Hybrid Current Sensor Circuit for Bandwidth and Resolution
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Solution Overview
Problem
Current magnetic current sensors face challenges in achieving a balance between bandwidth and resolution, with Hall-effect sensors offering high resolution but limited bandwidth, and coils providing wider bandwidth but limited to sensing AC currents, while also being prone to disturbance fields and power dissipation.
Innovation Solution
A magnetic field sensor circuit with a coil and dual-stage amplifier circuits, featuring a pole and zero at the same frequency to maintain an essentially flat transfer function, and temperature-dependent frequency drift compensation using matching temperature coefficients for resistors and the coil, along with a hybrid approach combining coil and Hall sensor paths for wide-band hybrid sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall-effect sensors are used for current sensing, then resolution is improved, but bandwidth is limited
Solution Approach 1:
The patent combines Hall-effect sensors and coils into a hybrid sensor system that integrates both sensing mechanisms. The Hall sensors provide high resolution for low-frequency measurements, while the coils extend the bandwidth to high frequencies, achieving a flat frequency response across the entire measurement range.
2Speed
If coils are used for current sensing, then bandwidth is improved, but direct current sensing capability is lost
Solution Approach 1:
The hybrid sensor system merges Hall sensors, which can sense DC currents, with coils that provide extended bandwidth. The combined system maintains DC sensing capability while achieving high-frequency response, eliminating the limitation of coil-only sensors.
3Speed
If coils are used for current sensing, then bandwidth is improved, but robustness to disturbance fields deteriorates
Solution Approach 1:
The patent employs a feedback mechanism with a second transfer function that has a zero at the same frequency as the pole in the first transfer function. This feedback compensates for the coil's susceptibility to disturbance fields, canceling out common-mode interference and improving robustness while maintaining extended bandwidth.
4Speed
If coils are used for current sensing, then bandwidth is improved, but power consumption increases
Solution Approach 1:
The hybrid system merges the low-power Hall sensor path for low-frequency measurements with the coil path activated only when high-frequency response is needed. This selective operation reduces overall power consumption compared to using coils exclusively, while still providing extended bandwidth capability.
5Speed
If pole compensation is implemented to extend bandwidth, then frequency response is improved, but temperature-dependent frequency drift occurs
Solution Approach 1:
The patent introduces temperature compensation by adjusting the parameters of the zero-frequency pole based on temperature measurements. The compensation mechanism dynamically changes the pole frequency to counteract temperature-dependent drift, maintaining stable frequency response across varying temperatures.
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 enables low-noise, high-bandwidth, high-accuracy current sensing with improved robustness to stray fields and reduced power consumption, achieving better energy efficiency and compact design.
Implementation Method 1
at least one coil (inductance) for measuring a magnetic field. For example, the magnetic field may be caused by an electrical current.
Implementation Method 2
a first stage amplifier circuit coupled to the coil and having a first transfer function with a pole at a first frequency. While the pole of the first transfer function at the first frequency may limit an overload effect from the coil caused by high frequency (AC) magnetic fields (currents)
Implementation Method 3
a second stage amplifier circuit coupled to an output of the first stage amplifier circuit and having a second transfer function with a zero at the first frequency. the zero of the second transfer function at the same first frequency may compensate this pole, resulting in an essentially flat overall transfer function around the first frequency
Implementation Method 4
a first filter circuit included in the first stage amplifier circuit is configured to have a temperature dependent frequency drift of the pole of the first transfer function. A second filter circuit included in the second stage amplifier circuit is configured to have a temperature dependent frequency drift of the zero of the second transfer function. the temperature dependent frequency drift of the pole of the first transfer function essentially corresponds to the temperature dependent frequency drift of the zero of the second transfer function
Data Source
AI summary
The present disclosure relates to a magnetic field sensor circuit including at least one coil for measuring a magnetic field, a first stage amplifier circuit coupled to the coil and having a first transfer function with a pole at a first frequency, and a second stage amplifier circuit coupled to an output of the first stage amplifier circuit and having a second transfer function with a zero at the first frequency. In some embodiments, a temperature dependent frequency drift of the pole of the first transfer function corresponds to a temperature dependent frequency drift of the zero of the second transfer function.