Patent Publication Number: US-2023146600-A1

Title: Foreign object detection based on transmitter input parameter

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 63/277,684 filed on Nov. 10, 2021. The entire content of U.S. Provisional Application No. 63/277,684 is incorporated herein by reference. 
    
    
     BACKGROUND OF THE SPECIFICATION 
     The present disclosure relates in general to integrated circuit devices in wireless power systems and, more particularly, to foreign object detection based on input parameters. 
     A wireless power system can include a transmitter having a transmission coil and a receiver having a receiver coil. In an aspect, the transmitter may be connected to a structure including a wireless charging region. In response to a device including the receiver being placed on the charging region, or in proximity to the charging region, the transmission coil and the receiver coil can be inductively coupled with one another to form a transformer that can facilitate inductive transfer of alternating current (AC) power. The transfer of AC power, from the transmitter to the receiver, can facilitate charging of a battery of the device including the receiver. 
     SUMMARY 
     In one embodiment, a semiconductor device for wireless power transmitter is generally described. The semiconductor device can include a driver circuit configured to drive a transmitter coil to provide wireless power to a wireless power receiver. The semiconductor device can further include a wireless power transmitter coupled to the driver circuit and configured to control the driver circuit. The wireless power transmitter can be configured to detect an object inductively coupled to a wireless power transmitter. The wireless power transmitter can be further configured to, prior to a power transfer stage between the wireless power transmitter and the wireless power receiver, measure an input parameter, the input parameter being one of an input current and an input power. The wireless power transmitter can be further configured to compare the measured input parameter with a predetermined value. The wireless power transmitter can be further configured to determine whether the object is a foreign object or the wireless power receiver based on a result of the comparison between the measured input parameter with the predetermined value. 
     In one embodiment, an apparatus for wireless power transmitter is generally described. The apparatus can include an integrated circuit. The integrated circuit can be configured to detect an object inductively coupled to a wireless power transmitter. The integrated circuit can be further configured to, prior to a power transfer stage between the wireless power transmitter and the wireless power receiver, measure an input parameter, the input parameter being one of an input current and an input power. The integrated circuit can be further configured to compare the measured input parameter with a predetermined value. The integrated circuit can be further configured to determine whether the object is a foreign object or the wireless power receiver based on a result of the comparison between the measured input parameter with the predetermined value. 
     In one embodiment, a method for operating a wireless power transmitter is described. The method can include detecting, by an integrated circuit, an object inductively coupled to a wireless power transmitter. The method can further include, prior to a power transfer stage between the wireless power transmitter and the wireless power receiver, measuring, by the integrated circuit, an input parameter, the input parameter being one of an input current and an input power. The method can further include comparing, by the integrated circuit, the measured input parameter with a predetermined value. The method can further include determining, by the integrated circuit, whether the object is a foreign object or the wireless power receiver based on a result of the comparison between the measured input parameter with the predetermined value. 
     The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. In the drawings, like reference numbers indicate identical or functionally similar elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram showing an example system that can implement foreign object detection based on transmitter input parameter in one embodiment. 
         FIG.  2    is a diagram showing an example implementation of the example system  100  of  FIG.  1    in one embodiment. 
         FIG.  3    is a diagram showing another example implementation of the example system  100  of  FIG.  1    in one embodiment. 
         FIG.  4    is a diagram showing another example implementation of the example system  100  of  FIG.  1    in one embodiment. 
         FIG.  5    is a flow diagram illustrating a process of implementing foreign object detection based on transmitter input parameter in one embodiment. 
         FIG.  6    is a flow diagram illustrating another process of implementing foreign object detection based on transmitter input parameter in one embodiment. 
         FIG.  7    is a flow diagram illustrating another process of implementing foreign object detection based on transmitter input parameter in one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In wireless charging applications and systems, prior to AC power transfer, the receiver can communicate messages to the transmitter to verify an identity of the receiver. The transmitter can begin the power transfer in response to verifying the identity of the receiver. During power transfer, foreign objects that may be in proximity to the transmission coil may cause an increase in power loss, and the foreign object may heat up to a point that can potentially create a hazardous situation. 
     The methods and systems described herein can provide a feature of foreign object detection before a power transfer stage without a need to add additional circuit components for injecting current or voltage to oscillate a transmission coil. Further, the foreign object detection described herein can be integrated as an additional feature to existing foreign object detection features without a need to add additional hardware or circuit components. 
       FIG.  1    is a diagram showing an example system  100  that can implement foreign object detection based on transmitter input parameter in one embodiment. The system  100  can be a wireless charging system that can facilitate wireless transfer of power and/or wireless transmission of data. The system  100  can include a transmitter  102  and a receiver  112  configured to be in communication with each other. The transmitter  102  can be a wireless power transmitter connected to a direct current (DC) power supply  101  that supply input power P in , and can transmit alternating current (AC) power from the connected DC power supply  101 . The transmitter  102  can include, or be coupled to, a controller  104  and a power driver  106 . The power driver  106  can include a coil, labeled as TX. In one embodiment, controller  104  can be implemented by an integrated circuit. The controller  104  can be configured to control and operate the power driver  106 . In an example, the controller  104  can be configured to control an input voltage V in  being supplied to power driver  106 , and can control the power driver  106  to drive the Coil TX to produce a magnetic field. In one embodiment, one or more of transmitter  102 , controller  104 , and/or power driver  106  can be packaged as a semiconductor device. The power driver  106  can drive the Coil TX at a range of frequencies and configurations defined by wireless power standards, such as the Wireless Power Consortium (Qi) standard, the Power Matters Alliance (PMA) standard, and/or the Alliance for Wireless Power (A for WP, or Rezence) standard. 
     The receiver  112  can be a wireless power receiver that can be located in, for example, a computing device, a mobile phone, a tablet device, a wearable device, and/or other electronic devices that can be configured to receive power wirelessly. The receiver  112  can include a controller  114  and a power rectifier  116 . The power rectifier  116  can include a coil, labeled as RX. The magnetic field produced by the Coil TX of the power driver  106  can induce a current in the Coil RX of the power rectifier  116 . The induced current can cause an amount of AC power  110  to be inductively transmitted from the power driver  106  to the power rectifier  116 . The power rectifier  116  can receive the AC power  110  and convert the AC power  110  into DC power having an output voltage V out , and can provide the output voltage V out  to a load  118 . The load  118  can be, for example, a battery charger configured to charge a battery, a DC-DC converter configured to supply a processor or a display, and/or other electronic components that requires the DC power to operate. 
     The transmitter  102  can be connected to a charger dock surface  120 . The charger dock surface can include a charging region  122 . The Coil TX can be in proximity to the charging region  122  such that a device being placed on the charging region  122  can receive the AC power  110  from the transmitter  102 . The transmitter  102  can be configured to monitor the charging region  122  of the charger dock surface  120  to detect if objects are being placed in the charging region  122  or removed from the charging region  122 . In response to detecting an object in the charging region  122 , the transmitter  102  can send a digital pulse and can listen for a response to determine if the object includes a receiver that can receive the AC power  110 . 
     In the example shown in  FIG.  1   , if the transmitter  102  detects the receiver  112  is placed on the charging region  122 , the transmitter can proceed to an identification stage. In response to the receiver  112  being placed on the charging region  122 , the Coil TX and the Coil RX may be within a distance with one other that is close enough to inductively coupled and form a transformer. The identification stage can include identifying the receiver  112  and obtaining configuration information  111  to create a power contract with the receiver  112 . In response to creating the power contract, the transmitter  102  can begin the power transfer stage to transfer the AC power  110  to the receiver  112 . To create the power contract, the receiver  112  may send communication packets indicating power transfer information such as, for example, an amount of power to be transferred to the receiver  112 , commands to increase, decrease, or maintain a power level of the AC power  110 , commands to stop a power transfer, etc. The power contract between the transmitter  102  and the receiver  112  may include these power transfer information. 
     In an aspect, when the system  100  is not in the power transfer stage, the receiver  112  may be disconnected from the load  118 . In response to the receiver  112  being disconnected from the load  118 , the load  118  is not drawing current or power from the receiver  112  (e.g., V out  can be zero). Since the load  118  is not drawing power from the receiver  112 , the amount of current or power drawn by the receiver  112  from the transmitter  102 , and the amount of current (i in ) or power (P in ) drawn by the transmitter  102  from the DC power supply  101 , may be reduced. Note that the input voltage V in  may remain constant even if i in  and P in  changes. The current (i in ) and power (P in ) can reflect a coupling condition between the Coil TX and another object, such as the Coil RX or a conductive object such as metal. For example, the current (i in ) and power (P in ) can be higher when there is an object on the charging region  122  than when there is only Coil RX coupled to the Coil TX (e.g., in non-power transfer stage or when load  118  is disconnected from the receiver  112 ). 
     To be described in more detail below, the controller  104  of the transmitter  102  can be configured to monitor the current (i in ) or power (P in ) being received by the transmitter  102 . When the system  100  is not in the power transfer stage, such as when the system is in the identification stage, the controller  104  can monitor any changes in current (i in ) or power (P in ) to detect whether a foreign object  124  is present or absent on the charging region  122  (or inductively coupled with the Coil TX) or not. For example, the controller  104  can detect an increase in current (i in ) or power (P in ) and, in response, determine that the Coil TX may have inductively coupled with a candidate object that may or may not be a foreign object. In an aspect, a foreign object can be a non-receiver that is brought into the range of the transmitter  102  (or Coil TX) and causes unwanted current (and/or heat) to be induced. These non-receivers can also be referred to as parasitic loads. The controller  104  can be configured to compare the detected increased value of current (i in ) or power (P in ) with a static or predetermined value to determine whether the candidate object inductively coupled to the Coil TX is the Coil RX, or the foreign object  124  (or whether foreign object  124  is present or absent on charging region  122 ). In one or more embodiments, the foreign object detection being performed by the transmitter  102  can be performed regardless of whether the receiver  112  is identified or verified in the identification stage. 
     If the increased value of current (i in ) or power (P in ) is greater than the predetermined value, then the Coil TX may be inductively coupled to the foreign object  124 . If the increased value of the input current (i in ) or the input power (P in ) is equal to or less than the predetermined value, then the Coil TX may be inductively coupled to the Coil RX. In another embodiment, if a difference between the increased value of the input current (i in ) or the input power (P in ) and the predetermined value is within a threshold range, then the Coil TX may be inductively coupled to the Coil RX. In response to the controller  104  determining that the Coil TX may be inductively coupled to the foreign object  124 , the controller  104  may not proceed to the power transfer stage. In response to the controller  104  determining that the Coil TX may be inductively coupled to the Coil RX, the controller  104  may proceed to the power transfer stage. 
     By using the input current (i in ) or the input power (P in ) to perform foreign object detection, the system  100  can detect foreign objects on the charging region  122  without a need to add additional circuit components to the transmitter  102 . For example, coil quality factor detection function which requires circuit components for injecting voltage or current to oscillate the Coil TX may not be needed if the system  100  can perform foreign object detection using current (i in ) or power (P in ) before the power transfer stage. 
       FIG.  2    is a diagram showing an example implementation of the example system  100  of  FIG.  1    in one embodiment. In one embodiment, the controller  104  can be configured to perform an input parameter test  202  before the power transfer stage. A result of the input parameter test  202  can indicate how an input parameter, such as input current (i in ) or input power (P in ), varies with a misalignment or distance  224  between a location of any foreign object (e.g., foreign object  124 ) and a reference point  222  on the charging region  122 . The reference point  222  can be a center of the charging region  122 , a predetermined reference location on the charging region  122 , or a predetermined reference point on the transmitter  102 , etc.  FIG.  2    shows a top perspective view  220  of the charging region  122 . Different locations of the foreign object  124  on the charging region  122  can change the distance  224 . 
     As shown in  FIG.  2   , a known pattern, or curve  204 , shows that if the Coil TX is inductively coupled with the RX coil only (before the power transfer stage), and if there is no foreign object on charging region  122 , the input current (i in ) can be fixed at i 0 =0.127 amperes (A) and may not be varying. If an input current measured by transmitter  102  (or controller  104 ) is the fixed input current i 0  then there is no foreign object interfering with the magnetic field between the Coil TX and the Coil RX. If any foreign object is within the charging region  122  (e.g., foreign object  124 ), then the input current (i in ) can deviate from fixed input current i 0 . An amount of deviation from the fixed input current i 0  can vary as the distance  224  varies. In other words, the location of the foreign object  124  with respect to the reference point  222  on the charging region  122  can change the amount of deviation of the input current from the fixed input current i 0 . The fixed input current i 0  can be stored in a memory device of controller  104   
     The input parameter test  202  can further produce a curve  206  that indicates how the input parameter (e.g., input current i in ) varies with distance  224 . In one embodiment, the input parameter test  202  can include measuring, by controller  104 , the input current in response to placement of an arbitrary foreign object (e.g., foreign object  124  or other foreign object) at different locations and/or at different distances  224  on charging region  122 . The input current corresponding to different values of distance  224  can be measured or recorded by controller  104 . The measured input current indicated by curve  206  can be stored as a reference pattern in the memory device of controller  104 . 
     In one embodiment, if a foreign object is within charging region  122 , the input current (i in ) can be greater than i 0  and can vary inversely with distance  224 . For example, curve  206  generated by the input parameter test  202  can indicate how the input current (i in ) varies with distance  224 . As shown by the curve  206 , as the distance  224  increases (e.g., from 0 millimeters (mm) to 16 mm), the input current (i in ) decreases. If the distance  224  between the foreign object and the reference point  222  is at a maximum (e.g., at 16 mm, or at an edge of charging region  122 ), a difference between curves  204 ,  206  is still present, indicating that as long as there is a foreign object in the charging region  122 , the input current (i in ) will remain different from the fixed input current i 0 . In one embodiment, the fixed input current i 0  can be used as a predetermined value (or a static parameter, or a previously measured parameter), and if the input current (i in ) of the transmitter  102  is greater than this predetermined value, then a foreign object (e.g., foreign object  124 ) can be considered as being present on the charging region  122 . 
     In one embodiment, if controller  104  detects an input current different from fixed input current i 0 , then controller  104  can determine that there may be a foreign object within the charging region  122  and/or a location of the foreign object with response to reference point  222 . For example, if controller  104  measures an input current of 0.16 A, controller  104  can determine that 0.16 A is different from the predetermined value of 0.127 A, and controller  104  can determine that there may be a foreign object located at approximately 7 mm away from reference point  222 . 
     In one embodiment, controller  104  can determine a predetermined threshold range  226  based on curves  204 ,  206 . For example, controller  104  can assign a difference between a minimum of curve  206  (e.g., the reference pattern) and a maximum of curve  204  (e.g., predetermined value or fixed input current i 0 ) as the predetermined threshold range  226 . If a difference between the predetermined value (e.g., fixed input current i 0 ) and the input current (i in ) is within predetermined threshold range  226 , then the transmitter  102  can determine that there may be no foreign object located in the charging region  122 . 
     In another embodiment, the input parameter test  202  can produce an input parameter variation pattern indicating how the input power (P in ) varies with distance  224 . The input power corresponding to different locations of the arbitrary foreign object on charging region  122  can be measured or recorded by controller  104 . The measured input power can be stored in a memory device of controller  104  and can be used for producing the input power variation pattern. 
       FIG.  3    is a diagram showing an example implementation of the example system  100  of  FIG.  1    in one embodiment. In one embodiment, the controller  104  can be configured to perform an operating frequency test  302  before the power transfer stage. A result of the operating frequency test  302  can indicate how an input parameter, such as the input current (i in ) or the input power (P in ), being received by the transmitter  102  varies with an operating frequency of the transmitter  102 . In  FIG.  3   , a known pattern, or curve  304 , shows how the input current (i in ) varies with an operating frequency of the transmitter  102  in response to the Coil TX being inductively coupled with the RX coil only (before the power transfer stage) without foreign objects on charging region  122 . If any foreign object is within the charging region  122  (e.g., foreign object  124 ), then the input current (i in ) can deviate from curve  304 . An amount of deviation from curve  304  can vary as the operating frequency varies. The known pattern or curve  304  can be stored in a memory device of controller  104 . 
     Operating frequency test  302  can further produce a curve  306  that indicates how the input parameter (e.g., input current i in ) varies with the operating frequency of transmitter  102 . In one embodiment, the operating frequency test  302  can include measuring, by controller  104 , the input current in response to different operating frequencies of transmitter  102  when an arbitrary foreign object (e.g., foreign object  124  or other foreign object) is placed on charging region  122 . As shown by curve  306 , if a foreign object is within charging region  122 , the input current (i in ) can be greater than the input current values indicated by curve  304 , and can vary inversely with the operating frequency of transmitter  102 . The input current corresponding to different operating frequencies of transmitter  102  can be measured or recorded by controller  104 . The measured input current indicated by curve  306  can be stored as a reference pattern in the memory device of controller  104 . 
     In one embodiment, controller  104  can measure a first value of an input parameter (e.g., input current i in  or input power P in ) and a second value of the input parameter. The first value of the input parameter can be a value when the operation frequency is a first operation frequency, and the second value of the input parameter can be a value when the operation frequency is a second operation frequency different from the first operation frequency. Controller  104  can determine whether an object in charging region  122  is a foreign object or a wireless power receiver based on the first value of the input parameter, the second value of the input parameter, the first operation frequency, and the second operation frequency. For example, controller  104  can determine whether the object in charging region  122  is a foreign object or a wireless power receiver by dividing a difference between the first value of the input parameter and the value of the second input parameter by a difference between the first operation frequency to the second operation frequency. 
     In one embodiment, one or more values among the curve  304  can be used as a predetermined value (or a static parameter, or a previously measured parameter), and if the input current (i in ) of the transmitter  102  is different from (e.g., greater than) this predetermined value, then controller  104  can determine that a foreign object is present on the charging region  122 . In another embodiment, if a difference between the curve  304  and the input current is within a predetermined threshold range  320 , then the transmitter  102  can determine that there may be no foreign object located in the charging region  122 . A sensitivity of the foreign object detection can be adjusted by adjusting this predetermined threshold range. 
     In one embodiment, controller  104  can determine predetermined threshold range  320  based on curves  304 ,  306 . For example, controller  104  can assign a difference between a minimum of curve  306  (e.g., the reference pattern) and a maximum of curve  304  (e.g., predetermined value) as the predetermined threshold range  320 . If a difference between the predetermined value and the input current (i in ) is within predetermined threshold range  320 , then the transmitter  102  can determine that there may be no foreign object located in the charging region  122 . 
     In another embodiment, the operating frequency test  302  can produce an input parameter variation pattern indicating how the input power (Pu) varies with the operating frequency of transmitter  102 . The input power corresponding to different operating frequencies of transmitter  102 , with a foreign object on charging region  122 , can be measured or recorded by controller  104 . The measured input power can be stored in the memory device of controller  104  and can be used for producing the input power variation pattern. 
       FIG.  4    is a diagram showing another example implementation of the example system  100  of  FIG.  1    in one embodiment. In one embodiment, the controller  104  can be configured to perform an input voltage test  402  before the power transfer stage. A result of the input voltage test  402  can indicate how the input current (i in ) to the transmitter  102  varies with an input voltage, denoted as V in , of the transmitter  102 . In  FIG.  4   , a curve  404  shows how the input current (i in ) varies with the input voltage V in  of the transmitter  102  in response to the Coil TX being inductively coupled with the RX coil only (before the power transfer stage). If any foreign object is within the charging region  122  (e.g., foreign object  124 ), then the input current (i in ) can deviate from curve  404 . An amount of deviation from curve  304  can vary as the input voltage V in  varies. The known pattern or curve  304  can be stored in a memory device of controller  104 . 
     Input voltage test  402  can further produce a curve  406  that indicates how the input current (i in ) varies with input voltage V in  of the transmitter  102  in response to a foreign object (e.g., foreign object  124 ) being located on the charging region  122  (before the power transfer stage). In one embodiment, the input voltage test  402  can include measuring, by controller  104 , the input current in response to different values of input voltage V in  when an arbitrary foreign object (e.g., foreign object  124  or other foreign object) is placed on charging region  122 . As shown by curve  406 , if a foreign object is within charging region  122 , the input current (i in ) can be greater than the input current values indicated by curve  404 , and can vary with input voltage V in . The input current corresponding to different input voltages can be measured or recorded by controller  104 . The measured input current indicated by curve  406  can be stored as a reference pattern in the memory device of controller  104 . 
     In one embodiment, controller  104  can measure a first value of an input parameter (e.g., input current i in  or input power P in ) and a second value of the input parameter. The first value of the input parameter can be a value when the input voltage V in  is a first input voltage, and the second value of the input parameter can be a value when the input voltage V in  is a second input voltage different from the first input voltage. Controller  104  can determine whether an object in charging region  122  is a foreign object or a wireless power receiver based on the first value of the input parameter, the second value of the input parameter, the first input voltage, and the second input voltage. For example, controller  104  can determine whether the object in charging region  122  is a foreign object or a wireless power receiver by dividing a difference between the first value of the input parameter and the value of the second input parameter by a difference between the first input voltage to the second input voltage. 
     In one embodiment, one or more values among the curve  404  can be used as a predetermined value (or a static parameter, or a previously measured parameter), and if the input current (i in ) of the transmitter  102  is different from (e.g., greater than) this predetermined value, then controller  104  can determine that a foreign object is present on the charging region  122 . In another embodiment, if a difference between the curve  404  and the input current is within a predetermined threshold range, then the transmitter  102  can determine that there may be no foreign object located in the charging region  122 . A sensitivity of the foreign object detection can be adjusted by adjusting this predetermined threshold range. 
     In one embodiment, controller  104  can determine predetermined threshold range  420  based on curves  404 ,  406 . For example, controller  104  can assign a difference between a minimum of curve  406  (e.g., the reference pattern) and a maximum of curve  404  (e.g., predetermined value) as the predetermined threshold range  420 . If a difference between the predetermined value and the input current (i in ) is within predetermined threshold range  320 , then the transmitter  102  can determine that there may be no foreign object located in the charging region  122 . 
     In another embodiment, the input voltage test  402  can produce an input parameter variation pattern indicating how the input power (P in ) varies with the input voltage V in . The input power corresponding to different input voltages, with a foreign object on charging region  122 , can be measured or recorded by controller  104 . The measured input power can be stored in the memory device of controller  104  and can be used for producing the input power variation pattern. 
       FIG.  5    is a flow diagram illustrating a process  500  being performed by a power transmitter to implement foreign object detection based on transmitter input parameter in one embodiment. The process  500  may include one or more operations, actions, or functions as illustrated by one or more of blocks  502 ,  504 ,  506 , and/or  508 . Although illustrated as discrete blocks, various blocks can be divided into additional blocks, combined into fewer blocks, eliminated, or performed in parallel, and/or performed in different order, depending on the desired implementation. 
     The process  500  can be performed by a wireless power transmitter (e.g., transmitter  102  in  FIG.  1    to  FIG.  3   ). In one embodiment, the blocks  502 ,  504 ,  506 , and  508  can be performed prior to a power transfer stage between the wireless power transmitter and a wireless power receiver. The process  500  can begin at block  502 . At block  502 , the transmitter can detect an object in a charging region (e.g., charging region  122  in  FIG.  1    to  FIG.  4   ). In one embodiment, the transmitter can detect the object in the charging region by detecting the object being inductively coupled to the transmitter. The detection of the object can be performed in a stage that is different from a power transfer stage of the transmitter. The process  500  can proceed from block  502  to block  504 . At block  504 , the transmitter can measure an input parameter being received at an input terminal of the transmitter. In one embodiment, the input parameter can be one of an input current and an input power. The process  500  can proceed from block  504  to block  506 . At block  506 , the transmitter can compare the measured input parameter with a predetermined value, such as a predetermined threshold. In one embodiment, the threshold can be a range of values. The process  500  can proceed from block  506  to block  508 . At block  508 , the transmitter can determine whether a foreign object is present or absent in the charging region, or determine whether the object in charging region  122  is the foreign object or a wireless power receiver, based on a result of the comparison between the measured input parameter with the predetermined threshold. In response to the result of the comparison indicating the measured input parameter is outside of the threshold, the transmitter can determine that the object is the foreign object. In response to the result of the comparison indicating the measured input parameter is within the threshold, the transmitter can determine that the object is the receiver. In one embodiment, the transmitter can determine a reference pattern corresponding to the foreign object. The transmitter can determine the threshold range based on the reference pattern and the predetermined value. 
       FIG.  6    is a flow diagram illustrating a process  600  being performed by a power transmitter to implement foreign object detection based on transmitter input parameter in one embodiment. The process  600  may include one or more operations, actions, or functions as illustrated by one or more of blocks  602 ,  604 ,  606 , and/or  608 . Although illustrated as discrete blocks, various blocks can be divided into additional blocks, combined into fewer blocks, eliminated, or performed in parallel, and/or performed in different order, depending on the desired implementation. 
     The process  600  can be performed by a wireless power transmitter (e.g., transmitter  102  in  FIG.  1    to  FIG.  3   ). In one embodiment, the blocks  602 ,  604 ,  606 , and  608  can be performed prior to a power transfer stage between the wireless power transmitter and a wireless power receiver. The process  600  can begin at block  602 . At block  602 , the transmitter can detect an object in a charging region (e.g., charging region  122  in  FIG.  1    to  FIG.  4   ). In one embodiment, the transmitter can detect the object in the charging region by detecting the object being inductively coupled to the transmitter. The detection of the object can be performed in a stage that is different from a power transfer stage of the transmitter. The process  600  can proceed from block  602  to block  604 . At block  604 , the transmitter can measure an input parameter being received at an input terminal of the transmitter. In one embodiment, the input parameter can be one of an input current and an input power. The process  600  can proceed from block  604  to block  606 . At block  606 , the transmitter can compare the measured input parameter with a predetermined value, such as a known or predetermined pattern indicating a relationship between the input parameter and another parameter. For example, the known pattern can indicate one of a relationship between the input parameter and a distance between a foreign object and a reference location on the charging region, a relationship between the input parameter and an operating frequency of the transmitter, and a relationship between the input parameter and an input voltage of the transmitter. Further, the predetermined value can correspond to instances where no foreign object is detected in the charging region. The process  600  can proceed from block  606  to block  608 . At block  608 , the transmitter can determine whether a foreign object is present or absent in the charging region, or determine whether the object in charging region  122  is the foreign object or a wireless power receiver, based on a result of the comparison between the measured input parameter with the predetermined pattern. In one embodiment, in response to the result of the comparison indicating the measured input parameter is greater than the predetermined value, the transmitter can determine that the object is the foreign object. In response to the result of the comparison being less than the predetermined value, the transmitter can determine that the object is the receiver. 
       FIG.  7    is a flow diagram illustrating a process  700  being performed by a power transmitter to implement foreign object detection based on transmitter input parameter in one embodiment. The process  700  may include one or more operations, actions, or functions as illustrated by one or more of blocks  702 ,  704 ,  706 , and/or  708 . Although illustrated as discrete blocks, various blocks can be divided into additional blocks, combined into fewer blocks, eliminated, or performed in parallel, and/or performed in different order, depending on the desired implementation. 
     The process  700  can be performed by a wireless power transmitter (e.g., transmitter  102  in  FIG.  1    to  FIG.  3   ). In one embodiment, the blocks  702 ,  704 ,  706 , and  708  can be performed prior to a power transfer stage between the wireless power transmitter and a wireless power receiver. The process  700  can begin at block  702 . At block  702 , the transmitter can detect an object in a charging region (e.g., charging region  122  in  FIG.  1    to  FIG.  4   ). In one embodiment, the transmitter can detect the object in the charging region by detecting the object being inductively coupled to the transmitter. The detection of the object can be performed in a stage that is different from a power transfer stage of the transmitter. The process  700  can proceed from block  702  to block  704 . At block  704 , the transmitter can measure an input parameter being received at an input terminal of the transmitter. In one embodiment, the input parameter can be one of an input current and an input power. The process  700  can proceed from block  704  to block  706 . At block  706 , the transmitter can compare the measured input parameter with a predetermined value, such as a fixed value of the input parameter. In one embodiment, the fixed value of the input parameter can be a fixed input current or a fixed input power measured by a controller of the transmitter when there are no foreign objects on the charging region. The process  700  can proceed from block  706  to block  708 . At block  708 , the transmitter can determine whether a foreign object is present or absent in the charging region, or determine whether the object in charging region  122  is the foreign object or a wireless power receiver, based on a result of the comparison between the measured input parameter with the fixed value of the input parameter. In one embodiment, in response to the result of the comparison indicating that the measured input parameter is different from the fixed value, the transmitter can determine that the object is the foreign object. In response to the result of the comparison indicating that the measured input parameter is same as the fixed value, the transmitter can determine that the object is the receiver. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements, if any, in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.