Touch Panel Controller Capacitance Offset Compensation
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Solution Overview
Problem
Capacitive touchscreen devices face challenges in accurately detecting touch inputs due to the large capacitance of electrodes and capacitance offsets between them, which interfere with the detection of minute changes in capacitance, such as hover touches.
Innovation Solution
A touch panel controller is designed to remove the capacitance of electrodes and compensate for capacitance offsets by simultaneously charging sensor lines with the same charge and sensing changes in capacitance through a driving unit and sensing unit, which applies driving signals and calculates voltage differences to detect touch positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-capacitance sensing method is used to detect small changes in capacitance, then measurement precision is improved, but device complexity increases due to the need to remove electrode capacitance and compensate for capacitance offsets
Solution Approach 1:
The patent extracts and removes the electrode capacitance from the measurement by using a separate sensing electrode that does not include the electrode capacitance in its measurement, thereby isolating the touch-induced capacitance change from the electrode capacitance
Solution Approach 2:
The patent introduces a sensing electrode as an intermediary element that mediates between the touch input and the measurement system, allowing capacitance changes to be detected without directly measuring the electrode capacitance that causes offset errors
2Measurement precision
If capacitance of electrodes is removed and capacitance offset is compensated, then measurement precision is improved, but device area and volume increase
Solution Approach 1:
The patent makes the sensing electrode serve multiple functions: it acts as both the sensing element for capacitance measurement and as part of the touch interface, eliminating the need for separate components that would increase device area
Solution Approach 2:
The patent merges the sensing function with the existing electrode structure by using the sensing electrode to perform both touch sensing and to compensate for electrode capacitance effects, thereby achieving improved precision without proportionally increasing device area
3Measurement precision
If capacitance of electrodes is removed and capacitance offset is compensated, then measurement precision is improved, but device volume increases
Solution Approach 1:
The patent extracts the capacitance offset compensation function from the main measurement path by using a separate sensing electrode, allowing the measurement system to focus only on touch-induced capacitance changes without needing additional volume for offset compensation circuitry
Solution Approach 2:
The patent creates a simplified copy of the electrode structure in the sensing electrode that replicates the essential capacitance characteristics without including the full electrode capacitance, thereby reducing the volume required for capacitance management
4Area of stationary object
If conventional capacitance sensing is used, then device area and volume are minimized, but common noise interference increases
Solution Approach 1:
The sensing electrode acts as an intermediary that isolates the measurement system from common noise sources by providing a dedicated sensing path that is reference to the driving signal, thereby rejecting common-mode noise while maintaining compact device area
Solution Approach 2:
The patent uses the sensing electrode to establish an equipotential reference that cancels out common noise voltages, allowing the measurement system to maintain small device area while achieving noise immunity through differential measurement
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 solution effectively reduces the capacitance of electrodes and compensates for offsets, enhancing the accuracy of touch input detection and reducing the device's area and volume, while minimizing common noise interference.
Implementation Method 1
A driving unit charging a plurality of sensor lines with the same charge by simultaneously applying a driving signal to the sensor lines
Implementation Method 2
A sensing unit senses a change in capacitance by calculating a difference in voltage levels between a voltage of each of the sensor lines and a voltage of the driving signal
Data Source
AI summary
A touch panel controller includes a signal driver charging a plurality of sensor lines extending in a direction with the same charge, by applying a driving signal to one sensor line of sensor lines and applying a mirrored driving signal mirrored from the driving signal to the remaining sensor lines of the sensor lines, and a sensor sensing a change in capacitance from the sensor lines, respectively.