Hall Current Sensor Self-Diagnosis Offset Cancellation
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Solution Overview
Problem
Current magnetic sensors using Hall elements face challenges in precision detection due to offset voltages, particularly in high-frequency inverter current measurement, where existing methods do not effectively address fault diagnosis and initial pull-in time optimization.
Innovation Solution
A current sensor with a self-diagnosis function, incorporating an offset component output circuit, reference signal unit, error signal generation circuit, and adaptive feedback control, which extracts and cancels offset components using a chopper clock and transconductance elements to enhance precision and fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Hall element is used for contactless current measurement, then non-contact detection capability is improved, but offset voltage causes measurement precision to deteriorate
Solution Approach 1:
The patent applies periodic switching of the Hall element drive current direction using a chopper clock signal. By alternately reversing the current direction at high frequency, the offset voltage is modulated to the chopper frequency while the signal of interest remains at DC or low frequency, enabling separation through frequency-domain filtering
Solution Approach 2:
The patent implements a feedback mechanism where the output signal is processed to extract the offset component at the chopper frequency, and this extracted offset is fed back through an inverting amplifier to cancel the original offset voltage, continuously maintaining measurement accuracy
2Measurement precision
If a chopper clock is used to modulate offset voltage, then offset cancellation capability is improved, but ripple noise is generated and measurement precision deteriorates
Solution Approach 1:
The patent extracts the offset component from the total output signal by using a band-pass filter tuned to the chopper frequency. This separates the harmful offset-related ripple from the useful signal, allowing selective removal of only the offset portion while preserving the measurement signal
Solution Approach 2:
The patent converts the harmful effect of offset modulation into a beneficial separation mechanism. By modulating the offset to a specific frequency (chopper clock frequency), it becomes easily distinguishable and extractable from the signal band, transforming what would be a broadband interference into a frequency-specific component that can be selectively filtered and cancelled
3Measurement precision
If spinning current method is applied to cancel Hall element offset, then offset voltage is reduced, but device complexity increases due to switch circuit requirements
Solution Approach 1:
The patent integrates the spinning current switching function into the existing chopper clock infrastructure already used for offset modulation. The same chopper clock signal that modulates the offset voltage also drives the current direction switching, making the system perform multiple functions (offset modulation, current switching, signal demodulation) without requiring separate dedicated switching circuits
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
Enables precise self-diagnosis and adaptive control for offset cancellation, reducing ripple noise and improving initial pull-in time, thereby enhancing the accuracy and reliability of current measurement in magnetic sensors.
Implementation Method 1
a magnetic sensor which uses a Hall element... This type of Hall element has a magneto-electric conversion function which generates a Hall electromotive force signal in accordance with the intensity of the magnetic field which is input to the Hall element
Data Source
AI summary
There are provided a current sensor which has a self-diagnosis function and a signal processing circuit. The current sensor is provided with an offset component output circuit 102 which extracts an offset component from an output signal of a Hall element 101 which includes a signal component and an offset component, a reference signal generator 103 which outputs a reference signal, and an error signal generation circuit 104 which generates an error signal based on an offset component which the offset component output circuit 102 outputs and a reference signal. The offset component output circuit 102 is provided with a signal amplification circuit 106 which amplifies the output of the Hall element 101 and outputs an output signal and offset component to a low frequency component and the other to a ripple component.