Sensor Abnormality Detection Circuit Simplification
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Solution Overview
Problem
Existing sensor systems with bridge circuits face increased circuit complexity due to the need for buffer units at bridge midpoints, which complicates the detection of abnormalities caused by drift or failure in sensor elements, such as magnetic sensors.
Innovation Solution
A simplified circuit configuration that omits buffer units by using a switch circuit to connect bridge midpoints to operational amplifier input terminals, allowing for abnormality detection based on the sum or difference of output signals from different operational amplifier states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffer units are provided at bridge midpoints to take out and add sinusoidal signals, then abnormality detection capability is improved, but circuit scale increases
Solution Approach 1:
The patent combines the signal buffering function with the abnormality detection function by using the same operational amplifiers and feedback resistors for both purposes. The buffer units at bridge midpoints are merged with the signal processing path, allowing the circuit to perform both signal extraction and abnormality detection without requiring separate dedicated components, thereby reducing overall circuit scale while maintaining detection capability
Solution Approach 2:
The operational amplifiers and feedback resistors are designed to serve multiple functions: they act as buffer units for signal extraction and simultaneously function as signal processing elements for abnormality detection. This multi-functionality eliminates the need for separate dedicated components, reducing circuit complexity while preserving the ability to detect drift and failures in the bridge circuit
2Measurement precision
If two bridge circuits are used to detect drift by adding sinusoidal signals, then abnormality detection accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent segments the detection process into two distinct operational states (first connection state and second connection state) rather than using two complete bridge circuits. The switch circuit alternates between connecting different bridge midpoints to different input terminals of the operational amplifier, enabling drift detection through temporal separation of measurements rather than spatial duplication of the entire bridge circuit
Solution Approach 2:
The patent introduces dynamic switching between different connection states using a switch circuit. The connections between bridge midpoints and operational amplifier input terminals are dynamically changed between first and second states, allowing the same hardware to perform multiple detection functions. This dynamic reconfiguration enables drift detection without requiring static duplication of bridge circuits
Data Source
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AI summary
Two input terminals (an inverting input terminal and a non-inverting input terminal) of an operational amplifier (30) in which an output voltage is fed back to the inverting input terminal via a feedback resistor (Rf), and two bridge midpoints (N1 and N2) of a bridge circuit (10) are connected via a switch circuit (20). A detection signal indicating a detection result of a physical amount of sensor elements (R1 to R4) is acquired based on a difference between an output signal Vi1 of the operational amplifier (30) in a case in which the switch circuit (20) is in a first connection state and an output signal (Vi2) of the operational amplifier (30) in a case in which the switch circuit (20) is in a second connection state, and an abnormality of the detection signal is determined based on a sum of the output signal (Vi1) and the output signal (Vi2).