Capacitive Sense Array Baseliner Circuit for Noise Compensation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Capacitive sensing systems face reduced sensitivity for touch detection due to spurious capacitance and noise signals, which can be caused by spurious charge or current received by the capacitive sense array when providing baseline capacitance.

Innovation Solution

A baseliner component is implemented to generate a baseline compensation signal using a sensor model and current conveyor, which includes multiple capacitors, differential amplifiers, and current mirrors to split and scale the current from the sensor model, providing compensation for spurious current or noise signals across each sense channel of the capacitive sense array.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If baseline capacitance is provided to capacitive sense channels, then the capacitive sensing system can operate, but spurious charge or current is received which reduces touch detection sensitivity

Engineering Contradiction:

Improvetouch detection sensitivityVSAvoidspurious current or noise signals

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent generates a baseline compensation signal that replicates the spurious charge or current effects, then subtracts this compensation signal from the sense channel outputs. By converting the harmful spurious signals into a useful compensation signal that can be deliberately generated and removed, the system eliminates the sensitivity reduction caused by baseline capacitance provision.

Inventive Principle:

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

Solution Approach 2:

The patent introduces a baseline compensation signal as an intermediary element that mediates between the baseline capacitance provision and the sense channel measurements. This compensation signal acts as a bridge, allowing the system to account for and remove spurious effects without directly modifying the baseline capacitance provision or the sense channel operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If baseline compensation signal is generated using sensor model and current conveyor, then noise and spurious signals are mitigated, but device complexity increases

Engineering Contradiction:

Improvetouch detection accuracyVSAvoidcircuits required for baseline compensation

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses a sensor model that copies or replicates the electrical characteristics of the actual capacitive sense channels. By creating an electrical model that mimics the behavior of real channels including their spurious signals, the system can generate accurate compensation signals without requiring complex physical compensation circuits for each channel.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent combines multiple functions into the baseline compensation generation process: the sensor model replicates channel behavior, the current conveyor generates and distributes compensation signals, and all sense channels receive unified compensation. This merging of functions reduces overall system complexity compared to implementing separate compensation mechanisms for each channel.

Inventive Principle:

Principle #5Merging (Combining)

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

The baseline compensation signal effectively enhances the sensitivity of touch detection by mitigating noise and spurious signals, improving the accuracy and reliability of capacitive touch sensing systems.

Implementation Method 1

A baseliner component is implemented to generate a baseline compensation signal using a sensor model and current conveyor, which includes multiple capacitors

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

differential amplifiers, and current mirrors to split and scale the current from the sensor model

Methodology Applied

Scientific EffectDifferential amplification:

Implementation Method 3

current mirrors to split and scale the current from the sensor model, providing compensation for spurious current or noise signals

Methodology Applied

Scientific EffectCurrent mirroring:

Data Source

PatentUS10429998B2Generating a baseline compensation signal based on a capacitive circuit

Publication Date: 2019.10.01 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

A capacitance-sensing circuit may include a plurality of channel inputs associated with measuring a capacitance of a unit cell of a capacitive sense array. The capacitance-sensing circuit may also include a baseliner component that is coupled to the plurality of channel inputs. The baseliner component may generate a baseline compensation signal using a capacitive circuit and may provide the baseline compensation signal to each of the plurality of channel inputs of the capacitive sense array.