Inductive Motion Sensing Circuit With Low-Noise Period Counting
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Solution Overview
Problem
Existing sensing devices for rotating bodies face challenges in miniaturization and power efficiency due to high power consumption and noise issues, particularly jitter noise, which complicates the design and increases manufacturing costs.
Innovation Solution
A sensing circuit with multiple oscillation circuits and sensing coils, each generating oscillation signals based on inductance changes, uses a frequency-divided reference oscillation signal and period counting filters to produce a robust output signal, reducing noise and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high frequency reference clock is used to sense rotation of the rotating body, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent divides the sensing function into multiple oscillation circuits (first and second oscillation circuits) with different sensing coils having different inductance values. This segmentation allows the system to use multiple reference clocks with different frequencies, where lower frequency clocks can be used for less critical measurements, reducing overall power consumption while maintaining measurement precision when needed.
Solution Approach 2:
The patent changes the frequency parameter of the reference clock by providing multiple reference clocks with different frequencies. The sensing circuit can select appropriate clock frequencies based on the sensing requirements, allowing the system to operate at lower power consumption levels by using lower frequency clocks when high precision is not required, while still achieving high measurement precision when high frequency clocks are used.
2Device complexity
If one sensing coil is used to sense the rotating body, then device complexity is reduced, but noise such as jitter causes sensing errors
Solution Approach 1:
The patent segments the sensing function by providing multiple oscillation circuits with different sensing coils (first sensing coil and second sensing coil) having different inductance values. Each sensing coil can sense different aspects of the rotating body's motion, and their combined output provides more reliable and accurate rotation sensing by reducing the impact of noise and jitter on any single sensing path.
3Reliability
If a separate complicated circuit is added to remove noise, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the noise filtering function by assigning different filtering characteristics to different oscillation circuits. Each oscillation circuit can be designed with appropriate filtering to handle specific noise types, eliminating the need for a single complex noise removal circuit while improving overall reliability through distributed noise management.
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 precise sensing of fine displacements with reduced noise and power consumption, simplifying the design and reducing manufacturing costs while maintaining high sensitivity.
Implementation Method 1
each of the first and second oscillation circuits including, respectively, first and second sensing coils having first and second inductance values depending on areas of overlap between the first and second sensing coils and the first and second pattern units
Implementation Method 2
The first oscillation circuit may include a first capacitor connected to the first sensing coil in parallel to contribute LC oscillation and to generate the first sensed oscillation signal
Data Source
AI summary
A sensing circuit in a device having a moving body in which a unit to be detected including first and second pattern units spaced apart from each other is formed includes an oscillation circuit unit including first and second oscillation circuits fixedly mounted on a substrate spaced apart from the unit to be detected, including, respectively, first and second sensing coils having first and second inductance values depending on areas of overlap between the first and second sensing coils and the first and second pattern units and outputting, respectively, first and second sensed oscillation signals based on the first and second inductance values; and a sensing circuit outputting an output signal having movement information of the moving body based on each period count value for each of the first and second sensed oscillation signals using a reference oscillation signal.