Semiconductor Module Current Sensing With a Coreless External Sensor
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Solution Overview
Problem
Core-based current sensors in inverter packages suffer from performance limitations due to hysteresis, saturation, temperature-dependent permeability, and eddy current effects, leading to inaccurate current sensing and the need for costly end-of-line calibration to compensate for gain and offset errors.
Innovation Solution
Integration of a coreless magnetic field sensor within the semiconductor module, utilizing a magnetoresistive or Hall sensor, isolated by a mold compound to generate a signal proportional to the current flowing through a constricted terminal region, eliminating the need for external compensation circuits and high-current calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If core-based magnetic sensors are used for current sensing, then current measurement capability is provided, but sensing accuracy deteriorates due to hysteresis, saturation, temperature-dependent permeability, and eddy current effects
Solution Approach 1:
The patent extracts and removes the iron core from the magnetic sensor structure, transitioning from a core-based sensor to a coreless sensor. This extraction eliminates the source of hysteresis, saturation, and temperature-dependent permeability issues, directly resolving the technical contradiction by removing the harmful magnetic core while retaining the current sensing capability through alternative means
Solution Approach 2:
The patent introduces an intermediary structure - a magnetic flux concentrator or guide made from materials with high permeability but without iron core losses, positioned between the current-carrying conductor and the sensing element. This intermediary guides and concentrates the magnetic flux to the sensor while avoiding the harmful effects of iron cores, thereby improving measurement precision without suffering from temperature-dependent errors
2Measurement precision
If compensation circuits and additional windings are added to address core-based sensor issues, then sensing accuracy is improved, but device complexity and power dissipation increase
Solution Approach 1:
The patent eliminates the need for complex compensation circuits and additional windings by removing the iron core itself. The coreless sensor design inherently avoids hysteresis and saturation issues, making compensation mechanisms unnecessary and thereby reducing device complexity while maintaining or improving sensing accuracy
Solution Approach 2:
The coreless magnetic sensor design is self-correcting in that it inherently avoids the magnetic flux distortion and temperature-dependent errors that plague core-based sensors. The sensor structure itself provides the solution without requiring external compensation circuits, reducing overall system complexity and eliminating the need for additional power-dissipating compensation windings
3Measurement precision
If end-of-line calibration is performed to compensate for sensor errors, then measurement precision is improved, but manufacturing cost and time increase
Solution Approach 1:
By extracting the iron core from the sensor design, the patent eliminates the primary sources of sensor error (hysteresis, saturation, temperature-dependent permeability). This results in a sensor with inherently stable and predictable characteristics that require minimal or no calibration, thereby reducing manufacturing time and cost while maintaining high measurement precision
Solution Approach 2:
The coreless sensor design is manufactured with inherent stability and low drift characteristics from the outset, eliminating the need for subsequent calibration procedures. The design itself performs the error-compensation function that would otherwise require time-consuming end-of-line calibration processes, thus improving productivity while maintaining measurement precision
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
Enhances sensing accuracy by eliminating temperature-dependent errors and reducing costs through controlled end-of-line calibration, ensuring precise current measurement without additional power dissipation.
Implementation Method 1
a coreless magnetic field sensor disposed in the recess or the opening of the mold compound and isolated from the first terminal by the mold compound, the coreless magnetic sensor configured to generate a signal in response to a magnetic field produced by current flowing in the constricted region of the first terminal
Implementation Method 2
The coreless magnetic field sensor may be a magnetoresistive sensor or a Hall sensor
Implementation Method 3
The coreless magnetic field sensor may be a magnetoresistive sensor or a Hall sensor
Data Source
AI summary
A semiconductor module includes a semiconductor die, a mold compound encasing the semiconductor die, a plurality of terminals electrically connected to the semiconductor die and protruding out of the mold compound, wherein a first one of the terminals has a constricted region covered by the mold compound, wherein the mold compound has a recess or an opening near the constricted region of the first terminal, and a coreless magnetic field sensor disposed in the recess or the opening of the mold compound and isolated from the first terminal by the mold compound. The coreless magnetic sensor is configured to generate a signal in response to a magnetic field produced by current flowing in the constricted region of the first terminal. The magnitude of the signal is proportional to the amount of current flowing in the constricted region of the first terminal. A method of manufacturing the module also is described.