Apparatus and method for a current sensor

Abstract

A current sensor may include a sense element disposed proximate a conductor. The current sensor may be configured to couple to a first magnetic field generated at the conductor when current flows in the conductor. An output electrically connected to the sense element can produce a signal that is representative of the flow of current in the conductor. The sense element may be oriented in a plane parallel to magnetic field lines of a second magnetic field generated by a load connected to the conductor.

What is claimed is: 
     
         1 . A current sensor comprising:
 a conductor;   a sense element configured to couple to a first magnetic field generated at a first location due to a flow of current in the conductor; and   an output electrically connected to the sense element and configured to produce a signal that is representative of the flow of current in the conductor,   the sense element oriented in a plane parallel to magnetic field lines of a second magnetic field, different from the first magnetic field, generated by a load electrically connected to the conductor at a second location different from the first location.   
     
     
         2 . The current sensor of  claim 1 , further comprising a substrate, wherein the sense element comprises an electrically conductive coil disposed on the substrate and adjacent the conductor. 
     
     
         3 . The current sensor of  claim 2 , further comprising a filter circuit, the filter circuit comprising the electrically conductive coil. 
     
     
         4 . The current sensor of  claim 3 , wherein the filter circuit is a bandpass filter. 
     
     
         5 . The current sensor of  claim 2 , wherein the substrate is disposed perpendicular to a printed circuit board (PCB) that carries the conductor. 
     
     
         6 . The current sensor of  claim 1 , wherein the load comprises a power transmitting element configured to generate an external magnetic field for wireless power transfer, wherein the external magnetic field constitutes the second magnetic field. 
     
     
         7 . The current sensor of  claim 6 , wherein the sense element comprises an electrically conductive coil, the current sensor further comprising a filter comprising the electrically conductive coil of the sense element, wherein the filter is tuned to a resonant frequency of the power transmitting element. 
     
     
         8 . The current sensor of  claim 1 , further comprising a capacitive shield disposed between the sense element and the conductor, the capacitive shield effective to prevent an electric field generated in the conductor from being capacitively coupled to the sense element. 
     
     
         9 . The current sensor of  claim 8 , wherein the capacitive shield comprises a conductive lead disposed adjacent to both the sense element and the conductor, wherein the conductive lead comprises a free first end and a second end configured to electrically connect to ground potential. 
     
     
         10 . The current sensor of  claim 1 , wherein the sense element comprises a first electrically conductive coil disposed on a first plane and at least a second electrically conductive coil disposed on at least a second plane spaced apart from the first plane. 
     
     
         11 . The current sensor of  claim 10 , further comprising a first capacitive shield configured to be disposed adjacent to both the first electrically conductive coil and the conductor, and at least a second capacitive shield configured to be disposed adjacent to both the second electrically conductive coil and the conductor. 
     
     
         12 . The current sensor of  claim 10 , wherein the first electrically conductive coil is connected in series with the second electrically conductive coil. 
     
     
         13 . The current sensor of  claim 10 , wherein the first electrically conductive coil comprises a first trace formed on a first layer of a multi-layer PCB and the second electrically conductive coil comprises a second trace formed on a second layer of the multi-layer PCB. 
     
     
         14 . The current sensor of  claim 10 , wherein the first electrically conductive coil is disposed on one side of the conductor and the second electrically conductive coil is disposed on another side of the conductor. 
     
     
         15 . The current sensor of  claim 10 , further comprising a filter circuit, the filter circuit comprising either or both the first electrically conductive coil and the second electrically conductive coil. 
     
     
         16 . The current sensor of  claim 1 , wherein the sense element comprises a first electrically conductive coil and at least a second electrically conductive coil, the first and second coils both spaced apart from each other on a same plane. 
     
     
         17 . A method of sensing a flow of current in a conductor comprising:
 generating a sensed signal by magnetically coupling to a first magnetic field arising from the conductor due to the flow of current in the conductor, the magnetic coupling occurring in a plane parallel to field lines of a second magnetic field generated by the flow of current through a load electrically connected to the conductor; and   generating an output signal from the sensed signal, the output signal representative of an amount of the flow of current through the conductor.   
     
     
         18 . The method of  claim 17 , wherein magnetically coupling to the first magnetic field includes inducing a current, using the first magnetic field, in a coil of electrically conductive material disposed adjacent the conductor and aligned in the plane parallel to field lines of the second magnetic field. 
     
     
         19 . The method of  claim 18 , further comprising filtering the sensed signal to attenuate frequency components in the sensed signal determined by a filter circuit that includes the coil of electrically conductive material. 
     
     
         20 . The method of  claim 18 , wherein the load comprises a power transmitting element configured to generate an external magnetic field for wireless power transfer, wherein the external magnetic field constitutes the second magnetic field. 
     
     
         21 . The method of  claim 17 , further comprising shielding the sensed signal from an electric field generated in the conductor so that the generated output signal is substantially free of influence from the electric field. 
     
     
         22 . The method of  claim 17 , wherein magnetically coupling to the first magnetic field includes coupling the first magnetic field to a first coil of electrically conductive material disposed adjacent the conductor and coupling the first magnetic field to a second coil of electrically conductive material disposed adjacent the conductor. 
     
     
         23 . An apparatus for sensing a flow of current in a conductor comprising:
 means for magnetically coupling to a first magnetic field arising from the conductor due to the flow of current in the conductor to generate a sensed signal, the means for magnetically coupling to a first magnetic field being aligned in a plane parallel to field lines of a second magnetic field generated by the flow of current through a load electrically connected to the conductor; and   means for generating an output signal from the sensed signal.   
     
     
         24 . The apparatus of  claim 23 , further comprising means for filtering the sensed signal, the means for filtering comprising the means for magnetically coupling to a first magnetic field. 
     
     
         25 . The apparatus of  claim 24 , wherein the means for magnetically coupling to a first magnetic field comprises a coil of electrically conductive material. 
     
     
         26 . The apparatus of  claim 24 , wherein the means for filtering is a bandpass filter. 
     
     
         27 . An apparatus for wirelessly transmitting charging power to a receiver device, comprising:
 a transmit coil;   a driver circuit electrically coupled to the transmit coil via a conductor, the driver circuit configured to drive the transmit coil with an alternating current via the conductor; and   a current sensor configured to sense a flow of current in the conductor, the current sensor comprising a sense coil configured to couple to a first magnetic field generated by the alternating current in the conductor to produce a signal that is indicative of the flow of current in the conductor,   the transmit coil configured to generate a second magnetic field for wirelessly transmitting charging power to the receiver device in response to being driven by the alternating current,   the sense coil oriented in a plane parallel to field lines of the second magnetic field.   
     
     
         28 . The apparatus of  claim 27 , further comprising a filter circuit, the filter circuit comprising the sense coil and a resistor and capacitor electrically connected to the sense coil. 
     
     
         29 . The apparatus of  claim 28 , wherein the filter circuit is a bandpass filter. 
     
     
         30 . The apparatus of  claim 27 , wherein the current sensor further comprises a capacitive shield disposed adjacent to the sense coil, the capacitive shield effective to prevent an electric field generated in the conductor from being capacitively coupled to the sense coil, wherein the capacitive shield comprises a second conductor disposed between the conductor and the sense coil.