Shared DC-DC Converter for Vehicle Power Supply
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Solution Overview
Problem
Existing DC-DC converters for electric vehicles face challenges in designing optimal battery chargers and on-board power supply stages due to large input and output voltage ranges, leading to high costs or suboptimal performance, especially in galvanically decoupled systems.
Innovation Solution
A system with a shared step-up/step-down converter is used for both the on-board power supply and battery charger, allowing for a similar power or voltage level design, eliminating the need for a separate buck converter and enabling optimal voltage-converting component design, with a power factor correction stage and galvanically decoupled DC-DC converter for improved efficiency and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate buck converter is added to the battery charger output, then the voltage can be matched to the on-board network, but the device complexity and cost increase
Solution Approach 1:
The patent merges the battery charger DC-DC converter with the on-board power supply step-up/step-down converter into a single shared converter. This eliminates the need for a separate buck converter in the battery charger, reducing device complexity while maintaining voltage matching capability through the shared converter's dual functionality.
Solution Approach 2:
The shared step-up/step-down converter is designed to perform multiple functions: it operates as the main power converter for the on-board power supply and simultaneously serves as the DC-DC converter for the battery charger. This multi-functionality eliminates the need for separate converters and reduces overall system complexity.
2Adaptability or versatility
If the DC-DC converter is designed for the entire voltage adjustment range, then it can handle all operating conditions, but the design becomes expensive and cannot work optimally
Solution Approach 1:
The patent employs a dynamic voltage ratio control strategy where the converter operates at different voltage ratios depending on the operating mode. The control unit adjusts the voltage ratio dynamically - using a first voltage ratio when the battery charger charges the on-board network, and a second voltage ratio when the on-board network charges the battery pack, allowing optimal performance across different operating conditions without requiring the converter to be designed for the entire voltage range simultaneously.
Solution Approach 2:
The patent changes the operating parameters of the shared converter based on the charging direction and voltage levels. By adjusting the voltage ratio parameter dynamically according to the specific charging scenario (vehicle-to-load or battery-to-vehicle), the converter can operate optimally in each mode without requiring expensive design margins for the full voltage range.
3Power
If the battery charger is designed for higher output power, then it can supply both the on-board network and high-voltage network, but the components must be designed for higher power levels
Solution Approach 1:
The patent segments the power flow into two separate paths from the shared converter: one path supplies the on-board power supply stage (including the galvanically decoupled DC-DC converter), and the other path supplies the battery pack through the second converter. This segmentation allows the shared converter to provide high total power while each downstream component can be designed for lower, more manageable power levels appropriate to its specific function.
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 solution allows for increased output power, improved efficiency in vehicle electrical systems, and enhanced electromagnetic compatibility by dividing power handling across components, enabling simultaneous charging of traction batteries and energy stores without increasing boost/buck converter capacity.
Implementation Method 1
a step-up/step-down converter (12), in particular a bidirectional boost/buck converter
Implementation Method 2
galvanically decoupled DC converters
Data Source
Figure 1~3
Figure 4~6
AI summary
The invention relates to a system (100) with a battery charging device (20) with output terminals and an vehicle electrical system power supply stage (10). The vehicle electrical system power supply stage has a step-up/step-down converter (12), which is designed to raise an input voltage of the vehicle electrical system power supply stage to an intermediate circuit voltage, a direct current intermediate circuit (13), which is coupled to the step-up/step-down converter (12) at intermediate circuit nodes (14a, 14b), and a vehicle electrical system d.c.-d.c. converter (11), which is coupled to the direct voltage intermediate circuit at the intermediate circuit nodes, and which is designed to convert the intermediate circuit voltage into a direct voltage for a vehicle electrical system (1, 2), the output terminals of the battery charging device (20) being coupled to the direct voltage intermediate circuit (13) via the intermediate circuit nodes (14a, 14b).