Touch Input Device Frequency Separation for Noise Reduction
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Solution Overview
Problem
Touch input devices face challenges in reducing noise interference between touch position sensing, touch pressure sensing, and display panel operations, which affects the accuracy of touch position and pressure sensing and the overall display quality.
Innovation Solution
The implementation of a touch input device design that separates the touch pressure sensing frequency from the horizontal synchronization signal frequency of the display panel, ensuring a gap of at least 5 kHz, and optionally aligning the touch position and pressure sensing frequencies within a 20 kHz range to avoid harmonic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the touch pressure sensing frequency is set close to the horizontal synchronization signal frequency to simplify timing control, then the device complexity is reduced, but noise interference increases and measurement precision deteriorates
Solution Approach 1:
The patent changes the frequency parameter of the touch pressure sensing signal to be different from the horizontal synchronization signal frequency. Specifically, it sets the touch pressure sensing frequency such that its harmonic frequencies do not overlap with the horizontal synchronization signal frequency, thereby avoiding noise interference while maintaining simplified timing control through frequency separation.
Solution Approach 2:
The patent introduces a frequency gap (first gap of 5 kHz and second gap of 20 kHz) as an intermediary buffer zone between the touch pressure sensing frequency and the horizontal synchronization signal frequency. This frequency gap acts as a mediator that prevents direct interference between the two signals while allowing both operations to proceed simultaneously.
2Device complexity
If the touch position sensing and touch pressure sensing use the same frequency to reduce the number of frequencies, then the device complexity is reduced, but noise interference between sensing operations increases
Solution Approach 1:
The patent changes the frequency parameter differentiation between touch position sensing and touch pressure sensing operations. By assigning different frequencies to these two sensing operations and ensuring that harmonic frequencies of the horizontal synchronization signal do not overlap with either sensing frequency, the patent eliminates mutual noise interference while maintaining operational simplicity.
3Productivity
If the horizontal synchronization signal frequency is increased to improve display refresh rate, then the display productivity is improved, but noise interference with touch sensing increases
Solution Approach 1:
The patent dynamically adjusts the touch pressure sensing frequency based on the horizontal synchronization signal frequency. By ensuring that the touch pressure sensing frequency and its harmonics maintain a sufficient frequency gap (5 kHz minimum, 20 kHz preferred) from the horizontal synchronization signal frequency, the patent allows high display refresh rates without compromising touch sensing accuracy.
Data Source
AI summary
A touch input device capable of detecting a touch position and touch pressure may be provided that includes: a display panel; a touch sensor including a touch electrode which is used to detect the touch position; and a pressure sensor including a pressure electrode which is used to detect the touch pressure. A harmonic frequency and a frequency of a horizontal synchronization signal, which is used to drive the display panel, do not exist within a first gap from a touch pressure sensing frequency which is used to drive the pressure sensor. The first gap may be 5 kHz.