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 method for determining the relative position of a metal object in relation to a user device and to a transmitter antenna of an inductive charging support when charging the user device. The method includes measuring the quality factor of the transmitter antenna, measuring the quality factor of the receiver antenna, and comparing the measured quality factor of the transmitter antenna with a predetermined quality factor threshold of the transmitter antenna and comparing the measured quality factor of the receiver antenna with a predetermined quality factor threshold of the receiver antenna so as to deduce therefrom the relative position of the metal object in relation to the user device and to the transmitter antenna or the absence of an interfering metal object.

A method for determining the relative position of a metal object in relation to a user device and to a transmitter antenna of an inductive charging support when charging the user device. The method includes measuring the quality factor of the transmitter antenna, measuring the quality factor of the receiver antenna, and comparing the measured quality factor of the transmitter antenna with a predetermined quality factor threshold of the transmitter antenna and comparing the measured quality factor of the receiver antenna with a predetermined quality factor threshold of the receiver antenna so as to deduce therefrom the relative position of the metal object in relation to the user device and to the transmitter antenna or the absence of an interfering metal object.

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.

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.

Systems, methods and apparatus for wireless charging are disclosed. A method for receiving power from a charging surface includes obtaining a combined current by combining currents induced in a plurality of receiving coils provided on a surface of the chargeable device in a first mode of operation, rectifying the combined current to obtain a battery charging current, and providing the battery charging current to a battery coupled to the chargeable device. In one example, the currents are induced through electromagnetic coupling by coils in a charging surface of a wireless charging device.

Systems, methods and apparatus for wireless charging are disclosed. A method for receiving power from a charging surface includes obtaining a combined current by combining currents induced in a plurality of receiving coils provided on a surface of the chargeable device in a first mode of operation, rectifying the combined current to obtain a battery charging current, and providing the battery charging current to a battery coupled to the chargeable device. In one example, the currents are induced through electromagnetic coupling by coils in a charging surface of a wireless charging device.

An electronic device may include: a resonance circuit which comprises a battery, a coil and a capacitor, and receives power wirelessly; a rectifier which rectifies AC power, provided from the resonance circuit, to DC power; a DC/DC converter which converts and outputs the DC power provided from the rectifier; a charger which charges the battery by using the converted power provided from the DC/DC converter; a first OVP circuit which selectively connects the coil to the capacitor; a second OVP circuit which is connected in parallel to the first OVP circuit; a detection circuit which detects a rectified voltage; a control circuit; and a communication circuit, wherein the control circuit, on the basis that the detected rectified voltage is equal to or greater than a first threshold voltage, controls the first OVP circuit so as to be in an off state so that the coil is not connected to the capacitor, and on the basis that the detected rectified voltage is less than a second threshold voltage, controls the first OVP circuit so that the first OVP circuit is switched from the off state to an on state so that the coil is connected to the capacitor, wherein the second threshold voltage may be smaller than the first threshold voltage.

An electronic device may include: a resonance circuit which comprises a battery, a coil and a capacitor, and receives power wirelessly; a rectifier which rectifies AC power, provided from the resonance circuit, to DC power; a DC/DC converter which converts and outputs the DC power provided from the rectifier; a charger which charges the battery by using the converted power provided from the DC/DC converter; a first OVP circuit which selectively connects the coil to the capacitor; a second OVP circuit which is connected in parallel to the first OVP circuit; a detection circuit which detects a rectified voltage; a control circuit; and a communication circuit, wherein the control circuit, on the basis that the detected rectified voltage is equal to or greater than a first threshold voltage, controls the first OVP circuit so as to be in an off state so that the coil is not connected to the capacitor, and on the basis that the detected rectified voltage is less than a second threshold voltage, controls the first OVP circuit so that the first OVP circuit is switched from the off state to an on state so that the coil is connected to the capacitor, wherein the second threshold voltage may be smaller than the first threshold voltage.

Methods, apparatus, systems and articles of manufacture are described for a wireless battery system. An example apparatus includes at least one memory, instructions, and processor circuitry to at least one of instantiate or execute the instructions to identify a first battery node to transmit an uplink command during a first superframe interval, transmit a downlink command to the first battery node and a second battery node, the first battery node to switch in the first superframe interval from a receive state to a transmit state in response to the downlink command, the first battery node to transmit the uplink command in the transmit state, and receive the uplink command from the first battery node in the first superframe interval.