Load Drive Circuit Diagnostic Verification Without Device Removal
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Solution Overview
Problem
Conventional load drive circuits within electronic control devices cannot detect abnormalities in the load after they have been built into the device, as existing methods require artificial creation of abnormal states to check the diagnostic circuit's operation.
Innovation Solution
A load drive circuit with independent drive and diagnostic circuits, where a drive-stop signal allows the diagnostic circuit to check its operation without detaching the circuit from the device, by monitoring load voltage or current during system initialization and shutdown processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diagnostic circuit checks the load by actually turning off the power supply of the load, then the diagnostic function can be verified, but the load cannot be driven normally and the check cannot be performed after the device is built into the control device
Solution Approach 1:
The circuit is divided into independent segments: the drive circuit (including switch element and current limit circuit) and the diagnostic circuit. This segmentation allows the diagnostic circuit to independently verify load abnormalities without affecting the normal operation of the drive circuit, resolving the contradiction between diagnostic verification and normal operation.
Solution Approach 2:
The diagnostic circuit performs preliminary verification of load abnormalities by monitoring current characteristics before the drive circuit actually drives the load. The current limit circuit pre-establishes safe current thresholds, and the diagnostic circuit checks whether the load current matches expected values during the drive-stop period, enabling diagnostic verification without actual load operation.
2Reliability
If the diagnostic circuit monitors load current during normal operation, then it can detect abnormalities, but it cannot distinguish between actual load faults and drive circuit failures
Solution Approach 1:
The current limit circuit acts as an intermediary between the drive circuit and diagnostic circuit. It provides a reference current signal that the diagnostic circuit uses to compare against the actual load current. This intermediary mechanism enables accurate abnormality detection without requiring complex monitoring circuits, as the current limit circuit already establishes the expected current profile during the drive-stop period.
3Duration of action of stationary object
If the drive circuit operates continuously to drive the load, then the load receives continuous power, but the diagnostic circuit cannot check its operation after the device is built into the control device
Solution Approach 1:
The drive circuit operates periodically with alternating phases: during the drive-stop period, the switch element is turned off and the diagnostic circuit verifies load abnormalities; during the drive period, the switch element is turned on and the load is driven normally. This periodic alternation between diagnostic verification and normal operation allows both functions to be fulfilled without conflict, with the current limit circuit maintaining continuous operation throughout both phases.
Data Source
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AI summary
According to the present invention, the operation of a diagnostic circuit within a load drive circuit, which has been built into an electronic control device, is checked without modifying the electronic control device or the like. The load drive circuit, which drives a load such as a solenoid using a DC power supply as a power supply, includes a drive circuit and a diagnostic circuit which is independently provided within the drive circuit. Upon input of a drive-stop signal from a control circuit that controls the drive circuit, the operation of at least the drive circuit stops, so that whether the diagnostic circuit, which diagnoses the condition of the load, is normally operating or not is checked in a condition in which the load drive circuit has been built into the electronic control device.