Current-Limiting Circuit Using Inductor Voltage for Short-Circuit Response
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Solution Overview
Problem
Existing electrical systems in battery-electrically powered vehicles, particularly those with low-impedance short circuits, lack effective mechanisms to quickly detect and mitigate overcurrents to prevent component damage.
Innovation Solution
A circuit arrangement comprising an inductor, limiting resistor, gate resistor, gate driver, current limiting control circuit, and semiconductor switch, which dynamically adjusts output impedance to control the semiconductor switch and limit current flow based on an overcurrent-related voltage drop across the inductor, enabling rapid detection and counteraction of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pyrotechnic battery disconnect system is used to interrupt current flow in the event of a short circuit, then component damage is prevented, but the response time is too slow (not in the millisecond range) and the system lacks effective overcurrent mitigation
Solution Approach 1:
The patent replaces the mechanical/pyrotechnic disconnect system with an electronic control system using a semiconductor switch (MOSFET or IGBT) that can be controlled electronically. This substitution enables much faster response times (in the microsecond range) compared to mechanical or pyrotechnic systems, while maintaining effective component protection through precise current monitoring and rapid switch interruption.
Solution Approach 2:
The circuit arrangement monitors its own current flow through the inductor and automatically triggers the semiconductor switch to interrupt overcurrents without external intervention. The system self-detects the overcurrent condition via the voltage drop across the inductor and self-actuates the protection mechanism, eliminating the need for separate sensing and actuation systems.
2Difficulty of detecting and measuring
If traditional voltage monitoring across a shunt is used to detect short circuits, then short circuit detection is achieved, but the system cannot quickly mitigate overcurrents or prevent component damage in the millisecond range
Solution Approach 1:
The patent introduces an inductor as an intermediary element in the current path. The inductor generates a voltage drop proportional to the rate of change of current (di/dt), which serves as an early warning signal for overcurrent conditions before they become dangerous. This intermediary provides a measurable electrical quantity that directly reflects the current dynamics, enabling faster and more reliable overcurrent detection compared to simple voltage monitoring across a shunt.
Solution Approach 2:
The circuit arrangement takes preliminary action by continuously monitoring the voltage drop across the inductor, which reflects the current derivative. This allows the system to detect the onset of overcurrent conditions before they reach dangerous levels and trigger the semiconductor switch to interrupt the current flow in advance, preventing component damage rather than merely responding after damage occurs.
3Speed
If a semiconductor switch with direct control is used, then fast response is achieved, but the system lacks dynamic impedance adjustment capability for precise current limiting
Solution Approach 1:
The patent implements dynamic control of the semiconductor switch by using the inductor's voltage drop (which is proportional to di/dt) as the control signal. This dynamic control approach allows the switch's effective impedance to be continuously adjusted in real-time based on the instantaneous current conditions. The system adapts its response characteristics dynamically, providing precise current limiting capability while maintaining fast response speeds, rather than using fixed impedance control.
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 circuit arrangement effectively protects components from damage by quickly responding to overcurrents, allowing for automatic resumption of power supply once the overcurrent subsides, thereby enhancing system availability.
Implementation Method 1
A first input terminal of the current limiting control circuit is electrically connected to the first terminal of the inductor and a second input terminal of the current limiting control circuit is electrically connected to the second terminal of the inductor, so that a voltage drop across the inductor, which is caused by an overcurrent-related current gradient in the circuit formed by the power source and the load, is present at the input of the current limiting control circuit.
Data Source
AI summary
A circuit arrangement for current limiting and an electrical system comprising such a circuit arrangement. An output terminal of a current limiting control circuit is connected to a control input of a semiconductor switch via a limiting resistor (RB). The current limiting control circuit is configured to change an output impedance of the current limiting control circuit at the output terminal. The semiconductor switch is configured to set a current (I) in a circuit between an electrical power source and a load. An inductor (L) is configured to be connected to the electrical power source and to a terminal of the load and an input of the current limiting control circuit is connected to the inductor (L). The current limiting control circuit is configured to detect an overcurrent-related voltage drop (VL) of the inductor (L) and reduce its output impedance to increase an output impedance of the semiconductor switch.