Touch Sensor Scan Signals for Low-EMI Touch Detection
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Solution Overview
Problem
Touch sensors in display devices experience electronic interference (EMI) that affects their operational reliability, leading to reduced performance.
Innovation Solution
A touch sensor design that utilizes sinusoidal scan signals with specific amplitude and frequency relationships between unit signals and gap signals to minimize EMI, allowing for accurate touch detection while reducing noise and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If touch sensors use conventional scan signals for touch detection, then touch sensing functionality is achieved, but electronic interference (EMI) increases affecting operational reliability
Solution Approach 1:
The patent applies periodic action by using sinusoidal scan signals with specific frequency characteristics. The scan signal is designed as a sinusoidal wave that periodically transitions between different voltage levels, allowing the touch sensor to detect touches while minimizing EMI generation. The periodic nature of the sinusoidal signal helps in distinguishing touch events from noise and reduces electromagnetic interference compared to conventional square wave signals.
Solution Approach 2:
The patent employs parameter changes by optimizing the frequency and amplitude characteristics of the scan signal. Specifically, the scan signal frequency is set within a range of 20 kHz to 200 kHz, and the amplitude is modulated to achieve optimal touch detection sensitivity while minimizing EMI. By changing these signal parameters, the system achieves better reliability with reduced electronic interference.
2Measurement precision
If higher amplitude scan signals are used to improve touch detection sensitivity, then measurement precision improves, but power consumption increases
Solution Approach 1:
The patent optimizes the amplitude parameter of the scan signal to achieve a balance between touch detection sensitivity and power consumption. The sinusoidal scan signal uses controlled amplitude modulation, where the amplitude is sufficient to detect touches accurately but not excessively high to waste power. This parameter optimization allows the system to maintain measurement precision while reducing energy consumption compared to conventional high-amplitude signals.
Solution Approach 2:
The periodic sinusoidal nature of the scan signal allows for efficient energy utilization. Instead of maintaining a constant high amplitude, the signal periodically varies, using higher amplitude only when needed for detection and lower amplitude during non-detection periods. This periodic variation reduces average power consumption while maintaining the ability to detect touches with high precision.
3Productivity
If conventional scan signals are used for touch detection, then touch sensing operation is maintained, but electronic interference affects internal components and reduces operational reliability
Solution Approach 1:
The patent uses periodic sinusoidal scan signals to perform touch sensing operations while minimizing EMI generation. The sinusoidal waveform naturally produces less electromagnetic radiation compared to abrupt square wave transitions, thereby reducing interference to internal components. The periodic operation maintains productivity by continuously monitoring for touches while the smooth waveform characteristics reduce harmful EMI effects.
Solution Approach 2:
By changing the signal waveform from conventional square waves to sinusoidal waves and optimizing the frequency parameter to 20-200 kHz, the patent reduces electronic interference to internal components. This parameter change maintains effective touch sensing operation while the sinusoidal characteristics and frequency selection minimize the generation and propagation of EMI throughout the device.
Data Source
AI summary
A touch sensor is provided. The touch sensor including: first touch electrodes; scan lines connected to the first touch electrodes; and a controller that applies a scan signal to each of the scan lines, wherein the scan signal includes a plurality of unit signals in a first time period and a second time period, and includes a gap signal in a gap period between the first time period and the second time period, and an amplitude of each of the plurality of unit signals is greater than an amplitude of the gap signal.