Vehicle ECU Shutoff Circuit for High-Voltage Isolation Failures
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Solution Overview
Problem
Existing electronic control units in electrically driven vehicles face reliability issues due to relay ON failures during vehicle collisions or circuit failures, leading to potential electric shocks when high-voltage power supply lines come into contact with the vehicle body.
Innovation Solution
Incorporating an external load switching element, a controller, a shutoff transistor, a diagnosis circuit, and an output holding circuit to reliably shut off connections between internal and external ground or power supply systems based on diagnosis signals, preventing electric shocks by ensuring the high-voltage power supply line is safely disconnected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay is used to control the high-voltage power supply line, then the power supply can be shut off during vehicle operation, but the relay may fail to turn off due to circuit failures or collisions, causing electric shock risk
Solution Approach 1:
A shutoff transistor is introduced as an intermediary component between the relay control circuit and the high-voltage power supply line. The transistor provides an additional control layer that can independently shut off power even when the relay fails, thereby eliminating the electric shock risk while maintaining normal power control functionality.
Solution Approach 2:
The shutoff transistor is configured to activate automatically upon detection of collision or circuit failure conditions, performing a preliminary protective action before the relay can cause harm. This preliminary shutoff mechanism ensures that power is disconnected proactively when abnormal conditions are detected.
2Reliability
If a cutting blade mechanism is used to forcibly shut off the relay during collision, then the high-voltage power supply line can be reliably shut off, but the harness must be replaced even when the relay does not have an ON failure
Solution Approach 1:
The mechanical cutting blade system is replaced with an electronic shutoff transistor mechanism. Instead of physically cutting the harness during collision, the transistor electronically disconnects the power supply through its switching action, achieving the same safety goal without mechanical damage to the harness.
Solution Approach 2:
The control system changes from direct relay control to transistor-based control with diagnostic monitoring. By monitoring the state of the relay control circuit and using the transistor as a controlled shutoff device, the system achieves reliable power disconnection without requiring physical harness replacement after minor incidents.
3Reliability
If the relay control circuit is monitored for failures, then relay ON failure can be detected, but additional monitoring circuits and complexity are required
Solution Approach 1:
The shutoff transistor serves multiple functions: it acts as a protective shutoff device during collision, a backup control mechanism when relay fails, and a controllable switch for normal operation. This multi-functionality reduces the need for separate dedicated monitoring and shutoff systems, thereby limiting the increase in overall circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a reliable and convenient electronic control unit that easily recovers from vehicle collisions or power supply shutoff failures, ensuring the high-voltage power supply line is safely shut off, thereby preventing electric shocks.
Implementation Method 1
a shutoff transistor that shuts off connection between an internal GND and an external GND or connection between an internal power supply system and an external power supply system
Data Source
AI summary
Provided is an electronic control unit mounted on an electrically driven vehicle, the electronic control unit being excellent in reliability and convenience in which recovery is easy while reliably shutting off a high-voltage power supply line at the time of collision of the vehicle or failure of a power supply shutoff circuit. The electronic control unit includes: an external load switching element that drives an external load; a controller that drives the external load switching element; a shutoff transistor that shuts off connection between an internal GND and an external GND or connection between an internal power supply system and an external power supply system; a diagnosis circuit that receives, as input, a diagnosis signal of a control circuit that controls the external load by the external load switching element, and a diagnosis signal of the controller, and outputs a diagnosis result; and an output holding circuit that holds an output signal of the diagnosis circuit, wherein the shutoff transistor shuts off the connection between the internal GND and the external GND or the connection between the internal power supply system and the external power supply system on the basis of the signal held by the output holding circuit.