Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
1998-08-12
2003-04-08
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S127000
Reexamination Certificate
active
06545456
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a Hall-effect current sensor package that enhances the performance of a Hall-effect current sensor.
BACKGROUND OF THE INVENTION
Electrical current sensors are known and are in wide use today throughout the electronics industry. One particular, type of current sensor is a Hall-effect sensor. In general, a Hall-effect type sensor may be employed to determine the amount of current passing through a conductor by sensing a magnetic field associated with the current, and in turn producing a Hall-effect output voltage that is proportional to the magnetic field.
The Hall effect is a well known phenomenon occurring in conductors and semiconductor materials wherein a current flowing generally perpendicular to a magnetic field induces a voltage perpendicular to both the field and current, which voltage is proportional to the product of the current and magnetic field.
More particularly, the Hall effect output voltage is the voltage produced across opposite edges of the conductor when placed in a magnetic field. The basis of this effect, which depends upon the deflection of charged particle moving in a magnetic field, is the Loreritz force. This force is in a direction mutually perpendicular to the particle movement and the magnetic field direction. As a result, an output voltage occurs across the--conductor. This output voltage has a magnitude that depends upon the magnetic field present, the Hall coefficient and the excitation current in the conductor.
When the excitation current is held constant, the output voltage is proportional to the magnetic field produced by the current being sensed or measured.
Hall effect sensors generally include a constant current source, a gapped toroid core (e.g., lamination stack) and a Hall effect generator extending into the gap of the core. Positioning of the Hall effect generator within the gap is important because inaccurate and unsteady positioning of the Hall-effect generator within the gap may result in the Hall-effect sensor malfunctioning.
Additionally, environmental factors may also impact the proper functioning of the Hall-effect sensor. More particularly, outside contaminants (e.g., dust, dirt, grime, oil, fluids) may hinder the operation of the Hall-effect sensor.
In view of the above, there is a need in the art for a packaging arrangement that provides for secure and stable positioning of the Hall-effect generator inside the air gap of the Hall effect sensor. Moreover, it would be desirable for such an arrangement to also afford for insulating the Hall-effect sensor such that an impeding effect on the sensor resulting from contaminants is mitigated.
SUMMARY OF THE INVENTION
The present invention provides for a Hall-effect sensor packaging and method thereof which provides for good and reliable positioning of a Hall-effect generator within a gap of a core (e.g., lamination stack, laminated toroid) of a Hall-effect sensor. In particular, the Hall-effect generator may be positioned in either of a lead frame or circuit board such that the Hall-effect generator is suitably positioned within the gap. Once the Hall-effect generator is properly positioned within the gap, the Hall-effect generator and at least a portion of the core is encapsulated by an insulative material.
The insulative material provides for maintaining the Hall-effect generator at a desired position within the gap substantially permanently. As a result, the Hall-effect sensor of the present invention affords for accurate and consistent current measurement. Furthermore, the insulative material may provide for shielding significant components of the Hall-effect sensor from contaminants (e.g., dust, dirt, grime, oil, fluids).
Additionally, the present invention affords for having a core gap of substantially minimal length which provides for enhanced sensitivity. As a result of the enhanced sensitivity, the present invention is highly conducive for low current measurement applications. The substantially minimal core gap length is achieved because the present invention mitigates the need to individually insulate the Hall-effect generator. Conventional Hall-effect generators like many semiconductor devices require suitable packaging (e.g., via plastic) in order to protect the device. The packaging tends to make the Hall-effect generator thicker thus requiring a relatively long core gap length. In the present invention, the Hall-effect generator does not require a thick packaging, and a substantially thin coating of protective material may be employed instead because the Hall-effect generator will be encapsulated in insulative material (e.g., plastic) along with at least a portion of the Hall sensor core. Such encapsulation provides suitable protection for the Hall-effect generator that is conventionally achieved by individually packaging the Hall-effect generator. Thus, the present invention provides for employing a Hall-effect generator with small thickness which in turn provides for employing a core gap length of substantially minimal thickness.
Furthermore, the insulative material may be shaped in a manner which facilitates packaging of the entire Hall-effect sensor. In other words, the outside shell of the insulative material may be suitably molded such as for example to facilitate insertion of a component into a printed circuit board.
Additionally, the insulative material may provide additional structural support for the Hall-effect sensor by integrating the core and a lead frame or circuit board (employed to house the Hall-effect generator) into one unit. A beneficial result of such integration is that the Hall-effect sensor becomes more robust to mechanical vibrations. The insulative material also affords for increasing the strength of coupling between the core and the lead frame or circuit board.
In accordance with one embodiment of the present invention, a Hall-effect sensor package for sensing electrical current in an electrical conductor is provided. The Hall-effect sensor package includes a ferromagnetic core having an air gap, the core allowing for the electrical conductor to pass there through. The Hall-effect sensor package also includes a Hall-effect generator, at least a portion of the Hall-effect generator being located within the air gap. A lead frame is coupled to the Hall-effect generator; and an insulative material is used to encapsulate the Hall-effect generator and at least a portion of the core and the lead frame.
Another embodiment of the present invention provides for a Hall-effect sensor package for sensing electrical current in an electrical conductor. The sensor package includes a ferromagnetic core having an air gap, the core allowing for the electrical conductor to pass there through. The sensor also includes a Hall-effect generator, at least a portion of the Hall-effect generator being located within the air gap; and a first printed circuit board coupled to the Hall-effect generator, the first printed circuit board adapted to couple to a remote second printed circuit board. The sensor package further includes an insulative material for insulating the Hall-effect generator from contaminants, the insulative material encapsulating the Hall-effect generator and at least a portion of the core and the first circuit board.
Still yet another embodiment of the present invention provides for a method for forming a Hall-effect sensor package which includes the step of: using an insulative material to encapsulate a Hall-effect generator within an air gap of a Hall-effect sensor.
Another embodiment of the present invention provides for a Hall-effect sensor package for sensing a sum of electrical currents in at least two electrical conductors. The sensor package includes a ferromagnetic core having an air gap, the core allowing for the at least two electrical conductors to pass there through; and a Hall-effect generator, at least a portion of the Hall-effect generator being located within the air gap. The sensor package further includes a lead frame coupled to the Hall-effect generator; and an insulative material which
Haensgen Steven T.
Kaishian Steven C.
Kannenberg Daniel G.
Murray Patrick S.
Radosevich Larwrence D.
Amin Himanshu S.
Gerasimow Alexander M.
Patidar Jay
Rockwell Automation Technologies Inc.
Walbrun William R.
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