Touch Sensing Circuit With Charge Injection for Parasitic Capacitance
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Solution Overview
Problem
The integration of touch sensing circuits and display drive circuits in TDDI chips results in increased chip area, and the self-capacitance detection method requires a compensation capacitor, further enlarging the chip area and complicating the circuit.
Innovation Solution
A touch detection device comprising a charge amplification circuit and a capacitance compensation circuit, where the charge amplification circuit receives and amplifies signals from a touch panel, and the capacitance compensation circuit injects compensation charges with a polarity related to the direction of excitation signal changes, effectively compensating for parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the touch sensing circuit and display drive circuit are integrated into a TDDI chip, then the circuit integration is improved, but the chip area increases
Solution Approach 1:
The patent combines the touch sensing circuit and display drive circuit into a single TDDI chip, achieving functional integration. This merging of previously separate circuits into one integrated device improves circuit integration while managing the area through shared resources and compact design.
2Measurement precision
If a compensation capacitor is provided inside the touch sensing circuit to offset parasitic capacitance, then the touch detection accuracy is improved, but the chip area further increases
Solution Approach 1:
The patent extracts the compensation function from a dedicated compensation capacitor and implements it through a compensation circuit that uses existing circuit elements and switching mechanisms. This extraction approach provides the necessary capacitance compensation without requiring additional capacitor area on the chip.
Solution Approach 2:
The compensation circuit is designed to perform multiple functions: it provides capacitance compensation for parasitic effects, enables touch detection, and works with the existing touch sensing circuitry. This multi-functionality eliminates the need for separate dedicated compensation components, reducing overall chip area.
3Measurement precision
If a compensation capacitor is provided inside the touch sensing circuit, then the parasitic capacitance compensation is improved, but the circuit complexity increases
Solution Approach 1:
The patent introduces a compensation circuit as an intermediary between the touch sensing electrode and the detection circuitry. This intermediary circuit actively compensates for parasitic capacitance effects through controlled charge injection and switching, providing accurate compensation without requiring a large dedicated compensation capacitor.
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 proposed solution improves the accuracy of touch detection by compensating for parasitic capacitance, reduces the circuit area required, and simplifies the circuit complexity compared to traditional methods.
Implementation Method 1
a capacitance compensation circuit connected to the sensing point of the touch panel and configured to inject compensation charges into the sensing point in a process during which a level of an excitation signal changes, wherein a polarity of the compensation charges is related to a direction of the level of the excitation signal changing
Data Source
AI summary
The present disclosure relates to a touch detection device and method, and an electronic apparatus. The touch detection device comprises: a charge amplification circuit connected to a sensing point of a touch panel and configured to receive an excitation signal and charges of the sensing point, amplify the charges of the sensing point, and output a capacitance change signal of the sensing point; and a capacitance compensation circuit connected to the sensing point of the touch panel and configured to inject compensation charges into the sensing point in a process during which a level of the excitation signal changes, wherein a polarity of the compensation charges is related to a direction of the level of the excitation signal changing. The embodiment of the present disclosure may compensate for or even eliminate the influence caused by the parasitic capacitance of the touch panel, improve the accuracy of touch detection, and save the circuit area.