Touch Screen Power Management for Noise Reduction
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Solution Overview
Problem
Touch screen devices experience noise interference from power systems, such as gate line voltage systems, which can corrupt touch sensing signals and have lasting effects on noise-sensitive components, even after the noise source is disabled.
Innovation Solution
Implementing a power management system that disables the charge pump during active touch sensing, using a voltage regulator to maintain gate voltage levels, and incorporating a post-noise stabilizing system to reset noise-sensitive components, along with a voltage boost system to enhance voltage magnitude during touch sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charge pump is enabled to provide gate line voltage, then the touch screen can operate, but noise is generated that corrupts touch sensing signals
Solution Approach 1:
The operation is divided into distinct phases: a first phase where the charge pump is enabled for gate line driving, and a second phase where the charge pump is disabled for noise-free touch sensing. This temporal segmentation allows the system to achieve both reliable display operation and accurate touch sensing by separating these conflicting functions in time.
Solution Approach 2:
The system periodically alternates between enabling and disabling the charge pump. During touch sensing intervals, the charge pump is disabled to eliminate noise, while during display refresh intervals, it is enabled to maintain gate line voltages. This periodic action resolves the contradiction by making the noise-generating operation intermittent rather than continuous.
2Measurement precision
If the charge pump is disabled during touch sensing to reduce noise, then touch sensing accuracy improves, but gate voltage levels may drop below desired thresholds
Solution Approach 1:
Before disabling the charge pump for touch sensing, the system performs preliminary actions to maintain gate voltage levels. A voltage regulator is configured to maintain gate voltage at or above desired thresholds during the charge pump disabled period, ensuring that when the charge pump restarts, the gate voltages are already stabilized and will not drop below thresholds.
Solution Approach 2:
A voltage regulator acts as an intermediary between the charge pump and the gate lines. When the charge pump is disabled, the voltage regulator maintains the gate voltage levels, preventing them from dropping below desired thresholds. This intermediary component ensures continuous voltage stability regardless of the charge pump state.
3Device complexity
If noise-sensitive components are not stabilized after noise exposure, then the system remains simple, but noise effects persist and corrupt subsequent sensing
Solution Approach 1:
The system implements a post-noise stabilizing system that quickly resets noise-sensitive components immediately after the charge pump is disabled. This rapid stabilization skips the period where noise effects would otherwise persist, quickly restoring the sensing components to a clean state ready for accurate touch detection.
Solution Approach 2:
The post-noise stabilizing system uses feedback mechanisms to detect when noise-sensitive components have been affected by charge pump noise and automatically triggers stabilization routines. This feedback loop ensures that noise effects are promptly corrected, maintaining sensing reliability without requiring overly complex preventive measures.
Data Source
AI summary
Reducing or eliminating the effects of noise that can be generated by a power system of a touch screen device, such as a gate line voltage system that applies voltage to gate lines of the touch screen, is provided. In one example, a power supply, such as a charge pump, can be disabled during active touch sensing, such that noise from the charge pump is not generated during touch sensing. In some examples, a voltage regulator can help to maintain the gate voltage level at or above a desired threshold. In some cases, noise entering the touch sensing system can have a lasting effect on noise-sensitive components, even after the noise source is disabled. In these cases, a post-noise stabilizing system can be included to stabilize, reset, etc., noise-sensitive components of the touch sensing system, which can help to reduce or eliminate the lasting effect of noise.