Vehicle Power Path Isolation for High-Current Safety Loads
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Solution Overview
Problem
Existing on-board electrical systems in motor vehicles face challenges in reliably conducting and disconnecting high currents, particularly in safety-critical applications like automated driving, where high safety requirements demand efficient current management to prevent overload and ensure robust operation.
Innovation Solution
The implementation of an additional path with a series resistor and a timer, which is closed during a critical state and reopened after a predetermined period, allows for reliable isolation and current limitation, preventing excessive energy loads on switching elements and ensuring safe disconnection of high currents, including inductive loads, while using metal resistors for energy absorption and diodes for voltage limitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main path is opened upon detection of a critical state to isolate the sub-on-board electrical systems, then reliability is improved, but high current disconnection capability deteriorates due to potential excessive energy loads on switching elements
Solution Approach 1:
The patent divides the current path into a main path with switching elements and an additional path with a fuse, allowing the system to segment the current flow during critical states. This enables reliable isolation while protecting switching elements from excessive energy loads by directing high currents through the fuse in the additional path.
Solution Approach 2:
The additional path acts as an intermediary mechanism between the main path and the electrical systems. During critical states, it provides an alternative current flow path that protects the switching elements in the main path from excessive energy loads while maintaining current disconnection capability through the fuse.
2Strength
If switching elements disconnect high currents directly, then current disconnection capability is improved, but the switching elements are exposed to excessively high energy loads
Solution Approach 1:
The additional path with the fuse serves as an intermediary that handles high current disconnection. When activated, it directs excessive currents through the fuse rather than through the switching elements, thereby protecting the switching elements from excessively high energy loads while maintaining effective current disconnection capability.
Solution Approach 2:
The fuse in the additional path is designed as a sacrificial component that can be replaced. It absorbs the excessive energy loads during critical states, protecting the more expensive and reusable switching elements. This allows the system to disconnect high currents reliably while minimizing energy damage to critical components.
3Reliability
If the additional path is kept closed during main path opening, then current limitation function is improved, but device complexity increases
Solution Approach 1:
The system uses detection means to monitor critical states and provides feedback control for the additional path. When a critical state is detected, the control unit activates the additional path to provide current limitation. This feedback mechanism ensures reliable current limitation while managing complexity through automated control based on system conditions.
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 enables robust and safe disconnection of high currents, preventing oscillations and ensuring the safety of power semiconductors, thereby maintaining the availability of safety-relevant loads and preventing motor vehicle breakdowns by controlled disconnection and reactivation of electrical systems.
Implementation Method 1
the additional path being used for current limitation and/or for absorbing energy during the switching process of the main path, in particular by means of at least one resistor arranged in the additional path, particularly preferably a metal resistor
Implementation Method 2
Metal resistors in particular, for example made of metal alloys, are distinguished by high energy absorption
Implementation Method 3
a voltage limitation, in particular a diode, particularly preferably a TVS diode, is activated or remains activated while the main path and/or additional path is open. A targeted voltage limitation which limits the current independently of a voltage drop across the switching element is thus achieved
Data Source
AI summary
A method for securing safety-relevant loads in a motor vehicle, including a main path arranged between a sub-on-board electrical system for a safety-relevant load of a motor vehicle and another sub-on-board electrical system for a non-safety-relevant load. The sub-on-board electrical system for the safety-relevant load is supplied with power by an energy store. The main path includes at least one switch, and at least one detector for detecting a current flowing through the main path. At least one additional path is provided which is connected in parallel with the main path, the additional path having at least one switch. The method includes: opening the main path upon detection of a critical state, i.e., an overcurrent and/or an undervoltage or overvoltage on the sub-on-board electrical system for the safety-relevant load. The additional path is closed or kept closed while the main path is open. The additional path is subsequently reopened.