Starter Voltage Step-Down Circuit for Lower Source Current Peaks
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Solution Overview
Problem
Existing starter systems for internal combustion engines in vehicles experience high electrical current loads on the voltage source during starting, leading to magnetic oversaturation and voltage drops, which can result in inefficiency and risk to the on-board voltage system.
Innovation Solution
A starter system incorporating a step-down converter, utilizing MOSFET switches and a converter inductance, including the starter winding, to regulate the starting voltage and current, preventing excessive loads on the voltage source by alternating the switch units to maintain efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high supply voltage is applied directly to the starter during starting operation, then the starter can generate sufficient torque to rev the engine, but excessively high electrical current flows through the voltage source causing magnetic oversaturation and voltage drops
Solution Approach 1:
A step-down converter is introduced as an intermediary device between the voltage source and the starter. This converter includes a converter inductance (comprising the starter winding), a first switch unit, and a second switch unit that alternates between conducting and non-conducting states. The step-down converter reduces the supply voltage to a lower starting operating voltage, thereby limiting the electrical current flowing through the voltage source while still providing sufficient power to the starter to generate the required torque for engine starting.
2Device complexity
If the starter winding serves as the converter inductance in the step-down converter, then the device structure is simplified, but the starter must simultaneously function as both motor and inductance component
Solution Approach 1:
The starter winding is designed to serve dual functions: it acts as both the motor winding that generates torque when current flows through it, and as the converter inductance that stores and releases energy during the switching cycles of the step-down converter. This multi-functionality eliminates the need for a separate inductance component, thereby simplifying the overall device structure while maintaining the required electrical characteristics for both starting operation and voltage conversion.
3Object-affected harmful factors
If the second switch unit alternates between conducting and non-conducting states, then the voltage applied to the starter is regulated to prevent excessive current, but the switching operation increases device complexity
Solution Approach 1:
The second switch unit operates by alternating between conducting and non-conducting states in a periodic manner. During the conducting state, current flows through the starter winding; during the non-conducting state, the current is interrupted and the stored energy in the converter inductance is released. This periodic switching action effectively regulates the average voltage applied to the starter, preventing excessive current peaks while still delivering sufficient power for engine starting. The control unit manages the switching timing to optimize performance.
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
The system reduces electrical current peaks, preventing voltage source overload and ensuring efficient starting operations with increased safety and reliability, allowing for smaller voltage sources and enhanced compatibility with hybrid vehicles.
Implementation Method 1
a step-down converter for providing a starting operating voltage for the starter in the starting operating state by stepping down a supply voltage provided by the voltage source
Implementation Method 2
The step-down converter comprises a converter inductance and a first switch unit
Implementation Method 3
the first switch unit comprises at least one first MOSFET switch, wherein a drain terminal of the at least one first MOSFET switch provides the first switch terminal of the first switch unit
Data Source
Figure 1
AI summary
A starter system for an internal combustion engine in a vehicle comprises a starter (12), a voltage source (14) for supplying the starter (12) with electrical energy in a starting operating state and a step-down converter (22) for providing a starting operating voltage for the starter (12) in the starting operating state by stepping down a supply voltage provided by the voltage source (14).