Capacitive Touch Sensing With Phase-Shifted Charge Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive sensing systems face challenges in noise immunity and measurement accuracy due to random telegraph signal noise and current mirror non-linearity, which affect the detection of touch or proximity.
Innovation Solution
The system employs a method of charging and discharging capacitive sensors, using multiple input terminals and transferring units with switching units to alternately couple charges to sample capacitors, and performs two conversions with half-cycle phase shifts to reduce noise impact, thereby improving noise immunity and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transferring unit is used to transfer charges from capacitive sensors, then the device complexity is reduced, but the measurement precision deteriorates due to current mirror non-linearity and random telegraph signal noise
Solution Approach 1:
The patent divides the charge transfer function into multiple independent transferring units (first transferring unit, second transferring unit, etc.), each handling charges from different capacitive sensors or different charge transfer phases. This segmentation allows parallel charge transfer operations, reducing the impact of non-linearity and noise in any single unit while maintaining overall system functionality.
Solution Approach 2:
The patent combines multiple charge transfer operations into a unified multi-phase cycle, where charges from multiple capacitive sensors are transferred through multiple transferring units in sequence or parallel. The switching unit coordinates these operations to merge the results into a single measurement output, achieving improved precision through combined measurements while managing complexity through systematic control.
2Measurement precision
If multiple input terminals and transferring units are used to improve noise immunity, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The switching unit serves multiple functions: it connects different input terminals to different transferring units, controls the timing of charge transfer operations, and coordinates the multi-phase measurement cycle. This multi-functionality reduces the need for separate dedicated components for each function, managing complexity while enabling multiple measurement channels.
Solution Approach 2:
The patent implements a periodic multi-phase measurement cycle where capacitive sensors are charged and discharged in sequence through different transferring units. This periodic operation allows time-multiplexed use of components, where the same physical components perform different functions at different phases, reducing the total number of components needed while maintaining high measurement precision through multiple samples.
3Reliability
If charges are transferred through multiple phases with half-cycle phase shifts, then the reliability of touch or proximity detection improves, but the measurement time increases
Solution Approach 1:
The patent implements continuous charge transfer operations where multiple capacitive sensors are charged and transferred in overlapping phases. While one sensor is being charged, another is having its charge transferred, maintaining continuous useful action throughout the measurement cycle. This reduces total measurement time compared to sequential operations while maintaining reliability through multiple phase-shifted measurements.
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 enhances the accuracy of capacitance change sensing by averaging errors and reducing the impact of noise, leading to improved noise immunity and more reliable touch or proximity detection.
Implementation Method 1
Touch or proximity to the capacitive sensor is determined by detecting a capacitance change between two opposite electrodes thereof
Implementation Method 2
The capacitance between the two electrodes of the capacitive sensor is measured by charging the capacitive sensor to a predetermined voltage and measuring the amount of charges charged to the capacitive sensor
Implementation Method 3
The measurement includes transferring the charges to a sample capacitor by discharging the capacitive sensor
Data Source
AI summary
A system for sensing touch or proximity include: a first number of input terminals configured to couple one or more capacitive sensors, a second number of transferring units configured to transfer charges from the one or more capacitive sensors through the first number of input terminals in transferring phases of cycles of the one or more capacitive sensor, wherein at least one of the first and second numbers is equal to or greater than two, and a first switching unit, coupled between the first number of input terminals and the second number of transferring units, configured to selectively electrically couple any one of the first number of input terminals to any one of the second number of transferring units in the transferring phases.