Apple Inc.
Wireless power devices with capacitive foreign object detection sensors

Abstract:

A wireless power transmitting device uses a wireless power transmitting coil to transmit wireless power signals to a wireless power receiving device. The wireless power transmitting coil is located in a housing. The housing has a circular outline and contains one or more magnets that couple to corresponding magnets in the wireless power receiving device to help align a wireless power receiving coil in the wireless power receiving device to the wireless power transmitting coil in the wireless power transmitting device. A circular array of capacitive sensor electrodes is supported by the housing at a location that overlaps the wireless power transmitting coil. Capacitive sensor measurements from the capacitive sensor array are analyzed to determine whether a foreign object such as a coin or paperclip is present between the housing and the wireless power receiving device.