Modulated Power Supply for In-Cell Capacitive Sensing
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Solution Overview
Problem
Capacitive touch sensing devices face challenges in detecting input objects due to parasitic capacitance from nearby conductive elements, particularly in 'in-cell' display embodiments where sensing electrodes are close to conductive components, reducing the accuracy of input detection.
Innovation Solution
A modulated power supply is used to drive both sensor and display electrodes with modulated signals, maintaining a constant voltage differential and reducing parasitic capacitance by synchronizing the modulation of the power supply with capacitive sensing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sensor electrodes are placed close to conductive elements in in-cell display embodiments, then integration density is improved, but parasitic capacitance increases reducing sensing accuracy
Solution Approach 1:
The patent applies preliminary anti-action by driving display electrodes with guard signals that preemptively counteract parasitic capacitance effects before they interfere with sensing operations. The guard signals are specifically designed to track and cancel the capacitive coupling between sensor electrodes and display electrodes, thereby eliminating the harmful parasitic effects while maintaining close physical integration.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the voltage levels and timing of guard signals applied to display electrodes. By modulating the display electrode voltages in synchronization with sensing operations and using different voltage levels during sensing versus display periods, the system adapts the electrical parameters to minimize parasitic capacitance impact while maintaining integration density.
2Productivity
If touch sensing and display updating are performed simultaneously, then productivity is improved, but interference from parasitic capacitance increases
Solution Approach 1:
The patent implements periodic action by dividing operation into alternating sensing periods and display update periods. During sensing periods, display electrodes are driven with guard signals to minimize parasitic capacitance while sensing occurs. During display update periods, normal display voltages are applied. This periodic switching enables both functions to operate effectively without mutual interference, achieving simultaneous productivity improvement while controlling parasitic effects.
Solution Approach 2:
The patent applies local quality by providing different electrical conditions to different regions or time periods: during sensing periods, display electrodes receive guard signals with specific voltage characteristics localized to the sensing operation, while during display periods, normal display voltages are applied. This localized adaptation of electrical conditions allows simultaneous operation without interference.
3Measurement precision
If guard signals are applied to display electrodes, then parasitic capacitance is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by using the existing display electrodes to serve dual functions: as display elements during display periods and as guard electrodes during sensing periods. The same physical structures perform multiple roles, eliminating the need for separate guard electrode structures and reducing overall device complexity while maintaining sensing accuracy through guard signal application.
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 ability to detect input objects by minimizing parasitic capacitance effects, allowing for simultaneous touch sensing and display updating without interference, thereby improving the accuracy and efficiency of capacitive sensing in integrated touch and display systems.
Implementation Method 1
parasitic capacitance between the sensor electrodes and conductive objects other than an input object
Data Source
AI summary
An input device comprising a display device having an integrated capacitive sensing device. The input device includes a plurality of sensor electrodes a plurality of display electrodes, a modulated power supply configured to provide a modulated reference signal, and a processing system. The processing system includes a sensor module configured to drive a plurality of sensor electrodes with a modulated capacitive sensing signal that is based on the modulated reference signal for capacitive sensing during a first time period. The processing system also includes a display driver module configured to drive a plurality of display electrodes of a display device with modulated signals based on the modulated reference signal during the first time period. The modulated signals cause voltage between the plurality of display electrodes and the plurality of sensor electrodes to remain substantially constant.