Dual-Path Current Sensor With Shared Calibration for Drift Control
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Solution Overview
Problem
Current sensing technologies face challenges in achieving accuracy and reliability due to sensitivity variations, offset errors, temperature variations, and lifetime drift in magnetic and resistive sensing elements, which are critical in safety-critical applications like automotive systems.
Innovation Solution
Implementing a current sensor with shared processing paths for magnetic field and resistive sensing, utilizing a shared processor for calibration of sensitivity, temperature, offset, and lifetime drift, ensuring equal but opposite temperature coefficients for magnetic field and resistive elements, and using a single temperature sensor for temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate calibration circuits are used for magnetic and resistive sensing paths, then each sensing path can be independently calibrated, but circuit area and power consumption increase
Solution Approach 1:
The patent merges separate calibration circuits for magnetic and resistive sensing paths into a single shared calibration circuit. The calibration module receives inputs from both sensing paths and performs calibration operations using common resources, thereby reducing circuit area while maintaining calibration capability for both heterogeneous sensing methodologies.
Solution Approach 2:
The calibration circuit is designed as a universal module that can calibrate both magnetic field sensing elements and resistive sensing elements. This multi-functional calibration circuit uses shared processors and common calibration signals to adjust sensitivity, offset, and temperature coefficients for both sensing paths, eliminating the need for separate dedicated calibration circuits.
2Measurement precision
If separate calibration circuits are used for magnetic and resistive sensing paths, then each sensing path can be independently calibrated, but power consumption increases
Solution Approach 1:
The patent merges separate calibration circuits for magnetic and resistive sensing paths into a single shared calibration circuit. The calibration module receives inputs from both sensing paths and performs calibration operations using common resources, thereby reducing circuit area while maintaining calibration capability for both heterogeneous sensing methodologies.
Solution Approach 2:
The calibration circuit is designed as a universal module that can calibrate both magnetic field sensing elements and resistive sensing elements. This multi-functional calibration circuit uses shared processors and common calibration signals to adjust sensitivity, offset, and temperature coefficients for both sensing paths, eliminating the need for separate dedicated calibration circuits.
3Reliability
If redundant identical circuits are used, then functional safety requirements are met, but device complexity increases
Solution Approach 1:
The patent employs asymmetric heterogeneous sensing elements (magnetic field sensing elements and resistive sensing elements) instead of symmetric identical redundant circuits. These different types of sensing elements provide diverse failure modes and complementary measurement capabilities, meeting functional safety requirements while reducing overall system complexity compared to identical redundant circuits.
Solution Approach 2:
The patent changes the parameter of sensing methodology from identical to heterogeneous, using different physical principles (magnetic field sensing vs. resistive voltage drop measurement). This parameter change allows the system to achieve redundancy and safety compliance through diversity rather than duplication, thereby reducing circuit complexity while maintaining reliability.
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
Enhances accuracy and reliability by reducing the need for separate calibrations, improving sensitivity and temperature compensation, and minimizing lifetime drift, thereby meeting safety standards like ASIL requirements.
Implementation Method 1
magnetic field sensing elements in proximity to a current-carrying conductor. The magnetic field sensing elements generate an magnetic field signal having a magnitude proportional to the magnetic field induced by the current through the conductor
Implementation Method 2
measuring a voltage drop across the conductor in order to thereby determine the level of current flow through the conductor based on the measured voltage drop and known resistance of the conductor
Data Source
AI summary
A current sensor for sensing a current through a conductor includes a magnetic field sensing element configured to generate a magnetic field signal indicative of a magnetic field associated with the current through the conductor, a first processing path responsive to the magnetic field signal and configured to generate a first current sensor output signal, a resistive element coupled to the conductor, a second processing path coupled across the resistive element and configured to measure a voltage across the resistive element and generate a second current sensor output signal, and a shared processor configured to calibrate the first processing path and second processing path. The shared processor can be configured to generate one or more of a sensitivity calibration signal, a temperature calibration signal, an offset calibration signal, or a lifetime drift calibration signal.