Touch Sensing Circuit Dual Integration for Accuracy
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Solution Overview
Problem
Capacitive touch sensing apparatuses face challenges in accurately determining touch inputs due to small changes in capacitance, requiring longer touch driving periods, which is difficult to achieve in time-division multiplexed systems where both display and touch panel driving periods are constrained within a frame period.
Innovation Solution
A touch sensitive display device with a touch sensing circuit that integrates touch sense signals over two predetermined durations to generate integrated signals, allowing for touch input detection by comparing these signals against a threshold, and utilizing a multi-integrator circuit to accumulate and analyze touch data efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a longer touch driving period is used to accurately detect touch inputs, then measurement precision is improved, but productivity deteriorates due to reduced frame rate and increased time consumption
Solution Approach 1:
The touch sensing operation is divided into multiple sub-periods within a single frame period. The touch sensor is driven in a time-division multiplexed manner with the display panel, where touch sensing is performed during specific time slots (e.g., during horizontal blanking periods or vertical blanking periods) rather than requiring a separate, extended time period. This segmentation allows accurate touch detection to be achieved within the constraints of the display frame rate.
Solution Approach 2:
The touch sensing circuit performs periodic sampling of the touch sensor during the frame period. By utilizing periodic action, the system accumulates touch sensing data over multiple cycles or time slots within one frame, thereby achieving accurate touch detection without extending the overall frame period. This periodic sampling approach maintains high frame rates while improving touch detection accuracy.
2Measurement precision
If a longer touch driving period is used to accurately detect touch inputs, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The touch sensing operations are arranged to be performed during predetermined time slots within the frame period, such as during horizontal blanking periods or vertical blanking periods, before the display rendering begins. By performing preliminary touch sensing actions during these idle time slots, the system accumulates sufficient sensing data without delaying the main display operation, thereby reducing the effective touch sensing time loss.
Solution Approach 2:
The touch sensing circuit dynamically adjusts its operation to utilize available time slots within the frame period. By dynamically allocating touch sensing operations to periods when display operations are not actively updating pixels, the system maximizes the use of available time resources, achieving accurate touch detection with minimal impact on overall system performance and time efficiency.
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
Enables accurate detection of touch inputs within a shorter sensing period, allowing for increased driving frequency and efficient operation in time-division multiplexed systems, even during high-frequency display panel driving modes.
Implementation Method 1
a touch sense signal indicating a change in self-capacitance of a driven electrode in response to a touch input on the driven electrode
Data Source
AI summary
A touch sensing circuit is configured to supply touch drive signals to electrodes of a touch sensitive display device and detect corresponding touch sense signals from the electrodes in response to the supplied touch drive signals, a touch sense signal indicating a change in self-capacitance of a driven electrode in response to a touch input on the driven electrode. The touch sensing circuit is further configured to integrate, for a first predetermined duration of time, a measure of each of the touch sense signals, to generate a first integrated signal corresponding to each touch sense signal; integrate, for a second predetermined duration of time, the first integrated signal, to generate a second integrated signal corresponding to each touch sense signal; and determine presence of one or more touch inputs on one or more of the electrodes based on the second integrated signal.