Abstract: A method of modeling a wireless power transfer system can include constructing a loss-split circuit model of the wireless power transfer system. The loss-split circuit model can include a plurality of resistance values corresponding to power losses in selected components of the power system. The method can further include performing a plurality of finite element analyses to determine the plurality of resistor values. The one or more resistance values can correspond to power losses associated with one or more of: a transmitter coil, a receiver coil, friendly metal associated with a transmitter, friendly metal associated with a receiver, and a foreign object.

Abstract: A wireless power system has a wireless power transmitting device with a wireless power transmitting coil and an inverter. The inverter and wireless power transmitting coil are used to transmit wireless power signals. The wireless power system also has a wireless power receiving device configured to receive the wireless power signals using a wireless power receiving coil. A rectifier in the wireless power receiving device rectifies alternating-current signals from the wireless power receiving coil and produces corresponding direct-current power. Power loss calculations may be used to help determine whether a foreign object might be present in the vicinity of a coupled wireless power transmitter and receiver. In an ecosystem with multiple models of transmitter and multiple models of receiver, model-dependent scaling factors may be maintained and exchanged between a given coupled transmitter and receiver pair to allow accurate power loss estimates to be made.

Abstract: An accessory for improving wireless power transfer efficiency in a wireless power transfer system can include a magnetic (e.g., ferrite) core dimensioned and positioned so as to reduce flux coupling from the PTx winding into friendly metal of the PRx and/or to enhance flux coupling from the PTx winding to the PRx winding. The core may define an aperture corresponding to an outer dimension (e.g., outer diameter) of the PRx winding. The core may further have an outer dimension selected to intercept sufficient flux to reduce flux coupling into the friendly metal of the PRx, such as an outer dimension corresponding to an outer dimension (e.g., outer diameter) of the PTx winding. The accessory may be a case for the PRx device or may be configured to be affixed to the face of the PTx device and may also include one or more alignment fixtures.