Capacitive Touch Circuit Signal Integration and Noise Suppression
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Solution Overview
Problem
Existing touch detection circuits face challenges in increasing signal integration efficiency while maintaining accuracy, particularly with the self-capacitance method, where the time allowed for detection is shortened due to increased touch panel electrode density and display driving signals, leading to noise interference.
Innovation Solution
A capacitive detecting circuit that includes an integration capacitor and operational amplifier, where electric charges are cumulatively added and inverted in polarity during charge and discharge cycles, allowing for repeated integration and enhanced noise suppression through the use of IIR and FIR filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the self-capacitance method is used for touch detection, then the detection speed increases, but the detection accuracy deteriorates due to noise interference from display driving signals and high electrode density
Solution Approach 1:
The patent segments the detection process into multiple discrete steps including charging period, first discharging period, second discharging period, and resetting period. By dividing the detection into separate phases with distinct functions, the circuit can effectively separate signal integration from noise accumulation, thereby maintaining detection speed while improving accuracy through structured temporal segmentation of operations
Solution Approach 2:
The patent implements periodic action by repeatedly cycling through charging and discharging phases multiple times before final detection. The detection circuit performs multiple charging-discharging cycles to accumulate signal information while resetting integration capacitors between cycles, allowing the system to maintain high detection speed through efficient periodic operation while improving accuracy through repeated measurement cycles that average out noise
2Manufacturing precision
If the electrode density of the touch panel is increased, then the touch panel resolution improves, but the detection time shortens leading to increased noise interference
Solution Approach 1:
The patent maintains continuity of useful action by implementing overlapping operation between the touch detection circuit and display driving circuit. The detection circuit continuously performs charging and discharging operations on integration capacitors during the display refresh cycle, ensuring that detection activities continue without interruption. This allows the system to maintain high resolution through dense electrodes while preserving sufficient detection time through continuous, efficient utilization of available time slots
Solution Approach 2:
The patent applies preliminary action by pre-charging the integration capacitor during a dedicated charging period before the actual detection phase. This preliminary charging ensures that the capacitor is ready for immediate signal integration when the detection window opens, maximizing the utilization of limited detection time. The pre-charged state allows the circuit to quickly transition into detection mode without losing valuable measurement time, thereby supporting high electrode density while maintaining adequate detection duration
3Measurement precision
If the detection period is extended to improve accuracy, then the signal integration improves, but the productivity of the touch detection system decreases
Solution Approach 1:
The patent segments the integration process into multiple parallel channels, each with its own integration capacitor dedicated to specific electrode groups. By dividing the detection task across multiple segmented integration paths, the system can perform signal integration on multiple channels simultaneously, thereby maintaining high integration accuracy for each channel while achieving high overall throughput through parallel processing of multiple electrode segments
Solution Approach 2:
The patent implements partial action by performing detection operations on only a subset of electrodes during each detection cycle rather than all electrodes simultaneously. The detection circuit selectively activates specific integration capacitors and electrode groups based on current detection needs, performing partial detection cycles that can be rapidly repeated. This approach allows the system to achieve sufficient integration accuracy for active electrodes while maintaining high productivity by quickly cycling through different electrode subsets across multiple frames
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 approach doubles the signal integration per unit time, shortens the detection period, and increases accuracy, enabling effective touch detection even in time-division scenarios with high-density touch panels and display driving.
Implementation Method 1
a capacitive detecting circuit connectable with a sensor capacitance includes an integration capacitor with an integration capacitance
Implementation Method 2
The circuitry inverts an electric charge to be added to the integration capacitance in polarity according to a direction of the electric charge
Data Source
AI summary
The touch detecting circuit is a capacitive detecting circuit correctable with a sensor capacitance, and includes an integration capacitance. In the touch detecting circuit, a sensor capacitance connected with the touch detecting circuit is charged and discharged; electric charges to input and output for charging and discharging the sensor capacitance are cumulatively added to the integration capacitance. The electric charges to he added to the integration capacitance are inverted in polarity according to directions of charge transfer accompanying the charge and discharge. Not only when charging the sensor capacitance, but also when discharging the sensor capacitance, the absolute values of electric charges to be moved are integrated and therefore, the amount of signals is doubled.