Physical Quantity Sensor Failure Diagnosis Timing
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Solution Overview
Problem
Physical quantity sensors face challenges in accurately diagnosing reference voltage failures due to temporary variations in reference voltages caused by signal processing and analog/digital conversion operations, leading to erroneous failure determinations.
Innovation Solution
A physical quantity detection circuit with a failure diagnosis circuit that monitors reference voltages and performs diagnosis at predetermined timings different from when these voltages vary temporarily, ensuring accurate detection of reference voltage generation circuit failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous monitoring of reference voltage is performed for failure diagnosis, then reliability of failure detection is improved, but measurement precision deteriorates due to temporary voltage variations during signal processing operations
Solution Approach 1:
The system performs preliminary actions by completing all signal processing operations (amplification, filtering, A/D conversion) before initiating failure diagnosis. The control circuit schedules these operations sequentially, ensuring the reference voltage is stable and free from operational variations when diagnosis measurements are taken, thus resolving the contradiction between continuous monitoring reliability and measurement precision
Solution Approach 2:
The system implements periodic action by alternating between signal processing periods and diagnosis periods. During signal processing, the reference voltage supplies power to active circuits causing temporary variations. During diagnosis periods, all processing circuits are inactive, allowing stable reference voltage measurements. This periodic scheduling enables both reliable failure detection and precise voltage measurements without interference
2Adaptability or versatility
If reference voltage is supplied to multiple circuits (signal processing circuit and A/D conversion circuit), then functionality of the physical quantity sensor is improved, but reliability deteriorates due to inability to distinguish which circuit causes voltage deviations
Solution Approach 1:
The system applies segmentation by dividing the diagnosis into distinct time segments: signal processing segment and failure diagnosis segment. During the diagnosis segment, all processing circuits are deactivated, isolating the reference voltage to only the essential circuits. This temporal segmentation allows the monitoring circuit to attribute voltage deviations to specific circuits with certainty, while maintaining full functionality during the processing segment
Solution Approach 2:
The system employs dynamics by making the circuit configuration changeable over time. The control circuit dynamically switches between operational mode (all circuits active) and diagnosis mode (processing circuits inactive). This dynamic reconfiguration enables the same reference voltage to serve multiple functions at different times while allowing precise failure attribution during diagnosis, resolving the contradiction between versatility and reliability
Data Source
AI summary
A physical quantity detection circuit includes a detection signal generation circuit that generates a detection signal according to a physical quantity based on an output signal of a physical quantity detection element that detects the physical quantity, an analog/digital conversion circuit that converts the detection signal into a digital signal, a reference voltage generation circuit that generates a reference voltage supplied to the analog/digital conversion circuit, and a failure diagnosis circuit that performs a failure diagnosis of the reference voltage generation circuit by monitoring the reference voltage and outputs a failure diagnosis signal indicating a result of the failure diagnosis, in which the failure diagnosis circuit performs the failure diagnosis at a predetermined timing different from a timing when the reference voltage varies temporarily according to an operation of the analog/digital conversion circuit.