Power Management Circuitry for Touch Display Parasitic Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Touch-sensitive devices operating in multiple power domains face challenges due to parasitic or stray capacitances between touch node electrodes and other components, leading to errors and offsets in touch outputs.
Innovation Solution
The implementation of power management circuitry that generates supply voltages for touch and display operations in guarded and non-guarded domains, using bootstrapped power supplies, DC-DC converters, and switches to maintain voltage references and reduce power consumption, while operating in pulse-width modulation or pulse-frequency modulation modes to optimize touch signal paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If touch sensor panels use transparent conductive plates to achieve substantial transparency, then the touch screen can be overlaid on the display, but parasitic or stray capacitances are introduced between touch node electrodes and other components
Solution Approach 1:
The device is divided into multiple power domains (first power domain for display, second power domain for touch sensing) with isolated voltage references. This segmentation allows the touch sensing circuitry to operate with a different voltage reference than the display circuitry, thereby reducing parasitic capacitance effects while maintaining transparency of the conductive plates.
Solution Approach 2:
A voltage reference circuit acts as an intermediary between the conductive plates and the second power domain. This intermediary provides a stable voltage reference that is isolated from the display power domain, reducing the harmful parasitic capacitance effects while allowing the transparent conductive plates to function properly for both display and touch sensing.
2Use of energy by moving object
If power management circuitry generates supply voltages for both touch and display operations, then power consumption can be optimized, but the system complexity increases with multiple power domains
Solution Approach 1:
The voltage reference circuit is designed to serve multiple functions: it provides voltage references for both the first power domain (display operations) and the second power domain (touch sensing operations). This multi-functionality allows a single circuit to manage power reference requirements across different operational modes, reducing overall system complexity while optimizing power consumption.
Solution Approach 2:
The power management system dynamically switches between different power domains based on operational requirements. The system can operate in display mode using the first power domain, touch sensing mode using the second power domain, or concurrent mode using both domains, allowing flexible adaptation to different operational states while managing complexity through controlled dynamic behavior.
3Device complexity
If the voltage reference for the second power domain is derived from the first power domain, then circuit simplicity is maintained, but parasitic capacitances cause errors and offsets in touch outputs
Solution Approach 1:
The voltage reference system is segmented into two independent references: one for the first power domain (display) and one for the second power domain (touch sensing). This segmentation isolates the touch sensing voltage reference from the display power domain, eliminating parasitic capacitance coupling while maintaining circuit simplicity through modular design.
Solution Approach 2:
An isolated voltage reference circuit acts as an intermediary for the second power domain, providing a stable reference voltage that is electrically isolated from the first power domain. This intermediary prevents parasitic capacitance effects from propagating to the touch output measurements, thereby improving measurement precision while maintaining reference circuit simplicity.
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 solution effectively reduces parasitic capacitances, improving the accuracy and noise resistance of touch sensing operations by maintaining stable voltage references and optimizing power usage across different power domains.
Implementation Method 1
In some examples, in the guarded domain, the power management circuit can be configured generate supply voltages using bootstrapped power supplies
Implementation Method 2
power management circuitry can comprise one or more DC-DC converters and one or more voltage regulators to generate one or more voltage references and one or more supply rails
Implementation Method 3
the power management circuitry can include switches configured to control generation of the supply voltages for guarded or non-guarded operation
Data Source
AI summary
An electronic device can be configured to operate in a plurality of operating modes to generate various stimulation signals for touch sensing operations. Switching circuitry can selectively couple one or more stimulation circuits to touch stimulation circuitry to reduce electromagnetic interference generated during transitions between the plurality of operating modes. The electronic device can transition from a stimulation phase to a termination phase at an arbitrary time, unconstrained by integration time requirements of accompany touch sensing circuitry.