Touch Display Device Jitter Suppression via PWM Sampling Control
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Solution Overview
Problem
Touch display devices experience jitter in digital sensing data due to source channel toggles during display periods, degrading touch performance.
Innovation Solution
A touch display device with a touch driver that includes a touch sensing circuit, a touch control circuit, and a sampling control circuit, which generates a pulse-width modulation (PWM) signal and controls the sampling timing to prevent jitter by advancing the sampling of touch sensing signals during the touch sensing period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the touch display device performs analog-to-digital conversion during the touch sensing period, then the touch sensing data can be obtained, but jitter is generated in the converted digital sensing data due to source channel toggle for display driving
Solution Approach 1:
The patent applies preliminary action by completing the analog-to-digital conversion of touch sensing signals before the display period begins. The touch driver circuit is configured to convert analog touch sensing signals to digital signals during the touch sensing period, and the converted digital signals are stored in a buffer. This ensures that the conversion is completed in advance, avoiding any interference from subsequent display channel toggles and eliminating jitter in the digital sensing data.
2Productivity
If the source channel is toggled for display driving during the touch sensing period, then the display can be updated, but jitter is generated in the converted digital sensing data
Solution Approach 1:
The patent applies segmentation by separating the touch sensing signal processing path from the display signal path. The touch driver circuit includes dedicated analog-to-digital conversion circuits for touch sensing signals that are independent from the display data output circuits. This segmentation ensures that toggling the source channel for display updates does not interfere with the stability and accuracy of touch sensing data conversion.
3Duration of action of stationary object
If the analog-to-digital conversion is performed during the display period, then the display driving can proceed without interruption, but the touch sensing performance is degraded due to jitter
Solution Approach 1:
The patent applies preliminary action by completing the analog-to-digital conversion of touch sensing signals before the display period begins. The touch driver circuit is configured to convert analog touch sensing signals to digital signals during the touch sensing period, and the converted digital signals are stored in a buffer. This ensures that the conversion is completed in advance, avoiding any interference from subsequent display channel toggles and eliminating jitter in the digital sensing data.
Data Source
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AI summary
A touch display device includes a touch panel which is time-divisionally driven into a touch sensing period and a display period by a synchronization signal and includes a plurality of touch electrodes; and a touch driver which drives the touch panel. The touch driver includes: a touch sensing circuit configured to supply a touch driving signal to each of the plurality of touch electrodes and samples an integral value of an analog touch sensing signal detected by each of the plurality of touch electrodes to output digital sensing data; a touch control circuit configured to generate a pulse width modulation PWM signal including a plurality of pulses and receives the sensing data to figure out a touch; and a sampling control circuit configured to output a sampling control signal which controls a sampling timing of the integral value of the touch sensing signal to the touch sensing circuit.