Abstract: Systems, methods and apparatus are disclosed for wireless power transfer using multiple receive coils. In one aspect a wireless power receiver is provided that is configured to receive wireless power from a wireless power transmit coil. The wireless power receiver includes a first receive coil having a first mutual coupling with the transmit coil. The wireless power receiver further includes a second receive coil having a second mutual coupling with the transmit coil. The wireless power receiver further includes a load coupled to at least one of the first receive coil and the second receive coil for receiving the wireless power.

Abstract: A wireless power transmitter includes a power transmit coil configured to generate a magnetic field for wirelessly coupling charging power to one or more receiver devices, the magnetic field having a magnetic field distribution over an area defining a charging region, a circuit configured to alter the magnetic field generated by the power transmit coil to alter the magnetic field distribution, and a controller operably coupled to the circuit, the controller configured to control the circuit to alter the magnetic field distribution responsive to a detected characteristic of the one or more receiver devices.

Abstract: This disclosure provides systems, methods, and apparatus for the limiting of voltage in wireless power receivers. In one aspect, an apparatus includes a power transfer component configured to receive power wirelessly from a transmitter. The apparatus further includes a circuit coupled to the power transfer component and configured to reduce a received voltage when activated. The apparatus further includes a controller configured to activate the circuit when the received voltage reaches a first threshold value and configured to deactivate the circuit when the received voltage reaches a second threshold value. The apparatus further includes an antenna configured to generate a signal to the transmitter that signals to the transmitter that the received voltage reached the first threshold value.

Abstract: An apparatus and method for lost power detection are described. In one implementation, an apparatus for wirelessly transferring power comprises a wireless power transmitter configured to wirelessly transmit power at a first power level sufficient to power or charge a chargeable device. The apparatus further comprises a controller configured to obtain a first power measurement of the first power level. The controller is further configured to determine a first adjusted power measurement of the first power measurement based on one or more tolerance values of the wireless power transmitter. The controller is further configured to determine a second adjusted power measurement of a second power measurement of a second power level received by the chargeable device based on one or more tolerance values of the chargeable device. The controller is further configured to determine if a power difference between the first and second adjusted power measurements exceeds a threshold value.

Abstract: An apparatus and method for lost power detection are described. In one implementation, an apparatus for wireless transferring power comprises a wireless power transmitter configured to wirelessly transmit power at a power level sufficient to power or charge a chargeable device. The apparatus further comprises a controller configured to determine a first and second power difference between a first and second power measurement and the second and a third power measurement of the power level provided by the wireless power transmitter at a first, second, and third sample time, respectively. The controller is further configured to determine a transmitter power difference between the first power difference and the second power difference. The controller is further configured to determine an absence or a presence of an object that affects consumption of power transmitted by the wireless power transmitter based at least on the transmitter power difference ?_T.

Abstract: A wireless power receiving element with capacitive coupling is described herein. The design allows for a wireless power receiving element that extends all the way around the band of a wearable electronic device. In an area where one end of the band clasps to the other, a capacitive coupling is provided, allowing the element to extend around the entire band without requiring a direct physical connection to complete this circuit.

Abstract: In a wireless charging system, a receiver device includes a second coil that performs a reactance shift. The reactance shift may be used to conform the device reactance to a reactance range, or to adjust a rectified voltage of the wireless power provided to the device electronics. The reactance shift differs from resonance matching in that the power transfer efficiency may be decreased.

Abstract: This disclosure provides systems, methods, and apparatus for the limiting of voltage in wireless power receivers. In one aspect, an apparatus includes a power transfer component configured to receive power wirelessly from a transmitter. The apparatus further includes a circuit coupled to the power transfer component and configured to reduce a received voltage when activated. The apparatus further includes a controller configured to activate the circuit when the received voltage reaches a first threshold value and configured to deactivate the circuit when the received voltage reaches a second threshold value. The apparatus further includes an antenna configured to generate a signal to the transmitter that signals to the transmitter that the received voltage reached the first threshold value.

Abstract: Systems, methods and apparatus are disclosed for detecting power losses due to induction heating in wireless power receivers. In one aspect, an apparatus for wireless power transfer comprises a power transfer component configured to transmit wireless power to a wireless power receiver at a power level sufficient to charge or power a load. The apparatus further comprises a communications receiver configured to receive a message from the wireless power receiver, the message comprising a group identifier. The apparatus further comprises a controller circuit operationally coupled to the power transfer component and the communications receiver and configured to determine a power loss value based on the group identifier, the power loss value indicative of power loss due to induction heating presented by one or more wireless power receivers that are members of a group associated with the group identifier.

Abstract: A wireless power transmitter includes a power transmit coil configured to generate a magnetic field for wirelessly coupling charging power to one or more receiver devices, the magnetic field having a magnetic field distribution over an area defining a charging region, a circuit configured to alter the magnetic field generated by the power transmit coil to alter the magnetic field distribution, and a controller operably coupled to the circuit, the controller configured to control the circuit to alter the magnetic field distribution responsive to a detected characteristic of the one or more receiver devices.

Abstract: In a wireless charging system, a receiver device includes a second coil that performs a reactance shift. The reactance shift may be used to conform the device reactance to a reactance range, or to adjust a rectified voltage of the wireless power provided to the device electronics. The reactance shift differs from resonance matching in that the power transfer efficiency may be decreased.

Abstract: Aspects of a protection circuit and method are disclosed. A transmit circuit generates a power transmit signal for powering the transmit antenna to generate a wireless field sufficient for wirelessly charging a device. A detection circuit senses a strength of an electromagnetic field received by the transmit antenna and further configured to generate an sense signal indicating the strength of the electromagnetic field received by the transmit antenna. A power control circuit controls a switch based at least partly on the sense signal. The power control circuit can attenuate an electrical coupling between the transmit antenna and the transmit circuit such that the received electromagnetic field is inhibited from damaging the transmit antenna or the transmit circuit.

Abstract: This disclosure provides systems, methods and apparatus for detecting wireless charging transmit characteristics. One aspect of the disclosure provides a method of detecting a transmit characteristic in a wireless power transmission device. The device includes a series element electrically coupled to a transmit coil. The method includes determining real and imaginary components of a first voltage at a first terminal of the series element. The method further includes determining real and imaginary components of a second voltage at a second terminal of the series element. The method further includes determining real and imaginary components of a current through the series element, based on the determined first and second voltages. The method further includes determining transmit characteristics such as nodal voltages, currents, power and impedances based on determined voltages and currents.

Abstract: Systems and methods for alignment and calibration of a wireless power transmitter and a wireless power receiver are disclosed. According to one aspect, a wireless power transmit coil is first aligned with a wireless power receive coil. An alignment signal is received indicated that the transmit coil and the receive coil are aligned is received by the wireless power transmitter. A signal indicative of a characteristic of an electrical signal received by the wireless power receiver is generated and communicated to the wireless power transmitter. A calibration feedback signal is generated to adjust a driving signal of the wireless power transmitter based on the received signal.

Abstract: Systems, methods, and apparatus for overvoltage protection in a wireless power receiver are disclosed. One aspect of the disclosure is a wireless power receiver apparatus. The apparatus includes an antenna circuit configured to wirelessly receive power, from a transmitter, at a level sufficient to power or charge a load, wherein the antenna circuit is electrically connected to an overvoltage protection circuit that is electrically connected between the antenna circuit and the load. The apparatus also includes a matching circuit electrically connected to the antenna circuit and a switching element electrically connected to the matching circuit. At least one of the matching circuit or the switching element is configured to control an amount of the received power flowing into the overvoltage protection circuit.

Abstract: Systems, methods and apparatus are disclosed for detecting power losses due to induction heating in wireless power receivers. In one aspect, an apparatus for wireless power transfer comprises a power transfer component configured to transmit wireless power to a wireless power receiver at a power level sufficient to charge or power a load. The apparatus further comprises a communications receiver configured to receive a message from the wireless power receiver, the message comprising a group identifier. The apparatus further comprises a controller circuit operationally coupled to the power transfer component and the communications receiver and configured to determine a power loss value based on the group identifier, the power loss value indicative of power loss due to induction heating presented by one or more wireless power receivers that are members of a group associated with the group identifier.

Abstract: An apparatus and method for lost power detection are described. In one implementation, an apparatus for wirelessly transferring power comprises a wireless power transmitter configured to wirelessly transmit power at a first power level sufficient to power or charge a chargeable device. The apparatus further comprises a controller configured to obtain a first power measurement of the first power level. The controller is further configured to determine a first adjusted power measurement of the first power measurement based on one or more tolerance values of the wireless power transmitter. The controller is further configured to determine a second adjusted power measurement of a second power measurement of a second power level received by the chargeable device based on one or more tolerance values of the chargeable device. The controller is further configured to determine if a power difference between the first and second adjusted power measurements exceeds a threshold value.

Abstract: An apparatus and method for lost power detection are described. In one implementation, an apparatus for wireless transferring power comprises a wireless power transmitter configured to wirelessly transmit power at a power level sufficient to power or charge a chargeable device. The apparatus further comprises a controller configured to determine a first and second power difference between a first and second power measurement and the second and a third power measurement of the power level provided by the wireless power transmitter at a first, second, and third sample time, respectively. The controller is further configured to determine a transmitter power difference between the first power difference and the second power difference. The controller is further configured to determine an absence or a presence of an object that affects consumption of power transmitted by the wireless power transmitter based at least on the transmitter power difference ?_T.

Abstract: This disclosure provides systems, methods and apparatus for detecting wireless charging transmit characteristics. One aspect of the disclosure provides a method of detecting a transmit characteristic in a wireless power transmission device. The device includes a series element electrically coupled to a transmit coil. The method includes determining real and imaginary components of a first voltage at a first terminal of the series element. The method further includes determining real and imaginary components of a second voltage at a second terminal of the series element. The method further includes determining real and imaginary components of a current through the series element, based on the determined first and second voltages. The method further includes determining transmit characteristics such as nodal voltages, currents, power and impedances based on determined voltages and currents.

Abstract: Aspects of a protection circuit and method are disclosed. A transmit circuit generates a power transmit signal for powering the transmit antenna to generate a wireless field sufficient for wirelessly charging a device. A detection circuit senses a strength of an electromagnetic field received by the transmit antenna and further configured to generate an sense signal indicating the strength of the electromagnetic field received by the transmit antenna. A power control circuit controls a switch based at least partly on the sense signal. The power control circuit can attenuate an electrical coupling between the transmit antenna and the transmit circuit such that the received electromagnetic field is inhibited from damaging the transmit antenna or the transmit circuit.