Timer Circuit Abnormality Detection in Electronic Control Apparatus
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Solution Overview
Problem
Existing electronic control apparatuses for vehicle engines face challenges in reliably detecting abnormalities in the timer circuit, particularly when the ignition switch is turned off before a predetermined time period has elapsed, leading to a reduced frequency of abnormality detection operations.
Innovation Solution
The electronic control apparatus includes a timer IC with a sub-power supply circuit always powered by the vehicle battery, allowing for a comprehensive judgment process involving multiple stages to assess the timer IC's functionality, including a first judgment process upon ignition switch changes and a second judgment process after a predetermined time period, ensuring accurate normal/abnormal determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the predetermined time period for abnormality detection is set to ensure full counter operation validation, then the reliability of timer circuit validation is improved, but the frequency of abnormality detection operations decreases
Solution Approach 1:
The abnormality detection process is divided into two distinct judgment stages: a first judgment process executed when the ignition switch transitions from off to on, and a second judgment process executed after a predetermined time period has elapsed. This segmentation allows each judgment to focus on specific validation aspects, with the first judgment providing frequent checks and the second judgment providing comprehensive validation after full counter operation, thereby resolving the contradiction between detection frequency and validation reliability.
2Loss of energy
If the ignition switch is turned off before the predetermined time period elapses, then power consumption is reduced, but the abnormality detection operation cannot be performed
Solution Approach 1:
The first judgment process is designed to be executed immediately when the ignition switch transitions from off to on, before the predetermined time period elapses. This preliminary action captures the state of the timer circuit at a known reference point, enabling abnormality detection to occur even if the ignition switch is turned off again before the full predetermined time period completes, thus maintaining detection capability while allowing power savings.
3Device complexity
If a single judgment process is used for timer abnormality detection, then the device complexity is reduced, but the judgment accuracy decreases
Solution Approach 1:
The detection system implements two distinct judgment processes with different execution timings and validation focuses. The first judgment process provides immediate detection capability upon ignition switch activation, while the second judgment process provides comprehensive validation after the predetermined time period. This dual-judgment segmentation enhances detection accuracy by capturing timer circuit behavior at multiple critical moments without requiring complex additional hardware.
Data Source
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AI summary
The electronic control apparatus includes a control section supplied with electric power through a power switch to operate, and a timer circuit always supplied with electric power to operate irrespective of an on/off state of the power switch. The control section is configured to perform a process in which the timer circuit is caused to make a reset-start after a frequency of a clock used in the timer circuit is changed from a first frequency for counting operation to a second frequency higher than the first frequency, and a process in which it is determined whether or not a count value of the timer circuit has reached its upper limit value when it is detected that a predetermined time has elapsed after the reset-start of the timer circuit on the basis of a count value of an internal timer of the timer circuit.