Capacitance Sensor Circuit With Clocked Comparison for Low Current
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Solution Overview
Problem
Capacitance sensor circuits face increased current consumption when the capacitance values of the variable and fixed capacitors are similar, leading to continuous current flow even after measurement operations are complete, which is inefficient.
Innovation Solution
A semiconductor integrated circuit that includes a reference capacitor and an amplifier circuit to determine if the capacitance of a capacitance variable capacitor has exceeded a reference value, using a clock signal to charge both capacitors and output a binary signal indicating the change in capacitance, thereby reducing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitance value of the capacitance variable capacitor and the capacitance value of the fixed capacitor are the same, then the differential amplifier always outputs the same potential, but the differential amplifier is not turned off and continues to pass current even though the measurement operation ends, causing increased current consumption
Solution Approach 1:
The patent implements periodic measurement operations where the differential amplifier is activated only during specific measurement intervals and turned off afterward. The control circuit periodically initiates measurement operations based on external triggers, allowing the amplifier to remain inactive between measurements, thus reducing continuous current consumption while maintaining measurement precision when needed.
Solution Approach 2:
The patent employs a control circuit that automatically manages the activation and deactivation of the differential amplifier based on measurement operation status. The system self-regulates by detecting when measurements are complete and automatically turning off the amplifier, eliminating the need for continuous operation and reducing energy consumption without compromising measurement capabilities.
2Reliability
If the differential amplifier is always on to ensure accurate capacitance comparison, then measurement reliability is maintained, but current consumption increases continuously
Solution Approach 1:
The system performs measurements periodically rather than continuously, activating the differential amplifier only during scheduled measurement intervals. This periodic operation maintains measurement reliability when data is needed while significantly reducing current consumption during non-measurement periods when the amplifier is turned off.
Solution Approach 2:
The patent applies different operational states to different time periods: during measurement intervals, the amplifier operates at full capability to ensure reliability, while between measurements, it is completely deactivated to minimize energy consumption. This temporal differentiation of operational quality resolves the contradiction between continuous reliability and energy efficiency.
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 detection of environmental changes without increasing current consumption, even when the capacitance values are similar, by using a binary signal to indicate capacitance changes, thus reducing power usage and optimizing circuit efficiency.
Implementation Method 1
a capacitance sensor circuit and a semiconductor integrated circuit... capacitance variable capacitor whose electrostatic capacitance changes corresponding to an environmental change... reference capacitor having a fixed electrostatic capacitance... amplifier circuit that charges the capacitance variable capacitor via a first node and charges the reference capacitor via a second node corresponding to a clock signal
Implementation Method 2
The lump of wax acts as a dielectric, and the liquid of the wax is absorbed by an absorption part arranged at a position adjacent to the capacitor when the temperature reaches a melting point of the wax
Data Source
AI summary
A semiconductor integrated circuit is capable of electrically connecting to a capacitance variable capacitor whose electrostatic capacitance changes corresponding to an environmental change between a first and a second capacitances and determines whether the electrostatic capacitance of the capacitance variable capacitor has changed to exceed a reference capacitance value. The semiconductor integrated circuit includes a reference capacitor having a fixed electrostatic capacitance between the first capacitance and the second capacitance as the reference capacitance value; and an amplifier circuit, charging the capacitance variable capacitor via a first node and charging the reference capacitor via a second node corresponding to a clock signal, amplifying a potential difference between a potential of the first node and a potential of the second node, and outputting a binary determination signal indicating whether the electrostatic capacitance of the capacitance variable capacitor has changed to exceed the reference capacitance value based on the amplified potential difference.