Magnetic Field Sensor Feedback Loop Attenuates Ripple
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Solution Overview
Problem
Magnetic field sensors using Hall Effect elements face issues with DC offset voltage and ripple generation due to chopping, which can reduce bandwidth and increase costs by requiring greater circuit components, especially when processing test signals alongside magnetic field signals.
Innovation Solution
A sensor circuit with feedback loops and a sigma-delta modulator to process and attenuate ripple and test signals, utilizing a digital integrator and DAC to subtract compensation signals from the main signal path, effectively reducing ripple and test signal components, thereby maintaining bandwidth and reducing saturation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If filters are used to remove ripple generated by chopping, then ripple is reduced, but bandwidth and response time are reduced
Solution Approach 1:
The patent implements a feedback loop that detects ripple components in the output signal and generates a compensating signal to cancel the ripple. The feedback circuit monitors the chopped signal, identifies ripple frequency components, and feeds back an inverted ripple signal to the summing junction, effectively canceling the harmful ripple without requiring bandwidth-reducing filters.
2Adaptability or versatility
If circuit components are designed with greater bandwidth to process both test signals and magnetic field signals, then signal processing capability is improved, but cost and area increase
Solution Approach 1:
The patent employs periodic time-multiplexed operation where the amplifier alternates between processing test signals and magnetic field signals. During test signal processing, the amplifier is configured with appropriate gain for test frequencies, and during magnetic field signal processing, it switches to magnetic sensing mode. This periodic switching allows a single amplifier to handle both signal types without requiring simultaneous high bandwidth for both, thereby reducing overall circuit area and cost.
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 significantly reduces ripple and test signal components, maintaining the dynamic range of the sensor and preventing saturation, while allowing for efficient processing of magnetic field signals without the need for extensive bandwidth or costly circuitry.
Implementation Method 1
Hall effect elements generate an output voltage proportional to a magnetic field
Implementation Method 2
A feedback circuit is coupled to receive the digital combined signal and extract the test signal
Data Source
AI summary
A sensor circuit may include one or more feedback loops to process and attenuate ripple and/or a test signal. The sensor circuit may comprise at least one magnetic field sensing element to generate a magnetic field signal representing a magnetic field to be measured, a test signal generator circuit configured to generate a test signal and combine the test signal with the magnetic field signal to generate a combined signal, and a signal path for processing the combined signal. The signal path may comprise an amplifier circuit to amplify the combined signal, an analog-to-digital converter (ADC) to convert the combined signal to a digital combined signal, and a feedback circuitry coupled to receive the digital combined signal and extract the test signal. A test comparator circuit compares the extracted test signal to a reference signal.