Current Conveyor Oscillator for Precise Mutual Capacitance Sensing
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Solution Overview
Problem
Conventional capacitance sensing devices face challenges in accurately determining the proximity of objects due to limitations in detecting subtle changes in capacitance, particularly in mutual capacitance sensing, which affects the precision of position detection in human interface devices.
Innovation Solution
The use of current conveyor based oscillator circuits that induce current variations in response to mutual capacitance between electrodes, generating oscillating signals that vary with object proximity, allowing for precise capacitance measurement through counter circuits or integrator circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitance sensing methods are used, then device complexity is reduced, but measurement precision deteriorates due to inability to detect subtle capacitance changes
Solution Approach 1:
The patent applies electrical oscillation (analogous to mechanical vibration) by using an oscillator circuit that generates periodic signals to drive the capacitance sensing electrodes. This oscillating approach enables detection of subtle capacitance changes through frequency and amplitude modulation, significantly improving measurement precision while maintaining manageable device complexity through standardized oscillator design.
Solution Approach 2:
The patent employs parameter changes by measuring variations in oscillation frequency, amplitude, and phase in response to capacitance changes. The oscillator circuit's output parameters (frequency, amplitude) are directly modulated by the sensed capacitance, enabling precise measurement through parameter extraction and analysis, thereby resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If mutual capacitance sensing is used, then position detection capability is improved, but sensitivity deteriorates due to subtle capacitance changes being difficult to detect
Solution Approach 1:
The patent implements periodic action by using an oscillator circuit that generates continuous periodic signals to excite the mutual capacitance between electrodes. The periodic nature of the oscillation amplifies subtle capacitance changes through cumulative effects over multiple cycles, enabling precise position detection while overcoming the difficulty of detecting minute capacitance variations that occur in mutual capacitance sensing.
Solution Approach 2:
The patent applies feedback by using the oscillator's output signal characteristics (frequency, amplitude, phase) that are modulated by the mutual capacitance to provide information about object position. The system continuously monitors these feedback parameters and uses them to determine precise position, thereby improving position detection precision while managing the difficulty of detecting subtle capacitance changes through signal processing.
3Measurement precision
If current conveyor based oscillators are used, then measurement precision is improved through linear relationship, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical or complex analog measurement systems with a current conveyor based oscillator circuit. The current conveyor is a standardized integrated circuit component that simplifies the overall device architecture while providing the necessary oscillation and measurement functions. This substitution maintains measurement precision through the linear relationship between oscillator parameters and capacitance while reducing overall device complexity compared to alternative high-precision approaches.
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
This approach enhances the accuracy of capacitance sensing by providing a linear relationship between oscillator period and sensed capacitance, enabling precise object position detection and improved sensitivity in human interface devices.
Implementation Method 1
A capacitance, as detected by sensor electrodes, may change as a function of the proximity of an object to the sensor electrodes
Implementation Method 2
A periodic signal may be transmitted on the Tx electrode 2602-1. Due to mutual capacitance (Cm), the electrical signal at the Tx electrode 2602-1 may induce a current on the Rx electrode 2602-0
Data Source
AI summary
A capacitance sensing system may include a current conveyor circuit coupled to receive induced current from a capacitance sensing structure at a low impedance current input port; and a comparator having an input coupled to a high impedance output port of the current conveyor circuit, and an output coupled to the current conveyor circuit by a feedback path and coupled to drive the capacitance sensing structure to generate the induced current.