Zonal Vehicle Power Supply Layout for 48V and 12V Loads
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Solution Overview
Problem
The existing in-vehicle power supply systems require multiple batteries for different voltage levels, leading to increased costs and power losses due to thick wire harnesses and voltage fluctuations when supplying power to large electric power loads.
Innovation Solution
An in-vehicle power supply system that uses a high-voltage DC/DC converter to step down voltage from several hundred volts to 48 volts, which is then distributed through a power supply trunk line to large electric power loads, reducing current and wire diameter, and uses zone ECUs with integrated DC/DC converters to step down 48 volts to 12 volts for small electric power loads, eliminating the need for booster circuits and minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple batteries for different voltage levels are used, then power supply requirements for both large and small electric power loads are met, but vehicle cost increases
Solution Approach 1:
The system divides the vehicle into zones with zone ECUs that independently manage power distribution. Each zone ECU contains a DC/DC converter that steps down 48V to 12V locally, eliminating the need for multiple centralized batteries and reducing system complexity while maintaining reliable power supply to different load types.
Solution Approach 2:
The 48V power supply system serves dual purposes: it directly powers large electric power loads and simultaneously serves as an input for DC/DC converters that generate 12V for small electric power loads. This multi-functional approach replaces the need for separate 12V and 48V battery systems.
2Loss of energy
If thick electric wires are used for power supply lines, then power loss is reduced when supplying large electric power loads, but wire harness cost and complexity increase
Solution Approach 1:
The system changes the voltage parameter from 12V to 48V for powering large electric power loads. Since power loss is proportional to the square of the current (P=I²R) and current is inversely proportional to voltage (I=P/V), increasing voltage by 4 times reduces current by 4 times, thereby reducing power loss by 16 times for the same load, allowing use of thinner wires.
3Reliability
If 12 volts is boosted to 48 volts using DC/DC converter at each large electric power load, then power supply voltage requirement is met, but vehicle cost increases
Solution Approach 1:
The DC/DC conversion function is extracted from individual large electric power loads and centralized in zone ECUs. Each zone ECU serves multiple loads, reducing the total number of DC/DC converters from one per load to one per zone, thereby reducing vehicle cost while still meeting voltage requirements.
4Reliability
If 48 volts is stepped down to 12 volts using DC/DC converter in zone ECU, then small electric power loads are powered, but power loss occurs during conversion
Solution Approach 1:
The DC/DC converter in each zone ECU provides not only the 12V power needed by small electric power loads but also excess 12V capacity that can support large electric power loads in that zone. This partial conversion approach reduces total conversion losses compared to converting 100% of 48V to 12V at every point.
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 reduces the diameter of power supply lines, minimizes power losses, and lowers the overall cost of the vehicle by eliminating the need for multiple batteries and booster circuits, while allowing for efficient power distribution to both large and small electric power loads.
Implementation Method 1
a first power supply unit (for example, DC/DC converter 12) configured to output electric power having a first voltage (for example, 48 volts) higher than a total power supply voltage required by the large electric power load and the small electric power load
Implementation Method 2
a step-down conversion unit (for example, DC/DC converter 16) disposed in a zone of one zone management unit of the plurality of zone management units and configured to convert the electric power having the first voltage into electric power having a second voltage (for example, 12 volts) lower than the first voltage
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An in-vehicle power supply system supplies electric power to a large electric power load and a small electric power load. The in-vehicle power supply system includes a first power supply unit to output electric power having a first voltage higher than a total power supply voltage required by the large and small electric power loads, zone management units to manage predetermined zones on the vehicle, a power supply trunk line unit connecting the first power supply unit and the zone management units and a step-down conversion unit disposed in a zone of one zone management unit of the zone management units and to convert the electric power having the first voltage into electric power having a second voltage lower than the first voltage. The power supply trunk line unit includes a high-voltage power supply line to distribute the electric power having the first voltage.