Current-Limiting Switch Circuit for Fast Overcurrent Response
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Solution Overview
Problem
Existing switch systems in voltage converters for rotating electrical machines, such as those in motor vehicles, are slow to react to overcurrents, which can exceed safety thresholds and damage electronic components due to latency in Hall effect sensor and control systems, leading to potential component damage.
Innovation Solution
A switch system with a current limiting device that reduces the control current to put the main switch in a semi-closed state without using the switch control circuit, allowing for quicker current limiting by regulating the variable resistance of the main switch, using paired transistors like npn bipolar transistors or MOSFETs, and incorporating a current limiting device that derives a bypass current from the control resistor to limit the main current to a safe threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Hall effect sensor and control system are used to detect and respond to overcurrents, then the main switch can be opened to protect components, but the reaction time is excessive (tens of μs) allowing overcurrents to reach damaging levels (several hundred amperes in less than 3 μs)
Solution Approach 1:
The current limiting device is pre-configured with paired transistors and resistors that automatically activate when overcurrent conditions are detected, eliminating the need for sequential sensing and control signaling. The bypass resistor is already in place to provide an immediate current path, and the paired transistors are biased to trigger instantly when voltage thresholds are exceeded, performing the protective action before the damaging current levels can fully develop
Solution Approach 2:
The patent replaces the electronic control system (Hall effect sensor + control circuit + switch driver) with a direct electrical response mechanism. The paired transistors sense the overcurrent condition through voltage division and automatically redirect current through the bypass resistor, substituting the slow electronic control loop with a faster direct electrical action that responds purely through voltage and current relationships without microsecond delays
2Reliability
If the main switch is opened quickly to limit current, then component damage is prevented, but the control current must be reduced significantly which affects the switch's ability to remain in a controlled closed state
Solution Approach 1:
The control current path is segmented into multiple independent branches: the main control path through the control resistor, and a bypass path through the paired transistors and bypass resistor. When overcurrent is detected, only the bypass path activates to divert excess current, while the main control path remains intact to maintain normal switch operation. This segmentation allows current limiting without compromising the switch's controlled closed state
Solution Approach 2:
The paired transistors act as intermediaries that sense the overcurrent condition and mediate the current distribution between the load and the bypass resistor. They detect the voltage drop across the control resistor and automatically adjust their conduction to divert only the excessive current portion, leaving the necessary control current intact for maintaining the switch in its closed state, thus protecting components while preserving operational 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
Enables faster reaction to overcurrents, reducing the risk of component damage by quickly limiting the main current to prevent excessive amperage levels that exceed the safe operating area of electronic components.
Implementation Method 1
the current flowing in the main supply line is measured by a Hall effect sensor
Data Source
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AI summary
The invention relates to a switch system (1) comprising a power line (2) for supplying a charge from a voltage source (+Vbat), the power line comprising a main switch (Q1) having a first main terminal (D) and a second main terminal (S) between which a main current (lp) is intended to pass, and a control terminal (G) for selectively putting the main switch (Q1) into a closed, open or semi-closed state, the main switch (Q1) in its semi-closed state being equivalent to a variable resistance controlled by the control terminal and connected between the first and second main terminal, characterized in that the switch system (1) further comprises a current limiting device (3) designed to cause a control current (lg) entering into the control terminal (G) to decrease when the main current (lp) exceeds a maximum current threshold, in order to cause the main switch (Q1) to pass from the closed state to the semi-closed state so as to limit the main current.