Charge Amplifier Touch Detection Circuit for Parasitic Capacitance
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Solution Overview
Problem
Parasitic capacitances in capacitive touch control panels lead to saturation of the charge amplifier output, preventing accurate touch action detection.
Innovation Solution
Utilize in-phase excitation signals with differing amplitudes to compensate for parasitic capacitances, reducing their influence on detection accuracy without additional hardware, thereby minimizing the detection circuit's area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parasitic capacitances are present in the sensor electrodes, then the charge amplifier output becomes saturated, but touch action detection becomes impossible
Solution Approach 1:
The patent applies preliminary anti-action by introducing excitation signals to the sensor electrodes before touch detection to pre-compensate for parasitic capacitances. The excitation signals are designed to generate charges that counterbalance the parasitic capacitance effects, preventing output saturation before it occurs during touch detection
Solution Approach 2:
The patent changes the electrical parameters of the sensor electrodes by applying excitation signals with specific amplitudes and phases. By adjusting these signal parameters, the system dynamically modifies the effective capacitance characteristics to eliminate parasitic capacitance influence while maintaining touch detection sensitivity
2Measurement precision
If additional hardware is added to eliminate parasitic capacitance influence, then detection accuracy improves, but detection circuit area increases
Solution Approach 1:
The patent implements self-service by enabling the sensor electrodes to compensate for their own parasitic capacitances using locally generated excitation signals. Each sensor electrode group independently applies compensation charges through its associated transistor, eliminating the need for external compensation circuits or additional hardware components
Solution Approach 2:
The patent merges the parasitic capacitance compensation function with the existing sensor electrode structure and drive circuitry. The excitation signal generation and compensation operations are integrated into the normal touch detection workflow, combining multiple functions into the same hardware resources without increasing circuit area
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
Effectively reduces the impact of parasitic capacitances on touch action detection while minimizing the detection circuit's area, enhancing detection accuracy and reducing chip size.
Implementation Method 1
the sensor electrodes have relatively large parasitic capacitances, including parasitic capacitances of wiring, which are mainly a parasitic capacitance C base1 between the sensor electrodes and a source line and between the sensor electrodes and a gate line, and a parasitic capacitance to ground C base2
Data Source
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AI summary
A detection circuit, a touch panel, and an electronic device. The circuit comprises: a charge amplifier, that comprises a first input terminal, a second input terminal, and an output terminal; a feedback capacitor, two terminals of which being electrically connected to the first input terminal and the output terminal respectively, and the feedback capacitor being connected in parallel to a first switch; and a sensor electrode, that is electrically connected to the first input terminal. A first excitation signal is applied to a thin film transistor (TFT) in the touch panel in which the detection circuit is located and a second excitation signal is applied to the second input terminal, the first excitation signal being the same phase as the second excitation signal, and the amplitude of the first excitation signal being greater than the amplitude of the second excitation signal. Thus, the impact of parasitic capacitance can be eliminated, and a touch action being unable to be detected due to charge amplifier output saturation is avoided.