Guarded Power Domains for Low-Parasitic Touch Display Supplies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Touch screens face errors and offsets due to parasitic or stray capacitances between touch node electrodes and other components, which can degrade touch sensing performance.
Innovation Solution
The implementation of power management circuitry that generates supply voltages in multiple power domains, including a guarded domain with a guard potential, using bootstrapped power supplies and DC-DC converters, to reduce parasitic capacitances and improve touch sensing accuracy.
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 display to form a touch screen, but parasitic or stray capacitances are introduced between touch node electrodes and other components
Solution Approach 1:
The device is divided into multiple isolated power domains (first power domain for touch sensing, second power domain for display). This segmentation electrically isolates the touch node electrodes from other components that generate parasitic capacitance, while maintaining transparency of the conductive plates in the touch sensor panel.
Solution Approach 2:
A guard buffer is introduced as an intermediary component that generates a guard potential to actively compensate for and cancel out parasitic capacitance effects. The power management circuitry acts as a mediator to coordinate switching between power domains and manage the guard potential generation.
2Measurement precision
If power management circuitry switches between guarded and non-guarded power domains, then parasitic capacitance is reduced and touch sensing accuracy is improved, but switching may degrade performance of touch and display operation
Solution Approach 1:
The system dynamically switches between guarded and non-guarded power domains based on operational requirements. The power management circuitry monitors touch and display operation states and transitions power domains accordingly, optimizing both accuracy and stability through adaptive domain switching.
Solution Approach 2:
The guard buffer generates the guard potential in advance before touch sensing operations begin. The power management circuitry pre-configures the appropriate power domain (guarded or non-guarded) based on predicted operational needs, ensuring smooth transitions without performance degradation.
3Use of energy by moving object
If supply rail voltage is held at a lower level to reduce power consumption, then energy efficiency is improved, but the voltage may be insufficient for proper touch and display operation
Solution Approach 1:
Different power domains are assigned different voltage levels according to their specific requirements. The first power domain (touch sensing) operates at a lower voltage to reduce power consumption, while the second power domain (display) operates at appropriate voltage levels for proper display function. Each domain's voltage is optimized for its local requirements.
Solution Approach 2:
The power management circuitry periodically adjusts supply rail voltages based on operational phases. During idle or low-activity periods, voltages are reduced to minimize power consumption. During active touch or display operations, voltages are increased to ensure proper functionality, creating a periodic voltage adjustment pattern.
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, enhancing the signal-to-noise ratio and dynamic range of touch sensing, allowing for more accurate detection of touch and proximity events with reduced noise and power consumption.
Implementation Method 1
parasitic or stray capacitances can exist between the touch node electrodes used for sensing touch on the touch sensor panels, and other components of the devices in which the touch sensor panels are included
Implementation Method 2
In the guarded domain, the power management circuit can be configured generate supply voltages using bootstrapped power supplies
Implementation Method 3
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
Data Source
AI summary
A power management circuit can comprise a direct-current-to-direct-current (DC-DC) converter and a guard buffer. The guard buffer can be referenced to a system ground and configured to generate a guard ground. The power management circuit can comprise a supply capacitor coupled to the DC-DC converter that can be referenced to system ground in a first mode and referenced to the guard ground in a second mode. A regulator can be coupled to the DC-DC converter and referred to system ground in the first mode, and decoupled and referred to guard ground in the second mode. The DC-DC converter can generate a first voltage in the first mode and a second voltage in the second mode, the second voltage greater than the first.