Single-Relay Brake Power Circuit for Accurate Self-Diagnosis
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Solution Overview
Problem
In an in-vehicle electric power supply system with a sub-battery and a semiconductor relay, there is a risk of current leakage through a parasitic diode during self-diagnosis of the brake system, leading to inaccurate diagnosis results when only one semiconductor relay is used.
Innovation Solution
The system includes a main battery, a sub-battery, a brake system connected to both batteries through one semiconductor relay, a diagnostic unit, and a control unit. The control unit is configured to set the voltage of the semiconductor relay's terminal connected to the sub-battery higher than the terminal connected to the brake system during self-diagnosis, preventing current flow through the parasitic diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If only one semiconductor relay is inserted between the sub-battery and the brake system, then the cost of the electric power supply system is reduced, but current leakage through the parasitic diode occurs during self-diagnosis, leading to inaccurate diagnosis results
Solution Approach 1:
The control unit performs preliminary voltage adjustment by discharging the sub-battery before the self-diagnosis process begins. This preliminary action establishes a voltage higher than the brake system voltage, creating a voltage differential that prevents current leakage through the parasitic diode during the subsequent diagnosis operation, thereby ensuring accurate diagnosis results while maintaining system cost-effectiveness
2Device complexity
If only one semiconductor relay is used, then the device complexity is reduced, but current flows through the parasitic diode during self-diagnosis, compromising system reliability
Solution Approach 1:
The control unit dynamically changes the voltage parameter of the sub-battery by controlling its discharge level. Before self-diagnosis, the sub-battery voltage is adjusted to be higher than the brake system voltage, which changes the electrical parameter landscape to prevent parasitic diode conduction. This parameter change ensures reliable diagnosis operation while maintaining the simplified single-relay structure
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
This configuration ensures accurate self-diagnosis results for the brake system by preventing current leakage through the parasitic diode, thereby maintaining the integrity of the diagnosis process.
Implementation Method 1
The semiconductor relay may include a parasitic diode that performs rectifying from the second terminal toward the first terminal
Implementation Method 2
The control unit is configured to perform discharge control of the sub-battery, based on the diagnosis start notified from the diagnostic unit. The control unit is configured to set voltage of the first terminal of the semiconductor relay to which the sub-battery is connected, such that the voltage of the first terminal is higher than voltage of the second terminal
Data Source
AI summary
An in-vehicle system includes a main battery, a sub-battery, a brake system that is connected to the main battery and also is connected to the sub-battery through one semiconductor relay, a diagnostic unit that performs diagnosis of the brake system, and a control unit that controls the sub-battery. The diagnostic unit is configured to perform notification regarding a diagnosis start of the brake system to the control unit, the control unit is configured to perform discharge control of the sub-battery, based on the diagnosis start notified from the diagnostic unit, and is configured to set voltage of a first terminal of the semiconductor relay to which the sub-battery is connected, such that the voltage of the first terminal is higher than voltage of a second terminal of the semiconductor relay to which the brake system is connected.