Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
2002-09-20
2004-08-24
Karlsen, Ernest (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S126000
Reexamination Certificate
active
06781359
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
FIELD OF THE INVENTION
This invention relates generally to electrical current sensors, and more particularly to a miniaturized current sensor having an integrated conductor.
BACKGROUND OF THE INVENTION
As is known in the art, one type of conventional electrical current sensor uses a Hall effect magnetic field transducer in proximity to a current-carrying conductor. The Hall effect device generates an output signal having a magnitude proportional to the magnetic field induced by the current through the conductor. Typical current sensors of this type include a gapped toroid magnetic flux concentrator, with the Hall effect device positioned in the toroid gap. The Hall effect device and toroid are assembled in a housing which is mountable on a printed circuit board. In use, a separate current-carrying conductor, such as a wire, is passed through the center of the toroid and is soldered to the printed circuit board, such as by soldering exposed ends of the wire to plated through-holes. Such devices tend to be undesirably large, both in terms of height and circuit board area.
Various parameters characterize the performance of Hall effect devices in current sensing applications, including sensitivity, which is the change in the output signal of the Hall effect device in response to a one ampere change through the conductor, and linearity, which is the degree to which the output signal varies in direct proportion to the current through the conductor. Important considerations in the use of Hall effect devices include the effect of stray magnetic fields and external magnetic noise on the device performance.
SUMMARY OF THE INVENTION
In accordance with the present invention, an integrated current sensor is provided with a conductor having a first notch substantially aligned with a second notch, a magnetic field transducer having at least a portion positioned in the first notch, and a magnetic core. The magnetic core is substantially C-shaped, with a central region and a pair of substantially parallel legs extending from the central region. At least a portion of the central region of the magnetic core is positioned in the second notch such that each leg covers at least a portion of a respective surface of the magnetic field transducer. In the illustrated embodiments, the magnetic field transducer is a Hall effect sensor containing a Hall effect element.
With this arrangement, the Hall effect sensor, the conductor, and the magnetic core are essentially locked in place relative to each other by the first and second notches and also by dimensional characteristics of the elements. As a result of the precise mechanical positioning of the elements, the sensitivity of the current sensor is highly repeatable and thus, tightly controlled. The magnetic core provides a sensitivity that is higher than otherwise possible and also provides a magnetic field across the Hall effect element that is substantially uniform.
In one embodiment, each of the legs of the magnetic core covers substantially an entire surface of the Hall effect sensor. This arrangement, in combination with the C-shape of the magnetic core, serves to reduce susceptibility to stray magnetic fields and external magnetic noise, to increase sensitivity and to improve the uniformity of the magnetic field across the Hall effect element.
At least a portion of the Hall effect sensor, conductor, and magnetic core are encapsulated with an electrically insulating material. The conductor is provided with a mechanism for mounting the current sensor to a printed circuit board, such as through-holes adapted to receive hardware, leads or tabs for inserting into printed circuit board through-holes or for surface mount soldering to pads. The resulting integrated current sensor provides a significantly smaller, single component alternative to the conventional gapped toroid design.
To achieve further integration, the Hall effect sensor contains circuitry for processing the output signal of the Hall effect element, including one or more signal amplifiers. Preferably, the circuitry also includes additional elements, such as digital-to-analog converters and counters, which can be controlled in order to trim performance parameters, such as sensitivity and quiescent offset voltage.
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PCT Search Report; PCT/US02/24008 dated Dec. 4, 2003.
: Japanese Provisional Publication of Patent No. 2001-339109; Published Dec. 7, 2001; Entitled: “Current Detection Device Equipped with Hall Device:” Applicant Sanken Electric Co., Ltd.
: Japanese Provisional Publication of Patent 2002-40058; Published Feb. 6, 2002; Entitled: “Current Detection Device Equipped with Hall Device:” Applicant: Sanken Electric Co., Ltd.
Dickinson Richard
Engel Ray
Pinelle Sandra
Sauber John
Stauth Jason
Allegro Microsystems Inc.
Daly, Crowley & Mofford LLP
Karlsen Ernest
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