DC/DC Converter Switching Logic for Automotive Ignition Durability
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Solution Overview
Problem
The frequent switching between first and second DC/DC converters in automobiles leads to a decrease in their durability due to high electric power consumption by low-voltage devices during ignition-on and ignition-off states, particularly when the ignition-off operation occurs shortly after ignition-on.
Innovation Solution
Implementing an electronic control unit that selectively switches between first and second DC/DC converters based on post-operation electric energy consumption, continuing first electric power supply processing when energy is below a threshold and switching to second electric power supply processing when energy exceeds the threshold, and incorporating a system main relay to manage these transitions during external charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching is made between first and second DC/DC converters based on ignition state, then electric power supply efficiency is improved, but the number of switching operations increases and durability of DC/DC converters decreases
Solution Approach 1:
The electronic control unit determines in advance whether to switch to the second DC/DC converter by evaluating the post-operation electric energy consumption. This preliminary assessment prevents unnecessary switching operations and prepares the system to maintain the first DC/DC converter operation when possible, thereby improving converter durability while ensuring efficient power supply.
Solution Approach 2:
The system uses feedback from the post-operation electric energy consumption to control the switching decision. By monitoring the actual energy consumption after ignition-on operation and comparing it with the predetermined threshold, the electronic control unit makes informed switching decisions that balance power supply efficiency with converter durability.
2Power
If the second DC/DC converter is used during ignition-on state, then electric power supply meets high demand, but switching frequency increases and converter durability decreases
Solution Approach 1:
The system changes the operating parameters by introducing a predetermined value for post-operation electric energy consumption as a threshold. This parameter change enables the system to adapt the DC/DC converter selection based on actual power demand characteristics, using the second converter only when necessary and maintaining the first converter for normal operations to extend durability.
3Device complexity
If switching logic is simplified, then control complexity is reduced, but ability to optimize power supply and protect converters is weakened
Solution Approach 1:
The electronic control unit automatically performs the evaluation and switching control based on the post-operation electric energy consumption. This self-service approach allows the system to optimize converter usage and protect against excessive switching without requiring complex external control logic or manual intervention, thereby maintaining simplicity while ensuring converter durability.
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 approach reduces the number of switches and relay operations, thereby enhancing the durability of DC/DC converters and associated components, while ensuring reliable power management and avoiding device unavailability due to automatic ignition-off.
Implementation Method 1
a first DC/DC converter connected to the high-voltage-system electric power line and the low-voltage-system electric power line, the first DC/DC converter being capable of supplying electric power of the high-voltage-system electric power line to the low-voltage-system electric power line with step down of voltage
Implementation Method 2
a second DC/DC converter connected to the high-voltage-system electric power line on the side closer to the charger than the first DC/DC converter and to the low-voltage-system electric power line, the second DC/DC converter having a rated output that is lower than the rated output of the first DC/DC converter and being capable of supplying electric power of the high-voltage-system electric power line to the low-voltage-system electric power line with step down of voltage
Data Source
AI summary
When ignition-on operation is made in first electric power supply processing during external charging, and a post-operation electric energy is not larger than a predetermined electric energy that is an electric energy consumption of a low-voltage device after the ignition-on operation, an automobile continues the first electric power supply processing. In the first electric power supply processing, from between a first DC/DC converter and a second DC/DC converter, only the second DC/DC converter is selected to run to supply electric power to a low-voltage-system electric power line. When the post-operation electric energy exceeds the predetermined electric energy, the automobile makes a switch to second electric power supply processing in which only the first DC/DC converter is selected to run from between the first DC/DC converter and the second DC/DC converter to supply electric power to the low-voltage-system electric power line.