Touch Sensing Apparatus Noise Reduction via Differential Signaling

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Solution Overview

Problem

Traditional touch sensing methods for integrated touch and display panels, such as those using OLEDs, face interference issues due to the inability to stop display driving, leading to noise that affects touch sensing accuracy, and existing solutions like time-division driving or increased sampling time require more power consumption.

Innovation Solution

A touch sensing method that employs a combination of to-sense and reference touch sensing circuits, where each circuit receives distinct signals to calculate capacitance differences, reducing noise interference and improving accuracy without the need for increased power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If time-division driving is used to avoid interference between display and touch sensing circuits, then interference is reduced, but display driving cannot be stopped in integrated panels leading to continuous noise

Engineering Contradiction:

Improvetouch sensing accuracyVSAvoidnoise from display operations

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and separates the touch sensing signal from the noisy display background by using differential signaling. A reference touch sensing circuit is introduced that mirrors the display noise but excludes the touch signal, allowing the touch signal to be extracted by subtracting the reference channel from the normal touch sensing channel.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The reference touch sensing circuit acts as an intermediary that captures and transmits the display noise to the differential amplifier. This intermediary channel enables the system to identify and eliminate noise without stopping the display driver, resolving the contradiction between continuous display operation and noise-free touch sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If analog or digital filters are used in touch sensing circuits to increase sampling time, then touch sensing accuracy is improved, but power consumption increases

Engineering Contradiction:

Improvetouch sensing accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional mechanical/time-based filtering approach (increasing sampling time) with an electronic signal processing approach (differential amplification). This substitution achieves noise filtering without extending the sampling period, thereby maintaining low power consumption while improving measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the signal processing parameter from time-domain filtering to frequency-domain differential processing. By using differential amplification, the system achieves noise rejection through parameter differentiation rather than temporal averaging, reducing the power-time trade-off.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If display driving is continued in integrated OLED/Mini LED panels, then display functionality is maintained, but noise is continuously generated affecting touch sensing

Engineering Contradiction:

Improvedisplay functionalityVSAvoidnoise affecting touch sensing

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful display noise into a useful reference signal. The reference touch sensing circuit deliberately captures the display noise and feeds it to the differential amplifier, where it is subtracted from the normal touch channel. This transforms the previously harmful noise into a beneficial reference for noise cancellation, allowing continuous display operation without compromising touch sensing.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11995269B2Touch sensing apparatus with noise reduction and electronic device including the same

Publication Date: 2024.05.28 NOVATEK MICROELECTRONICS CORP

AI summary

A touch sensing method, apparatus for a touch panel, and electronic device are provided. The method includes: determining a first number of to-sense touch sensing circuits, and determining a second number of reference touch sensing circuits, each to-sense touch sensing circuit having a corresponding reference touch sensing circuit; causing each to-sense touch sensing circuit to receive a touch excitation signal TX1, and apply TX1 to a corresponding touch sensitive cell and receive a touch sensing signal therefrom, and output a first output signal; causing each reference touch sensing circuit to receive a touch reference signal DC/TX2, and apply DC/TX2 to a corresponding touch sensitive cell and receive a reference sensing signal therefrom, wherein DC/TX2 and TX1 are different signals; and obtaining, according to respective first and second output signals, a capacitance difference of capacitances sensed by each to-sense touch sensing circuit and its corresponding reference touch sensing circuit.