Pressure Sensing Circuit Timing for Low-Noise Touch Input
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Solution Overview
Problem
Touch input devices face challenges in minimizing noise and maintaining uniform pressure sensing sensitivity, particularly due to the integration of pressure sensors, which can interfere with the operation and accuracy of touch input systems.
Innovation Solution
The implementation of a touch input device design that includes a display module, a substrate, and a pressure sensor positioned between the display module and the substrate, along with a pressure sensing circuit that outputs a predetermined voltage, allowing for the detection of pressure magnitude based on voltage output. This design incorporates a pressure sensing node, a current source, and a switch that are turned on and off in specific time periods to optimize sensitivity and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is integrated between the display module and substrate, then pressure sensing capability is improved, but noise in the pressure detection is increased
Solution Approach 1:
The patent applies periodic action by implementing a driving circuit that applies a periodic driving voltage to the pressure sensor and uses a sampling circuit that operates in periodic time slots (first time slot for sampling pressure signal, second time slot for sampling noise). This periodic operation allows separation of the pressure sensing function from noise interference, enabling accurate pressure detection while minimizing noise impact.
Solution Approach 2:
The patent introduces an intermediary approach by using a differential amplification circuit that processes the difference between signals from two pressure sensors. This intermediary processing method allows the system to extract the actual pressure information while canceling out common-mode noise, thereby improving measurement precision without sacrificing noise immunity.
2Measurement precision
If pressure sensing circuit components are added, then pressure detection accuracy is improved, but device complexity is increased
Solution Approach 1:
The patent merges multiple functions into integrated circuits. The driving circuit, sampling circuit, and amplification circuit are combined into a unified pressure sensing system that operates as a cohesive unit. This integration reduces the number of discrete components and simplifies the overall device structure while maintaining high pressure detection accuracy through coordinated operation of the merged circuit functions.
Solution Approach 2:
The pressure sensing circuit is designed with multi-functionality, where the same circuit architecture can detect both touch pressure magnitude and touch location. The driving circuit and sampling circuit serve multiple purposes: they drive the pressure sensor, sample the pressure signal, and can be configured to detect different types of touch inputs. This universality reduces device complexity by eliminating the need for separate dedicated circuits for different sensing functions.
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 configuration effectively detects pressure magnitude while minimizing noise and maintaining consistent sensitivity, enhancing the overall performance and accuracy of touch input systems by isolating noise sources and ensuring precise pressure detection.
Implementation Method 1
the pressure sensor includes a first sensor electrode and a second sensor electrode disposed to face each other with a predetermined distance therebetween, and has a capacitance value according to a distance between the first sensor electrode and the second sensor electrode
Implementation Method 2
the pressure sensor includes a piezoelectric layer, and the piezoelectric layer has a capacitance value according to a distance between the first sensor electrode and the second sensor electrode
Data Source
AI summary
A touch input device may be provided that includes a display module; a substrate which is disposed under the display module; a pressure sensor which is disposed between the display module and the substrate; and a pressure sensing circuit which outputs a predetermined voltage. The touch input device detects the pressure magnitude on the basis of the voltage output from the pressure sensing circuit. The pressure sensing circuit includes a pressure sensing node NA; a switch serially connected between a power voltage VDDA and the pressure sensing node; a current source serially connected between the pressure sensing node and the ground; and an output node No. The current source is turned on during a first time period t1 every cycle. The switch is turned on every cycle during a third time period t3 separated from the first time period t1 by a predetermined time period.