Pixel Settling in Integrated Display and Capacitive Sensing
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Solution Overview
Problem
Integrated display and capacitive sensing devices face challenges in minimizing display artifacts due to transient variations in supply voltage and pixel settling caused by the long horizontal blanking interval, leading to inconsistent display performance.
Innovation Solution
A processing system is implemented that includes source drivers for display electrodes and sensing circuitry for capacitive sensing, with a controller initiating a long horizontal blanking interval and an equalizer activating circuitry to equalize power drawn during display updating and sensing periods, thereby mitigating display artifacts by managing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long horizontal blanking interval is initiated during capacitive sensing, then capacitive sensing can be performed, but transient variations in supply voltage occur causing display artifacts
Solution Approach 1:
The patent applies preliminary anti-action by enabling display pixel settling during the long horizontal blanking interval before capacitive sensing begins. The controller is configured to allow a settling period where display electrodes are driven with display voltages to stabilize pixel states before the sensing operation starts, thereby preventing display artifacts that would otherwise occur due to voltage transients during sensing.
Solution Approach 2:
The patent implements preliminary action by pre-charging or pre-discharging display pixel capacitors during the horizontal blanking interval before capacitive sensing. The source drivers prepare the display electrodes by establishing stable voltage levels and charging pixel capacitors in advance, so that when sensing begins, the display pixels are already settled and won't produce artifacts during the sensing operation.
2Reliability
If display pixels are driven during display updating, then display performance is maintained, but power consumption varies between display updating and sensing periods
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the power consumption during capacitive sensing to match the power consumption during display updating. The controller monitors the power drawn from supplies during sensing operations and dynamically controls the source drivers or sensing circuitry to consume equivalent power, thereby maintaining consistent power levels and preventing supply voltage transients that would cause display artifacts.
Solution Approach 2:
The patent implements parameter changes by modifying sensing parameters during the capacitive sensing operation to equalize power consumption. The controller adjusts sensing voltage levels, sensing duration, or electrode drive patterns dynamically to ensure that the power drawn during sensing matches the power drawn during display updating, thereby stabilizing supply voltage and eliminating display artifacts.
Data Source
AI summary
An example method of performing capacitive sensing and display updating in an integrated capacitive sensing device and display device includes driving a plurality of display electrodes with one or more display voltages from one or more supplies during a first time period, the one or more voltages configured to drive the display pixels. The method further includes initiating a long horizontal blanking interval during a second time period. The method further includes driving a plurality of sensor electrodes with one or more sensing voltages from the one or more supplies during the second time period to perform capacitive sensing. The method further includes activating first circuitry during one of the first time period or the second time period to draw current to equalize power drawn from the one or more supplies during the first and second time periods within a threshold.