METHODS AND APPARATUS FOR ONLINE FOREIGN OBJECT DETECTION IN WIRELESS CHARGING SYSTEMS

Methods and apparatus for online foreign object detection for use with wireless charging systems. In an embodiment, an apparatus is provided that comprises a resonant circuit having a foreign object detection (FOD) coil that is energized by an online power transfer coil. The resonant circuit outputs a time-decaying resonate signal that indicates whether or not a foreign object is present. The apparatus also comprises a determination circuit that determines a decay time from the time-decaying resonate signal, and a detector circuit that outputs a detection signal having a first state when the decay time is greater than a threshold value to indicate that a foreign object is not present. The detector circuit also outputs the detection signal having a second state when the decay time is not greater than the threshold value to indicate that a foreign object is present.