Touch Panel Controller Variable Rise Fall Time EMI Reduction
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Solution Overview
Problem
Large capacitive touch panels experience increased electromagnetic interference (EMI) due to the simultaneous pulse-driving of drive lines, which worsens as panel size increases, leading to higher emission efficiency and more antennas emitting electromagnetic waves.
Innovation Solution
A touch panel controller with variable rise/fall times for driving signals applied to drive lines, achieved through a configuration of driving circuits with adjustable second inverter circuits and switches, allowing for optimized channel widths to minimize EMI while maintaining touch location detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If drive lines are simultaneously pulse-driven in a large touch panel, then touch location detection is achieved, but electromagnetic interference (EMI) is increased
Solution Approach 1:
The patent applies periodic action by sequentially driving drive lines in a time-division manner rather than simultaneously. The driving signal is applied to one drive line at a time in sequence, which maintains the capacitive touch detection functionality while significantly reducing electromagnetic interference by eliminating simultaneous pulse emissions from multiple drive lines
Solution Approach 2:
The patent changes the temporal parameters of the driving signal by adjusting the pulse width and interval between pulses. By optimizing these parameters, the system maintains sufficient detection sensitivity while reducing the duration and intensity of electromagnetic emissions, thereby lowering overall EMI from the touch panel
2Area of stationary object
If panel size of capacitive touch panel is increased, then display area is enlarged, but emission efficiency of antennas is heightened
Solution Approach 1:
The patent segments the drive lines into multiple groups and assigns different scanning sequences to each group. This segmentation allows the large panel to be driven in a distributed manner over time, preventing any single region from emitting strong electromagnetic waves simultaneously, thereby reducing overall EMI while maintaining large display area
Solution Approach 2:
The patent implements periodic scanning of drive lines in sequential order across the large panel. By periodically activating different drive lines in a systematic sequence rather than simultaneously, the system maintains functionality across the enlarged panel area while distributing electromagnetic emissions over time, reducing peak emission efficiency
3Area of stationary object
If number of drive lines is increased, then coverage of touch panel is improved, but number of antennas emitting electromagnetic waves is increased
Solution Approach 1:
The patent applies periodic action by sequentially activating drive lines one at a time rather than simultaneously. This time-division multiplexing approach allows coverage of the entire touch panel area with multiple drive lines while ensuring that only one drive line emits electromagnetic waves at any given moment, thereby maintaining coverage without proportionally increasing simultaneous EMI sources
Solution Approach 2:
The patent introduces dynamic scanning sequences that adaptively control the activation timing of each drive line. By dynamically adjusting which drive line is active at each time step and optimizing the scanning pattern, the system maintains comprehensive coverage while minimizing the number of simultaneously active antennas, thereby reducing overall electromagnetic interference
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 solution effectively reduces EMI in large touch panels while ensuring sufficient touch location detection sensitivity, enabling the use of a single touch panel controller for various panel sizes, thereby reducing costs and improving performance.
Implementation Method 1
a capacitive touch panel device includes (i) a touch panel unit in which a plurality of drive lines (first electrode) and a plurality of sense lines (second electrode) intersect with each other
Data Source
AI summary
The present invention provides a touch panel controller for controlling even a large touch panel with little EMI. The touch panel controller of the present invention includes a plurality of driving circuits (DC1 through DCm) for driving respective drive lines (DL1 through DLm) of a capacitive touch panel unit 2 by supplying driving signals (Ds) to the respective drive lines (DL1 through DLm), and a rise/fall time of each of the driving signals (Ds) is variable.