Capacitive Touch Sensing Circuit for Multi-Phase Charge Compensation
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Solution Overview
Problem
Capacitive touch panels face challenges in managing increased external capacitance, which requires a large compensation capacitor area, limiting the internal charge detection range and increasing noise susceptibility.
Innovation Solution
A capacitive touch sensing circuit with a charge compensation method that operates in multiple phases to effectively offset large external capacitance using a smaller internal capacitance, reducing the required compensation capacitance area and enhancing internal sensing range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external capacitance is increased to improve charge detection range, then the internal pre-filled capacitor must increase with the same amount, resulting in a large increase in the area of the compensation capacitor
Solution Approach 1:
The charge compensation process is divided into multiple phases (first phase, second phase, third phase, fourth phase) with different switch configurations. This segmentation allows the system to achieve compensation without requiring a large capacitor area by using time-multiplexed charge transfer operations.
Solution Approach 2:
The capacitive touch sensing circuit operates in periodic phases, repeatedly performing charge compensation cycles. The switches are controlled to conduct in specific patterns during different phases, creating a periodic charge transfer process that effectively compensates for external capacitance without requiring large capacitor area.
2Reliability
If external capacitance is increased to offset external capacitor, then the compensation capacitor area increases, limiting the internal charge detection range
Solution Approach 1:
The circuit uses dynamically controlled switches that change their conduction state across different phases. This dynamic switching allows the same circuit components to serve multiple functions: compensating for external capacitance during some phases and detecting internal charge during others, thereby maintaining both reliability and adaptability without area trade-offs.
Solution Approach 2:
The circuit changes operational parameters (switch states, phase timing) to achieve different functions. By controlling which switches conduct during different phases, the system can adjust between compensation mode and detection mode, allowing the same hardware to adapt to different operational requirements without physical area constraints.
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 allows for effective operation in heavy load capacitive sensing environments by repeatedly compensating external capacitance, reducing the compensation capacitance area and improving internal capacitance sensing range.
Implementation Method 1
a capacitor, the capacitor being coupled between the input terminal and the output terminal of the integrator
Data Source
AI summary
A capacitive touch sensing circuit includes a first switch˜a fifth switch, an internal capacitor, an integrator and a capacitor. The first switch and an external capacitor are coupled in series between a first voltage and a ground voltage, one terminal of the second switch is coupled between the first switch and the external capacitor, and one terminal of the third switch is coupled to the other terminal of the second switch. The fourth switch and the internal capacitor are coupled in series between a second voltage and the ground voltage, wherein the second voltage is a negative value of the first voltage, and one terminal of the fifth switch is coupled to the other terminal of the second switch and the other terminal of the fifth switch is coupled between the fourth switch and the internal capacitor. One input terminal of the integrator is coupled to the other terminal of the third switch, the other input terminal of the integrator is coupled to a reference voltage, and the output terminal of the integrator outputs an output voltage. The capacitor is coupled between the input terminal and the output terminal of the integrator.