Touch Sensor Noise Rejection via Polarity Timing
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Solution Overview
Problem
Display devices with integrated touch sensors face reduced precision due to noise from the display device's common voltage polarity inversion, requiring complex noise removal circuits.
Innovation Solution
A display device with a touch sensor that initiates a scan operation after the common voltage has switched from one polarity to another and ends before returning to the original polarity, avoiding noise interference without using dedicated noise removal circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strobe signal generation circuit and noise-removed current signal generation circuit are used to remove noise from common voltage polarity inversion, then the signal-to-noise ratio and position detection precision are improved, but the device structure becomes complicated
Solution Approach 1:
The patent extracts and removes the harmful noise component generated by common voltage polarity inversion from the touch sensor output signal. By identifying the noise as a differential mode signal and using a differential amplifier configuration, the circuit selectively amplifies only the common mode signals (touch sensor outputs) while rejecting the differential mode noise, thereby extracting the useful signal while discarding the harmful noise component.
Solution Approach 2:
The patent integrates the noise removal function into the existing touch sensor readout circuitry by using the differential amplifier that is already required for reading touch sensor signals. The same differential amplifier structure serves both to read the touch sensor outputs and to reject the common voltage inversion noise, eliminating the need for separate dedicated noise removal circuits.
2Object-affected harmful factors
If dedicated noise removal circuits are implemented, then noise from common voltage polarity inversion is effectively removed, but the manufacturing cost and circuit integration complexity increase
Solution Approach 1:
The patent merges the noise removal function with the touch sensor signal readout function in a single differential amplifier circuit. By combining these two functions into one circuit block, the patent achieves effective noise rejection while simplifying the overall circuit structure, reducing the number of components, and easing manufacturing integration.
Solution Approach 2:
The differential amplifier circuit automatically performs noise rejection as an inherent function of its operation. The circuit self-adjusts to reject the common voltage inversion noise through its differential configuration, without requiring additional control circuits or complex processing, thereby achieving noise removal through the natural operation of the amplifier itself.
Data Source
AI summary
Provided is a display device with a touch sensor that can avoid the influence of noise originating from the polarity inversion of a common voltage of the display device without using special circuitry. The display device with a touch sensor includes a sensor output readout circuit (21) that is sequentially connected to multiple sensor electrodes in a touch sensor unit (7) and outputs signal voltages that correspond to the electrical characteristics of the electrodes, a sensor control circuit (23) that supplies a control signal to the sensor output readout circuit (21), and a coordinate computation circuit (22) that detects a contact position based on the signal voltages. The sensor control circuit (23) causes a scan operation, in which the sensor output readout circuit (21) is sequentially connected to all of the sensor electrodes of the touch sensor unit (7) and outputs the signal voltages, to start after the common voltage has switched from a first polarity to a second polarity, and to end before the common voltage returns to the first polarity.