Capacitive Touch Panel Offset Reduction via Mode Switching
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Solution Overview
Problem
Conventional signal processing circuits for electrostatic capacity type touch panels face issues with noise interference leading to malfunction and are unable to detect multi-touch inputs, as they rely on single input types that lose capacitance differences when multiple sense lines are touched.
Innovation Solution
A signal processing circuit with multiple sense lines and a drive line, incorporating both differential and single input type sensor circuits, along with variable capacitors for calibration and a switching control circuit to alternate between modes, allowing for detection of capacitance differences and adjustments to minimize noise interference and enable multi-touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single input type signal processing circuit is used, then the device complexity is reduced, but the reliability deteriorates due to noise interference causing malfunction
Solution Approach 1:
The patent implements a dynamic switching mechanism that alternates between single-input and differential-input modes based on operational requirements. The switching control circuit enables the system to transition between circuit configurations, allowing optimization of either simplicity or noise tolerance depending on the touch detection scenario.
Solution Approach 2:
The signal processing circuit is designed to perform multiple functions by incorporating both single-input and differential-input capabilities within the same circuit architecture. This multi-functional design allows the circuit to handle both noise-sensitive applications and simple touch detection tasks using the same hardware platform.
2Reliability
If a differential input type signal processing circuit is used, then the reliability is improved by noise tolerance, but the adaptability deteriorates as it cannot detect multi-touch inputs
Solution Approach 1:
The system dynamically switches between differential-input mode for noise tolerance and single-input mode for multi-touch detection. This temporal separation of functions allows the circuit to excel at one task at a time while maintaining both capabilities through controlled mode transitions.
Solution Approach 2:
The patent segments the touch detection functionality into distinct operational modes handled by separate circuit paths. The switching control circuit acts as a gatekeeper, routing signals through appropriate processing paths based on the desired detection mode, effectively dividing the unified circuit into functional segments.
3Manufacturing precision
If offset calibration is performed with variable capacitors connected in parallel, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The patent uses variable capacitors to dynamically adjust circuit parameters during calibration. By changing the capacitance values of these variable capacitors, the system can compensate for manufacturing variations and achieve precise offset calibration, directly manipulating electrical parameters to correct hardware imperfections.
Solution Approach 2:
The calibration circuit performs self-adjustment through automated offset calibration procedures. The system uses its own internal resources (variable capacitors and control logic) to correct its own manufacturing errors without requiring external calibration equipment, enabling factory or field calibration.
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
The solution enhances noise tolerance and sensitivity, enabling reliable single-touch detection while allowing for stable multi-touch input recognition by switching between differential and single input modes, effectively addressing the limitations of conventional systems.
Implementation Method 1
a first sensor circuit of a differential input type which selects the first and second sense lines out of the plurality of sense lines and detects a difference between a capacitance of a first electrostatic capacitor formed between the first sense line and the drive line and a capacitance of a second electrostatic capacitor formed between the second sense line and the drive line
Implementation Method 2
a second sensor circuit of a single input type which selects the first sense line out of the plurality of sense lines and detects a change in the capacitance of the first electrostatic capacitor formed between the first sense line and the drive line
Implementation Method 3
first and second variable capacitors for calibration adjusting an offset in an output voltage of the first sensor circuit, and a switching control circuit to control the first and second sensor circuits so that either the first sensor circuit or the second sensor circuit is put in operation and to control the first and second variable capacitors for calibration so that the first and second variable capacitors are connected in parallel to each other when the second sensor is put in operation
Data Source
AI summary
This invention offers a signal processing circuit of an electrostatic capacity type touch panel which is capable of switching between a differential input mode and a single input mode and has an extended adjustable range of an offset in the single input mode. The signal processing circuit of this invention includes a first sensor circuit of a differential input type, a second sensor circuit of a single input type, a third and fourth electrostatic capacitors that are variable capacitors for calibration to adjust the offset in an output voltage of the first sensor circuit, and a switching control circuit to control so as to put in operation one of the first and second sensor circuits. The switching control circuit also controls so that the third and fourth electrostatic capacitors for calibration are connected in parallel to each other when the second sensor circuit is put in operation.