Touch Panel Controller Using Differential Amplification for Line Dependency Correction
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Solution Overview
Problem
Conventional touch panel systems require multiple measurements to accurately detect capacitance changes, leading to slow processing speeds due to large noise components and line dependency issues in capacitance values.
Innovation Solution
A touch panel controller that drives multiple drive lines using an orthogonal code sequence and employs differential amplifiers to correct line dependency, allowing for accurate capacitance value detection with fewer measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are performed to accurately detect capacitance changes, then measurement precision is improved, but processing speed deteriorates
Solution Approach 1:
The sense lines are divided into multiple groups, with each group processed by a dedicated differential amplifier. This segmentation allows parallel processing of multiple sense lines simultaneously, improving processing speed while maintaining measurement precision through differential measurement techniques.
Solution Approach 2:
The driving section sequentially applies drive signals to different drive lines in periodic cycles. By alternating the application of drive signals and using orthogonal code sequences, the system achieves accurate capacitance measurements through time-multiplexed operation, resolving the contradiction between measurement accuracy and processing speed.
2Measurement precision
If conventional driving methods are used, then device complexity is reduced, but measurement precision deteriorates due to line dependency
Solution Approach 1:
The system performs preliminary calibration by measuring capacitance values under known conditions before actual touch detection. This preliminary action establishes reference data that compensates for line dependency effects, improving measurement precision without adding complex real-time correction mechanisms.
Solution Approach 2:
The driving section varies the amplitude and timing parameters of drive signals according to orthogonal code sequences. By changing these parameters systematically, the system achieves accurate capacitance measurements while maintaining relatively simple circuit architecture, as the complexity is managed through signal parameter modulation rather than circuit complexity.
3Measurement precision
If differential amplifiers are used to improve measurement precision, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple differential amplifiers are merged into a unified measurement system where each amplifier processes a specific group of sense lines. This merging approach maintains measurement precision for each channel while achieving overall system efficiency through coordinated operation, preventing exponential growth in device complexity.
Solution Approach 2:
Each differential amplifier is designed to handle multiple sense lines within its group, providing multi-functional capability. This universality reduces the total number of amplifiers needed compared to having one amplifier per sense line, thereby improving measurement precision without proportionally increasing device complexity.
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 configuration enables faster and more accurate detection of capacitance changes by reducing noise components and correcting line-dependent variations, improving the signal-to-noise ratio and preventing differential amplifier saturation.
Implementation Method 1
the capacitance detecting device detects the touch of the finger or pen by detecting a change in capacitance value of an electrostatic capacitor that corresponds to a part of a touch panel
Implementation Method 2
a differential amplifier for amplifying a difference between the first linear sum and the second linear sum
Data Source
AI summary
A touch panel controller (1), which can accurately detect changes in capacitance values of respective first and second electrostatic capacitors which are touched, includes: a driving section (4) for driving drive lines (DL1 through DL4) on the basis of a code sequence so as to drive (i) electrostatic capacitors (C31 through C34) provided between the respective drive lines (DL1 through DL4) and a sense line (SL3) and (ii) electrostatic capacitors (C41 through C44) provided between the respective drive lines (DL1 through DL4) and a sense line (SL4) so that (i) a first linear sum of first capacitance values of the respective electrostatic capacitors (C31 through C34) is outputted from the sense line (SL3) and (ii) a second linear sum of second capacitance values of the respective electrostatic capacitors (C41 through C44) is outputted from the sense line (SL4); a differential amplifier (5) for amplifying a difference between the first linear sum and the second linear sum; and a saturation prevention control section (8) for correcting a line dependency between the first capacitance values and the second capacitance values.