Magnetic Feedback Delta-Sigma Modulator Sensor Circuit
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Solution Overview
Problem
Existing semiconductor magnetic field sensor measurement circuits require significant complexity for calibration via induced magnetic fields, often necessitating additional calibration sources and filtering, which complicates the measurement process.
Innovation Solution
A delta-sigma analog-to-digital converter circuit with a magnetic feedback path that self-calibrates by inducing a magnetic field to cancel sensor output voltage, using a current loop inductively coupled to the sensor, and a chopper amplifier to reduce noise, allowing for automatic calibration and reduced error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration source and detector are implemented to calibrate the sensor circuit via induced magnetic field, then the sensor gain can be calibrated, but the circuit complexity increases significantly
Solution Approach 1:
The patent combines the calibration function with the existing sensor output path by using the sensor's own output to drive a feedback current loop that generates the calibration magnetic field. This merges the calibration source function into the sensor circuit itself, eliminating the need for separate calibration sources and detectors while achieving accurate gain calibration through the feedback mechanism.
Solution Approach 2:
The patent implements a feedback mechanism where the sensor output voltage is converted to a feedback current that flows through a current loop, generating a magnetic field that feeds back to the sensor. This feedback loop automatically calibrates the sensor gain by equating the induced magnetic field effect with the sensor's voltage output, providing self-calibration without external equipment.
2Measurement precision
If calibration is performed periodically or out of the detection band, then the sensor can be calibrated, but additional filtering circuitry is required
Solution Approach 1:
The patent enables continuous calibration by operating the feedback mechanism within the same frequency band as the sensor's detection range. The feedback current loop continuously generates the calibration magnetic field at the operating frequency, allowing calibration to occur continuously rather than periodically or out-of-band, thereby eliminating the need for additional filtering circuitry to separate calibration and detection signals.
3Temperature
If Hall effect sensor is used in feedback path of operational amplifier, then temperature compensation can be provided, but offset variation and 1/f noise remain significant
Solution Approach 1:
The patent replaces the conventional operational amplifier feedback path with a magnetic feedback mechanism using a current loop that generates magnetic field feedback to the sensor. This substitution eliminates the direct voltage feedback path that introduces offset and 1/f noise, while maintaining temperature compensation through the magnetic feedback loop. The magnetic coupling provides inherent isolation that blocks low-frequency noise and offset propagation.
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 solution provides a compact, noise-immune digital output with reduced sensor variation errors and 1/f noise, achieving self-calibration without adding complexity to the measurement and calibration circuits.
Implementation Method 1
One or more current loops is implemented around the sensor and stimulated with a signal having known characteristics, inducing an AC magnetic field at the sensor
Implementation Method 2
The output of the quantizer of the delta-sigma modulator is magnetically coupled to the body of the semiconductor magnetic field sensor, providing a feedback path that causes a magnetic field to be imposed at the sensor that cancels the voltage produced at the output of the sensor
Implementation Method 3
Hall effect sensors and other semiconductor magnetic field sensors are widely used in applications in which it is desirable to provide a measurement of DC magnetic fields and relatively low frequency AC magnetic fields
Data Source
AI summary
A magnetic field feedback delta-sigma modulator sensor circuit, provides accurate magnetic field measurements without requiring complex additional calibration circuitry. The output of the semiconductor magnetic field sensor, which may be a Hall effect sensor, is coupled to the input of the delta-sigma modulator loop filter. The output of the quantizer of the delta-sigma modulator is magnetically coupled to the magnetic field sensor, producing a field that causes the output of the sensor to be canceled for frequencies in the band of the modulator loop filter. The output of the quantizer is provided to a current output digital-to-analog converter, which feeds a current loop that is inductively coupled to the sensor body. A chopper amplifier can be provided between the output of the sensor and the modulator loop filter input to reduce 1/f noise and bias current and output terminals can be rotated to further reduce 1/f noise and offset.