MEMS Acceleration Sensor with Variable Overlapping Area Capacitor
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Solution Overview
Problem
Interdigital MEMS acceleration sensors face challenges in miniaturization and integration due to large finger structures and nonlinear capacitance-distance relationships, which affect accuracy and are sensitive to temperature variations.
Innovation Solution
A capacitance detection circuit and method that converts acceleration into a linear capacitance value using a variable overlapping area capacitor, facilitating data processing and integration, and a capacitance detection circuit that converts this value into a square wave signal for easy monitoring, with a dielectric layer enhancing sensitivity and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interdigital finger structures are used in MEMS acceleration sensors, then sensitivity is improved, but device area and complexity increase
Solution Approach 1:
The sensor is divided into multiple independent capacitive sensing units arranged in an array. Each unit consists of separate fixed electrodes and movable proof mass portions, allowing parallel measurement of acceleration components while reducing the footprint of individual sensing elements compared to traditional interdigital structures.
Solution Approach 2:
The patent transitions from planar interdigital finger structures to a three-dimensional capacitive configuration where fixed electrodes are positioned on a substrate and movable proof mass portions are suspended above them. This vertical arrangement utilizes the third dimension (height) to achieve high sensitivity without proportionally increasing the planar area.
2Device complexity
If traditional capacitive sensing is used, then结构简单 is achieved, but temperature drift and measurement precision worsen
Solution Approach 1:
Different regions of the sensor have specialized functions: fixed electrodes provide stable reference capacitance with temperature compensation characteristics, while movable proof mass portions respond to acceleration. The dielectric layer between them is optimized for specific permittivity to enhance sensitivity while maintaining temperature stability.
Solution Approach 2:
The sensor utilizes changes in capacitance parameters (capacitance value, permittivity) in response to acceleration-induced displacement. The measurement system detects these parameter changes and converts them to acceleration signals, with temperature compensation achieved by monitoring parameter variations under different thermal conditions.
3Measurement precision
If capacitance detection circuit is added, then measurement precision is improved, but device complexity and energy consumption increase
Solution Approach 1:
The capacitance detection circuit is integrated with the capacitive sensing array on the same chip. Multiple sensing units share common readout circuitry, including signal amplification and analog-to-digital conversion modules, reducing overall circuit complexity compared to having separate detection circuits for each sensor element.
Solution Approach 2:
The detection circuit is designed to handle multiple sensing units simultaneously through multiplexed readout. The same circuit infrastructure serves both capacitance measurement and temperature compensation functions, reducing the need for separate dedicated circuits for each function.
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 enables accurate and sensitive acceleration detection with improved integration and temperature stability, facilitating applications such as vehicle collision detection and activation of safety measures like airbags.
Implementation Method 1
a capacitor configured to charge; a detection sub-circuit configured to convert a capacitance value of the capacitor into a detection signal
Implementation Method 2
with a dielectric layer enhancing sensitivity and temperature stability
Data Source
Figure 1~2
Figure 3A
Figure 3B~4
AI summary
An acceleration sensor, a capacitance detection circuit and method, an acceleration processing circuit and method, a storage medium and an electronic device are provided. The acceleration sensor (100) includes: a base (101); a fixed electrode (103) fastened on the base (101); and a mass (102) movable relative to the fixed electrode (103). The mass (102) includes a conductive electrode (104), the conductive electrode (104) and the fixed electrode (103) are configured to form a capacitor, and a capacitance of the capacitor is variable due to movement of the mass (102) relative to the base (101).