Touch Sensing Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
The characteristic parameters of elements in touch sensing circuits tend to drift due to manufacturing processes, temperatures, and aging, leading to errors in voltage reading and erroneous touch event sensing.
Innovation Solution
A touch sensing circuit with a compensating module that provides a compensating voltage at a first node in response to control signals, a read control module that transfers the sensed voltage to the first node, and a driving module that outputs a signal associated with the sensed voltage, using a combination of transistors and capacitors to stabilize the voltage reading and eliminate errors caused by threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch sensing circuits are used, then the circuit structure is simple, but the voltage reading accuracy deteriorates due to threshold voltage drift of transistors
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in a lookup table before operation. The threshold voltage drift compensation is performed by retrieving pre-computed values based on measured threshold voltages, rather than performing complex real-time calculations. This approach improves measurement precision while keeping the actual runtime circuit complexity manageable through pre-processing.
Solution Approach 2:
The patent introduces an intermediary compensation mechanism that mediates between the drifted threshold voltage and the accurate voltage reading. A compensation circuit calculates the threshold voltage drift and applies a corrective offset to the sensed voltage, acting as an intermediary that eliminates the harmful effect of transistor parameter drift without requiring complete redesign of the sensing circuit.
2Measurement precision
If threshold voltage drift is compensated in real-time, then the voltage reading accuracy is improved, but the processing time increases
Solution Approach 1:
The patent performs the computationally intensive threshold voltage compensation calculations in advance and stores the results in a lookup table. During actual touch sensing operations, the system only needs to perform simple table lookups and additions, dramatically reducing processing time while maintaining high measurement precision. This separates the heavy computational burden from the time-critical sensing operation.
Solution Approach 2:
The patent implements periodic calibration to measure transistor threshold voltages at scheduled intervals rather than continuously. Between calibration periods, the stored compensation values are used, reducing the frequency of complex measurements and calculations. This periodic approach maintains accuracy while minimizing the time loss associated with frequent recalibration.
3Adaptability or versatility
If the touch sensing circuit operates under varying temperatures and aging conditions, then the circuit remains operational, but the characteristic parameters drift causing sensing errors
Solution Approach 1:
The patent implements feedback by continuously measuring the actual threshold voltage of transistors in the sensing circuit and using this measurement to adjust the compensation values. The system reads back the threshold voltage, compares it with expected values, and applies appropriate compensation from the lookup table. This closed-loop feedback mechanism enables the circuit to adapt to temperature variations and aging effects while maintaining reliable sensing accuracy.
Solution Approach 2:
The patent compensates for environmental effects by dynamically changing the compensation parameters based on measured threshold voltages. The lookup table contains compensation values for different threshold voltage conditions, and the system selects the appropriate compensation parameter set based on actual measurements. This allows the circuit to maintain accuracy across varying temperatures and aging conditions by adapting its operating parameters.
Data Source
AI summary
Disclosed is a touch sensing circuit which includes: a compensating module configured to provide a compensating voltage at a first node in response to control signals from a plurality of control signal lines; a read control module configured to transfer a voltage sensed by a touch sensing electrode to the first node in response to a read control signal from a read control signal line, so that the first node has a voltage which is a sum of the compensating voltage and the sensed voltage; and a driving module configured to provide an output signal associated with the sensed voltage to an output signal line in response to the voltage of the first node. Also disclosed are a touch panel and a display device.