Touch-Sensing Analog Front End for Display Noise Suppression
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Solution Overview
Problem
The proximity of touch panels to display panels, which use metal materials, results in significant noise interference that can cause errors in touch signals due to the close distance, leading to poor signal-to-noise ratios and operational limitations in analog front-end circuits.
Innovation Solution
An analog front-end circuit design incorporating a reference voltage source, capacitors, and amplifiers with specific capacitance and resistance values, along with an integrator circuit and analog-to-digital converter, to minimize noise interference by using capacitors and resistors strategically between input and output ends, and between the touch sensor and display panel, effectively controlling signal gain and noise suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the touch panel is placed close to the display panel to improve display performance, then the display performance is improved, but noise interference from the display panel increases causing errors in touch signals
Solution Approach 1:
The patent introduces a shielding electrode as an intermediary layer between the touch panel and display panel. This shielding electrode acts as a mediator that blocks the harmful electromagnetic noise from the display panel while allowing the touch signals to pass through, thus resolving the contradiction between close placement for display performance and noise interference prevention
Solution Approach 2:
The patent extracts and separates the noise cancellation function from the main touch sensing function by introducing a dedicated shielding electrode and corresponding noise cancellation circuitry. This allows the noise interference to be independently managed and eliminated without affecting the primary touch sensing operation
2Illumination intensity
If metal materials are used to replace transparent material in the touch panel, then the display performance is improved, but noise interference from the display panel increases
Solution Approach 1:
The shielding electrode serves as a protective intermediary that shields the metal-based touch panel from electromagnetic noise generated by the display panel, allowing the benefits of metal materials (improved display performance) to be retained while mitigating the resulting noise interference
3Object-affected harmful factors
If capacitors and resistors are strategically placed to control signal gain and noise suppression, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The amplifier circuit is designed to perform multiple functions simultaneously: it amplifies the touch signals, rejects common-mode noise from the display panel, and maintains signal integrity. This multi-functionality reduces the need for separate dedicated noise cancellation circuits, thereby limiting the increase in device complexity while still achieving effective noise reduction
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
The proposed solution effectively reduces noise interference, maintaining the output voltage close to the reference voltage, thereby enhancing the signal-to-noise ratio and preventing clipping from display noise, ensuring accurate touch signal amplification and conversion.
Implementation Method 1
a second capacitor disposed between the first input end and the second input end
Implementation Method 2
an amplifier including a first input end receiving a touch sensing signal from a touch sensor, a second input end receiving a reference signal from the first capacitor, and an output end outputting an output signal
Implementation Method 3
a reference voltage source, a first capacitor coupled to the reference voltage source through a switch
Data Source
AI summary
An analog front-end circuit includes a reference voltage source, a first capacitor, an amplifier, and a second capacitor. The first capacitor is coupled to the reference voltage source through a switch. The amplifier includes a first input end receiving a touch sensing signal from a touch sensor, a second input end receiving a reference signal from the first capacitor, and an output end outputting an output signal. The second capacitor is disposed between the first input end and the second input end.