Hybrid Magnetic Field Sensor With DC Rejection for High-Bandwidth Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hybrid magnetic field sensors face limitations in accurately measuring fast-switching currents due to low-frequency current sensing architectures, leading to high-frequency magnetic field component measurement inaccuracies, and require large DC decoupling capacitors, off-chip components, and DC servo loops that introduce noise, offset, and bandwidth limitations.
Innovation Solution
Implementing a direct current (DC) component rejection path coupled with a high-frequency magnetic field component path, using either digital- or analog-based solutions that eliminate the need for DC decoupling capacitors, incorporating a Continuous-Time Sigma-Delta Analog-to-Digital Converter (CT-ΣΔ ADC) and digital or analog components to generate a DC component cancellation signal, and integrating this with an AC magnetic field component sensor path to reduce DC offsets and quantization noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional low-frequency current sensing architectures are used, then DC and low-frequency magnetic field components can be measured, but high-frequency magnetic field component measurement accuracy deteriorates
Solution Approach 1:
The sensor system is divided into two separate sensing paths: a high-frequency path using coil-based sensors for AC magnetic field components, and a low-frequency path using Hall sensor elements for DC and low-frequency magnetic field components. Each path is optimized for its frequency range, with the Hall sensor path having its output coupled to the high-frequency path to enable accurate high-frequency measurements while maintaining DC measurement capability.
2Adaptability or versatility
If DC decoupling capacitors are used to separate high-frequency and low-frequency paths, then frequency separation is achieved, but device area and component count increase
Solution Approach 1:
The invention extracts and eliminates the need for large DC decoupling capacitors by using a different architectural approach. Instead of relying on capacitive coupling to separate frequency paths, the system uses direct coupling of the Hall sensor output to the high-frequency path with electronic filtering to achieve frequency separation, thereby removing the area-consuming capacitors from the sensor chip.
3Measurement precision
If DC servo loops are implemented to reject DC offsets, then DC offset reduction is achieved, but bandwidth limitations and noise are introduced
Solution Approach 1:
The invention introduces an intermediary filtering mechanism that processes the combined signal from both sensing paths. A filter is applied to the output of the high-frequency path to remove residual DC components and low-frequency noise, providing DC offset rejection without requiring a DC servo loop that would limit bandwidth. This intermediary filtering approach maintains the high bandwidth capability while achieving the desired DC rejection performance.
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 approach enables high-bandwidth, high-accuracy hybrid current sensors with reduced DC offsets, eliminating the need for external components and overcoming bandwidth limitations, thus enhancing sensor performance for applications requiring high-frequency measurements.
Implementation Method 1
incorporating a Continuous-Time Sigma-Delta Analog-to-Digital Converter (CT-ΣΔ ADC)
Implementation Method 2
DC magnetic field component sensor path implementing Hall sensor elements
Implementation Method 3
AC magnetic field component sensor path implementing coil-based sensor elements
Data Source
AI summary
The described techniques address issues associated with hybrid current or magnetic field sensors used to detect both low- and high-frequency magnetic field components. The hybrid sensor implements a DC component rejection path in the high-frequency magnetic field component path. Both digital and analog implementations are provided, each functioning to generate a DC component cancellation signal to at least partially cancel a DC component of a current signal generated via the high-frequency magnetic field component path. The hybrid sensor provides a high-bandwidth, high-accuracy, and low DC offset hybrid current solution that also eliminates the need for DC decoupling capacitors in the high-frequency path. A modification is also described for implementing a Sigma-Delta (ΣΔ) quantization noise reduction path to reduce the quantization noise and to improve accuracy.