Self-Capacitance Touch Driving Circuit With Code Division Sensing
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Solution Overview
Problem
The self-capacitance sensing scheme in touch display devices faces limitations in improving signal-to-noise ratio (SNR) and sensitivity due to the inability to apply varying waveforms for touch driving signals, as both driving and sensing signals are provided through a single touch line.
Innovation Solution
Implementing a code division sensing effect by using a multiplexer to output a code division sensing signal from touch electrodes, which allows for improved SNR and sensitivity by sensing multiple touch electrodes in a code division form, and applying a multiple frequency sensing scheme to reduce noise and prevent saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a code division waveform varying over time is applied to a driving electrode in the mutual-capacitance sensing scheme, then the signal-to-noise ratio and sensitivity of touch sensing are improved, but this approach cannot be applied to the self-capacitance sensing scheme where both driving and sensing signals are provided through one touch line
Solution Approach 1:
The patent segments the touch sensing process into multiple time slots, where different touch electrodes are sensed sequentially during different time periods. This time-division multiplexing allows code division waveforms to be applied to driving electrodes while still enabling self-capacitance sensing through the same touch line, resolving the contradiction between improved sensitivity and applicability to self-capacitance schemes.
Solution Approach 2:
The patent implements periodic switching between driving and sensing modes for different touch electrodes. By periodically applying code division waveforms to driving electrodes and periodically switching the touch line between driving and sensing functions, the system achieves both improved touch sensing sensitivity through code division and compatibility with self-capacitance sensing schemes.
2Speed
If multiple touch electrodes are sensed simultaneously, then the sensing speed is improved, but the touch driving circuit may become saturated and power consumption increases
Solution Approach 1:
The patent divides the touch electrode sensing into multiple groups, where each group is sensed during different time slots. This segmentation allows parallel sensing of multiple electrodes within each time slot while preventing circuit saturation by limiting the number of simultaneously active electrodes, thus maintaining both high sensing speed and circuit reliability.
Solution Approach 2:
The patent applies partial action by sensing only a subset of touch electrodes simultaneously in each time slot rather than all electrodes at once. This approach maintains high sensing speed through parallel processing of multiple electrodes while avoiding circuit saturation by controlling the number of active sensing operations at any given moment.
3Measurement precision
If the touch driving signal level is increased to improve sensing accuracy, then the signal-to-noise ratio is improved, but power consumption increases and circuit saturation may occur
Solution Approach 1:
The patent uses periodic application of high-level driving signals only during sensing time slots, while using lower power levels during display time slots. This periodic high-power operation improves signal-to-noise ratio and sensing accuracy when needed, while reducing overall power consumption by limiting high-power signal application to only the necessary sensing periods.
Solution Approach 2:
The patent applies excessive driving signal levels partially, only during the sensing time slots and only for the specific electrodes being sensed at that moment. This partial application of high power levels improves sensing accuracy during critical measurement periods while minimizing overall power consumption by avoiding continuous high-power operation across all electrodes.
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 approach enhances the SNR and sensitivity of touch sensing, reduces power consumption, and prevents saturation of the touch driving circuit by controlling the touch driving signal levels, while also stabilizing the touch driving process.
Implementation Method 1
a multiplexer connected to the touch electrodes through the touch lines and outputting a code division sensing signal obtained by adding, in a code division form, touch sensing signals provided from a plurality of touch electrodes selected by code division control signals
Implementation Method 2
a capacitance-based touch sensing scheme has become widespread in use which includes detecting a touch presence, a touch coordinate, and the like based on a change in capacitance formed across a plurality of touch electrodes arranged in a display panel
Data Source
AI summary
Embodiments of the present disclosure relate to a touch display device, a touch driving circuit, and a touch driving method, and more specifically, to a touch display device, a touch driving circuit, and a touch driving method for enabling a signal-to-noise ratio (SNR) and sensitivity of touch sensing to be improved by implementing a code division sensing effect for the self-capacitance sensing scheme.