DC-DC Converter Control for Hybrid Vehicle Cold Starts
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Solution Overview
Problem
Existing hybrid vehicles face challenges in reducing the weight and size of the low-voltage electric circuit while maintaining efficient power supply to electrical loads, particularly the electric starter motor during cold starts.
Innovation Solution
A control method for a hybrid road vehicle that integrates the low-voltage electric circuit with the high-voltage electric circuit using an electronic DC-DC power converter, which activates only during cold-start conditions to supply additional power to the electric starter motor from the high-voltage storage system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the storage device of the low-voltage electric circuit is eliminated and the nominal power of the electronic DC-DC power converter is increased to more than 10 kW, then the weight and size of the low-voltage electric circuit are reduced, but the total manufacturing costs significantly increase
Solution Approach 1:
The patent applies partial action by keeping the low-voltage storage device rather than eliminating it completely. The system uses a hybrid configuration where the storage device provides baseline power and the DC-DC converter supplements power only when needed (during cold starts or high-demand scenarios). This avoids the excessive cost of a high-power converter while still achieving weight reduction compared to a fully independent low-voltage system.
Solution Approach 2:
The DC-DC power converter is designed to serve multiple functions: it can operate in continuous mode for normal power transfer, in peak-power mode during cold starts, and can bidirectionally transfer power if needed. This multi-functionality allows a single component to replace what would otherwise require multiple specialized components, reducing overall system cost while maintaining weight benefits.
2Reliability
If the storage device of the low-voltage electric circuit is eliminated and the electronic DC-DC power converter is designed to always remain active, then the power supply to electrical loads is ensured, but the electronic DC-DC power converter is continuously stressed and requires a more expensive designing
Solution Approach 1:
The patent implements dynamic operation of the DC-DC power converter through a control unit that monitors system conditions and adjusts converter operation accordingly. The converter operates continuously in a low-power standby mode to maintain readiness, but transitions to high-power operation only when needed (detected through temperature sensors during cold starts or load monitoring). This dynamic approach ensures reliability while avoiding continuous high-stress operation that would require overly robust and expensive design.
Solution Approach 2:
The system uses periodic monitoring and conditional activation where the control unit continuously monitors temperature and load conditions, activating the DC-DC converter in periodic cycles only when cold-start conditions are detected or power demand exceeds storage device capabilities. This periodic engagement pattern maintains system reliability while significantly reducing cumulative stress on the converter compared to continuous full-power operation.
3Power
If the nominal power of the electronic DC-DC power converter is increased from approximately 2 kW to more than 10 kW, then the electric power that can be delivered is increased, but the total weight saved turns out to be modest
Solution Approach 1:
The patent optimizes the DC-DC power converter parameters by selecting a nominal power rating (around 2-5 kW) that matches the typical operational requirements, rather than oversizing it to 10+ kW for peak cold-start conditions. The control system compensates for the lower nominal power by managing power delivery timing and duration, activating the converter only when cold-start conditions are detected. This parameter optimization achieves adequate power delivery without the excessive weight penalty of a high-power converter design.
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 a reduction in the size and weight of the low-voltage storage system while ensuring a quick and safe start of the internal combustion engine, even in cold conditions, with reduced manufacturing costs and complexity.
Implementation Method 1
an electronic DC-DC power converter, which activates only during cold-start conditions to supply additional power to the electric starter motor from the high-voltage storage system
Data Source
AI summary
A road vehicle comprising: an internal combustion engine; an electric starter motor; a high-voltage electric circuit provided with a first storage system; a low-voltage electric circuit provided with a second storage system and directly connected to the electric starter motor; an electronic DC-DC power converter, which connects the low-voltage electric circuit and the high-voltage electric circuit to one another; and a control unit configured, in the presence of a turned-on condition of the road vehicle and when the internal combustion engine is off, to activate the electronic DC-DC power converter so as to transfer power to be at least partially supplied to the electric starter motor from the high-voltage electric circuit to the low-voltage electric circuit only in case of a cold-start condition of the internal combustion engine.