage magnetic field. A power transfer coil configured to transmit or receive power includes: an inner coil; a first outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and the other end connected to one end of the inner coil; and a second outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second outer coil, the second outer coil having one end connected to a second terminal and the other end connected to the other end of the inner coil.

A wireless charging device includes a casing, a transmitter driving board and a transmitter coil assembly. The wireless charging device is used for charging a receiver coil of a mobile device. The transmitter driving board generates a first heat source. The transmitter driving board has a first thermal resistance. The transmitter coil assembly generates a second heat source. The transmitter coil assembly has a second thermal resistance. There is an interfacial thermal resistance between the transmitter coil assembly and the transmitter driving board. A product of a power dissipation of the second heat source and the second thermal resistance is lower than 15. The interfacial thermal resistance is higher than or equal to two times the first thermal resistance. A product of a power dissipation of the first heat source and the first thermal resistance is lower than or equal to 80.

A wireless charging device includes a casing, a transmitter driving board and a transmitter coil assembly. The wireless charging device is used for charging a receiver coil of a mobile device. The transmitter driving board generates a first heat source. The transmitter driving board has a first thermal resistance. The transmitter coil assembly generates a second heat source. The transmitter coil assembly has a second thermal resistance. There is an interfacial thermal resistance between the transmitter coil assembly and the transmitter driving board. A product of a power dissipation of the second heat source and the second thermal resistance is lower than 15. The interfacial thermal resistance is higher than or equal to two times the first thermal resistance. A product of a power dissipation of the first heat source and the first thermal resistance is lower than or equal to 80.

A resonant induction wireless power transfer coil assembly designed for low loss includes a wireless power transfer coil, a non-saturated backing core layer adjacent the wireless power transfer coil, an eddy current shield, a gap layer between the backing core layer and the eddy current shield, and an enclosure that encloses the wireless power transfer coil, backing core layer, gap layer and eddy current shield. The gap layer has a thickness in a thickness range for a given thickness of the backing core layer where eddy current loss in the eddy current shield is substantially flat over the thickness range. A thickness of the backing core layer and a thickness of the gap layer are selected where a total power loss comprising power loss in the backing core layer plus eddy current loss over the gap layer is substantially minimized.

A magnetic conductive substrate is provided and is used for wireless charging or wireless communication. The magnetic conductive substrate includes a first magnetic conductive layer, a second magnetic conductive layer, and a third magnetic conductive layer. The first magnetic conductive layer has a first magnetic permeability, the second magnetic conductive layer has a second magnetic permeability, and the third magnetic conductive layer has a third magnetic permeability. The second magnetic conductive layer is disposed between the first magnetic conductive layer and the third magnetic conductive layer, the first magnetic permeability is different from the second magnetic permeability, and the second magnetic permeability is different from the third magnetic permeability.

A magnetic conductive substrate is provided and is used for wireless charging or wireless communication. The magnetic conductive substrate includes a first magnetic conductive layer, a second magnetic conductive layer, and a third magnetic conductive layer. The first magnetic conductive layer has a first magnetic permeability, the second magnetic conductive layer has a second magnetic permeability, and the third magnetic conductive layer has a third magnetic permeability. The second magnetic conductive layer is disposed between the first magnetic conductive layer and the third magnetic conductive layer, the first magnetic permeability is different from the second magnetic permeability, and the second magnetic permeability is different from the third magnetic permeability.

A power transmitter (101) comprises a driver (201) generating a drive signal for a transmitter coil to generate a power transfer signal during a power transfer time interval and an electromagnetic test signal during a foreign object detection time interval. A set of balanced detection coils (207, 209) comprise two detection coils arranged such that signals induced in the two detection coils by an electromagnetic field generated by the transmitter coil compensate each other. A foreign object detector (205) is coupled to the detection coils and performs foreign object detection during the foreign object detection time interval. The foreign object detector (205) is arranged to detect a foreign object in response to a property of a signal from the detection coils meeting a foreign object detection criterion. A transformer (1101) has a primary winding and a secondary winding coupled in series with the set of balanced detection coils A compensation circuit (1103) is coupled to the primary winding and arranged to generate a compensation drive signal for the primary winding which offsets a combined voltage of the set of detection coils.