Inductive power transmitter

Abstract

An inductive power transmitter comprising: a converter configured to generate at least two object detection signals at substantially different frequencies, at least one transmitting coil configured to generate a magnetic field based on the object detection signals, and a controller configured to determine or measure circuit parameter(s) in relation to the coil to determine the inductance of the coil at each of the frequencies, and determine whether and/or what kind of object is present depending on a change in inductance between each of the frequencies.

1 . A wireless power transmitter comprising:
 a wireless power transfer coil coupled to a converter and configured to generate a magnetic field using a first object detection signal of a first frequency and configured to generate a magnetic field using a second object detection signal of a second frequency; and   a controller coupled to the wireless power transfer coil and configured to:
 determine a first parameter representing inductance of the wireless power transfer coil responsive to generating the first object detection signal, 
 determine a second parameter representing inductance of the wireless power transfer coil responsive to generating the second object detection signal, 
 determine whether an object is present adjacent to the wireless power transmitter, and 
 in accordance with a determination that the object is present, identify a type of object that is present adjacent to the wireless power transmitter using the first parameter and the second parameter. 
   
     
     
         2 . The wireless power transmitter of  claim 1 , wherein identifying the type of object that is present adjacent to the wireless power transmitter using the first parameter and the second parameter comprises comparing the first parameter and the second parameter to at least one threshold. 
     
     
         3 . The wireless power transmitter of  claim 1 , wherein the converter is configured to drive the wireless power transfer coil at a wireless power transmission frequency based on the type of object that is present. 
     
     
         4 . The wireless power transmitter of  claim 1 , further comprising a plurality of wireless power transfer coils that includes the wireless power transfer coil. 
     
     
         5 . The wireless power transmitter of  claim 4 , wherein the controller is further configured to: activate a first subset of the plurality of wireless power transfer coils based on a location of the object. 
     
     
         6 . The wireless power transmitter of  claim 5 , wherein the controller is configured to activate the first subset of the plurality of wireless power transfer coils based on the type of object that is present. 
     
     
         7 . The wireless power transmitter of  claim 1 , wherein one of the first and second frequencies is greater than 500 kHz. 
     
     
         8 . The wireless power transmitter of  claim 1 , wherein the wireless power transfer coil is further configured to generate a plurality of additional object detection signals at frequencies that are different from the first and second frequencies. 
     
     
         9 . The wireless power transmitter of  claim 8 , wherein the controller is further configured to determine a plurality of additional parameters, each parameter of the plurality of additional parameters representing inductance of the wireless power transfer coil responsive to generating the plurality of additional object detection signals. 
     
     
         10 . The wireless power transmitter of  claim 9 , wherein identifying the type of object that is present further comprises identifying the type of object using the plurality of additional parameters. 
     
     
         11 . The wireless power transmitter of  claim 10 , wherein the frequencies of the plurality of additional object detection signals are selected from:
 a first range of frequencies which spans the first frequency; and   a second range of frequencies which spans the second frequency.   
     
     
         12 . A method comprising:
 using a wireless power transfer coil of a wireless power transmitter, generating a magnetic field using a first object detection signal of a first frequency and generating a magnetic field using a second object detection signal of a second frequency;   determining a first parameter representing inductance of the wireless power transfer coil responsive to generating the first object detection signal;   determining a second parameter representing inductance of the wireless power transfer coil responsive to generating the second object detection signal;   determining whether an object is present adjacent to the wireless power transmitter; and   in accordance with a determination that an object is present adjacent to the wireless power transmitter, identifying a type of object that is present adjacent to the wireless power transmitter using the first parameter and the second parameter.   
     
     
         13 . The method of  claim 12 , wherein identifying the type of object that is present adjacent to the wireless power transmitter using the first parameter and the second parameter comprises comparing the first parameter and the second parameter to at least one threshold. 
     
     
         14 . The method of  claim 12 , further comprising driving the wireless power transfer coil at a wireless power transmission frequency based on the type of object that is present. 
     
     
         15 . The method of  claim 12 , further comprising activating a first subset of a plurality of wireless power transfer coils that includes the wireless power transfer coil in accordance with a location of the object, wherein activating the first subset of wireless power transfer coils is comprises activating the first subset based on the type of object that is present. 
     
     
         16 . The method of  claim 12 , further comprising generating a plurality of additional object detection signals at frequencies that are different from the first and second frequencies, and further comprising determining a plurality of additional parameters, each parameter of the plurality of additional parameters representing inductance of the wireless power transfer coil responsive to generating the plurality of additional object detection signals, wherein identifying the type of object that is present further comprises identifying the type of object that is present using the plurality of additional parameters. 
     
     
         17 . A non-transitory computer-readable storage medium storing software configured to be executed by one or more controllers of an electronic device having a wireless power transfer coil, the software including instructions for:
 using the wireless power transfer coil to generate a magnetic field using a first object detection signal of a first frequency and to generate a magnetic field using a second object detection signal of a second frequency;   determining a first parameter representing inductance of the wireless power transfer coil responsive to generating the first object detection signal;   determining a second parameter representing inductance of the wireless power transfer coil responsive to generating the second object detection signal;   determining whether an object is present adjacent to the electronic device; and   in accordance with a determination that the object is present adjacent to the electronic device, identifying a type of object that is present using the first parameter and the second parameter.   
     
     
         18 . The non-transitory computer-readable storage medium of  claim 17 , the software further including instructions for:
 comparing the first parameter and the second parameter to at least one threshold to identify the type of object that is present adjacent to the electronic device.   
     
     
         19 . The non-transitory computer-readable storage medium of  claim 17 , the software further including instructions for:
 driving the wireless power transfer coil at a wireless power transmission frequency based on the type of object that is present.   
     
     
         20 . The non-transitory computer-readable storage medium of  claim 17 , the software further including instructions for:
 generating a plurality of additional object detection signals at frequencies that are different from the first and second frequencies;   determining a plurality of additional parameters, each parameter of the plurality of additional parameters representing inductance of the wireless power transfer coil responsive to generating the plurality of additional object detection signals; and   using the plurality of additional parameters to identify the type of object that is present.