Touch Screen Signal Processing Circuit Noise Utilization
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Solution Overview
Problem
Touch screen devices face instability in identifying touch locations due to noise interference, which distorts output waveforms and makes it difficult to determine accurate touch coordinates.
Innovation Solution
A signal processing circuit that utilizes noise voltage as a driving voltage when noise is present, allowing the sensing channels to connect the driving line to a bypass line, enabling the identification of touch locations even in noisy conditions by using the noise voltage as an input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sensing line signal processing circuit is used, then the circuit structure is simple, but the touch location identification becomes unstable when noise is present
Solution Approach 1:
The patent converts the harmful noise signal into a useful driving voltage source. When noise is detected in the sensing line, the system switches to using the noise voltage as the driving voltage for the sensing channel, thereby transforming the harmful interference into a beneficial signal source that enables continued touch detection functionality.
Solution Approach 2:
The patent implements a dynamic switching mechanism that adapts the circuit operation mode based on noise conditions. The system dynamically selects between two operating modes: normal mode using power source voltage when noise is absent, and noise utilization mode when noise is present, thereby optimizing reliability under varying environmental conditions without requiring a completely different circuit design.
2Reliability
If the sensing channel uses power source voltage as driving voltage, then the circuit operation is stable under normal conditions, but the touch detection fails when noise interferes with the sensing line
Solution Approach 1:
The patent implements a dynamic switching mechanism that adapts the circuit operation mode based on noise conditions. The system dynamically selects between two operating modes: normal mode using power source voltage when noise is absent, and noise utilization mode when noise is present, thereby optimizing reliability under varying environmental conditions without requiring a completely different circuit design.
Solution Approach 2:
The patent employs a feedback mechanism where the system continuously monitors the sensing line for noise presence. Based on this feedback, the control unit automatically switches between operating modes, ensuring that the touch detection system adapts to environmental conditions and maintains accuracy whether noise is present or absent.
3Reliability
If additional circuitry is added to handle noise interference, then the touch detection stability improves, but the device complexity increases
Solution Approach 1:
The patent makes existing circuit components multi-functional. The sensing channel and driving line can operate in two different modes: using power source voltage under normal conditions, or using noise voltage when interference is present. This universality allows the same hardware to handle both normal and noisy environments without requiring separate dedicated circuits for each condition.
Solution Approach 2:
The patent enables the noise signal to serve the system itself by using the noise voltage as a driving voltage source. Instead of requiring external noise cancellation circuits or additional signal sources, the system utilizes the available noise signal to maintain its functionality, thereby avoiding additional circuitry while improving reliability.
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
Enables stable and accurate identification of touch locations on a touch screen even in the presence of noise, without requiring additional circuitry, by selectively using noise voltage as an input voltage in the signal processing circuit.
Implementation Method 1
A sensor capacitor Cs is connected to a plurality of sensing lines that are arranged on a touch screen panel in one direction
Implementation Method 2
The pre-charge switch PC is turned on in a pre-charge mode for a given time and thus a power supply terminal voltage VDD is pre-charged in the sensor capacitor Cs through the pre-charge switch PC
Implementation Method 3
the readout switch RO is turned on in a readout mode for a given time and thus the voltage charged in the sensor capacitor Cs is transferred to the analog sensing channel 11 through the readout switch RO
Data Source
AI summary
A signal processing circuit of a touch screen is provided. The signal processing circuit can include driving and sensing lines arranged to interact with one another in a touch screen panel, power sources supplying power to each of the driving lines, and sensing channels detecting touch by sensing a mutual capacitance on a node where the sensing line interacts with the driving line. The circuit can also include driving line switches selectively connecting the power sources to the driving lines, channel switches selectively connecting the sensing channels to the sensing lines, and a bypass line allowing the driving line to be connected to the sensing line by operation of the channel switches.