Systems, methods, and apparatus for foreign object detection loop based on inductive thermal sensing
First Claim
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1. An apparatus for detecting a presence of an object located in a power transfer area of a wireless power transmitter, the apparatus including:
- a first inductive sense circuit and a second inductive sense circuit, each including a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that varies as a function of a temperature of the object when the object is exposed to an alternating magnetic field generated by the wireless power transmitter in the power transfer area at an operating frequency of the wireless power transmitter,each of the first and second inductive sense circuits comprising a location for measuring the electrical characteristic and configured to reduce a disturbance voltage measured at the location; and
a controller configured to;
schedule an exposure cycle for the alternating magnetic field generated by the wireless power transmitter,transmit a signal to the wireless power transmitter to control the exposure cycle for the alternating magnetic field,measure the electrical characteristic of each sense coil over time based on measuring at least one of a voltage and a current signal at the location of each of the first and second inductive sense circuits,suppress effects of the disturbance voltage at fundamental and harmonic frequencies of the wireless power transmitter by filtering to achieve a target detection sensitivity of the apparatus,determine a first correlation result between the measured electrical characteristic and the exposure cycle for the first sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle and determine a second correlation result between the measured electrical characteristic and the exposure cycle for the second sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle, anddetermine the presence of the object based on a comparison of the first correlation result with the second correlation result.
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Abstract
This disclosure provides systems, methods and apparatus for detecting foreign objects. An apparatus for detecting a presence of an object is provided. The apparatus includes a coil configured to inductively sense a presence of an object based on an electrical characteristic of the coil that varies as a function of a temperature of the object when the object is exposed to an alternating magnetic field. The apparatus further includes a controller configured to detect a change in the electrical characteristic.
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Citations
23 Claims
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1. An apparatus for detecting a presence of an object located in a power transfer area of a wireless power transmitter, the apparatus including:
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a first inductive sense circuit and a second inductive sense circuit, each including a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that varies as a function of a temperature of the object when the object is exposed to an alternating magnetic field generated by the wireless power transmitter in the power transfer area at an operating frequency of the wireless power transmitter, each of the first and second inductive sense circuits comprising a location for measuring the electrical characteristic and configured to reduce a disturbance voltage measured at the location; and a controller configured to; schedule an exposure cycle for the alternating magnetic field generated by the wireless power transmitter, transmit a signal to the wireless power transmitter to control the exposure cycle for the alternating magnetic field, measure the electrical characteristic of each sense coil over time based on measuring at least one of a voltage and a current signal at the location of each of the first and second inductive sense circuits, suppress effects of the disturbance voltage at fundamental and harmonic frequencies of the wireless power transmitter by filtering to achieve a target detection sensitivity of the apparatus, determine a first correlation result between the measured electrical characteristic and the exposure cycle for the first sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle and determine a second correlation result between the measured electrical characteristic and the exposure cycle for the second sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle, and determine the presence of the object based on a comparison of the first correlation result with the second correlation result. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting a presence of an object located in a power transfer area of a wireless power transmitter, comprising:
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sensing the presence of the object based on an electrical characteristic of a sense coil of first and second sense circuits that varies as a function of a temperature of the object when the object is exposed to an alternating magnetic field generated by the wireless power transmitter in the power transfer area at an operating frequency of the wireless power transmitter; reducing a disturbance voltage measured at a location for measuring the electrical characteristic of the respective sense circuit at the operating frequency of the wireless power transmitter; scheduling an exposure cycle for the alternating magnetic field; transmitting a signal to the wireless power transmitter to control the exposure cycle for the alternating magnetic field; generating the alternating magnetic field based upon the exposure cycle; measuring the electrical characteristic of each sense coil over time based on measuring at least one of a voltage and a current signal at the location of each of the first and second inductive sense circuits; suppressing effects of the disturbance voltage at fundamental and harmonic frequencies of the wireless power transmitter by filtering to achieve a target detection sensitivity; determining a first correlation result between the measured electrical characteristic and the exposure cycle for the first sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle and determining a second correlation result between the measured electrical characteristic and the exposure cycle for the second sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle, and determining the presence of the object based on a comparison of the first correlation result with the second correlation result. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification