Sensor and method for foreign object detection in induction electric charger
First Claim
1. A device for detecting foreign objects near a primary coil of an induction charger, comprising:
- a sensor array located adjacent to the primary coil of the induction charger, the array covering at least a portion of the primary coil area, and containing sensors, each sensor configured to output a sensing signal in response to magnetically coupling a high frequency alternating magnetic field produced by the primary coil, the magnetic field produced by the primary coil having a spatial distribution of magnetic intensity that varies by location across the primary coil area, each sensor of the array being configured to have a magnetic field sensing sensitivity that is inversely proportional to the magnetic intensity of the magnetic field produced by the primary coil at a location of the sensor with respect to the primary coil area; and
a controller coupled to the sensors, the controller configured to scan the sensing signal of each sensor in the array, compute a two-dimensional convolution transform on the received sensing signals, the two-dimensional convolution transform being configured to detect sharp changes of two dimensional images of magnetic intensity produced by a combination of the primary coil and the foreign object, the sharp changes indicating the presence of the foreign object proximate to the sensors and compute a modified two-dimensional convolution transform on the sensing signals received from the sensors in the array, where the sensors in the array are juxtaposed with a magnetic intensity produced by the primary coil, which undergoes an inversion that changes a direction of the magnetic intensity produced by the primary coil thereby determining from the scanned sensing signals, which sensors in the array are outputting a sensing signal indicating presence of the foreign object proximate to the sensors, the foreign object causing a perturbation in the high frequency alternating magnetic field near the sensors.
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Abstract
The invention detects foreign objects FO near a primary coil 100 of an induction charger. A sensors 111 of a sensor array 110 output sensing signals in response to magnetically coupling the alternating magnetic field 103 produced by the primary coil. A controller 165 connected to each sensor 111 scans the sensing signals and determines whether there is a foreign object perturbing the magnetic field 103 near a sensor. The magnetic field has a spatial distribution that varies by location across the primary coil area. Each sensor has a magnetic field sensing sensitivity that is inversely proportional to the magnetic intensity of the magnetic field produced by the primary coil at a location of the sensor, to reduce the collective dynamic range of the signals, thereby contributing to maintaining a high accuracy in signal sampling. A reference sensor coil 155 compensates for magnetic field drift of the primary coil.
41 Citations
14 Claims
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1. A device for detecting foreign objects near a primary coil of an induction charger, comprising:
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a sensor array located adjacent to the primary coil of the induction charger, the array covering at least a portion of the primary coil area, and containing sensors, each sensor configured to output a sensing signal in response to magnetically coupling a high frequency alternating magnetic field produced by the primary coil, the magnetic field produced by the primary coil having a spatial distribution of magnetic intensity that varies by location across the primary coil area, each sensor of the array being configured to have a magnetic field sensing sensitivity that is inversely proportional to the magnetic intensity of the magnetic field produced by the primary coil at a location of the sensor with respect to the primary coil area; and a controller coupled to the sensors, the controller configured to scan the sensing signal of each sensor in the array, compute a two-dimensional convolution transform on the received sensing signals, the two-dimensional convolution transform being configured to detect sharp changes of two dimensional images of magnetic intensity produced by a combination of the primary coil and the foreign object, the sharp changes indicating the presence of the foreign object proximate to the sensors and compute a modified two-dimensional convolution transform on the sensing signals received from the sensors in the array, where the sensors in the array are juxtaposed with a magnetic intensity produced by the primary coil, which undergoes an inversion that changes a direction of the magnetic intensity produced by the primary coil thereby determining from the scanned sensing signals, which sensors in the array are outputting a sensing signal indicating presence of the foreign object proximate to the sensors, the foreign object causing a perturbation in the high frequency alternating magnetic field near the sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for detecting foreign objects near a primary coil of an induction charger, comprising:
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sensing, by each of a plurality of sensors in a sensor array covering at least a portion of the primary coil, a high frequency alternating magnetic field produced by the primary coil, the magnetic field produced by the primary coil having a spatial distribution of magnetic intensity that varies by location across the primary coil area, each sensor of the array being configured to have a magnetic field sensing sensitivity that is inversely proportional to the magnetic intensity of the magnetic field produced by the primary coil at a location of the sensor with respect to the primary coil area; scanning, by a controller coupled to the sensor array, sensor signals output by the plurality of sensors in the sensor array, in response to the sensors magnetically coupling the high frequency alternating magnetic field produced by the primary coil; computing a two-dimensional convolution transform on the sensing signals received from the sensors in the array, the two-dimensional convolution transform being configured to detect sharp changes of two dimensional images of magnetic intensity produced by a combination of the primary coil and the foreign object, the sharp changes indicating the presence of the foreign object proximate to the sensors; computing a modified two-dimensional convolution transform on the sensing signals received from the sensors in the array, where the sensors in the array are juxtaposed with a magnetic intensity produced by the primary coil, which undergoes an inversion that changes a direction of the magnetic intensity produced by the primary coil; and determining, by the controller coupled to the sensor array, whether there is at least one sensor in the sensor array that is outputting a sensor signal indicating presence of a foreign object proximate to the sensor, which is perturbing the high frequency alternating magnetic field near the sensor. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification