Variable Resistance Current Sensor for Wide Dynamic Range
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Solution Overview
Problem
Current sensors face challenges in accurately measuring a wide dynamic range of currents in motor vehicles, particularly in electric and hybrid drives, due to high resolution and EMC interference issues, which increase costs and complexity.
Innovation Solution
A current sensor design where the resistance element's resistance varies with current, maintaining a constant percentage resolution and using a controlled resistance element with a reference voltage, potentially anti-proportional to current, and incorporating field effect transistors and control loops to manage interference and extend measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used for current measurement, then the measurement can be performed with simple circuitry, but the required dynamic range and accuracy cannot be achieved simultaneously
Solution Approach 1:
The patent applies dynamics by making the resistance element's resistance value variable rather than fixed. The resistance dynamically adjusts based on the current magnitude through control loops and feedback mechanisms, allowing the same circuit to accurately measure both low currents (10mA) and high currents (1000A) without requiring multiple fixed resistors or complex switching circuits.
Solution Approach 2:
The patent changes the resistance parameter of the resistance element as a function of current. By controlling the resistance to decrease when current increases and increase when current decreases, the system maintains optimal measurement conditions across the entire dynamic range, eliminating the need for multiple fixed resistance values and reducing circuit complexity.
2Measurement precision
If high-resolution AD converters are used to measure low voltages, then measurement accuracy improves, but EMC resistance decreases and costs increase
Solution Approach 1:
The patent introduces an intermediary approach by using a controlled resistance element that transforms the current measurement into a voltage measurement with optimized characteristics. The resistance element acts as a mediator that adapts its value to maintain suitable voltage levels for measurement, reducing the impact of EMC interference while maintaining resolution.
Solution Approach 2:
The patent employs feedback control loops that continuously monitor the measurement conditions and adjust the resistance element accordingly. This feedback mechanism ensures that the voltage across the resistance element remains within optimal ranges for ADC conversion, maintaining both resolution and EMC immunity across the full current range.
3Adaptability or versatility
If the resistance element is designed with fixed resistance, then the circuit is simple, but the measurement range is limited
Solution Approach 1:
The patent makes the resistance element dynamic rather than static. The resistance value automatically adapts to the current being measured through control loops, enabling the single resistance element to handle the full range from 10mA to 1000A without requiring multiple fixed resistance elements or complex switching mechanisms.
Solution Approach 2:
The patent designs the resistance element to serve multiple functions across different measurement ranges. By controlling the resistance to vary with current, a single element performs the work of multiple fixed resistors, achieving universal measurement capability from 10mA to 1000A while keeping the circuit relatively simple.
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 design achieves precise current measurement across a large dynamic range with reduced interference and cost, using standard microcontrollers and maintaining high EMC resistance, allowing for accurate battery state and condition monitoring in electric vehicles.
Implementation Method 1
the electrical resistance of the resistance element decreases when the current through the resistance element increases and/or that the electrical resistance of the resistance element increases when the current through the resistive element decreases
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to a current sensor (1) comprising at least one resistance element (2) on which voltage (U GS ) for measuring the current (i Mess ) flowing through the resistance element (2) is detected. Said resistance element (2) is designed so that at least, within a defined measurement range of the current sensor, the electric resistance of the resistance element reduces when the current (i Mess ) flowing through the resistance element increases.