Capacitive Sensor Driving for EMI Reduction Without Frequency Changes
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Solution Overview
Problem
Existing sensor devices face challenges in reducing electromagnetic interference (EMI) while maintaining a high signal-to-noise ratio (SNR) without altering the frequency of driving signals, as both electromagnetic interference and signal noise affect each other, impacting display quality and sensing sensitivity.
Innovation Solution
The sensor device employs a method where the sensor driver transmits driving signals to at least two first sensors during a first period and not to the rest, while transmitting an offset signal to at least one second sensor during the same period and receiving sensing signals from other second sensors, with distinct waveforms and pulse ratios in different periods, using amplifiers connected to DC power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the frequency band of the driving signal is changed to avoid EMI, then electromagnetic interference is reduced, but finding an additional appropriate frequency band becomes difficult
Solution Approach 1:
Instead of changing the frequency band of the driving signal, the patent changes the time-domain characteristics by applying different waveforms (e.g., sine wave, triangle wave, square wave) and adjusting the duty cycle of the driving signal. This parameter change in the time domain achieves EMI reduction without requiring frequency band changes.
2Object-affected harmful factors
If the size of the driving signal is reduced to avoid EMI, then electromagnetic interference is reduced, but the signal to noise ratio is reduced
Solution Approach 1:
The patent employs periodic switching of different waveforms and duty cycles in a time-division manner. During certain time periods, a first waveform with a specific duty cycle is applied, and during other periods, a second waveform with a different duty cycle is applied. This periodic variation reduces EMI while maintaining adequate signal strength for sensing.
Solution Approach 2:
The driving signal characteristics (waveform type, duty cycle) are dynamically changed over time rather than remaining static. The sensor driver adaptively switches between different signal configurations to optimize both EMI reduction and sensing performance.
3Measurement precision
If driving signals are transmitted to all first sensors simultaneously, then sensing coverage is maximized, but electromagnetic interference with the display device increases
Solution Approach 1:
The patent divides the sensing operation into multiple time periods, where in each period only a subset of first sensors is activated with driving signals while other sensors remain inactive or are activated in subsequent periods. This time-division multiplexing approach segments the simultaneous activation of all sensors, reducing peak EMI while maintaining overall sensing coverage.
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 effectively reduces EMI while maintaining SNR without changing the frequency of driving signals, enhancing both display quality and sensing sensitivity.
Implementation Method 1
second sensors forming a capacitance with the first sensors
Data Source
AI summary
A sensor device of the disclosure includes first sensors, second sensors forming a capacitance with the first sensors, and a sensor driver configured to transmit driving signals to the first sensors and receive sensing signals from the second sensors. The sensor driver simultaneously transmits driving signals to at least two first sensors during a first period and does not transmit driving signals to the rest of the first sensors during the first period, and the sensor driver transmits an offset signal to at least one of the second sensors during the first period and receives the sensing signals from at least two of the second sensors other than the at least one of the second sensors during the first period.