Multiplexer Noise Cancellation in In-Cell Touch Displays
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Solution Overview
Problem
Flat panel display devices face issues with switching noise and electromagnetic interference (EMI) due to high-frequency multiplexer driving control signals, which also cause image quality defects in in-cell touch displays from common voltage stabilization delays.
Innovation Solution
A multiplexer system utilizing k pairs of switching transistors, where each pair includes a first switching transistor controlled by a MUX control signal and a second switching transistor controlled by a pseudo MUX control signal with an opposite phase, to selectively distribute data signals from the data driving circuit to k data lines, canceling out rising and falling edges of the MUX control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a multiplexer is used to reduce the number of data integrated circuits, then manufacturing cost is reduced and device complexity is lowered, but switching noise and electromagnetic interference increase due to high-frequency driving control signals
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the harmful high-frequency switching signals to generate corresponding noise signals that are intentionally introduced to cancel out the original noise. The noise cancellation circuit generates noise signals with opposite phases to the switching noise, transforming the harmful noise into a beneficial cancellation mechanism that reduces overall EMI and switching noise.
Solution Approach 2:
The patent introduces a noise cancellation circuit as an intermediary component between the multiplexer and the data lines. This intermediary generates noise signals that interact with the switching noise to produce cancellation effects. The noise cancellation circuit acts as a mediator that processes the harmful signals and transforms them into beneficial cancellation waves, reducing the overall electromagnetic interference without affecting the normal data transmission function.
2Speed
If high-frequency multiplexer driving control signals are used, then data signal distribution speed is improved, but image quality deteriorates due to common voltage stabilization delays in in-cell touch displays
Solution Approach 1:
The patent converts the harmful effect of high-frequency switching signals into a beneficial cancellation mechanism. The noise cancellation circuit generates noise signals with opposite phases to the high-frequency switching signals, transforming the speed advantage into a controlled phenomenon. The cancellation noise counteracts the destabilizing effect on common voltage, allowing high-speed data distribution without image quality deterioration.
Solution Approach 2:
The patent implements a feedback mechanism where the noise cancellation circuit continuously monitors the switching signals and generates corresponding cancellation noise in real-time. This feedback loop ensures that the common voltage remains stabilized despite high-frequency switching, maintaining image quality while preserving fast data signal distribution capability.
Data Source
AI summary
Disclosed herein is a flat panel display device capable of reducing switching noise and electromagnetic interference noise caused by driving of a multiplexer and stabilizing a common voltage in an in-cell touch flat panel display device. Discloses is a multiplexer controlled by k MUX control signals and k pseudo MUX control signals to selectively supply the data signal supplied from each output channel of the data driving circuit to k data lines. The multiplexer includes k pairs of switching transistors. Each pair of switching transistors include a first switching transistor controlled by one of the k MUX control signals to supply a data signal output from the one output channel of the data driving circuit to one data line, and a second switching transistor controlled by one of the k pseudo MUX control signals having a phase opposite to that of the one of the k MUX control signals.