Magnetic Sensor Output Circuit for Stable Fault Detection
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Solution Overview
Problem
Existing magnetic sensor devices face challenges in accurately detecting abnormalities such as disconnection or short circuits due to variations in the resistance value of the pull-up resistor, which affects the input voltage level and complicates normal operation in safety-critical automotive systems.
Innovation Solution
Incorporating a voltage divider circuit and an amplifier to control the gate voltage of a MOS transistor, ensuring that the output voltage is determined by the reference voltage and voltage dividing ratio, thereby isolating the effect of resistance variations in the pull-up resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pull-up resistor is used to determine the input voltage level of the discrimination circuit, then the circuit can operate with simple configuration, but the input voltage level varies due to manufacturing variations in the resistor value
Solution Approach 1:
The patent introduces a voltage divider circuit as an intermediary between the pull-up resistor and the discrimination circuit. This voltage divider circuit includes resistors whose ratio is precisely controlled, and it mediates the voltage signal to eliminate the effect of pull-up resistor variations. The voltage divider acts as a buffer that isolates the discrimination circuit from manufacturing variations in the pull-up resistor, thereby maintaining stable input voltage levels for abnormality detection.
2Ease of manufacture
If the resistance value of the pull-up resistor is varied due to manufacturing variation, then the input voltage level changes, but this makes abnormality detection less accurate
Solution Approach 1:
The patent changes the critical parameter from the absolute resistance value of the pull-up resistor to the ratio of resistances in the voltage divider circuit. By making the discrimination circuit insensitive to absolute resistance values and dependent only on the stable resistance ratio, manufacturing variations in individual resistors no longer affect the input voltage level. This parameter transformation ensures that abnormality detection accuracy is maintained despite component tolerances.
3Ease of operation
If the input voltage level is determined by multiple components (resistor 54, constant current circuit 53, transistor 52, and pull-up resistor 58), then the circuit functionality is achieved, but the system becomes more complex and sensitive to component variations
Solution Approach 1:
The patent extracts the voltage level determination function from the complex interaction of multiple components (resistor 54, constant current circuit 53, transistor 52, and pull-up resistor 58) and isolates it into a dedicated voltage divider circuit. This separation allows the discrimination circuit to receive a stabilized voltage signal that is independent of variations in the other components, thereby reducing the overall system complexity in terms of sensitivity to component variations while maintaining full functionality.
Data Source
AI summary
Provided are a magnetic sensor, which is capable of accurately determining abnormalities, such as disconnection and a short circuit, of wiring of a magnetic sensor device, and the magnetic sensor device. An output control circuit of the magnetic sensor includes a voltage divider circuit, which is connected to an output terminal of the magnetic sensor, and an amplifier, which is configured to control a gate voltage of a MOS transistor, which is connected to the output terminal of the magnetic sensor, so that a voltage of the voltage divider circuit and a reference voltage become equal to each other, with the result that an output voltage of the magnetic sensor is determined by the reference voltage and a voltage dividing ratio of the voltage divider circuit.