Capacitance Sensor Circuit for Low-Power IC Tags
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Solution Overview
Problem
IC tags with large capacitance sensors face challenges in detecting capacitance changes without increasing current consumption, leading to potential power supply issues and malfunctions, especially when using wireless power supply with limited current capacity.
Innovation Solution
A semiconductor device with a capacitance sensor circuit that includes a series connection of a sensor capacitor and a reference capacitor, using a determination circuit to compare potentials and determine capacitance changes, thereby reducing current consumption during charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitor with large capacitance is used to detect environmental changes, then the detection sensitivity is improved, but the current consumption for charging increases
Solution Approach 1:
The patent applies dynamic switching control to the charging circuit, where the charging current is supplied only during the detection phase and switched off during other operations. The control circuit dynamically manages the charging process based on detection requirements, enabling large capacitance sensors to be used while minimizing overall current consumption in wireless power-supplied IC tags.
2Speed
If a large capacitance capacitor is charged at high speed, then the detection response is improved, but the power supply potential decreases causing malfunction
Solution Approach 1:
The patent implements periodic charging action where the capacitor is charged only during specific detection time intervals rather than continuously. The charging circuit is activated periodically to supply charging current, and the control circuit manages the timing to ensure detection is performed at appropriate intervals. This periodic approach allows sufficient charging speed during detection while preventing continuous high current draw that would destabilize the power supply in wireless power-supplied systems.
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
Enables the detection of capacitance changes in large capacitance sensors while minimizing current consumption, preventing power supply issues and ensuring reliable operation in wireless power-supplied IC tags.
Implementation Method 1
a sensor capacitor that changes a capacitance thereof according to an environmental change
Data Source
AI summary
A semiconductor device includes first and second electrode pads for externally connecting two electrodes of a sensor capacitor that has a capacitance that changes according to an environmental change. The semiconductor device further includes a capacitor having a pair of electrodes, one of the pair of electrodes being connected to the first electrode pad, a capacitance circuit having a reference capacitance, and a determination circuit that includes first and second relay terminals. The determination circuit is configured to send a charging current from the first relay terminal to the other electrode of the capacitor and send a charging current from the second relay terminal to the capacitance circuit, and determine whether or not the size of a potential of the first relay terminal is greater than the size of a potential of the second relay terminal, thereby determining whether a capacitance of the sensor capacitor has changed or not.