PATENT DOCUMENT

Publication Number: US-9537353-B1
Application Number: US-201414295249-A
Country: US
Kind Code: B1

Title: Methods for detecting mated coils

Abstract:
Methods and systems for improved efficiency when an inductive power transmitter associated with an inductive power transfer system experiences a low-load or no-load condition. More particularly, methods and systems for detecting when an inductive power receiver is absent or poorly connected to an inductive power transmitter. The inductive power transmitter includes, in one example, a current peak monitor coupled to an inductive power transmit coil. The current peak monitor waits for a current peak resulting from spatial displacement of a magnetic field source within the inductive power receiver, indicating to the inductive power transmitter that the inductive power receiver is moving, or has moved, toward the inductive power transmitter. Other examples include one or more Hall effect sensors within the inductive power transmitter to monitor for the magnetic field source of the inductive power receiver.

Claims:
We claim: 
     
       1. An adaptive power control system for an electromagnetic induction power transfer apparatus comprising:
 a signal receiver; 
 a sensor configured to detect the presence and absence of an electromagnetic induction power receiving apparatus; 
 a power supply with an active state and an inactive state, configured to switch between the active state and the inactive state at a selectable duty cycle; and 
 a power-transmitting inductor coupled to the power supply; 
 wherein:
 the inactive state of the power supply is controlled at least in part in response to a signal received from the signal receiver; and 
 the inactive state of the power supply is controlled at least in part in response to a signal received from the sensor. 
 
 
     
     
       2. The adaptive power control system of  claim 1 , wherein the power supply is set to the inactive state in the absence of a signal received from the signal receiver. 
     
     
       3. The adaptive power control system of  claim 1 , wherein the signal is received when the power supply is in the inactive state. 
     
     
       4. The adaptive power control system of  claim 1 , wherein the signal received from the signal receiver is a signal sent from an electromagnetic induction power receiving apparatus having a power-receiving inductor and positioned inductively proximate the power-transmitting inductor. 
     
     
       5. The adaptive power control system of  claim 4 , wherein the signal comprises a verification that the electromagnetic induction power receiving apparatus is prepared to receive power. 
     
     
       6. The adaptive power control system of  claim 4 , wherein the signal comprises a verification that the electromagnetic induction power receiving apparatus unable to receive power. 
     
     
       7. The adaptive power control system of  claim 1 , wherein the signal is received when the power supply in either the active state or the inactive state. 
     
     
       8. The adaptive power control system of  claim 1 , wherein the signal receiver is coupled to the power-transmitting inductor and configured to sense changes in inductive load to the power-transmitting inductor. 
     
     
       9. The adaptive power control system of  claim 1 , wherein the sensor comprises one or more magnetic field sensors. 
     
     
       10. The adaptive power control system of  claim 1 , wherein the sensor comprises one or more optical sensors. 
     
     
       11. The adaptive power control system of  claim 1 , wherein the sensor comprises one or more strain sensors coupled to an alignment magnet. 
     
     
       12. The adaptive power control system of  claim 1 , wherein the sensor comprises one or more accelerometers. 
     
     
       13. The adaptive power control system of  claim 1 , wherein the sensor comprises one or more capacitive sensors. 
     
     
       14. A method of activating a transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry comprising a transmit coil, the method comprising:
 providing an interface surface for mating to an inductive power receiving apparatus comprising at least one magnetic field source; 
 monitoring the transmit coil for a current spike; and 
 activating the transmit circuitry in response to the current spike. 
 
     
     
       15. The method of  claim 14 , further comprising:
 upon determining that a current spike has occurred, verifying that the current spike is associated with a magnetic field source associated with an inductive power receiving apparatus before activating the transmit circuitry. 
 
     
     
       16. A method of activating a transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry comprising a transmit coil, the method comprising:
 providing an interface surface for mating to an inductive power receiving apparatus comprising at least one magnetic field source; 
 monitoring with a processor one or more magnetic field sensors for an indication of a proximity of the magnetic field source; and 
 activating the transmit circuitry in response to determining the proximity of the magnetic field source is at least lower than a selected threshold. 
 
     
     
       17. The method of  claim 16 , wherein the one or more magnetic field sensors comprise at least one of the group consisting of Hall sensors, reed switches, and giant magnetoresistance sensors. 
     
     
       18. A method of activating a transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry comprising a transmit coil, the method comprising:
 providing an interface surface for mating to an inductive power receiving apparatus; 
 monitoring one or more proximity sensors for an indication of a proximity of the inductive power receiving apparatus to the interface surface; 
 determining if a proximity of a magnetic field source is at least lower than a selected threshold; 
 verifying that the inductive power receiving apparatus is ready to receive transmitted power; and 
 activating the transmit circuitry. 
 
     
     
       19. The method of  claim 18 , wherein the one or more proximity sensors comprise at least one of the group consisting of Hall sensors, reed switches, giant magnetoresistance sensors, capacitive sensors, and optical sensors.

Description:
TECHNICAL FIELD 
     Embodiments described herein relate to electromagnetic power transfer systems, and in particular to systems and methods for improving the efficiency of no- and low-load conditions of an inductive power transmitter. 
     BACKGROUND 
     Many electronic devices include one or more batteries that may require recharging from time to time. Such devices may include electric vehicles, cell phones, smart phones, tablet computers, laptop computers, wearable devices, navigation devices, sports devices, health devices, medical devices, location tracking devices, accessory devices, home appliances, peripheral input devices, remote control devices, and so on. 
     A number of battery-powered electronic devices may recharge internal batteries wirelessly by accepting inductive power provided by an inductive power transmitter. For instance, a battery-powered electronic device (“accessory”) adapted to accept inductive power may be positioned on a surface of a transmitter (“dock”) adapted to produce inductive power. In these systems, an electromagnetic coil within the dock (“transmit coil”) may produce a time-varying electromagnetic flux to induce a current within an electromagnetic coil within the accessory (“receive coil”). The accessory may use the received current to replenish the charge of a rechargeable battery. 
     In many examples, a dock associated with an inductive power transfer system may consume substantial power when the accessory is absent. 
     Accordingly, there may be a present need for a system and method for efficiently, rapidly, and wirelessly delivering useful power to a battery-powered electronic device. 
     SUMMARY 
     Embodiments described herein may relate to, include, or take the form of methods and systems for managing the efficiency of an inductive power transmitter associated with an inductive power transfer system under no-load conditions. Such embodiments can include an inductive power transmitter and an inductive power receiver. 
     Certain embodiments described herein may relate to or take the form of a method of activating transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry including at least one transmit coil, the method including at least the steps of providing an interface surface for mating to an inductive power receiving apparatus, monitoring one or more proximity sensors for an indication of a proximity of the inductive power receiving apparatus to the interface surface, determining if the proximity of the magnetic field source may be at least lower than a selected threshold, verifying that the inductive power receiving apparatus may be ready to receive transmitted power, and thereafter activating the transmit circuitry. 
     Certain embodiments described herein may relate to or take the form of a method of activating transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry including at least one transmit coil, the method including at least the steps of providing an interface surface for mating to an inductive power receiving apparatus comprising at least one magnetic field source, monitoring with a processor one or more magnetic field sensors for an indication of a proximity of the magnetic field source, and activating the transmit circuitry in response to determining the proximity of the magnetic field source may be at least lower than a selected threshold. 
     Certain further embodiments described herein may relate to or take the form of a method of activating transmit circuitry associated with an inductive power transmission apparatus, the transmit circuitry including at least a transmit coil, the method including at least the steps of providing an interface surface for mating to an inductive power receiving apparatus comprising at least one magnetic field source, monitoring the transmit coil for a current spike, and activating the transmit circuitry in response to the current spike. 
     Other embodiments described herein may relate to an adaptive power control system for an electromagnetic induction power transfer apparatus. The electromagnetic induction power transfer apparatus may include at least a signal receiver, a sensor configured to detect the presence and absence of an electromagnetic induction power receiving apparatus, a power supply with an active state and an inactive state that is configured to switch between the active state and the inactive state at a selectable duty cycle, and a power-transmitting inductor coupled to the power supply. In such an embodiment, the inactive state of the power supply may be controlled at least in part in response to a signal received from the signal receiver, and the inactive state of the power supply may be controlled at least in part in response to a signal received from the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Reference will now be made to representative embodiments illustrated in the accompanying figures. It should be understood that the following descriptions are not intended to limit the disclosure to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the described embodiments as defined by the appended claims. 
         FIG. 1A  depicts a front perspective view of an example inductive power transfer system in an unmated configuration. 
         FIG. 1B  depicts a front perspective view of an example inductive power transfer system in an alternate unmated configuration. 
         FIG. 1C  depicts the example inductive power transfer system of  FIG. 1A  in a mated configuration. 
         FIG. 2  depicts a simplified signal flow block diagram of a sample inductive power transfer system. 
         FIG. 3A  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 3B  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 3C  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 3D  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 3E  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 3F  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . 
         FIG. 4  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to periodically ping for an inductive power receiver. 
         FIG. 5  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor a transmit coil for a current induced by motion of an alignment magnet associated with an inductive power receiver. 
         FIG. 6  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for mechanical agitation associated with placing an inductive power receiver on the inductive power transmitter. 
         FIG. 7  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor an optical communication link for a response from an inductive power receiver. 
         FIG. 8  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor a magnetic field sensor for the presence of an alignment magnet associated with an inductive power receiver. 
         FIG. 9  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for capacitive changes associated with placing an inductive power receiver on the inductive power transmitter. 
         FIG. 10  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for strain or tension changes within an alignment magnet within an inductive power transmitter resulting from attraction to an alignment magnet associated with an inductive power receiver. 
     
    
    
     The use of the same or similar reference numerals in different drawings indicates similar, related, or identical items. 
     DETAILED DESCRIPTION 
     Embodiments described herein may relate to or take the form of systems and methods for improved efficiency of power transfer across an inductive power transfer interface. Other embodiments described herein relate to systems and methods for improved efficiency of power transfer when an inductive power transmitter experiences a low-load or no-load condition. 
     An inductive power transfer system may include an inductive power-transmitting component or device to transmit power and an inductive power-receiving component or device to receive power. In some examples, a battery-powered electronic device includes an inductive power-receiving component configured to charge one or more internal batteries. Example battery-powered electronic devices may include media players, media storage devices, personal digital assistants, tablet computers, cellular telephones, laptop computers, smart phones, styluses, global positioning sensor units, remote control devices, wearable devices, electric vehicles, home appliances, location tracking devices, medical devices, health devices, sports devices, accessory devices, and so on. Example inductive power transmitting devices may include docks, stands, clips, plugs, mats, attachments, and so on. 
     In many examples, a battery-powered electronic device (“accessory”) may be positioned on a power-transmitting device (“dock”). In these systems, an electromagnetic coil within the dock (“transmit coil”) may produce a time-varying electromagnetic flux (“transmitting power”) to induce a current within an electromagnetic coil within accessory (“receive coil”). In other examples, a transmit coil may produce a static electromagnetic field and may physically move, shift, or otherwise change its position to produce a spatially-varying electromagnetic flux to induce a current within the receive coil. 
     The accessory may use the received current to replenish the charge of a rechargeable battery (“receiving power”) or to provide power to operating components. In other words, when the accessory is positioned on the dock, the dock may transmit power via the transmit coil to the receive coil of the accessory. 
     In many cases, the dock may be configured to provide sustained power transmission to the accessory for a selected or otherwise limited time. For example, the dock may suspend sustained power transmission once the rechargeable battery of the accessory is replenished. In other examples, the dock may be configured to vary the amount of power transmitted to the accessory in response to changes in the power requirements of the accessory. For example, the dock may use information received or measured from the accessory to dynamically, intelligently, and rapidly adjust the power transmitted to the accessory. 
     In other embodiments, the dock may suspend sustained power transmission upon determining that the accessory has been removed from the dock. For example, the dock may include a processor that may be adapted to monitor a load condition of the transmit coil to determine when an accessory is removed. When the processor determines that the accessory is removed (i.e., “no-load condition”), the dock may suspend sustained power transmission and may enter a periodic ping mode during which the dock may intermittently transmit power. In other examples, when the processor determines that the accessory has substantially reduced its power requirements (i.e., “low-load condition”), the dock may suspend sustained power transmission and may enter the periodic ping mode. The processor may monitor the transmit coil during each ping for a load condition that may indicate that an accessory is present. After the processor determines that the accessory has returned, the dock may revert to the sustained power transmission mode. 
     In another embodiment, the dock and accessory may utilize a communication channel to mutually advertise various device modes, states, or requirements. For example, the accessory and dock may each include a wireless transceiver. The wireless transceiver may be any suitable communication technology such as, Wi-Fi, radio, Bluetooth, near field communication (“NFC”), optical, or infrared communication technology. In these embodiments, the dock may periodically ping for the accessory over the communication channel to determine whether the accessory is present and ready to receive transmitted power. For example, the dock may periodically request a response from an accessory over Wi-Fi. The accessory may respond via Wi-Fi that the accessory is ready to receive transmitted power. After the processor determines that the accessory has returned, the dock may revert to the sustained power transmission mode. 
     In other embodiments, the dock may monitor various sensors to determine whether an accessory is present and ready to receive transmitted power. For example, the dock may include an optical sensor such as an infrared proximity sensor. When the accessory is placed on the dock, the infrared proximity sensor may report to the aforementioned processor that the accessory is present. The processor may, optionally, use another method or structure to verify the presence of the accessory. Examples of different sensors that may be suitable include a mass sensor, a mechanical interlock, switch, button or the like, a Hall effect sensor, or other electronic sensor. Continuing the example, after the optical sensor reports that the accessory may be present, the processor may activate a wireless communication channel to attempt to communicate with the accessory. After the processor determines that the accessory has returned, the dock may revert to the sustained power transmission mode. 
     In other examples, magnetic field sensors may be used to assist the processor in determining whether an accessory is present. For example, in certain embodiments, a Hall sensor may be used. A Hall sensor may be configured to monitor for a magnetic field source within the accessory. For example, the accessory may include a permanent magnet to assist the accessory with aligning to the dock. A Hall sensor within the dock may detect the presence of the magnetic field and may report to the aforementioned processor that the accessory may be present. 
     Again, the processor may, optionally, use another means to verify the presence of the accessory as a method of double-checking the output from the Hall sensor. For example, after the Hall sensor reports that the accessory may be present, the processor may activate a wireless communication channel to attempt to communicate with the accessory. In another example, the processor may enter the aforementioned periodic ping mode. In further examples, the processor may verify the presence of the accessory by other suitable means. After the processor determines that the accessory has returned, the dock may revert to the sustained power transmission mode. 
     In other examples, multiple magnetic field sensors may be used to assist the processor in determining whether an accessory is present. For example, in certain embodiments, more than one Hall sensor may be used. For example, a first Hall sensor may be configured to monitor for a magnetic field source present within the accessory and may be adapted to detect the magnitude of magnetic or electromagnetic fields oriented along a first axis. A second Hall sensor may be adapted to detect fields oriented along a different axis. In these examples, the two Hall sensors may be configured to operate together to detect the presence of the magnetic field and may report to the aforementioned processor that the accessory is present. After the processor determines that the accessory has returned, the dock may revert to the sustained power transmission mode. 
     In many examples, a signal derived from the signals of multiple sensors may be of sufficient quality that signal amplification and/or filtering may be unnecessary. In these examples, the power required to operate more than one sensor may be less than the power required to operate a single sensor and a corresponding amplifier. 
     In other embodiments, the dock may include one or more physical switches to determine whether an accessory is present and ready to receive transmitted power. For example, the dock may include a normally open switch, button, latch or other mechanical or electrical element that is closed when an accessory is placed on the dock. The switch may be coupled to the aforementioned processor. After the processor determines that the accessory has closed the switch, the dock may verify that the accessory is present or, in the alternative, may immediately revert to the sustained power transmission mode. 
       FIG. 1A  depicts a front perspective view of an example inductive power transfer system in an unmated configuration. The system  100  may include an inductive power receiver  104  and an inductive power transmitter  102 . In the illustrated embodiment, the inductive power transmitter  102  may be connected to mains power (i.e., power outlet) by power cord  108 . In other embodiments, the inductive power transmitter  102  may instead be battery operated. In still further examples, the inductive power transmitter  102  may be both battery operated and may include a power cord  108 . 
     Furthermore, although the embodiment depicted in  FIG. 1A  is shown with the power cord  108  coupled to the housing of the inductive power transmitter  102 , the power cord  108  may be connected to the inductive power transmitter  102  by any suitable means. For example, the power cord  108  may be removable and may include a connector that is sized to fit within an aperture or receptacle opened within the housing of the inductive power transmitter  102 . 
     In various implementations and embodiments, either or both of the inductive power transmitter  102  and the inductive power receiver  104  may be included within or as a component of any kind or type of electronic device such as cell phones, smart phones, tablet computers, laptop computers, wearable devices, navigation devices, sports devices, health devices, medical devices, accessory devices, peripheral input devices, and so on. For example, the inductive power receiver  104  may be included within the housing of a cellular telephone. In such an example, the inductive power receiver may be entirely or partially concealed by the housing of the cellular telephone. In other examples, the inductive power receiver  104  may be included along a back surface of an electronic device. In still other embodiments, the inductive power receiver  104  may be included as an accessory for an electronic device. For example, the inductive power receiver  104  may be included within a protective case for a cellular telephone. 
     As shown, the inductive power receiver  104  may include a lower surface that may interface with, align or otherwise contact an interface surface  106  of the inductive power transmitter  102 . In this manner, the inductive power receiver  104  and the inductive power transmitter  102  may be positionable with respect to each other. In certain embodiments, the interface surface  106  may be configured in a particular shape that mates with a complementary shape of the inductive power receiver  104 . For example, as illustrated, the interface surface  106  has a concave shape following a select curve. A bottom surface of the inductive power receiver  104  has as a convex shape following the same or substantially similar select curve as the interface surface  106 . 
     The geometry of the bottom surface of the inductive power transmitter  104  may encourage alignment within complimentary geometry of the interface surface  106 . In the example of a circular convex and circular concave shape of the interface surface  106  and the bottom surface of the inductive power receiver  104 , the complementary shapes may discourage imperfect or partial alignment, as shown for example in  FIG. 1B . In such an embodiment, the inductive power receiver  104  may slide down the concave interface surface  106  to align with the inductive power transmitter  102 , as shown, for example, by  FIG. 1C . 
     In other embodiments, the interface surface  106  has another shape, for example a convex shape or a planar shape. In other examples, the interface surface has multiple faces or facets that encourage alignment of the inductive power receiver  104  with the inductive power transmitter  102 . In many embodiments, the interface surface  106  is axially symmetric while in others, the surface may be axially asymmetric. 
     Although shown with the inductive power receiver  104  as sized with a lateral cross-section less than that of the inductive power transmitter  102 , such a relationship is not required. For example, in certain embodiments, the inductive power receiver  104  has a horizontal cross-section larger than the inductive power transmitter  102 . 
       FIG. 2  depicts a simplified signal flow block diagram of a sample inductive power transfer system. The inductive power transfer system  200  may include an inductive power transmitter  202  and an inductive power receiver  304  separated by an air gap. The inductive power receiver  304  is depicted positioned on a top surface of the inductive power transmitter  202 , although such a configuration is not required. 
     The inductive power transmitter  202  may include a clock  206  connected to a processor  208  and a direct current converter  212 . The clock  206  can generate one or more timing signals for the inductive power transfer system  200 . The processor  208  may be coupled to a power supply  210  such as a direct current power supply. In certain embodiments, the processor  208  may control the state of the direct current converter  212 , which has power input from the power supply  210 . In one embodiment, the clock  206  generates periodic signals that are used by the processor  208  to activate and deactivate switches in the direct current converter  212 . The switches may convert the direct current from the power supply  210  to alternating current suitable for exciting a transmit coil  214 . 
     The transmitter  202  of the inductive power transfer system  200  may be configured to provide a time-varying signal to the transmit coil  214  in order to induce a voltage within the receive coil  314  in the receiver through inductive coupling with the transmit coil  214 . In this manner, power may be transferred from the transmit coil  214  to the receive coil  314 . The signal produced in the receive coil  314  may be received by a direct current converter  310  that converts the signal into a direct current signal. Any suitable direct current converter  310  can be used in the inductive power transfer system  200 . For example, in one embodiment, a rectifier may be used as a direct current converter. A programmable load such as a processor  308  may then receive the direct current signal. 
       FIG. 3A  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C , showing a simplified block diagram within a housing of an example inductive power-receiving device and a simplified block diagram within a housing of an example inductive power-transmitting device. As illustrated, the inductive power receiver  304  may include one or more receive coils  314 . In some embodiments, the receive coil  314  may have a tilted or semi-conical shape, or a curved surface, to follow a curvature of the housing of the inductive power receiver  304 . In other embodiments, the receive coil  314  has a substantially planar shape. 
     The inductive power receiver  304  may also include processor  308 . The processor  308  may be coupled to or more transitory or non-transitory storage media, and a battery  318 . The battery  318  may include, but may not necessarily be limited to, a battery power source, a capacitive power source, or a combination thereof. The processor  308  may execute one or more instructions, sequentially or otherwise, that are stored in the storage medium in order to perform one or more device operations of the inductive power receiver  304 . The processor  308  may also be coupled to one or more sensors. For example, a temperature sensor and may be operably connected to the battery  318  or the processor  308  such that, if a select temperature threshold is reached, the processor  308  may selectively disable one or more components or processes. 
     Similarly, the inductive power transmitter  202  may also include processor  208 , one or more transitory or non-transitory storage media, a power source  218 , and a transmit coil  214 . As with the receive coil  314 , in many embodiments, the transmit coil  214  may have a tilted or semi-conical shape to follow a curvature of the housing of the inductive power transmitter  202 . 
     In addition, the inductive power receiver  304  and the inductive power transmitter  202  may each include a wireless communication interface  318  and  218  respectively. The communication interface  318  and  218  can provide electronic communications between the inductive power receiver  304  and the inductive power transmitter  202  or any other external communication network, device or platform, such as but not limited to wireless interfaces, Bluetooth interfaces, USB interfaces, Wi-Fi interfaces, TCP/IP interfaces, near field communication (“NFC”), optical interfaces, infrared interfaces, network communications interfaces, or any conventional communication interfaces. The wireless communication interfaces  318  and  218  may be adapted for communication between the processors  208  and  308  to mutually advertise various modes, states, or requirements of the inductive power receiver  304  or the inductive power transmitter  202 . For example, the inductive power transmitter  202  may periodically ping for the inductive power receiver  304  over a communication channel established by the wireless communication interfaces  318  and  218  to determine whether the inductive power receiver  304  is present and ready to receive transmitted power. 
     More particularly, the inductive power transmitter  202  may periodically request (“ping”) a response from the inductive power receiver  304  over Wi-Fi. The processor  308  may receive a signal from the communication interface  318  and may respond that the inductive power receiver  304  is ready to receive transmitted power. The processor  208  may receive the response via the communication channel and may begin, continue, or revert to a sustained power transmission mode by exciting the transmit coil  214 . 
       FIG. 3B  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . As with the embodiment depicted in  FIG. 3A , the example inductive power transfer system includes an inductive power transmitter  202  and an inductive power receiver  304 . The inductive power receiver  304  may include a processor  308 , a battery  316 , and a receive coil  314 . In addition, the inductive power receiver  304  may include one or more magnetic field source  320 , such as a permanent magnet. The magnetic field source  320  may be oriented to produce a magnetic field along any axis. The inductive power transmitter  202  may include a processor  208 , a power source  216 , and a transmit coil  214 . The inductive power transmitter  202  may include a Hall sensor  218  coupled to the processor  208 . 
     The Hall sensor  218  may report information about nearby magnetic fields to the processor  208 . The processor  208  can use the magnetic field data to determine whether the detected magnetic fields originate at the magnetic field source  320 , or from another magnetic field source. For example, the processor  208  may monitor for a magnetic field of particular amplitude, or within a particular range. For example, if the processor  208  determines that a detected magnetic field has an amplitude greater than a selected minimum and smaller than a selected maximum, the processor  208  may presume that the magnetic field source  320 , and thus the inductive power receiver  304 , is present and ready to receive power. In another example, the processor  208  may determine that a detected magnetic field has an amplitude less than a selected minimum, or greater than a selected maximum. In this example, the processor  208  may presume that the detected magnetic field is not associated with the inductive power receiver  304 . In a further example, if the processor  208  determines that a detected magnetic field is oriented along a particular axis, the processor  208  may presume that the inductive power receiver  304  is present. 
     After the processor  208  determines that the inductive power receiver  304  is present, the processor  208  can activate a wireless communication channel (not shown) to attempt to communicate with the inductive power receiver  304  to verify or confirm that the inductive power receiver  304  is ready to receive inductive power. After verification, the inductive power transmitter  202  may begin transmitting inductive power. 
     In another example, the inductive power receiver  304  may apply a signal to the receive coil  314  that can be detected by the Hall sensor  218 . For example, the signal may be a direct current signal that excites a static electromagnetic field in the receive coil  314 . The static electromagnetic field may be detected by the Hall sensor  218  and reported to the processor  218 . In another example, the signal may be a direct current signal that changes amplitude over time. The Hall sensor  218  may detect the amplitude of the electromagnetic field as it changes in the receive coil  314  as a result of the signal. The processor  218  may analyze the variation in the amplitude of the detected magnetic field to determine whether the inductive power receiver  304  is present. In some examples, the signal may include digital information encoded in the changing amplitude. The processor  218  may decode and use the information for a variety of tasks. For example, the signal may include one or more authentication tokens that the processor  218  may use to determine whether the inductive power receiver  304  is permitted or authorized to receive inductive power from the inductive power transmitter  202 . In another example, the signal may include information relating to the state of the inductive power transmitter  202  such as information relating to temperature, battery level, usage statistic, current load requirements, user information, or any other information. 
     In other examples, the Hall sensor  218  may not be required for detecting the presence or absence of the inductive power receiver  304 . For example, the processor  218  may monitor the transmit coil  214  for a current peak that may be the result of movement of the magnetic field source  320 . One may appreciate that motion of a permanent magnet may produce a time or spatially-varying electromagnetic flux that may induce an electrical current within a nearby electromagnetic coil. 
     Continuing the example, the processor  218  may monitor for a sudden peak in the within the transmit coil  214 . If a peak is not detected, the processor  218  may continue monitoring the transmit coil for current. On the other hand, if a peak is detected, the processor  218  may attempt to verify that an induced current sensed in the transmit coil is actually the result of the placement of an inductive power receiver  304  on the inductive power transmitter  202 . 
     In other examples, multiple magnetic field sensors may be used to assist the processor in determining whether an accessory is present.  FIG. 3C  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . As with the embodiment depicted by  FIG. 3B , the inductive power transfer system includes an inductive power transmitter  202  and an inductive power receiver  304 . 
     The inductive power receiver  304  includes a processor  308 , a battery  316 , and a receive coil  314 . In addition, the inductive power receiver  304  may include one or more magnetic field sources  320   a ,  320   b . The magnetic field sources  320   a ,  320   b  may be oriented along the same axis or, for example as illustrate, may be oriented along a different axis. The inductive power transmitter  202  may include a processor  208 , a power source  216 , and a transmit coil  214 . The inductive power transmitter  202  may include multiple Hall sensors  218   a ,  218   b  each coupled to the processor  208 . In many examples, a first Hall sensor  218   a  may be adapted to detect the magnitude of magnetic or electromagnetic fields oriented along a first axis. A second Hall sensor  218   b  may be adapted to detect fields oriented along a different axis. 
     In these examples, the two Hall sensors  218   a ,  218   b  may be configured to operate together to detect the presence of the magnetic field of the magnetic field source  320  and may report that information to the processor  208 . After the processor  208  determines that the inductive power receiver  304  has returned, the inductive power transmitter  202  may revert to or enter the sustained power transmission mode. 
       FIG. 3D  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . In the illustrated embodiment, the processors  208 ,  308  may also be coupled to respective optical communication interfaces  218 ,  318  respectively. The optical communication interfaces  218 ,  318  may be any number of suitable optical communication interfaces. For example, in one embodiment, one or both of the optical communication interfaces may include a one or more light emitting diodes and one or more phototransistors. In this example, a light emitting diode within the optical communication interface  218  may convey a signal to a phototransistor within the optical communication interface  318 . The signal may include a request for confirmation that the inductive power receiver  304  is ready to receive power. Thereafter, the processor  308  may instruct a light emitting diode within the optical communication interface  318  to convey a signal back to the optical communication interface  218  that the inductive power receiver  304  is ready to receive power. In other examples, optical communication between the optical communication interfaces  218  and  318  may be one-way. For example, the optical communication interfaces  218  and  318  may mutually advertise various electronic device states of the inductive power transmitter  202  and the inductive power receiver  304 . 
     In other embodiments, either of the optical communication interfaces  218 ,  318  may be a passive optical element such a lens or reflector configured to reflect light of a particular wavelength or in a particular pattern. In one example, the optical communication interface  318  may be passive. The optical communication interface  218  may illuminate a light emitting diode that may produce light that can reflect from the passive optical communication interface  318 . In some examples, the optical communication interface  218  may pass light from a light emitting diode positioned elsewhere, for example with a light guide or light pipe. 
     A passive optical communication interface may include a bar code readable by optical communication interface  218 . The optical communication interface  218  may communicate to the processor  208  the read image. Thereafter, the processor  208  determines that the passive optical communication interface, and thus the inductive power receiver  304 , is present and ready to receive inductive power. 
       FIG. 3E  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . As with the embodiment depicted by  FIG. 3A , the example inductive power transfer system may include an inductive power transmitter  202  which may include a processor  208  coupled to a power source  216  and a transmit coil  214 . The inductive power transfer system may also include an inductive power receiver  304  which may include a processor  308  coupled to a battery  316  and a receive coil  314 . In this embodiment, the inductive power transmitter may include one or more switches  218 . The switch  218  may be a normally open switch such that when the inductive power receiver  304  is placed on the inductive power transmitter  202 , the switch is closed. In these embodiments the switch  218  may be coupled to the processor  208  such that when the switch  218  is closed, the processor  208  may determine that the inductive power receiver is ready to receive power. After the processor  208  determines that the inductive power receiver  304  has returned, the inductive power transmitter  202  may revert to or enter the sustained power transmission mode. 
       FIG. 3F  depicts a side cross-section view of an example inductive power transfer system taken along line  4 - 4  of  FIG. 1C . As with the embodiment depicted by  FIG. 3A , the example inductive power transfer system may include an inductive power transmitter  202  which may include a processor  208  coupled to a power source  216  and a transmit coil  214 . The inductive power transfer system may also include an inductive power receiver  304  which may include a processor  308  coupled to a battery  316  and a receive coil  314 . In the illustrated embodiment, the processor  208  may be coupled to a sensor  218 . The sensor  218  may be adapted to detect for the presence of the inductive power receiver  304 . 
     In certain examples, the sensor  218  may be configured to detect mechanical agitation of the inductive power transmitter  202  associated with physically placing the inductive power receiver  304  on the interface surface of the inductive power transmitter  202 . In such an example, the sensor  218  may be an accelerometer, gyroscope, piezoelectric, piezoresistive, strain, tension, pressure, or any other force-sensitive sensor. 
     After the sensor  218  reports that the inductive power receiver  304  is present, the processor  208  may activate a wireless communication channel (not shown) to attempt to communicate with the inductive power receiver  304 . In another example, the processor  208  may enter the periodic ping mode. In further examples, the processor  208  may verify the presence of the inductive power receiver  304  by other suitable means. After the processor  208  determines that the inductive power receiver  304  has returned, the inductive power transmitter  202  may revert to the sustained power transmission mode. 
       FIG. 4  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to periodically ping for an inductive power receiver. The method may begin at step  402  in which an inductive power transmitter may ping for a receiver. For example, both the transmitter and receiver may include a wireless communication channel to mutually advertise various device modes, states, or requirements, such as power requirements. In one example, the receiver and transmitter may each include a wireless transceiver. The wireless transceiver may any suitable communication technology such as, Wi-Fi, radio, Bluetooth, near field communication (“NFC”), optical, or infrared. In these embodiments, the transmitter may periodically send a signal interrogating for the presence of the receiver over the communication channel. For example, the transmitter may periodically request a response from the receiver over Wi-Fi. The receiver may respond via Wi-Fi that the receiver is ready to receive transmitted power. The transmitter may receive the response at step  404  or, in the alternative, if the transmitter does not receive a response, the transmitter may revert to step  402 . After the transmitter receives the response from the receiver, the transmitter may active inductive power transmission circuitry at  406 . 
       FIG. 5  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor a transmit coil for a current induced by motion of an alignment magnet associated with an inductive power receiver. The method may begin at  502  in which a processor associated with an inductive power transmitter may monitor a transmit coil for a current peak resulting from the movement of a magnetic field source such as a magnet. 
     In many examples, motion of a permanent magnet nearby a coil may produce a time or spatially-varying electromagnetic flux that may induce an electrical current within the transmit coil. Accordingly, the processor may monitor for a sudden peak in the current at  504 . If a peak is not detected, the processor may continue monitoring the transmit coil for current. On the other hand, if a peak is detected, the method may continue at  506 , in which the processor may initiate a verification process. The verification process may attempt to verify that an induced current sensed in the transmit coil is actually the result of the placement of an inductive power receiver on the inductive power transmitter. 
     The verification process may begin at step  506  in which the inductive power transmitter may ping for a receiver over, for example, a wireless communication channel as described with respect to the method illustrated by  FIG. 4 . The verification process may wait at  508  for a response from the receiver. In another example, the transmitter may activate the transmit coil to send a small amount of power for a selected period of time. In these embodiments, the processor may monitor for a load experienced by the transmit coil. A load to the transmit coil may verify that an inductive power receiver is receiving power. If a load is not detected, the method may stop the verification process and return to  502 . If, alternatively, a load is detected, transmit circuitry may be activated at  510 . 
       FIG. 6  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for mechanical agitation associated with placing an inductive power receiver on the inductive power transmitter. The method may begin at  602  in which a processor associated with an inductive power transmitter may monitor a sensor for agitation resulting from placing a receiver on a transmitter. In many examples, the receiver may cause a measurable agitation when it is placed on a transmitter. 
     Accordingly, the processor may monitor for an agitation at  604 . If an agitation is not detected, the processor may continue monitoring. Alternatively, if an agitation is detected, the method may continue at  606 , in which the processor may initiate a verification process. The verification process may attempt to verify that the sensed agitation is actually the result of the placement of an inductive power receiver on the inductive power transmitter. The verification process may begin at step  606  in which the inductive power transmitter may ping for a receiver over, for example, a wireless communication channel as described with respect to the method illustrated by  FIG. 4  or by periodically transmitting power and monitoring for a load to a transmit coil as described with respect to the method illustrated by  FIG. 5 . If, alternatively, the presence of the receiver is verified, transmit circuitry may be activated at  610 . 
       FIG. 7  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor an optical communication link for a response from an inductive power receiver. The method may begin at step  702  in which an inductive power transmitter may ping for a receiver over an optical communication link. For example, both the transmitter and receiver may include a light transmitter and a light sensor. In other examples, the transmitter may include a camera (e.g., charge-coupled device, complementary metal-oxide semiconductor devices) that may be configured to read an image, number, code, or pattern disposed on a surface of the receiver. In still further examples, the transmitter may include an infrared or optical light proximity sensor. 
     In these embodiments, the transmitter may periodically request a response from the receiver over the optical communication link. The receiver may respond via the optical communication link that the receiver is ready to receive transmitted power. Alternately, the transmitter may detect that the receiver is present based upon feedback from the optical sensor included there. The transmitter may receive the response at step  704  or, in the alternative, if the transmitter determines that the receiver is not present, the transmitter may revert to step  702 . After the transmitter determines that the receiver is present, the transmitter may active inductive power transmission circuitry at  706 . 
       FIG. 8  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor a magnetic field sensor for the presence of an alignment magnet associated with an inductive power receiver. The method may begin at  802  in which a processor associated with an inductive power transmitter may monitor one or more magnetic field sensors (e.g., Hall sensors, reed sensors, micro-electromechanical devices, magnetic field/magnetic anomaly sensors, giant magnetoresistance sensors, and the like) resulting from the movement of a magnetic field source such as a magnet. 
     In many examples, motion of a permanent magnet nearby a coil may produce a time or spatially-varying electromagnetic flux that may be measurable by a magnetic field sensor. In other examples, a magnetic field sensor may be adapted to measure a static magnetic field. Accordingly, the processor may monitor for a magnetic field at  804 . If a magnetic field is not detected, the processor may continue monitoring. Alternately, if a magnetic field is detected, the method may continue at  806 , in which the processor may initiate a verification process. The verification process may attempt to verify that magnetic field sensed is actually the result of the placement of an inductive power receiver on the inductive power transmitter. 
     The verification process may attempt to verify that an induced current sensed in the transmit coil is actually the result of the placement of an inductive power receiver on the inductive power transmitter. The verification process may begin at step  806  in which the inductive power transmitter may ping for a receiver over, for example, a wireless communication channel as described with respect to the method illustrated by  FIG. 4  or by periodically transmitting power and monitoring for a load to a transmit coil as described with respect to the method illustrated by  FIG. 5 . If, alternatively, the presence of the receiver is verified, transmit circuitry may be activated at  810 . 
     In many examples more than one magnetic field sensor may be used. The magnetic field sensors may be oriented in different directions to increase sensitivity. In still further examples, the magnetic field sensors may be calibrated to prefer a particular magnetic field strength. For example, the magnetic field sensors may report to the processor that the receiver is present only if the detected magnetic field is within a particular strength range. In other embodiments, the magnetic field sensors may report to the processor that the receiver is present only if the detected magnetic field is above a particular threshold. In other embodiments, the magnetic field sensors may be configured to read a particular magnetic signature of a receiver. For example, the receiver may contain multiple permanent magnets that each have different field strength. The magnetic field sensors may be adapted to recognize the combination of permanent magnets as an authentication that the receiver is present and ready to receive power. 
     In still further embodiments, alternating magnetic field sensors may be used. In these examples, a receiver may transmit an alternating magnetic field to a transmitter containing an alternating magnetic field sensor configured to detect the receiver&#39;s transmission. 
       FIG. 9  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for capacitive changes associated with placing an inductive power receiver on the inductive power transmitter. The method may begin at  902  in which a processor associated with an inductive power transmitter may monitor for capacitance changes corresponding to the placement of a receiver on the transmitter. For example, the transmitter may include one or more capacitive plates that may detectably change capacitance in the presence of a receiver. Accordingly, the processor may monitor for a capacitive change at  904 . If a receiver is not detected, the processor may continue monitoring. Alternately, if a receiver detected, the method may continue at  906 , in which the processor may initiate a verification process. The verification process may attempt to verify that capacitance change sensed is actually the result of the placement of an inductive power receiver on the inductive power transmitter. 
     The verification process may attempt to verify that the capacitance change sensed in the transmit coil is actually the result of the placement of an inductive power receiver on the inductive power transmitter. The verification process may begin at step  906  in which the inductive power transmitter may ping for a receiver over, for example, a wireless communication channel as described with respect to the method illustrated by  FIG. 4  or by periodically transmitting power and monitoring for a load to a transmit coil as described with respect to the method illustrated by  FIG. 5 . If, alternatively, the presence of the receiver is verified, transmit circuitry may be activated at  910 . 
       FIG. 10  depicts a flow chart illustrating example steps of a method of selectively activating transmit circuitry associated with an inductive power transmitter adapted to monitor for strain or tension changes within an alignment magnet within an inductive power transmitter resulting from attraction to an alignment magnet associated with an inductive power receiver. The method may begin at  1002  in which a processor associated with an inductive power transmitter may monitor or more strain sensors coupled to an alignment magnet within a transmitter. 
     In many examples, a receiver may include an alignment magnet that is positioned to align with a corresponding alignment magnet within the transmitter. When the receiver is positioned nearby the transmitter, the alignment magnets may attract one another. In some examples, a sensor may be positioned above or below the alignment magnet within the transmitter such that when the magnets attract, the sensor experiences tension if positioned below or compression if positioned above. In other examples, two or more sensors may be used. The sensors may be affixed or otherwise coupled to the magnet or the housing of the transmitter using any suitable means. 
     The processor may monitor for a change in the tension or compression of the sensor in the current at  1004 . If a change in the tension or compression of the sensor is not detected, the processor may continue monitoring. Alternately, if a change in the tension or compression of the sensor is detected, the method may continue at  1006 , in which the processor may initiate a verification process. The verification process may attempt to verify that for a change in the tension or compression of the sensor is actually the result of the placement of an inductive power receiver on the inductive power transmitter. The verification process may begin at step  1006  in which the inductive power transmitter may ping for a receiver over, for example, a wireless communication channel as described with respect to the method illustrated by  FIG. 4  or by periodically transmitting power and monitoring for a load to a transmit coil as described with respect to the method illustrated by  FIG. 5 . If, alternatively, the presence of the receiver is verified, transmit circuitry may be activated at  1010 . 
     In the present disclosure, the methods disclosed may be implemented as sets of instructions or software readable by a device. Further, it is understood that the specific order or hierarchy of steps in the methods disclosed are examples of sample approaches. In other embodiments, the specific order or hierarchy of steps in the method can be rearranged while remaining within the disclosed subject matter. The accompanying method claims present elements of the various steps in a sample order, and are not necessarily meant to be limited to the specific order or hierarchy presented. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20140603
Publication Date: 20170103
Grant Date: 20170103
Priority Date: 20140603
Inventors: Bossetti Chad A.
ALVES JEFFREY M.
GOLKO ALBERT J.
TERLIZZI JEFFREY J.
GRAHAM CHRISTOPHER S.
HERBST STEVEN G.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J17/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0042", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0042", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 57682451