Power Relay Fixing Detection in Dual-Supply Electronic Control
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Solution Overview
Problem
Existing electronic control devices struggle to detect the fixing of a power supply relay when it cannot be turned off, even if the power supply to the microcomputer is cut off.
Innovation Solution
An electronic control device is designed with a relay drive circuit, an electronic circuit operating at a first power supply voltage, and a monitoring unit that monitors the first power supply voltage when turned off, allowing detection of the relay's fixing state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power supply relay cannot be turned off (on-fixing abnormality), then the power supply voltage continues to be supplied to the electronic control device, but the microcomputer cannot detect the relay fixing state when power supply is cut off
Solution Approach 1:
The monitoring unit performs voltage monitoring and stores the monitoring result before the power supply is completely cut off. By capturing the voltage state in advance when the relay should be off, the system preserves evidence of relay fixing abnormality even though the microcomputer will subsequently lose power and cannot perform detection.
Solution Approach 2:
A dedicated monitoring unit acts as an intermediary between the power supply voltage and the microcomputer. This monitoring unit independently monitors the voltage state and stores results in a storage unit, serving as a bridge that preserves abnormality information even when the main microcomputer cannot operate due to power cutoff.
2Loss of energy
If the power supply to the microcomputer is cut off when the relay should be off, then battery exhaustion is prevented, but the ability to detect relay fixing is lost
Solution Approach 1:
The monitoring unit captures and stores the voltage monitoring result before power is completely cut off to the microcomputer. This preliminary action preserves the relay state information (whether the relay is improperly fixed in the on position) so that the information is not lost when the microcomputer loses power.
Solution Approach 2:
The monitoring unit and storage unit are given special properties to maintain operation or retain data independently of the main microcomputer's power state. The storage unit specifically preserves the monitoring result with different retention characteristics than the microcomputer's memory, ensuring information survival during power cutoff.
Data Source
AI summary
Even when a power supply relay cannot be turned off and when power supply to a microcomputer is normally cut off, fixing of the power supply relay is detected. An electronic control device 100 according to an aspect of the present invention includes a relay drive circuit 13 that controls on and off of a power supply relay 12 according to information about the on and off of power supply, an electronic circuit (first power supply system block 110, microcomputer 102) that operates at a first power supply voltage (V1) supplied from a battery 10 through the power supply relay 12, and a monitoring unit (second power supply system block 120) that monitors the first power supply voltage when the power supply is turned off, and holds a monitoring result, the first power supply voltage reflecting presence or absence of fixing of the power supply relay.