Integrated Current Sensor Layout for Isolation and Stray Field Immunity
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Solution Overview
Problem
Current current sensors face limitations in voltage isolation and are susceptible to errors caused by stray magnetic fields, which affect the accuracy of current measurement.
Innovation Solution
The proposed current sensor design includes a lead frame, an integrated circuit with Hall effect sensors, and strategically aligned magnetic concentrators to provide high-voltage isolation and immunity from stray magnetic fields, using a combination of a lead frame, an isolation spacer, and magnetic concentrators to concentrate and detect magnetic flux, while the Hall effect sensors generate output voltages proportional to the current flow, and summation circuitry cancels out stray field-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic flux concentrators are added to concentrate magnetic field for sensing, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The magnetic flux concentration system is segmented into multiple discrete concentrators (first and second magnetic flux concentrators) positioned at different locations. Each concentrator independently concentrates magnetic flux from its respective region onto the sensing element, allowing modular design and fabrication while achieving comprehensive field concentration
Solution Approach 2:
The magnetic flux concentrators extend in the vertical dimension (z-direction) above the substrate, creating a three-dimensional magnetic flux concentration path. This vertical dimension allows the concentrators to capture magnetic flux from a larger spatial volume and guide it effectively to the Hall effect sensor, improving measurement precision without increasing in-plane device complexity
2Reliability
If isolation spacer is introduced to provide high voltage isolation, then reliability is improved, but device complexity increases
Solution Approach 1:
The isolation spacer serves as an intermediary component positioned between the lead frame (carrying high voltage) and the integrated circuit (sensing elements). This intermediate element provides electrical isolation and mechanical support, protecting sensitive circuitry from high voltage while maintaining a relatively simple overall device structure
Solution Approach 2:
The isolation spacer is strategically placed only in regions where voltage isolation is required, specifically between the lead frame and the integrated circuit. This localized approach provides high voltage isolation where needed while minimizing the addition of structural complexity to other parts of the device
3Measurement precision
If multiple Hall effect sensors are used to cancel stray field errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple Hall effect sensors are arranged symmetrically with respect to the magnetic flux concentrators. The sensors measure magnetic fields at different locations, and their outputs are combined (subtracted) to cancel out stray magnetic field components while preserving the differential signal from the current being measured. This counterbalancing approach eliminates stray field errors without requiring complex external compensation 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
The solution achieves high-voltage isolation and immunity from stray magnetic fields, ensuring accurate current measurement by concentrating magnetic flux and canceling out stray field errors, thereby enhancing the reliability of current sensing.
Implementation Method 1
a magnetic field generated by the flow of current through an electrical conductor is concentrated inside a magnetic core
Implementation Method 2
The integrated circuit includes a Hall effect sensor. The first magnetic concentrator is aligned with the current input segment and overlaps the Hall effect sensor
Data Source
AI summary
In one example, circuitry is formed in a semiconductor die. A magnetic concentrator is formed on a surface of the semiconductor die and over the circuitry. An isolation spacer is placed on a lead frame. The semiconductor die is placed on the isolation spacer, and the magnetic concentrator is aligned to overlap the lead frame. Electrical interconnects are formed between the semiconductor die and the lead frame.