Capacitance Detection Circuit With Multi-Step Baseline Cancellation
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Solution Overview
Problem
Flexible screens with capacitive touch technology face challenges in self-capacitance detection due to high baseline capacitance, leading to small capacitance variations that are easily overwhelmed by noise, requiring large chip areas and high costs for baseline capacitance cancellation.
Innovation Solution
A capacitance detection circuit with a control module, charge transfer module, drive module, and cancellation module that performs M times of charge cancellations to generate an output voltage, allowing for improved cancellation efficiency and reduced capacitance requirements for the cancellation capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-going baseline capacitance cancellation is performed in flexible screens, then capacitance detection can be achieved, but the chip area becomes excessively large and costs increase
Solution Approach 1:
The patent segments the baseline capacitance cancellation process into multiple discrete steps (first cancellation step, second cancellation step, third cancellation step). Each step uses a different cancellation capacitor connected through switches to cancel different portions of the baseline capacitance. This segmentation allows the system to handle large baseline capacitance values without requiring a single large cancellation capacitor, thereby reducing the overall chip area.
Solution Approach 2:
The patent employs dynamic switching mechanisms where switches selectively connect different cancellation capacitors to the detection electrode at different time stages. The cancellation capacitors are dynamically configured based on the magnitude of baseline capacitance, allowing adaptive cancellation without requiring fixed large-capacitance components. This dynamic approach optimizes chip area utilization while maintaining detection precision.
2Measurement precision
If on-going baseline capacitance cancellation is performed in flexible screens, then capacitance detection can be achieved, but manufacturing costs increase
Solution Approach 1:
By dividing the cancellation process into multiple stages with smaller cancellation capacitors, the patent reduces the total capacitance value required in each component. This segmentation allows for the use of smaller, less expensive capacitors and reduces the overall chip area, directly lowering manufacturing costs while maintaining the ability to detect small capacitance variations in flexible screens.
Solution Approach 2:
The patent uses multiple cancellation capacitors that can be designed with identical or standardized values, allowing for mass production and economies of scale. Rather than requiring one large custom capacitor, the system uses several smaller standardized capacitors, simplifying the manufacturing process and reducing costs through standardized component production.
3Length of moving object
If flexible screen thickness is reduced, then flexibility is improved, but baseline capacitance increases significantly
Solution Approach 1:
The patent addresses the increased baseline capacitance resulting from reduced screen thickness by segmenting the cancellation process into multiple steps. Each step uses a smaller cancellation capacitor to cancel a portion of the baseline capacitance, making the overall cancellation process manageable despite the high baseline capacitance values caused by the thin flexible screen structure.
Solution Approach 2:
The patent changes the operational parameters of the capacitance detection system by introducing multi-stage cancellation with varying cancellation capacitor values. This parameter change allows the system to adapt to the high baseline capacitance conditions created by thin flexible screens, enabling accurate detection of small capacitance variations despite the altered physical dimensions.
4Measurement precision
If multi-stage charge cancellation is performed, then cancellation efficiency is improved, but detection time increases
Solution Approach 1:
The patent segments the cancellation process into multiple rapid sequential steps, each using smaller cancellation capacitors. While there are multiple steps, each step is quick and uses minimal capacitance transfer time. The segmentation allows for more efficient charge transfer in each step compared to a single large-capacitor approach, improving overall cancellation efficiency while keeping total detection time acceptable.
Solution Approach 2:
The patent employs periodic switching between different cancellation capacitors in a structured sequence. This periodic action allows the system to systematically cancel baseline capacitance in controlled intervals, optimizing the balance between cancellation completeness and detection speed. The rhythmic switching pattern enables efficient use of circuit resources while maintaining acceptable detection timing.
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
The solution effectively cancels large baseline capacitance with a small cancellation capacitor, reducing noise and costs, and enhances detection sensitivity for flexible screens.
Implementation Method 1
the principle of self-capacitance detection is detecting a capacitance of a capacitor formed between a detection electrode and a system ground
Implementation Method 2
the charge transfer module is configured to convert a charge of the capacitor to be detected, subject to the M times of charge cancellations, to generate an output voltage
Data Source
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AI summary
The present disclosure relates to the field of touch technologies, and in particular, to a capacitance detection circuit, a capacitance detection method, a touch chip, and an electronic device. The capacitance detection circuit includes: a control module, a charge transfer module, a processing module, a drive module, and a cancellation module. The control module is configured to control the drive module to charge a capacitor to be detected. The cancellation module is configured to perform M times of charge cancellations on the capacitor to be detected. The charge transfer module is configured to convert a charge of the capacitor to be detected, subject to the M times of charge cancellations, to generate an output voltage. The processing module is configured to determine, according to the output voltage, a capacitance variation of the capacitor to be detected. According to the present disclosure, cancellation efficiency of a cancellation circuit can be improved, and requirements on a capacitance of a cancellation capacitor can be lowered. Even a capacitance of a relatively small cancellation capacitor can cancel a baseline capacitance of a relatively large capacitor to be detected, costs are reduced, and noise of each cancellation voltage source is significantly reduced.