Foreign object detection using hybrid inductive and capacitive sensing

An apparatus for detecting foreign objects in an inductive wireless power transfer system, based on one or more of an inductive effect and a capacitive effect, the apparatus comprising:

• a first sense circuit comprising a first electrical conductor, the first electrical conductor forming a loop of an inductive sense element and terminating in a first terminal and a second terminal;
• a second sense circuit comprising a second electrical conductor, the second electrical conductor forming an electrode of a capacitive sense element and having a third terminal;
• and
• a measurement circuit, the measurement circuit configured to:
• measure a first electrical characteristic between the first terminal and the second terminal and a second electrical characteristic between the first terminal and the third terminal;
• and
• a controller configured to:
• jointly use the measured first and second electrical characteristics to determine a presence of the foreign object and to discriminate whether the foreign object is a metallic object or a non-metallic object based on a change in the measured first and second electrical characteristics.