Sense Coil Mutual Impedance Detection for Small Metal Objects

The patent introduces a sense coil as an intermediary element that indirectly detects the presence of foreign objects through mutual impedance changes, rather than directly detecting the objects themselves. This intermediary approach enhances detection sensitivity for small metallic objects while the measurement of mutual impedance between sense coils provides temperature compensation, improving reliability across varying temperatures.

The patent utilizes changes in mutual impedance parameters between sense coils to detect foreign objects. By monitoring parameter changes in the electrical characteristics of the sense coils rather than physical properties, the system achieves both high detection sensitivity and temperature stability, as electrical impedance measurements are less affected by temperature variations compared to other measurement methods.

The patent divides the detection area into multiple zones by deploying multiple sense coils in an array configuration. Each sense coil independently contributes to detection coverage, allowing the system to achieve large-area monitoring while maintaining manageable complexity through modular deployment. The segmentation approach enables scalable system design where coils can be added or removed based on specific application requirements.

The sense coils serve multiple functions simultaneously: they act as both sensing elements for foreign object detection and as part of the inductive power transfer system. This multi-functionality reduces overall system complexity by eliminating the need for separate detection and power transfer components, allowing the same coil structure to fulfill both detection and power transfer roles.