US Patent 11791659 Inductive power transmitter

An inductive power transmitter comprising: a converter configured to generate at least two object detection signals at substantially different frequencies, at least one transmitting coil configured to generate a magnetic field based on the object detection signals, and a controller configured to determine or measure circuit parameter(s) in relation to the coil to determine the inductance of the coil at each of the frequencies, and determine whether and/or what kind of object is present depending on a change in inductance between each of the frequencies.