Chopper-Stabilized Sensor Circuit With Digital Ripple Feedback
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Solution Overview
Problem
Magnetic field sensors using Hall Effect elements face issues with undesirable DC offset voltage and ripple generation due to chopping techniques, which can be reduced but often result in reduced bandwidth and response time.
Innovation Solution
A sensor circuit incorporating a chopper-stabilized amplifier, sigma-delta modulator, and feedback circuit with demodulation, digital integration, and digital-to-analog conversion to reduce ripple, avoiding analog demodulation issues and allowing full dynamic range for digitizing magnetic field signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional filter arrangements are used to reduce ripple, then ripple is effectively reduced, but bandwidth and response time are reduced
Solution Approach 1:
The patent implements a feedback circuit that receives the output signal, extracts the ripple component at the chopping frequency, and feeds back an inverted ripple signal to cancel the original ripple. This active feedback mechanism reduces ripple without requiring passive filters that would limit bandwidth and response time.
Solution Approach 2:
The patent introduces an intermediary ripple extraction circuit that separates the ripple component from the main signal, allowing selective processing. By extracting and inverting only the ripple portion through this intermediary stage, the system can eliminate harmful ripple while preserving the full bandwidth of the original signal.
2Measurement precision
If chopping technique is used to reduce DC offset voltage, then DC offset is reduced, but ripple is generated in the signal
Solution Approach 1:
The patent converts the harmful ripple generated by chopping into a beneficial cancellation signal. By detecting the ripple at the chopping frequency and inverting it, the system transforms the harmful artifact into a useful counter-signal that eliminates the ripple when combined with the original output, while preserving the DC offset correction benefits of chopping.
Solution Approach 2:
The feedback circuit continuously monitors the output signal, identifies the ripple component generated by chopping, and feeds back an inverted version to cancel it. This creates a closed-loop system that maintains DC offset correction while actively suppressing the harmful ripple byproduct.
3Measurement precision
If chopper stabilized amplifier is used to reduce offset and low frequency noise, then offset and flicker noise are reduced, but spectral components and ripple are generated
Solution Approach 1:
The patent employs a feedback mechanism that specifically targets the spectral components and ripple generated by the chopper stabilized amplifier. By extracting these frequency-specific components and feeding back inverted signals, the system eliminates the harmful artifacts while preserving the beneficial offset and noise reduction.
Solution Approach 2:
An intermediary ripple extraction and processing stage is introduced between the chopper stabilized amplifier and the final output. This intermediary circuit selectively processes only the unwanted spectral components at the chopping frequency, allowing them to be removed without affecting the amplifier's beneficial low-frequency 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
The solution effectively reduces ripple to an acceptable level, maintaining sensor bandwidth and response time, and prevents saturation by processing only the sensed magnetic field signal, not the chopper-generated ripple.
Implementation Method 1
Hall Effect elements generate an output voltage proportional to a magnetic field
Data Source
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AI summary
A sensor circuit (100) is provided with a chopper-stabilized amplifier circuit (102) configured to receive a signal (104a, 104b) from at least one magnetic sensing element (104), a sigma-delta modulator - SDM (132) configured to receive a signal (128) from the chopper-stabilized amplifier circuit, and a feedback circuit configured to reduce ripple in a signal generated by the chopper-stabilized amplifier circuit. The feedback circuit includes a demodulator (142) to demodulate a signal (132a) from the SDM in a digital domain by inverting a bit stream of the signal from the SDM according to a frequency chopping rate, a digital integrator (148) configured to integrate an output signal (142a) of the demodulator to form an integrated signal (148a), and a digital-to-analog converter - DAC (152) configured to convert the integrated signal to an analog signal (152a) and provide the analog signal to the chopper-stabilized amplifier circuit.