Hybrid Capacitive and Inductive Sensing With a Single Sense Unit
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Solution Overview
Problem
Existing touch sensors require separate sense elements and circuits for capacitive and inductive sensing, making it costly and space-consuming to detect different types of objects, especially in small form factor devices.
Innovation Solution
A hybrid sensing circuit that can operate in both capacitive and inductive modes using a single sense unit, employing a signal generator and charge measurement circuit to measure capacitance and inductance, allowing detection of various objects using combined capacitive and inductive sensing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate sense elements and circuits are used for capacitive and inductive sensing, then detection capability for different object types is improved, but device complexity and space consumption increase
Solution Approach 1:
The patent implements a single sense unit that can operate in both capacitive and inductive sensing modes by switching between different excitation frequencies. The sense unit includes a sense electrode and associated circuitry that can detect both capacitive objects (through self-capacitance or mutual-capacitance) and inductive objects (through inductance changes), eliminating the need for separate sense elements for different object types
Solution Approach 2:
The patent employs dynamic mode switching where the sensing circuit can transition between capacitive mode and inductive mode based on the type of object being detected. The circuit uses different excitation frequencies (first frequency for capacitive, second frequency for inductive) and switches between measurement modes to adapt to different sensing requirements, allowing one sense unit to perform multiple functions
2Adaptability or versatility
If multiple separate circuits are implemented for capacitive and inductive sensing, then object detection versatility is improved, but the device form factor increases
Solution Approach 1:
The patent merges capacitive sensing circuitry and inductive sensing circuitry into a single integrated sensing unit. The sense unit shares common components including the sense electrode, excitation signal generator, and measurement circuitry, combining what would traditionally be separate circuits into one unified structure that occupies less space
Solution Approach 2:
The single sense unit is designed to perform both capacitive sensing (detecting conductive or capacitive objects) and inductive sensing (detecting ferrous or non-ferrous metal objects) functions, making it a universal sensor that replaces multiple specialized sensors and reduces the overall device footprint
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient detection of different types of objects, including ferrous and non-ferrous metals, within a single device form factor by switching between capacitive and inductive sensing modes, reducing the need for multiple sense elements and circuits.
Implementation Method 1
a first measurement of a capacitance of the sense unit is taken by the charge measurement circuit when the first signal is applied to the sense unit by the signal generator
Implementation Method 2
a second measurement of an inductance of the sense unit is taken by the charge measurement circuit when the second signal is applied to the sense unit by the signal generator
Data Source
AI summary
An apparatus for inductive sensing or capacitive sensing is described. The apparatus may include a signal generator to output on a first terminal a first signal in a first mode and a second signal in a second mode. The apparatus may include a charge measuring circuit to receive on a second terminal a third signal in the first mode and a fourth signal in the second mode. The third signal is representative of an inductance of a sense unit coupled between the first terminal and the second terminal. The fourth signal is representative of a capacitance of the sense unit.