Capacitive Touch Sensing with Charge Sharing Compensation
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Solution Overview
Problem
Existing touch detection devices face challenges in accurately detecting hovering objects and force inputs due to the dominance of intrinsically inherent capacitance, which masks the small changes in capacitance caused by these inputs, especially in compact devices where parasitic capacitance values are high and changes in capacitance from user interactions are minimal.
Innovation Solution
A method and apparatus that utilize a compensation capacitor to precharge and share charges with a self-capacitor and electrode capacitor in parallel or series configurations, allowing for the detection of changes in capacitance caused by hovering objects and force inputs by compensating for the parasitic capacitance, thereby enhancing sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a self-capacitance touch screen uses an X-Y orthogonal arrangement of conductors, then each capacitive sensor functions as a line sensor and can sense and track a single touch, but it cannot support multiple touches
Solution Approach 1:
The patent divides the touch detection function into two independent parts: X-line sensors for horizontal position detection and Y-line sensors for vertical position detection. By segmenting the sensing function across multiple independent line sensors arranged in orthogonal directions, the system achieves both single touch tracking and multiple touch support through coordinated operation of these segmented sensing elements.
Solution Approach 2:
The patent makes the capacitive sensors serve multiple functions by using the same X-Y conductor arrangement for both single touch tracking and multiple touch detection. The line sensors function universally to detect touch events at different locations and numbers, eliminating the need for separate sensing mechanisms for different touch scenarios.
2Adaptability or versatility
If a mutual-capacitance touch screen uses an X-Y orthogonal arrangement of conductors with grid sensors at intersections, then multiple touches can be sensed and tracked, but the complexity of independently sensing all grid sensors increases
Solution Approach 1:
The patent segments the sensing function by using independent X-line and Y-line sensor groups that operate separately. Each line sensor group independently senses its respective direction, and the controller integrates the results to determine touch positions and numbers. This segmentation reduces the complexity of individually managing each grid sensor while maintaining multiple touch capability.
Solution Approach 2:
The patent merges the sensing results from multiple independent line sensors into a unified touch detection system. By combining the X-line and Y-line sensing data through the controller, the system achieves comprehensive multiple touch detection without requiring complex individual sensing circuits for each grid intersection.
3Quantity of substance
If the distance between electrodes in a capacitive sensor is reduced to increase capacitance, then the capacitance value increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent changes the capacitance parameter by using a dielectric material with high dielectric constant between the electrodes, rather than relying solely on reducing the distance between electrodes. This parameter change approach increases capacitance value while avoiding the manufacturing precision issues associated with tight electrode spacing tolerances.
Solution Approach 2:
The patent employs a composite dielectric structure between the electrodes that combines multiple materials with different dielectric properties. This composite material approach achieves high capacitance values through the high dielectric constant of the material composition, eliminating the need for precision-controlled electrode spacing.
4Volume of moving object
If parasitic capacitance values are high in compact devices, then the device size is reduced, but the detection sensitivity for hovering objects and force inputs decreases
Solution Approach 1:
The patent extracts and isolates the parasitic capacitance from the sensing circuit by using a separate compensation capacitor. This extracted parasitic capacitance is then compensated for through the compensation capacitor, allowing the sensing circuit to focus on detecting the small capacitance changes caused by hovering objects and force inputs without interference from the high parasitic capacitance.
Solution Approach 2:
The patent introduces a compensation capacitor as an intermediary element between the sensing circuit and the parasitic capacitance. This intermediary capacitor mediates the effect of parasitic capacitance by providing a compensating charge that offsets the parasitic capacitance influence, thereby enhancing the detection sensitivity for small capacitance changes in compact devices.
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 enables efficient detection of hovering objects and force inputs with improved sensitivity and accuracy, overcoming the limitations of inherent capacitance interference, even in devices with high parasitic capacitance values, by actively managing the equivalent capacitance to isolate the self-capacitance changes.
Implementation Method 1
A general self-capacitance touch screen uses an X-Y orthogonal arrangement of conductors. In this case, each capacitive sensor functions as a line sensor, and thus only one piece of X-sensing information and one piece of Y-sensing information are respectively provided by an X-line sensor group and a Y-line sensor group every time the touch screen is scanned.
Implementation Method 2
When a user approaches a sensor, interference to an electric field formed between the two electrodes occurs to prevent a part of electric charges from being accumulated on the sensor. Therefore, an amount of electric charges accumulated on the sensor is reduced, and consequently the capacitance is reduced.
Data Source
AI summary
Disclosed is a method of detecting a hovering object, the method including: an operation of precharging a compensation capacitor and a parallel capacitor, which is obtained by connecting in parallel a self-capacitor formed between an object hovering over a touch panel and an electrode of the touch panel and a parasitic capacitor of the touch panel, with a predetermined voltage; a first charge sharing operation of sharing charges by connecting the parallel capacitor and the compensation capacitor in series; a second charge sharing operation of sharing charges by connecting the parallel capacitor and the compensation capacitor in parallel; and an operation of outputting an electrical signal provided by the parallel capacitor while the parallel capacitor and the compensation capacitor are connected in parallel.