A new metal object detection (MOD) system appropriate for high-power inductive power transfer (IPT) systems such as EV chargers and cordless home appliances is proposed. An asymmetric triangular gradiometer structure based on two vertically stacked triangular spiral coils is newly introduced to overcome a chronic low signal-to-noise (SNR) issue in conventional MOD detection coils. A signal processing circuit is newly designed based on an analog divider circuit to distinguish small variances in the detection coil output, which come from an existence of metal objects (MOs), under the high noise environment. The proposed MOD system was fabricated and experimentally verified with a 1kW IPT system and reference MOs in Ki standard, which is an international standard for cordless kitchen platform published by the Wireless Power Consortium (WPC). The results showed that the output voltage of the proposed MOD system varies more than 200 mV for a steel disk having a diameter of 15 mm, which is the smallest MO in Ki standard, apart 5mm from the Tx coil surface.
