Touch Panel Controller Multiplexing Sense Lines
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Solution Overview
Problem
Self-capacitance touch panels face challenges in detecting capacitance with high accuracy due to undesired signal components and require a large number of amplifiers, making it difficult to adapt existing mutual-capacitance touch panel controllers.
Innovation Solution
A touch panel controller that multiplexes sense lines by using a drive circuit to drive electrodes multiple times with a code series, a code multiplication unit to read linear sum signals, and a detection circuit to calculate capacitance changes using inverse matrices, reducing the number of amplifiers needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sense lines are multiplexed using a single operational amplifier, then the number of amplifiers is reduced, but measurement precision deteriorates due to undesired signal components
Solution Approach 1:
The patent divides the multiplexing process into multiple sequential stages, where different groups of sense lines are connected to the operational amplifier at different time periods. This segmentation allows the system to process multiple sense lines using a single amplifier while maintaining measurement accuracy through time-division multiplexing.
Solution Approach 2:
The patent employs periodic switching of sense lines to the operational amplifier, where each sense line is sequentially connected in a periodic manner. This periodic action enables the single amplifier to service multiple sense lines over time while maintaining signal integrity and reducing error components through controlled timing.
2Measurement precision
If self-capacitance method is used with all electrodes as sense electrodes, then resolution and signal intensity improve, but undesired signal components increase
Solution Approach 1:
The patent extracts and separates the desired capacitance signal from the undesired signal components by using sequential switching and selective connection of sense lines to the operational amplifier. This extraction process isolates the useful capacitance information while filtering out error components through the multiplexing architecture.
Solution Approach 2:
The patent introduces switch elements as intermediary components between the sense lines and the operational amplifier. These switch elements act as mediators that selectively connect specific sense lines to the amplifier at specific times, enabling the system to process multiple sense lines while maintaining signal quality and reducing error components.
3Adaptability or versatility
If existing mutual-capacitance touch panel controller is used for self-capacitance touch panel, then device compatibility is improved, but detection accuracy deteriorates
Solution Approach 1:
The patent designs a controller architecture that can function in both mutual-capacitance and self-capacitance modes by using configurable switch elements and multiplexing circuits. This universal design allows the same hardware controller to adapt to different touch panel types while maintaining detection accuracy through mode-specific configuration of the multiplexing architecture.
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 configuration allows for high-quality capacitance detection with reduced error components and a simpler structure, suitable for self-capacitance touch panels like fingerprint sensors, enhancing resolution and signal intensity.
Implementation Method 1
a touch panel that detects a capacitance or a change in the capacitance between multiple electrodes and a touch detection target
Data Source
AI summary
Sense lines in a self-capacitance touch panel are multiplexed. A touch panel controller (3) includes a drive circuit (4) that drives drive lines (D0 through D(K−1)), based on a drive code series, a code multiplication unit (11) that reads multiple linear sum signals along the sense lines (S0 through S(M−1)), based on the charges of detection electrodes (E) and performs an inner product computation with a detection code series, and a detection circuit (6) that detects a capacitance or a change in the capacitance.