Touch Sensor Drive Electrodes Phase Multiplexing
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Solution Overview
Problem
Current touch sensors face inefficiencies in simultaneously driving and sensing multiple capacitive nodes, limiting the speed and accuracy of touch detection and location determination.
Innovation Solution
A touch sensor system that simultaneously drives multiple drive electrodes with different dominant frequencies and senses corresponding sense electrodes, allowing for simultaneous measurement of capacitive nodes and improved touch detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple capacitive nodes are driven sequentially, then the device complexity is reduced, but the touch detection speed and accuracy deteriorate
Solution Approach 1:
The patent applies periodic action by driving multiple capacitive nodes with alternating current signals at different phases. Each capacitive node is driven with a sinusoidal signal, and by varying the phase of these signals, the system can sequentially activate different nodes without requiring separate control circuits for each node. This allows parallel measurement of multiple nodes while maintaining manageable control complexity through phase-based multiplexing.
Solution Approach 2:
The patent utilizes parameter changes by modulating the frequency and phase of the drive signals to distinguish between different capacitive nodes. By changing the phase parameter of the AC signals, the system can selectively drive and measure specific nodes. The controller varies these parameters to enable simultaneous measurement of multiple capacitive nodes, thereby increasing touch detection speed without proportionally increasing device complexity.
2Measurement precision
If multiple capacitive nodes are measured simultaneously, then the touch location determination accuracy is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The system employs periodic action with alternating current signals to enable simultaneous measurement of multiple capacitive nodes. Each node is driven with an AC signal at a specific phase, and the phase-locked detection circuitry can simultaneously measure all nodes by referencing their phase relationships. This approach allows parallel measurement of multiple nodes, improving touch location accuracy while keeping the measurement process manageable through standardized phase-based detection.
Solution Approach 2:
The patent implements feedback mechanisms where the controller continuously monitors the capacitance changes at each capacitive node and processes this information to determine touch location. The system uses the phase information from the drive signals as feedback to identify which nodes are being activated and to distinguish between different touch inputs, thereby maintaining measurement precision while simplifying the detection process through intelligent signal processing.
3Measurement precision
If different drive frequencies are used for multiple drive electrodes, then the measurement precision is improved, but the use of energy increases
Solution Approach 1:
The patent applies periodic action by using alternating current signals with different phases rather than significantly different frequencies. This approach allows the system to distinguish between multiple capacitive nodes through phase discrimination, which is more energy-efficient than using high-frequency signals for each node. The controller processes the phase information to identify node activations, achieving measurement precision while minimizing energy consumption compared to traditional multi-frequency approaches.
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 enables quicker and more accurate detection of touch locations, including distinguishing between active stylus and passive object inputs, by processing multiple capacitive nodes in a shorter time frame.
Implementation Method 1
The drive and sense electrodes may be capacitively coupled to one another across a space between the drive and sense electrodes
Implementation Method 2
When an object touches or comes within proximity of the surface of the capacitive touch screen, a change in capacitance may occur within the touch screen at the location of the touch or proximity
Data Source
AI summary
In one embodiment, a method comprises generating, by a controller, a plurality of drive signals. The method further includes simultaneously transmitting, by the controller, the plurality of drive signals to a plurality of drive electrodes disposed on a touch sensor. The method further includes sensing a sense electrode of a plurality of sense electrodes disposed on the touch sensor. The sensing comprises measuring, for each drive electrode of the plurality of drive electrodes, at least one value indicative of a capacitance between the sense electrode and the drive electrode.