Low-power ping transition to wireless power receiver mode

Abstract

To provide an electronic device that is selectively operable in a wireless power receiver mode for receiving power from a wireless power transmitter and a wireless power transmitter mode for transmitting power to an accessory.SOLUTION: A wireless power transfer coil; a rectifier coupled to the wireless power transfer coil and operable in a wireless power receiver mode to convert an AC voltage induced in the wireless power transfer coil by a wireless power transmitter to a DC voltage for use by an electronic device; An inverter operable to convert a DC voltage to an AC voltage that is applied to the wireless power transfer coil in a wireless power transmitter mode, and a controller and communication circuit that activates a wireless power receiver mode in response to detecting one or more object detection pings from the wireless power transmitter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 680,816, entitled "Detection and Coil Operation in Wireless Power Transfer," filed August 8, 2024, U.S. Provisional Application No. 63 / 802,717, entitled "Low Power Ping Transition to Wireless Power Receiver Mode," filed May 9, 2025, U.S. Provisional Application No. 63 / 802,722, entitled "Frequency Sweep to detect Attached Wireless Power Transmitter or Receiver," filed May 9, 2025, and U.S. Provisional Application No. 63 / 802,728, entitled "Ultra Low Power Object Detection," filed May 9, 2025, all of which are incorporated herein by reference in their entireties. [Background technology]

[0002] Wireless power transfer is used in a variety of electronic devices, such as smartphones, tablet computers, smart watches, wireless earphones, styluses, etc., which may employ wireless power transfer to facilitate charging of batteries within the devices and / or to power the devices during operation. Summary of the Invention

[0003] Wireless power transmission may use one or more techniques to detect whether a wireless power receiver is inductively coupled and ready for wireless power transmission operation.

[0004] An electronic device selectively operable in a wireless power receiver mode for receiving power from a wireless power transmitter and a wireless power transmitter mode for transmitting power to an accessory may include a wireless power transmission coil; a rectifier coupled to the wireless power transmission coil and operable, in the wireless power receiver mode, to convert an AC voltage induced in the wireless power transmission coil by the wireless power transmitter to a DC voltage for use by the electronic device; an inverter coupled to the wireless power transmission coil and operable, in the wireless power transmitter mode, to convert the DC voltage to an AC voltage applied to the wireless power transmission coil; and a controller and communications circuit that activates the wireless power receiver mode in response to detecting one or more object detection pings from the wireless power transmitter.

[0005] The controller and communications circuitry may further detect an object in proximity to the electronic device by transmitting a plurality of low power object detection pulses using the wireless power transmission coil and detecting responses to the low power object detection pulses associated with the object, the low power object detection pulses being generated by the controller and communications circuitry without the use of a rectifier or inverter, and in response to detecting the object, identify the object as at least one of a wireless power receiver and a wireless power transmitter by performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter, and in response to identifying the object as a wireless power receiver, activate a wireless power transmitter mode, and in response to identifying the object as a wireless power transmitter, activate a wireless power receiver mode.

[0006] The response to the low-power object detection pulse associated with the object may be a change in one or more electrical or magnetic parameters of a circuit including the wireless power transmission coil. The low-power object detection pulse may be generated by a low-power object detection pulse injection circuit separate from the inverter and coupled to the wireless power transmission coil. The low-power object detection pulse injection circuit may include a detection circuit responsive to changes in one or more electrical or magnetic parameters of the circuit including the wireless power transmission coil. The one or more frequency sweeps may be a continuous frequency sweep across a frequency range of interest. The one or more frequency sweeps may be a plurality of discrete frequencies across a frequency range of interest. Performing the one or more frequency sweeps to identify one or more resonant frequencies of the object may include driving the wireless power transmission coil with an inverter. Performing the one or more frequency sweeps to identify one or more resonant frequencies of the object may include driving the wireless power transmission coil with an auxiliary circuit.

[0007] The wireless power transmitter may be characterized by a first resonant frequency, the first resonant frequency being at least one of a frequency associated with a matching wireless power transmitter intended to operate with the electronic device or a frequency different from a resonant frequency of a wireless power receiver intended to operate with the electronic device. The wireless power receiver may be characterized by a second resonant frequency and a third resonant frequency, a valley may be located between the second resonant frequency and the third resonant frequency, the valley may be at a higher frequency than the first resonant frequency, and one or more of the second resonant frequency and the third resonant frequency and the valley may be at a frequency different from a frequency associated with a matching wireless power receiver intended to operate with the electronic device or a resonant frequency of a wireless power transmitter intended to operate with the electronic device.

[0008] The wireless power transmission coil may be a single coil. The rectifier and the inverter may be configured with the same switching element. At least one of activating the wireless power transmitter mode and activating the wireless power receiver mode may include loading additional firmware corresponding to the respective one of the modes. Activating the wireless power transmitter mode may include transmitting one or more object detection pings, wherein the interval between at least two of the one or more object detection pings is randomized.

[0009] A method performed by a wireless power transmission controller and communications circuit of an electronic device operable in a wireless power receiver mode for receiving power from a wireless power transmitter or in a wireless power transmitter mode for transmitting power to an accessory may include detecting one or more object detection pings from the wireless power transmitter and activating the wireless power receiver mode in response to detecting one or more object detection pings from the wireless power transmitter.

[0010] The method may further include detecting an object proximate to the electronic device, where detecting the object proximate to the electronic device includes transmitting a plurality of low power object detection pulses using a wireless power transmission coil of the electronic device and detecting a response to the low power object detection pulses associated with the object, where the low power object detection pulses may be generated by a controller and communications circuitry without using a rectifier or inverter of a wireless power transmission system of the electronic device; identifying the object as at least one of a wireless power receiver and a wireless power transmitter in response to detecting the object, where identifying the object as at least one of a wireless power receiver and a wireless power transmitter may include performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter; and activating a wireless power transmitter mode in response to identifying the object as a wireless power receiver and transmitting power to the accessory using wireless power transmission circuitry of the electronic device; and activating a wireless power receiver mode in response to identifying the object as a wireless power transmitter. The response to the low-power object detection pulse associated with the object may be a change in one or more electrical or magnetic parameters of a circuit including the wireless power transmission coil.

[0011] The wireless power transmitter may be characterized by a first resonant frequency, the first resonant frequency being at least one of a frequency associated with a matching wireless power transmitter intended to operate with the electronic device or a frequency different from a resonant frequency of a wireless power receiver intended to operate with the electronic device. The wireless power receiver may be characterized by a second resonant frequency and a third resonant frequency, a valley may be located between the second resonant frequency and the third resonant frequency, the valley may be at a higher frequency than the first resonant frequency, and one or more of the second resonant frequency and the third resonant frequency and the valley may be at a frequency different from a frequency associated with a matching wireless power receiver intended to operate with the electronic device or a resonant frequency of a wireless power transmitter intended to operate with the electronic device.

[0012] Activating the wireless power transmitter mode may include transmitting one or more object detection pings, wherein an interval between at least two of the one or more object detection pings is randomized.

[0013] A controller and communication circuit for a wireless power transmission system of an electronic device, wherein the electronic device is selectively operable in a wireless power receiver mode to receive power from a wireless power transmitter and in a wireless power transmitter mode to transmit power to an accessory, may be configured to detect one or more object detection pings from the wireless power transmitter and to activate the wireless power receiver mode in response to detecting one or more object detection pings from the wireless power transmitter.

[0014] The controller and communications circuitry may be further configured to: detect an object in proximity to the electronic device using the wireless power transmission coil of the electronic device to transmit a plurality of low power object detection pulses; and detect a response to the low power object detection pulses associated with the object, wherein the low power object detection pulses are generated by the controller and communications circuitry without using a rectifier or inverter of the wireless power transmission system of the electronic device; identify the object as at least one of a wireless power receiver and a wireless power transmitter by performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter; activate a wireless power transmitter mode in response to identifying the object as a wireless power receiver; and activate a wireless power receiver mode in response to identifying the object as a wireless power transmitter. [Brief explanation of the drawings]

[0015] [Figure 1] 1 shows a simplified block diagram of a wireless power transfer system.

[0016] [Figure 2A] 1 illustrates an electronic device capable of wirelessly transmitting power and a wireless power receiver capable of wirelessly receiving power. [Figure 2B] 1 illustrates an electronic device capable of wirelessly transmitting power and a wireless power receiver capable of wirelessly receiving power.

[0017] [Figure 3] 1 shows a flowchart of an operating technique for an electronic device capable of wirelessly transmitting power and a wireless power receiver capable of wirelessly receiving power.

[0018] [Figure 4]1 shows a flowchart of a first inductive triggering technique for a wireless power transmitter mode of an electronic device.

[0019] [Figure 5] 10 illustrates a timing sequence for a first inductive triggering technique for a wireless power transmitter mode of an electronic device.

[0020] [Figure 6] 1 shows a simplified diagram of a wireless power transmission system illustrating aspects related to a second inductive triggering technique of a wireless power transmitter mode of an electronic device.

[0021] [Figure 7] 10 illustrates a timing sequence for a second inductive triggering technique for a wireless power transmitter mode of an electronic device.

[0022] [Figure 8] 1 shows a flowchart of an inductive triggering technique for selecting a wireless power transmitter or a wireless power receiver mode in an electronic device.

[0023] [Figure 9] 1 shows a simplified schematic diagram of an ultra-low power object detection injection and detection circuit and a low power ping detection circuit for an electronic device.

[0024] [Figure 10] 1 illustrates a timing sequence of a detection and identification technique for a wireless power receiver in an electronic device.

[0025] [Figure 11] 1 shows a series of identification frequency response curves for detection and identification of a wireless power receiver or a wireless power transmitter by an electronic device.

[0026] [Figure 12A] 10 illustrates an alternative timing sequence for detecting and identifying a wireless power receiver or a wireless power transmitter in an electronic device. [Figure 12B] 10 illustrates an alternative timing sequence for detecting and identifying a wireless power receiver or a wireless power transmitter in an electronic device. [Figure 12C] 10 illustrates an alternative timing sequence for detecting and identifying a wireless power receiver or a wireless power transmitter in an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0027] In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings in this disclosure represent structures and devices in block diagram form in order to avoid obscuring the present invention. In the interest of clarity, not all features of an actual implementation are described herein. Moreover, the language used herein has been chosen solely for purposes of readability and explanation, and not to limit or restrict the disclosed subject matter. Rather, the appended claims are intended for such purposes. Any trademarks referenced herein are intended to identify examples only and are the property of their respective owners.

[0028] Various embodiments of the disclosed concepts are illustrated in the accompanying drawings, by way of example, and not by way of limitation, wherein like reference numerals indicate like elements. For simplicity and clarity of illustration, where considered appropriate, reference numerals have been repeated among different drawings to indicate corresponding and / or similar elements. Additionally, numerous specific details have been described to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the relevant associated functionality being described. References to "an," "one," or "another" embodiment in the present disclosure do not necessarily refer to the same or different embodiments, but rather to at least one. A given drawing may be used to illustrate multiple embodiments or multiple species of the present disclosure, and not all elements in the drawing may be required for a given embodiment or species. A reference numeral, if provided in a given drawing, may refer to the same element throughout the drawings, but may not be repeated in all drawings. The drawings are not to scale unless otherwise indicated and the proportions of certain parts may be exaggerated to better show the details and features of the present disclosure.

[0029] FIG. 1 shows a simplified block diagram of a wireless power transfer system 100. The wireless power transfer system includes a power transmitter (PTx) 110 that transmits power wirelessly to a power receiver (PRx) 120, such as via inductive coupling 130. The power transmitter 110 can receive input power, which is converted by an inverter 114 to an AC voltage having specific voltage and frequency characteristics. The inverter 114 can be controlled by a controller / communications module 116, which operates as described further below. In various embodiments, the inverter controller and communications module can be implemented in a common system, such as a system based on a microprocessor, microcontroller, or the like. In other embodiments, the inverter controller can be implemented by a separate controller module and communications module having means for communication therebetween. The inverter 114 can be configured using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc., fabricated using silicon, silicon carbide, or gallium nitride devices).

[0030] The inverter 114 can deliver the generated AC voltage to the transmitter coil 112. In addition to the wireless coil that enables magnetic coupling to the receiver, the transmitter coil block 112 shown in FIG. 1 may include tuning circuit components, such as additional inductors and capacitors, that facilitate operation of the transmitter under different conditions, such as different degrees of magnetic coupling to the receiver or different operating frequencies. The wireless coil itself can be configured in a variety of different ways. In some embodiments, the wireless coil can be formed as a winding of wire wound around a suitable bobbin. In other embodiments, the wireless coil can be formed as a trace on a printed circuit board. Other arrangements are possible and can be used in conjunction with the various embodiments described herein. The wireless transmitter coil can also include a core of magnetically permeable material (e.g., ferrite) configured to affect the magnetic flux pattern of the coil in a manner suitable for a particular application. The teachings herein can be applied in conjunction with any of a wide variety of transmitter coil arrangements suitable for a given application.

[0031] The PTx controller / communications module 116 can monitor the power transmit coil and use information derived therefrom to control the inverter 114 as appropriate for a given situation. For example, the controller / communications module can be configured to operate the inverter 114 at a given frequency or output voltage depending on a particular application. In some embodiments, the controller / communications module can be configured to receive information from the PRx device and control the inverter 114 accordingly. This information can be received via the power transmit coil (i.e., in-band communication) or via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communications module 116 can detect and decode signals (such as voltage, frequency, or load variations) imposed on the magnetic link by the PRx to receive the information, and can instruct the inverter to modulate the delivered power by manipulating various parameters (such as voltage, frequency, etc.) of the generated voltage to transmit the information to the PRx. In some embodiments, the controller / communications module may be configured to communicate data to the PRx employing frequency shift keying (FSK) communications, in which the frequency of the inverter signal is modulated. The controller / communications module 116 may be configured to detect amplitude shift keying (ASK) communications or load modulation-based communications from the PRx. In either case, the controller / communications module 126 may be configured to vary the current drawn at the receiver side to manipulate the waveform seen on the Tx coil to deliver information from the PRx to the PTx. For out-of-band communications, additional modules may be provided to enable communication between the PTx and PRx, such as WiFi, Bluetooth, or other wireless links, or any other suitable communications channel.

[0032] As noted above, controller / communications module 116 may be, for example, a single module located on a single integrated circuit, or may be comprised of multiple modules / devices located on different integrated circuits, or a combination of integrated circuits and discrete circuits having both analog and digital components. The teachings herein are not limited to any particular arrangement of controller / communications circuitry.

[0033] The PTx device 110 may optionally include other systems and components, such as a separate communications module 118. In some embodiments, the communications module 118 can communicate with a corresponding module tag in the PTx via the power transfer coil. In other embodiments, the communications module 118 can communicate with a corresponding module using a separate physical channel 138.

[0034] As described above, the wireless power transmission system also includes a wireless power receiver (PRx) 120. The wireless power receiver may include a receiver coil 122 that may be magnetically coupled 130 to the transmitter coil 112. Similar to the transmitter coil 112 described above, the receiver coil block 122 shown in FIG. 1 may include tuning circuit components, such as additional inductors and capacitors, to facilitate operation of the transmitter under different conditions, such as different degrees of magnetic coupling to the receiver or different operating frequencies. The wireless coil itself may be configured in a variety of different ways. In some embodiments, the wireless coil may be formed as a winding of wire wound around a suitable bobbin. In other embodiments, the wireless coil may be formed as a trace on a printed circuit board. Other arrangements are possible and may be used in conjunction with the various embodiments described herein. The wireless receiver coil may also include a core of magnetically permeable material (e.g., ferrite) configured to affect the magnetic flux pattern of the coil in a manner suitable for a particular application. The teachings herein may be applied in conjunction with any of a wide variety of receiver coil arrangements suitable for a given application.

[0035] The receiver coil 122 outputs an AC voltage induced therein by magnetic induction through the transmitter coil 112. This output AC voltage may be provided to a rectifier 124, which provides DC output power to one or more loads associated with the PRx device. The rectifier 124 may be controlled by a controller / communications module 126, which operates as described further below. In various embodiments, the rectifier controller and communications module may be implemented in a common system, such as a microprocessor-, microcontroller-, or other based system. In other embodiments, the rectifier controller may be implemented by a separate controller module and communications module having means for communication therebetween. The rectifier 124 may be configured using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc., fabricated using silicon, silicon carbide, or gallium nitride devices).

[0036] The PTx controller / communications module 126 can monitor the receiver coil and use information derived therefrom to appropriately control the rectifier 124 depending on given circumstances. For example, the controller / communications module can be configured to operate the rectifier 124 to provide a given output voltage depending on a particular application. In some embodiments, the controller / communications module can be configured to transmit information to the PTx device to effectively control the power delivered to the receiver. This information can be received and transmitted via the power transmit coil (i.e., in-band communication) or can be transmitted via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communications module 126 can transmit information to the PTx, for example, by modulating the load current or other electrical parameters of the received power. In some embodiments, the controller / communications module 126 can be configured to detect and decode signals (such as voltage, frequency, or load variations) applied by the PTx to the magnetic link in order to receive information from the PTx. In some embodiments, the controller / communications module 126 may be configured to receive frequency shift keying (FSK) communications, in which the frequency of the inverter signal is modulated to communicate data to the PRx. The controller / communications module 126 may be configured to generate amplitude shift keying (ASK) communications or load modulation-based communications from the PRx. In either case, the controller / communications module 126 may be configured to vary the current drawn at the receiver to manipulate the waveform seen on the Tx coil to deliver information from the PRx to the PTx. For out-of-band communications, additional modules may be provided to enable communication between the PTx and PRx, such as WiFi, Bluetooth, or other wireless links, or any other suitable communications channel.

[0037] As mentioned above, the controller / communications module 126 may be, for example, a single module provided on a single integrated circuit, or may be comprised of multiple modules / devices provided on different integrated circuits, or a combination of integrated circuits and discrete circuits having both analog and digital components. The teachings herein are not limited to any particular arrangement of controller / communications circuitry. The PRx device 120 may optionally include other systems and components, such as a communications (“comms”) module 128. In some embodiments, the communications module 128 can communicate with a corresponding module in the PTx via a power transfer coil. In other embodiments, the communications module 128 can communicate with a corresponding module or tag using a separate physical channel 138.

[0038] Many variations and extensions of the wireless power transmission system 100 described above are possible, and the teachings below are applicable to any such variations and extensions.

[0039] 2A-2B illustrate an electronic device 220 (also referred to herein as device 220) capable of wirelessly receiving or transmitting power, and a wireless power receiver (PRx) 230 capable of wirelessly receiving (and optionally transmitting) power. In some embodiments, device 220 may be a smartphone, but may also be other types of electronic devices, such as a tablet computer, notebook computer, etc. PRx 230 may be a smartphone, but may also be other types of electronic devices, such as a tablet computer, notebook computer, etc. PRx 230 also includes an accessory device for use with device 220 or other electronic devices. In some embodiments, PRx 230 may be an accessory for electronic device 220, such as a smartwatch, wireless earphone charging case, stylus, etc., paired in some manner with the electronic device. (Such pairing may, but need not, use Bluetooth or other protocols.) To facilitate wireless power transmission, PRx 230 may include wireless power receiver circuitry, such as that described above with respect to FIG. 1. For simplicity, only a wireless power receiving coil 232 is shown in FIGS. 2A-2B. Similarly, device 220 may include a wireless power receiver circuit as described above, as well as a wireless power transmitter circuit. In some cases, the wireless power receiver circuit and the wireless power transmitter circuit of device 220 may share one or more components. For example, a single wireless power transmission coil 222 may be used both as a wireless power receiving coil when device 220 is operating as a wireless power receiver to receive power from a wireless power transmitter (not shown), and as a wireless power transmitting coil when device 220 is operating as a wireless power transmitter, as described in more detail herein. Other components of the wireless power transmission circuit of device 220 may also be used in both the wireless power receiver mode and the wireless power transmitter mode.For example, common control and communication circuitry may be used in both operating modes, and a common switching device may be used as an inverter in wireless power transmitter mode and as a rectifier in wireless power receiver mode.

[0040] FIG. 2A shows the electronic device 220 and the PRx 230 separated from one another in both a plan view and a cross-sectional view. FIG. 2B shows the electronic device 220 and the PRx 230 overlapping so as to be positioned to facilitate wireless power transfer from the electronic device 220 to the PRx 230. As shown, this overlap allows for alignment of the respective wireless power transmission coils to facilitate wireless power transfer. Finally, as also shown in FIG. 2B , an external power source 227 may also be connected to the electronic device 220. When such an external power source is connected, power from the external power source 227 may be delivered to the PRx 230 by the electronic device 220 operating in wireless power transmitter mode. Finally, although the description herein refers to the electronic device as being capable of operating as a wireless power transmitter or a wireless power receiver and the PRx 230 as being capable of operating as a receiver, the reverse is also possible. For example, the PRx 230 may be capable of operating as a wireless power receiver or a wireless power transmitter, and the electronic device 230 may either be capable of bidirectional wireless power transfer or be a receiver only. Thus, the principles described herein are equally applicable to any type of electronic device or PRx and should not be limited to any particular examples given herein.

[0041] FIG. 3 shows a flowchart 300 of an operating technique for an electronic device capable of wirelessly receiving or transmitting power and a PRx capable of wirelessly receiving power. The process may be performed by any suitable control circuitry and / or processor of the electronic device. This may include, but is not necessarily limited to, the controller and communication circuitry of such a device's wireless power transmission system, as described above. For purposes of the following description, various actions or decisions will be described as being performed by a device (e.g., electronic device 220), with the understanding that it is the device's appropriate control circuitry and / or processor that is used to perform such actions or decisions. Furthermore, while various actions and decisions are described in a particular order, in some cases, various actions or decisions may be performed in a different order, simultaneously, or potentially even omitted. Therefore, the following description should not be construed as implying any particular order unless such order is expressly or implicitly required by the nature of the particular actions or decisions.

[0042] The process may begin at start block 341. Then, in block 342, the device may determine whether a “wireless power transmission (WPTx) mode” is available. As used herein, “wireless power transmission mode” may be considered synonymous with a wireless power transmitter mode of operation in which the device operates as a wireless power transmitter to deliver power to a PRx device. Such power may, but need not, be used by the PRx device to charge its own battery. In either case, in block 342, various conditions or signals may be used to indicate that the wireless power transmission mode is available. For example, a device being plugged into an external power source (as described above with respect to FIG. 2B) may be one such indication. If external power is available, the device has sufficient power to deliver power to the PRx and does not need to receive power wirelessly for its own purposes. Additionally or alternatively, the device's battery charge status may be used to indicate whether the wireless power transmission mode is available. That is, if the device's battery charge is above a certain threshold, it may be possible to deliver power to the PRx device. Conversely, if the device's battery charge falls below a certain threshold (which may be the same or a different threshold), the device may not have sufficient power reserves to deliver power to the PRx device. Additionally or alternatively, explicit user actions can be used alone or in conjunction with other conditions or signals to indicate the availability of the wireless power transmission mode. Device orientation can be one such user action. For example, a smartphone positioned face-down can allow the user to place the PRx device on the back of the smartphone, allowing the respective wireless power transmission coils to couple. Other orientations may be appropriate for different device types. In some applications, a physical switch or user interface affordance can be provided to allow the user to indicate that the wireless power transmission mode should be used.Each of the aforementioned signals, as well as other signals, may be used separately or in various combinations to indicate that a wireless power transmission mode is available.

[0043] If it is determined in block 342 that a wireless power transmission mode is not available, it may be determined in block 344 whether a wireless power transmitter device (PTx) is detected. If not, the process may return to start block 341. Otherwise, if a wireless power transmitter is detected, the electronic device 220 may receive power from the wireless power transmitter device in block 350. It may be determined in block 351 whether charging of the internal battery of the electronic device 220 is complete. If not, receiving wireless power from the wireless power transmitter may continue. If so, the process may end (block 349) and optionally return to start block 341. Additionally or alternatively, receiving wireless power from the wireless power transmitter in block 350 need not be limited to charging the device's internal battery. For example, the received wireless power may be used to power the electronic device 220; in such a case, it may be desirable to continue receiving wireless power from the wireless power transmitter indefinitely as long as the electronic device 220 is consuming power.

[0044] Returning to block 341, if it is determined that a wireless power transmission mode is available, the device may determine in block 343 whether a PRx is detected. Such a PRx is capable of receiving wireless power from a device operating in wireless power transmitter mode, but such a PRx may also be capable of operating as a wireless power transmitter itself, as described above. If a PRx is not detected in block 343, it may be determined in block 344 whether a wireless power transmitter is present, as described above. Otherwise, if a wireless power receiving PRx is detected in block 343, it may be determined in block 345 whether sufficient power is available to deliver power to the PRx device. This may be determined by whether an external power device is connected, the state of charge of the device's own battery, etc. Such a determination may be made as described above with respect to block 342, and may either be performed again if used to indicate availability of a wireless power transmission mode, performed independently, or omitted entirely at this stage in favor of a similar determination made in conjunction with block 342. In the illustrated example, if sufficient power is not available, the technique ends (block 349) and may optionally return to the start block 341. Otherwise, the technique may proceed to PRx authentication in block 346.

[0045] In block 345, PRx authentication may be performed to verify that the device is suitable to wirelessly receive power from a device operating in wireless power transfer mode. Various authentication schemes and communication modes may be used depending on the requirements of a particular system. In some applications, authentication may be omitted. In either case, authentication may rely on an exchange of data, i.e., communications, between the PRx and the device, which are used by the device to identify the PRx and verify its suitability to wirelessly power the device, and optionally even determine appropriate wireless power transfer parameters (e.g., power level, operating frequency, etc.) based on the authentication. Communication between PRx devices may be in-band communication, achieved by modulation of one or more characteristics of the wireless power transfer link (e.g., voltage or current amplitude, frequency, etc.), or out-of-band communication using an alternative communication channel, such as Bluetooth, Wi-Fi, or NFC (near field communication). In some cases, the device may authenticate the PRx using its own resources. In other cases, the device may communicate with a second device over a network to perform or assist in authentication. In either case, if the PRx is not authenticated, the process may end (block 349), optionally returning to start block 341. Otherwise, if the PRx device is authenticated, wireless power transfer to the PRx may begin (block 347).

[0046] In block 347, the device may transfer power to the PRx / accessory. In block 348, it may be determined whether charging of the PRx's internal battery is complete. If not, wireless power transfer may continue. If so, the process may end (block 349) or, optionally, return to start block 341. Additionally or alternatively, the wireless power transfer from the device to the PRx in block 347 need not be limited to charging the device's internal battery. For example, the received wireless power may also be used to power an electronic device, and in such a case, it may be desirable to continue receiving wireless power from the wireless power transmitter indefinitely or to discontinue such wireless power transfer based on some other condition, such as the availability of an external power connection or a sufficient battery level in the electronic device.

[0047] Initiation of the wireless power transmission mode described above with reference to Figure 3 can be based on various triggering techniques. In some cases, such a mode may be triggered by inductive detection and at least some in-band communication between the device and the PRx. Such configurations are described in more detail below with respect to Figures 4-7.

[0048] FIG. 4 shows a flowchart 500 of a first inductive triggering technique for a wireless power transmitter mode of an electronic device (e.g., electronic device 220) capable of wirelessly receiving or transmitting power. As noted above, the flowchart shows example steps in a particular order, but certain steps can be omitted, other steps can be added, and / or the order of at least some steps can be changed as appropriate for a given embodiment. In this case, triggering of the wireless power transmission mode of device 220 is based on inductive detection of a PRx using the device's wireless power transmission circuitry to detect corresponding circuitry in the PRx. Otherwise, flowchart 500 can be considered a subset, simplification, or variation of flowchart 300 described above with respect to FIG. 3. As noted above, the techniques shown in the flowchart can be performed by the device, such as by the device's wireless power transmission controller and communication circuitry and / or any other control circuitry and / or processor of such device, in conjunction with or in place of the process illustrated by the flowchart of FIG. 3.

[0049] Beginning at start block 561, the process may proceed to block 562, where it is determined whether a PRx device is inductively detected. This inductive detection may be performed according to a technique defined by a standard, such as the Qi standard mentioned above, or according to a proprietary technique. Generally, such techniques include periodically measuring one or more electrical or magnetic properties of the device's magnetic circuit, such as the quality factor Q of the device's wireless power transmission coil. This Q factor differs depending on whether the measurement is performed "outdoors," when no PRx is present, or when a PRx device is present. This difference can be used to determine whether a PRx is present. Furthermore, the combined Q may differ depending on whether the PRx device's wireless power transmission coil is open-circuited or short-circuited, as described in more detail below. Because there are many electrical and magnetic properties that are affected by the presence or absence (i.e., proximity) of a wireless power receiver, other parameters, such as resonant frequency, may be used instead or in addition.

[0050] If a PRx device is not inductively detected, the process returns to start block 561, where it may periodically check for the presence of a PRx (or potentially a wireless power transmitter, as described in more detail below). Otherwise, if a potential PRx is detected in block 562, the device may send a wireless power receiver query to the PRx in block 563. That is, the device may transmit an in-band signal by modulating the signal delivered to the wireless power transmission coil. This query may follow a standard, such as the Qi standard mentioned above, or may follow a proprietary protocol. In either case, the intent is to establish communication with the potential PRx by sending a message that causes the PRx to respond in a known manner that allows its identification. Thus, in block 564, the device may listen for a wireless power receiver response. This response may follow expectations corresponding to the standard and / or proprietary protocol in use. In some embodiments, the device may be configured to attempt to establish communication according to multiple protocols, such as one or more standardized protocols and / or one or more proprietary protocols, to enable interoperability with a variety of wireless power receiver devices.

[0051] It may be desirable to have a time limit on the amount of time the device spends waiting for a response from the PRx. Thus, in block 565, the device may determine whether a timeout interval has elapsed. If the timeout in block 565 has expired, the device may infer that the potential PRx detected in block 562 is actually a wireless power transmitter. Thus, in block 566, the device may send an expected PRx response to the (inferred) wireless power transmitter. As noted above, this response may follow one or more standard protocols, such as those defined by the Qi standard, and / or may follow one or more proprietary protocols. In either case, this may result in the device operating as a wireless power receiver and, therefore, receiving power from such a wireless power transmitter (block 567). The timeout interval may be selected to enable error-free establishment of communication and power transfer with a wireless power transmitter operating according to a standard or proprietary scheme. For example, according to at least some embodiments of the Qi standard, a timeout interval of 19 ms may enable the device to establish communication with a wireless power transmitter operating according to such a Qi standard. That is, if the PRx begins transmitting a wireless power receiver response to the device by 19 ms after the initial inductive detection of block 562, the necessary negotiation between the device and PRx can continue with the device operating in wireless power transmitter mode. Otherwise, if a wireless power receiver response does not begin to be received before the timeout interval (e.g., 19 ms), the device can transition to wireless power receiver mode and establish communication with the wireless power transmitter before the standardized timeout / communication failure interval expected by the wireless power transmitter. Further aspects of the timing of such signals are described in more detail below with respect to FIG. 5.

[0052] Otherwise, if the device determines in block 565 that the timeout has not expired, then in block 568 the device may determine whether an expected wireless power receiver response has been received. As described above, such a response may be defined by either a standard or proprietary communication scheme, such as a ping or other message according to the Qi protocol, or a modulation of the wireless power transmission signal by the PRx that is understood by the device as identifying the PRx device. In either case, if an appropriate response is received, the device may operate in wireless power transmission mode and send power to the PRx (block 569). Otherwise, the device may continue to listen for a response until the timeout expires, causing the device to operate in wireless power receiver mode as described above.

[0053] FIG. 5 illustrates a timing sequence 600 for a first inductive triggering technique for a wireless power transmitter mode of an electronic device (e.g., electronic device 220) capable of wirelessly receiving or transmitting power. The timing sequence includes a primary device sequence and a secondary PRx sequence. The timing sequence 600 illustrates a series of actions or events 671-680b occurring over specific time intervals, indicated by a capital "T" followed by an odd number (e.g., T1, T3, ..., T15), with each timer interval having a corresponding start or end time indicated by a lowercase "t" followed by an even number (e.g., t0, t2, ..., t14). Additionally, PRx times and time intervals are indicated with a "-1" suffix. There may be an initialization period 671 during interval T1, initiated by the device, beginning at time t0 and ending at time t2.

[0054] Following initialization, there may be a transmission intended to inquire whether the detected device is a wireless power receiver. In FIG. 5, this is shown as frequency-shift keying (FSK) transmission 672 because, according to the Qi standard (and in at least some proprietary wireless power transmission schemes), wireless power transmitters communicate in-band with wireless power receivers via FSK communication. That is, the wireless power transmitter (in this case, a device operating in wireless power transmitter mode) communicates with the receiver by modulating the frequency of a signal applied to the wireless power transmit coil and detectable at the wireless power receive coil to encode the message to be transmitted. However, in some embodiments, any suitable query of the detected potential PRx may be used. As shown in FIG. 5, the FSK transmission 672 occurs during interval T3, which begins at time t2 and ends at time t4. However, it is not necessary for the FSK transmission 672 or other equivalent receiver query to occur immediately after initialization, as other intervening activity may be present. In either case, following the FSK transmission 672, the device may enter an ASK listen period 673, which may occur during a period T5, beginning at time t4 (i.e., at the end of the FSK transmission 672 or other equivalent query) and ending at time t6, which may be the timeout interval described above. Again, this is called ASK listen because, according to the Qi standard and at least some proprietary wireless power transmission schemes, the wireless power receiver communicates in-band with the wireless power transmitter by amplitude shift keying (ASK), in which the magnitude of the power or current drawn by the wireless power receiver is modulated to encode information to be transmitted from the wireless power receiver to the wireless power transmitter.

[0055] At time t6, corresponding to the timeout period mentioned above, device operation branches depending on whether the device receives an appropriate wireless power receiver response from potential PRx. If no response is received, the upper branch is followed, and the device operates in a wireless power receiver mode initiated by engaging in an ASK transmission 674. Again, this is referred to as an ASK transmission because at least some standard and proprietary wireless power transmission schemes allow the wireless power receiver to engage in in-band communication with the wireless power transmitter via amplitude shift keying. However, other appropriate wireless power receiver-initiated communication can be used depending on the wireless power transmission scheme used. This communication can occur during interval T7, which begins at time t6 (i.e., the expiration of the timeout interval) and continues until time t8. Then, during interval T9, which begins at time t8 and continues until time t10, the device can enter negotiation 675, during which a wireless power transmission agreement can be negotiated and agreed upon. Thereafter, starting at time t10, during interval T11, the device can wirelessly receive power from the wireless power transmitter. As described, this reception of wireless power transmission can continue until the device's battery is fully charged, or even thereafter if the device is powering other systems from the received wireless power.

[0056] Otherwise, if an appropriate wireless power receiver response is received by the device from PRx, the device can operate in the wireless power transmitter mode shown in the lower branch of the device portion of FIG. 5. That is, negotiation 679a may occur during interval T13, beginning at or before time t6 and ending at time t12. The device can then send power 680a during interval T15, beginning at time t12 and continuing until time t14, which may be associated with PRx's battery being fully charged, PRx being removed from proximity with the device, or PRx otherwise no longer needing to receive wireless power from the device. These operations may also correspond to PRx's operations shown in the lower PRx path of timing sequence 600.

[0057] More specifically, PRx may begin with initialization 677 during interval T3-1, which begins at time t0-1 and ends at time t4-1. The exact timing of this initialization interval relative to PRx device operation is not critical, but it is expected to occur and complete early enough for PRx to receive the above-described FSK transmission 672, which prompts an ASK transmission 678 by PRx back to the device, which occurs during interval T5-1, which begins at time t4-1 and is shown to end at or before time t6, i.e., the timeout described above. As noted above, this communication is described as an ASK communication because it is used in at least some standard and proprietary wireless power transfer and band communication schemes, although other communication modes may be used if desired. Otherwise, the exact timing of ASK transmission 678 (or other equivalent communication) is not critical, other than that the message must be transmitted long enough for the device to detect and continue operation in wireless power transmitter mode, and then, if not, revert to wireless power receiver mode as described above. Thus, if a partial communication is received to allow the device to enter wireless power transmitter mode and establish wireless power transmission to PRx, either the ASK transmit 678 communication may be completed before timeout T6, or the device may extend the ASK listen 673 interval. In either case, starting at time t6, PRx may engage in negotiation 679b, which corresponds to negotiation 679a described above with respect to the device. These occur during the same interval T13 described above. Once the negotiation is complete, PRx may perform power receive 680b during interval T15, which corresponds to power transmit 680a described above and also occurs during the same interval.

[0058] The timing described above is merely an example, and in some cases, the basic principles described may be implemented with slightly different timing. It may be desirable to select the timing with several objectives in mind, such as allowing the device to return to wireless power receiver mode before the wireless power transmitter determines that a communication failure has occurred, and / or allowing the device to enter wireless power transmission mode and establish wireless power transmission with the PRx as quickly as possible to provide a better user experience. Otherwise, the specific timing requirements may be determined by the particular wireless power transmission scheme employed, and potentially include any in-band communication timing associated with such wireless power transmission scheme, whether they are defined by a standard (such as the Qi standard) or by one or more proprietary schemes.

[0059] A first inductive triggering scheme for a device's wireless power transmitter mode was described above with reference to Figures 4 and 5. This first inductive triggering scheme uses specific timing of communications sent and received by the device to enable the device to infer whether it should enter wireless power transmitter mode and deliver power to the PRx, or enter wireless power receiver mode to receive power from the wireless power transmitter. Figures 6 and 7 illustrate a second inductive triggering scheme that can be used in a similar or alternative manner. This alternative can be considered a "handshake" alternative in that it relies on special signaling that does not interfere with, but is not necessarily defined by, the standardized timing configuration described above.

[0060] 6 shows a simplified diagram 700 of a wireless power transmission system illustrating aspects related to a second inductive triggering technique of a wireless power transmitter mode of an electronic device (e.g., electronic device 220) capable of wirelessly receiving or transmitting power. In the simplified schematic, the wireless power transmitter, i.e., device, is represented by an inverter 714 and a wireless power transmit coil 712. Other components, such as controller and communication circuitry, wireless power receiver circuitry, and omitted wireless power transmit circuitry, are omitted for simplicity but can also be included as described above. The remaining components of simplified diagram 700 are a simplified diagram of a PRx, represented by a wireless power receive coil 722 and a rectifier 724. Other components, such as controller and communication circuitry, additional wireless power receiver circuitry, and the like, are omitted for simplicity but can also be included as described above.

[0061] The PRx circuit also includes switches 782a and 782b, as well as a rectifier short-circuit control and switch node voltage detection circuit 781. The latter may be part of the PRx circuit as described above and may be constructed using any suitable combination of analog, digital, and / or programmable circuitry and / or logic operating as described in more detail below. The rectifier short-circuit control and switch node voltage detection circuit 781 may monitor the voltage at the switch node of the rectifier 724, represented by points A and B, to detect whether the device's inverter 714 is operating. The rectifier short-circuit control and switch node voltage detection circuit 781 may also control switches 782a and 782b to selectively short-circuit (or open-circuit) the PRx's wireless power receive coil 722 to alter the electrical or magnetic circuit characteristics visible to the device via its coupling to the wireless power transmit coil 712. As described below with reference to FIG. 7 , this configuration and its controlled operation may enable inductive detection and triggering of a wireless power transmitter mode in the device when a suitable PRx is brought within range of the device.

[0062] 7 illustrates a timing sequence 800 for a second inductive triggering technique for a wireless power transmitter mode of an electronic device (e.g., electronic device 220) capable of wirelessly receiving or transmitting power. The left side of FIG. 7 illustrates operations that may be performed by the device, e.g., by wireless power transfer control and communication circuitry as described above. The right side of FIG. 7 illustrates operations that may be performed by a PRx, e.g., by wireless power transfer control and communication circuitry as described above. Corresponding operations are labeled with reference numbers ending in "a" for the device / wireless power transmitter and "b" for the PRx device.

[0063] Starting at block 891a, the device can periodically send “low power pings” to detect when a potential wireless power receiver (PRx) is in proximity. Such low power pings can follow a standardized wireless power transmission protocol, such as the Qi standard described above, or can follow a proprietary wireless power transmission protocol. By way of example, a low power ping is an electrical impulse provided to the wireless power transmission ping at a power lower than the typical voltage and / or wattage levels used for wireless power transmission. Once a potential PRx is detected, in block 892 the device can temporarily enable an inverter for a short period of time, e.g., on the order of tens of milliseconds, thereby delivering a small amount of power to the potential PRx and performing the operations described below even if the device has a dead battery with other shortfalls in internal power. After this short period, the device can stop inverter operation and measure one or more electrical or magnetic characteristics of the circuit, such as quality factor (Q), resonant frequency, inductance, etc., which are affected in known ways based on the presence of a PRx and can be further used to identify the PRx or obtain other information about the PRx and / or the wireless power link, as described further below.

[0064] In response to the low power ping 891a and / or brief operation of the device's inverter as described above, PRx may wake up (block 891b) and detect that the inverter has stopped (block 893b). For example, the control circuitry of PRx may include the rectifier short-circuit control and switch node voltage detection circuit 781, as described above with reference to FIG. 6. In response to the device deactivating its inverter, PRx may short-circuit its wireless power receiving coil (block 894b), for example, by closing switches 782a and 782b, as described above with reference to FIG. 6, also under the direction of the rectifier short-circuit control and switch node voltage detection circuit 781. This short-circuiting of PRx's wireless power receiving coil may be performed in block 894a by PRx determining the quality factor Q, resonant frequency f res , and / or other suitable electrical or magnetic parameters of the wireless power transmission circuit. By comparing the measured quality factor Q and / or other parameters from block 893a with the corresponding measurements made in block 894a, the device can detect (at block 894b) that a PRx has shorted its wireless power receiving coil and can therefore infer that a potential PRx is present and can take further action to identify or characterize such a PRx device.

[0065] More specifically, operations 895a and 896a may be repeated multiple times. Operation 895a includes starting the inverter and stopping it again after a short period of time. By way of example, this time may be on the order of tens of milliseconds, as described above. This starting and stopping of the inverter may have at least two functions. One is to provide signals and associated timing for communication with the potential PRx, which may be detected by voltage fluctuations at the rectifier switch node, as described above. Another purpose is to provide a small amount of power transfer that may be used to power the PRx's wireless power receiving circuitry, even if the PRx's own battery or other internal power source does not have enough power to do so. After each inverter start / stop cycle, the device may measure a quality factor Q and / or other parameters to detect individual shorts or opens in the PRx wireless power receiving coil via the PRx device's control circuitry, which may be used to encode identification information, as described below.

[0066] Corresponding to device operations 895a and 896a, the PRx can perform operations 895b and 896b, which can also be repeated multiple times. In operation 895b, the PRx device (using its controller circuitry) can detect the stop of inverter operation and, accordingly, in operation 896b, either short-circuit its wireless power receiving coil (e.g., by closing switches 782a and 782b) or not short-circuit the coil (e.g., by opening switches 782a and 782b). This allows the device to detect different quality factor Q and / or other parameter values ​​in operation 896a. As a result, the PRx can communicate data, such as digitally encoded data using 1s and 0s corresponding to whether the PRx shorts its wireless power receiving coil depending on the inverter start / stop operation performed by the device. Thus, each start / stop cycle can allow (for example) a single bit of data to be communicated from the PRx to the device. If the cycle is repeated (for example) 32 times, 32 bits of data can be transmitted. This may include a digital identifier of the PRx, allowing the device to determine whether the PRx is a device that can properly provide wireless power by activating a wireless power transmitter mode of operation of the device (operation 897a). This exchange of information from the PRx to the device by selectively shorting the PRx wireless power transmission coil may be thought of as a "handshake."

[0067] In some cases, operation 897a may include further verification or authentication of the PRx device before initiating wireless power transfer. For example, some wireless power receivers may be able to communicate with the device over other channels, such as Bluetooth, WiFi, or NFC. In some cases, this auxiliary channel may also be used for authentication of the PRx, either alone or in conjunction with a “handshake.” That is, the PRx may communicate its identification information over one of the other channels, and such identification information may be used by the device to authenticate the wireless power receiver, either independently of or in combination with the handshake data. In either case, if authentication is successful, wireless power transfer may be initiated in operation 897a; otherwise, the device may return to the initiation of operations shown in FIG. 7 , e.g., periodic low-power pings to detect the presence of the PRx. Correspondingly, if authentication is successful, the PRx device may initiate wireless power transfer (operation 897b), and the resulting initiation of wireless power transfer may be completed according to either a standard protocol or a proprietary protocol, as described elsewhere herein.

[0068] FIG. 8 shows a flowchart of an inductive triggering technique 801 for selecting a wireless power transmitter mode or a wireless power receiver mode in an electronic device capable of operating as either a wireless power transmitter or a wireless power transmitter, as described above. In some applications, the electronic device may have firmware, such as firmware stored in and / or executed by control and communication circuitry, as described above. In some cases, such firmware may be capable of operating the wireless power transmission circuitry to operate both as a wireless power receiver and as a wireless power transmitter, in which case the triggering technique 801 of FIG. 8 may be a mode selection of the combined firmware. In other applications, there may be separate firmware modules associated with wireless power transmitter operation and wireless power receiver operation, in which case mode selection may also include loading the appropriate firmware once the electronic device (e.g., operating via its wireless power transmission system control and communication circuitry) determines the desired mode of operation. In either case, the technique may begin at block 841, where the electronic device is operating in a hybrid mode, which may enable the device to detect when a wireless power receiver or a wireless power transmitter is in proximity to the electronic device. When a wireless power receiver is brought into proximity, the electronic device can operate in a wireless power transmitter mode. Alternatively, when a wireless power transmitter is brought into proximity, the electronic device can operate in a wireless power receiver mode.

[0069] At block 842, the electronic device can perform what is described herein as ultra-low power object detection, or uLPOD. This uLPOD operation is described in more detail below with reference to FIGS. 9 and 10. For purposes of this description, uLPOD mode can be considered a very low-power technique for detecting the presence of an object in proximity to an electronic device. In some prior art wireless power transfer systems, object detection operations were achieved using low-power pings (LPPs) that used a wireless power transfer circuit (such as an inverter in a wireless power transmitter) to provide intermittent pulses to a wireless power transfer coil. The presence of an object, such as a foreign object or a corresponding wireless power transfer device, can change the magnetic and / or electrical properties of the wireless power transfer circuit, thus enabling detection of such an object by measuring the response to such intermittent pulses / low-power pings. However, using a wireless power transfer circuit for this purpose can, at least in some cases, result in higher power consumption, which may be undesirable for some implementations. 9, alternative circuitry can be provided to stimulate the wireless power transmission coil of an electronic device with periodic pulses having smaller magnitudes and lower frequencies than conventional LPP or other similar pulses, thus enabling object detection with lower power consumption. As an example, uLPOD pulses can be provided to the wireless power transmission coil at a frequency of 10 Hz by auxiliary circuitry. If a change in a circuit parameter corresponding to the presence of an object is not detected within a certain period T1 (e.g., on the order of hundreds of milliseconds), the operations at block 842 can continue until such an object is detected.

[0070] Otherwise, if the presence of an object is detected in block 842 by the response to the uLPOD pulse, further identification steps can be performed in block 843 to identify the approaching object. These techniques, described in more detail below with reference to FIGS. 10 and 11 , can be used to characterize whether the object is a wireless power receiver device or a wireless power transmitter device. In some embodiments, this can include a frequency sweep signal applied to the wireless power transmission coil, and the frequency response is used to characterize the object as a wireless power transmitter, a wireless power receiver, a foreign object, free air, etc. If the detected object is identified as a wireless power transmitter, processing can proceed to block 851 and select a path toward operating the electronic device in wireless power receiver mode, as described in more detail below. Otherwise, if the detected object is characterized as a wireless power receiver in block 843, the electronic device can proceed to block 844 and operate in wireless power transmitter mode. In some implementations, if the detected object is characterized as not a wireless power transmitter, processing defaults from block 843 to 844. As will be explained in more detail below, the identification process can take on the order of tens of milliseconds.

[0071] Continuing to operate the electronic device in wireless power transmitter mode, in block 844, the electronic device may, for example, use its wireless power transmission system control and communication circuitry to provide a low power ping (LPP) to determine whether the putative wireless power receiver device is in a stable position suitable for initiating wireless power transmission. In some embodiments, this may include operations compliant with one or more industry standard protocols for wireless power transmission, such as the Qi family of wireless power transmission standards promulgated by the Wireless Power Consortium, including, but not limited to, the Magnetic Power Profile (MPP) standard. In some embodiments, the operations of block 844 may also or alternatively include one or more proprietary protocols for detecting that the wireless power receiving device is in a stable position for establishing wireless power transmission. The operations of block 844 may continue until the wireless power receiving object settles into a position suitable for initiating wireless power transmission.

[0072] Then, in block 845, the electronic device can initiate a digital ping and FSK handshake to initiate wireless power transmission with the wireless power receiving device. In some embodiments, this can be done according to an industry-standard wireless power transmission protocol, such as the Qi protocol described above. In other embodiments, this can alternatively or additionally be done according to a proprietary wireless power transmission protocol. In many cases, such as wireless power transmission devices operating according to the Qi protocol, a wireless power transmitter can communicate with a wireless power receiver using in-band communication achieved by modulating the wireless power signal using frequency shift keying, where data is encoded by perturbing the frequency of the wireless power transmission signal (e.g., by the wireless power transmitter modulating the switching frequency of its inverter). Similarly, a wireless power receiver can communicate with a wireless power transmitter using in-band communication achieved by modulating the wireless power signal using amplitude shift keying (ASK), where data is encoded by perturbing the amplitude of the wireless power transmission signal (e.g., by the wireless power receiver modulating its load).

[0073] Thus, after initiating the FSK handshake in block 845, the electronic device may wait for an ASK acknowledgment from the wireless power receiving device in block 846. In some cases, there may be a timeout (e.g., a first threshold T3). If the ASK acknowledgment is not received within this time frame (which may be defined by the standard or proprietary protocol in use, but need not be specified), the digital ping may be stopped in block 849, and the electronic device may transition to a receiver mode path, as described in more detail below. Otherwise, if an ASK acknowledgment is received from the device, the digital ping process may be extended in block 847, and the electronic device transitions to a wireless power transmitter operating mode in block 848, which may include loading the full wireless power transmitter firmware, if necessary.

[0074] Part of the hybrid operation mode of block 841 may also include monitoring, in block 850, for object detection signals, such as low-power pings or ultra-low-power object detection (uLPOD) pulses, associated with the wireless power transmitter. This operation may be continuous or intermittent and may occur in parallel with the object detection operations described above. When the electronic device is in proximity to the wireless power transmitter, the wireless power transmitter will emit object detection signals, for example, according to one or more of the techniques described above and / or the Qi standard. If these object detection signals are detected, the electronic device may infer that it is in proximity to a wireless power transmitter and may therefore initiate a wireless power receiver mode of operation. In some cases, the presence of a wireless power transmitter in proximity to the electronic device may also be detected by the presence of a rectifier output voltage (Vrect) in the electronic device's wireless power transmission system induced by a low-power ping or other equivalent operation.

[0075] In either case, if an object detection ping or rectifier output voltage Vrect is detected, then in block 851 the electronic device may determine whether its rectifier output voltage Vrect has reached a determined threshold within a second time threshold T4. This is also the point the process reaches if an ASK acknowledgment is not received in block 846 described above. In either case, if Vrect has not reached the programmed threshold within time threshold T4, processing may return to block 841 and continue in the detection mode described above. Otherwise, if so, the electronic device may operate in a wireless power receiver mode (block 852), which may include loading a wireless power receiver firmware module if necessary.

[0076] 9 shows a simplified schematic diagram 900 of an ultra-low power object detection (uLPOD) pulse injection circuit 955a and a uLPOD and low power ping (LPP) detection circuit 955b for an electronic device. As described above, a wireless power transmitter may include an inverter 114 that drives a wireless power transmit coil 112. Similarly, a wireless power receiver may include a rectifier 124 driven by a wireless power receive coil 122. For an electronic device capable of operating as either a wireless power transmitter or a wireless power receiver, the coil may be generalized to a wireless power transmission coil 952, which may be coupled to an inverter and / or rectifier (which may use the same switching device or separate switching devices, as desired) represented by inverter / rectifier 954. As mentioned above, it may be advantageous to provide uLPOD pulses that stimulate the wireless power transmission coil 952 to detect the presence of an object (such as a foreign object, a wireless power transmitter, or a wireless power receiver) in proximity to the electronic device, while using less power than would be consumed by using an inverter / rectifier 954 to provide these signals.

[0077] To that end, a uLPOD injection circuit 955a may be provided coupled to the wireless power transmission coil 952. The uLPOD injection circuit 955a may be part of the controller and communication circuitry of the electronic device's wireless power transmission system, or may be a separate circuit as appropriate for a given embodiment. Accordingly, the uLPOD injection circuit 955a may include the uLPOD injection circuitry described above with reference to FIG. 8 and below with reference to FIG. 10 to generate uLPOD pulses. For example, these pulses may be provided at a relatively low rate (e.g., 10 Hz) and have a relatively small value (e.g., 1.2 V). In some embodiments, a 1.2 V square wave generator may be provided to generate such pulses. However, this is merely one example, and other waveforms of other amplitudes and / or frequencies may be used, as appropriate, to achieve desired uLPOD pulses that may consume less power than object detection techniques that rely on an inverter / rectifier 954 to generate LPP or similar pulses. The system may also include a uLPOD / LPP detection circuit 955b that can monitor the wireless power transmission coil 952 to measure its response to the uLPOD. Such circuitry may include voltage and / or current sensors, amplifiers, sample-and-hold circuits, comparators, analog-to-digital converters, mixers, etc., depending on the measurement technology used. The uLPOD injection circuit 955a and the uLPOD / LPP detection circuit 955B may be selectively alternately coupled to the wireless power transmission coil by appropriate switching circuitry or the like. Because wireless power signals may be large enough to damage uLPOD circuits configured to operate at much lower amplitudes and power levels, additional protection circuitry may also be provided that selectively disables the uLPOD circuitry in response to the received wireless power signal.

[0078] In some embodiments, the uLPOD / LPP detection circuit 955b may include additional circuitry for detecting low power pings (LPPs), such as those provided by wireless power transmitters operating according to one or more of the Qi standards described above. Depending on the details of the system, this may be the same circuitry as the uLPOD detection circuit described above, or may be separate circuitry appropriate to a given embodiment and the respective characteristics of the uLPOD and LPP signals.

[0079] 10 shows a timing sequence for a detection and identification technique 1000 for a wireless power receiver in an electronic device. The timing sequence 1000 may include an object detection segment 1061, which may correspond to block 842 described above with reference to FIG. 8. The timing sequence 1000 may also include an identification segment 1064, which may correspond to block 843 described above with reference to FIG. 8. The timing sequence 1000 may also include a low power ping (LPP) segment 1067, which may correspond to block 844 described above with reference to FIG. 8. The timing sequence 1000 may also include a digital ping and FSK / ASK handshake segment 1068, which may correspond to blocks 845-848 described above with reference to FIG. 8.

[0080] More specifically, the object detection segment 1061 may include transmitting multiple uLPOD pulses 1062. As described above, these pulses may be transmitted at a relatively low rate (e.g., 10 Hz) and may have a relatively low magnitude (e.g., 1.2 V), although other pulse rates and magnitudes may also be used. During this time, the electronic device may monitor the response of its wireless power transmission coil so that the presence of an object, such as a foreign object, wireless power receiver, or wireless power transmitter, can stress the wireless power transmission coil in such a way that a response to the uLPOD pulses can be detected, for example, using the circuitry described above with reference to FIG. 9 . Optionally, during the object detection phase, the electronic device may increase the pulse rate of the uLPOD pulses if the response indicates that a device may be present. For example, the uLPOD pulses 1063 may be transmitted at shorter intervals (e.g., 50 ms) to confirm that a device has been brought into proximity; more frequent measurements or observations may provide a more reliable indication.

[0081] The identification segment 1064 can be performed in various ways. In some embodiments, one or more frequency scans or sweeps 1065, 1066 can be performed. As described in more detail below with reference to FIG. 11 , various objects detected by the object detection segment 1061 can respond differently at different frequencies. That is, the effects of these various objects on the electrical and magnetic properties of the circuitry including the wireless power transmission coil of the electronic device can cause different responses, as described below with reference to FIG. 11 . Thus, by performing one or more frequency scans 1065, 1066, the type of object brought within range of the electronic device can be characterized as a wireless power receiver (resulting in activation of a wireless power transmitter mode of the electronic device), a wireless power transmitter (resulting in activation of a wireless power receiver mode of the electronic device), or a foreign object (e.g., resulting in reduced and / or inhibited wireless power transmission).

[0082] The frequency scans 1065, 1066 may be performed using the wireless power transmission circuitry itself (e.g., the inverter 114 of the wireless power transmission circuitry within the electronic device) or may be performed by auxiliary circuitry (e.g., the uLPOD injection and detection and LPP detection circuitry 955). In either case, the circuitry may be operated to provide a signal that sweeps a desired frequency range, and the response may be measured at various frequencies. By detecting one or more peaks (corresponding to resonant frequencies, as described below), objects in proximity to the electronic device may be characterized as wireless power receivers, wireless power transmitters, foreign objects, etc. In some embodiments, the frequency range may be from about 600 kHz to about 2 MHz, although a particular range of interest may correspond to a designed wireless power transmission frequency, corresponding device characteristics, etc. The frequency sweep may be implemented by providing a continuous sweep of the range of interest, or in some embodiments, by providing discrete signals at fixed intervals across the range. For example, the frequency range of interest may be divided into intervals of 25 kHz to 100 kHz. In this latter case, each frequency step may be operated for a given period, e.g., about 0.5 ms, although other times may be used. This may result in several to several tens of measurements at different frequencies being used to generate a response curve such as that described below with reference to Figure 11. Thus, by characterizing this curve, objects in proximity to the electronic device may be identified, as described in more detail below.

[0083] Assuming that the identification segment 1064 (e.g., associated frequency scans 1065, 1066) determines that the object detected during the object detection segment 1061 is a wireless power receiver, the electronic device may initiate a low-power ping 1067, as described above with respect to block 844 of FIG. 8 . The electronic device's wireless power transmitter mode operation may then continue with a digital ping (DP) in a digital ping and FSK / ASK handshake segment 1068. These may be followed by an FSK handshake initiation (1069a) and an ASK handshake response 1069b from the wireless power receiver. As described above, the result may be the establishment of wireless power transmission from the electronic device to the wireless power receiver according to either an industry-standard wireless power transmission protocol or a proprietary wireless power transmission protocol. In either case, the establishment of wireless power transmission may be indicated to the user by a chime or other audible, visual, or other feedback mechanism following the negotiation and establishment of wireless power transmission.

[0084] FIG. 11 shows a plot 1100 of a series of identification frequency response curves 1171-1174 for detection and identification of a wireless power receiver or a wireless power transmitter by an electronic device. These response curves 1171-1174 can correspond to exemplary responses to a frequency sweep or scan, as described above. Curve 1171 can correspond to free air, meaning that the resonant peak is simply the resonant peak of the electronic device's own wireless power transmission circuitry unaffected by external components. In some embodiments, this curve can correspond to a single peak at a frequency of approximately 800 kHz, although this can vary depending on the structure of the electronic device itself, its wireless power transmission circuitry (including its designed operating frequency), etc. Curve 1172 can correspond to a wireless power transmitter device. In at least some embodiments, such a device can be characterized by a single peak, e.g., located at approximately 600 kHz, although this can also vary depending on the configuration of the electronic device, the wireless power transmitter, their respective wireless power transmission circuitry (including their designed operating frequency), etc. This transmitter peak or resonant frequency can be a known frequency associated with the wireless power transmitter intended to operate with the device. This transmitter peak or resonant frequency may also be any frequency known to be different from the receiver resonant frequency associated with a wireless power receiver intended to operate with the device. Curve 1173 may correspond to a wireless power receiver. In at least some embodiments, such a device may be characterized by a double peak with a valley between them, such as the illustrated valley at 850 kHz, although this may also vary depending on the configuration of the electronic device, the wireless power receiver, their respective wireless power transmission circuitry (including their designed operating frequency), etc. These receiver peak or resonant frequencies and / or corresponding valley frequencies may be known frequencies associated with a wireless power receiver intended to operate with the device. These receiver peak or resonant frequencies and / or corresponding valley frequencies may also be any frequency known to be different from the transmitter resonant frequency associated with a wireless power receiver intended to operate with the device.Finally, a foreign object (ie, an object that is neither a wireless power transmitter nor a wireless power receiver) may be characterized by some other pattern, such as the illustrated peak at 1 MHz in curve 1174.

[0085] When implementing a given electronic device and its wireless power transfer system, the known characteristics of such device, along with the expected characteristics of the wireless power transmitter and / or receiver expected to operate with it, can allow a designer to set appropriate thresholds or other criteria for resonant peak and / or valley frequencies and / or magnitudes to identify objects as desired. Accordingly, the control and communication circuitry of the wireless power transfer system of the electronic device can perform one or more frequency sweeps or scans as described above, and monitor and characterize the response as described above using signal processing circuitry such as voltage and / or current sensors, sample-and-hold circuits, analog-to-digital converters, envelope detectors, comparators, etc., to determine whether an object detected by the uLPOD detection sequence is a wireless power transmitter or a wireless power receiver, thereby allowing the electronic device to select an appropriate operating mode for its wireless power transfer circuitry.

[0086] 12A-12C illustrate alternative timing sequences for the detection and identification of a wireless power receiver or a wireless power transmitter within an electronic device. FIG. 12A illustrates an example 1201, such as that illustrated in FIG. 10 above, in which the electronic device detects a wireless power receiving device and operates as a wireless power transmitter to provide power to the wireless power receiver. Operation in such a mode has been described above and will not be repeated in detail here. Generally, detection segment 1261 corresponds to detection segment 1061 with its associated uLPOD pulse. Similarly, identification segment 1264 corresponds to identification segment 1064, which includes the frequency scan described above. These are followed by LPP segment 1267, which corresponds to LPP segment 1067, and digital ping / handshake segment 1268, which corresponds to digital ping and FSK / ASK handshake segment 1068. The frequencies, timing, etc. illustrated in this example are merely exemplary, and other timing intervals may be provided. In general, to provide a suitable user experience, it may be desirable to provide a relatively short interval, such as the illustrated t2, between initial device detection and establishment of electronic device operation as a wireless power transmitter (or receiver). In some embodiments, interval t2 may be on the order of approximately 700 ms. To accomplish this, the latter uLPOD pulses may have a total duration t3, which may be on the order of approximately 300 ms. The frequency scan 1264 may be completed in less than a certain time interval t4, which may be on the order of approximately 20 ms. Finally, the digital ping and FSK / ASK handshake interval t5 may be on the order of approximately 200 ms. Again, these values ​​are merely examples and may vary depending on the particular application, etc.

[0087] FIG. 12B illustrates an example 1202 in which an electronic device detects a wireless power transmitter device and operates as a wireless power receiver to receive power from the wireless power receiver. The upper sequence illustrates the operation of the wireless power transmitter (PTx), and the lower sequence illustrates the operation of the electronic device. Initially, the wireless power transmitter may be operating in an LPP mode (e.g., as defined by one or more of the Qi standards discussed above). At the same time, the electronic device may be operating in a detection mode 1261, including a uLPOD signal, as described above. At time 1271, the electronic device detects the LPP signal from the wireless power transmitter and may therefore initiate initiation of a wireless power receiver operation mode for the electronic device, as described above with reference to block 850 and subsequent blocks of FIG. 8. As a result, the wireless power transmitter PTx may continue its LPP operation and initiate a digital ping phase EP68 according to the operation protocol. Correspondingly, upon transitioning to a wireless power receiver operating mode, the electronic device can enter wireless power receiver mode and begin monitoring its rectifier output voltage Vrect at 1272 and establishing wireless power transmission (reception) according to the associated protocol. As with the example of FIG. 12A , the illustrated timing is merely exemplary. For example, the interval t3 between more frequent uLPOD pulses may be approximately 185 ms. Once in receiver mode, if the device does not detect a low-power ping from the transmitter within an interval t6, e.g., on the order of one second, the device can resume transmitting uLPOD pulses 1273, which may continue for an interval t7, e.g., up to several seconds. In other words, if the electronic device is unable to establish wireless power transmission (reception) from the wireless power transmitter PTx, as indicated by the uLPOD signal 1273, it can resume searching for a wireless power transmitter or wireless power receiver object, as described above with reference to FIG. 8.

[0088] FIG. 12C illustrates an example 1203 in which two electronic devices, each capable of bidirectional wireless power transmission operation (i.e., as a wireless power transmitter and as a wireless power receiver), are brought into close proximity. The top sequence illustrates the operation of a first such device (Device 1), and the bottom sequence illustrates the operation of a second such device (Device 2). Initially, each device may be within a detection segment 1261a / 1261b, as described above with reference to FIGS. 12A and 12B. In some cases, one device or the other device (in this case, the second device) may have a different time interval, T_uLP_spa (i.e., uLPOD signal interval), to prevent a race condition associated with both devices simultaneously transmitting and receiving uLPOD signals. In either case, once each device detects the other using uLPOD operation as described above, each device can independently transition to its respective identification interval 1264a / 1264b. As a result, each device can perform one or more frequency sweeps or scans as described above. Again, one or the other device (in this case, the second device) may have a scan offset interval T_scan_spa that causes its scan to occur after the scan of the first device. As a result, the first device detects the second device as a wireless power receiver and begins its LPP operation 1267. The second device may detect this LPP signal from the first device and therefore proceeds to operate as a wireless power receiver, with the understanding that the first device is a wireless power transmitter. The timing of the various operations and intervals may generally be similar to those described above.

[0089] In some embodiments, one or both devices can randomize the time interval between the end of a frequency sweep or scan for identifying the other device and a subsequent LPP pulse. In another embodiment, one or both devices can randomize the time interval between the first LPP pulse and a subsequent LPP pulse. This can account for situations where two devices step through a sequence at substantially the same time, which can prevent the devices from detecting each other's LPP pulses because the respective LPP pulses sent to each device can "drown out" the signal associated with the LPP from the other device, effectively preventing the devices from detecting each other's LPP pings. Randomizing the intervals between LPP pulses, for example, between the first and second pulses and between the second and subsequent pulses, can mitigate problems associated with such collisions.

[0090] As a result, the second device can transition to a wireless power receiver operating mode. Thus, the first device can enter a digital ping phase 1268, which may include an FSK handshake. Correspondingly, the second device, now in wireless power receiver mode, can begin monitoring its rectifier output voltage Vrect at 1272 and establishing wireless power transmission according to a relevant protocol, such as the industry-standard Qi protocol or a proprietary protocol. This may include the ASK portion of the handshake. Once the devices establish wireless power transmission, they can apply device-to-device power transfer policies to determine which devices may have transmit and receive roles that differ from those initially negotiated according to the above operations. For example, a condition may ensure that the second device provides power to the first device, even if the second device later detects the other and thus may receive an LPP signal from the first device operating in wireless power transmitter mode. In that case, the devices can renegotiate their transmitter / receiver relationship according to an appropriate policy. Details of such policies are beyond the scope of this application, but they may be based on the relative state of charge of the batteries of each device, the total battery capacity of each device, etc.

[0091] The foregoing describes various features and embodiments of wireless power transmission devices capable of operating in a wireless power transmitter mode or a wireless power receiver mode, as well as techniques for transitioning between such modes. Such configurations may be used in a variety of applications, but may be particularly advantageous when used in combination with electronic devices such as mobile phones, tablet computers, laptop or notebook computers, and wireless power receivers, including accessories such as wireless headphones and styluses. Furthermore, while numerous specific features and various embodiments have been described, it should be understood that, unless otherwise stated as mutually exclusive, the various features and embodiments may be combined in various permutations in a particular implementation. Accordingly, the various embodiments described above are provided by way of example only and should not be construed as constituting the scope of the present disclosure. Various modifications and variations can be made to the principles and embodiments herein without departing from the scope of the present disclosure and without departing from the scope of the claims.

[0092] The above describes an exemplary embodiment of a wireless power transmission system capable of transmitting certain information between PTxs and PRxs in the system. The present disclosure contemplates that the passing of this information improves the ability of devices to provide wireless power signals to each other in an efficient manner to facilitate battery charging, such as by sharing the devices' power handling capabilities with each other. Entities implementing the present technology should take care to ensure that well-established privacy policies and / or practices are adhered to, to the extent any sensitive information is used in a particular implementation. Specifically, such entities would be expected to implement and consistently apply privacy practices generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Implementers should inform users of where personally identifiable information is expected to be transmitted in the wireless power transmission system and allow users to "opt in" or "opt out" of participation. For example, such information may be presented to users when they place a device on a power transmitter if the power transmitter is configured to poll for sensitive information from power receivers.

Claims

1. 1. An electronic device selectively operable in a wireless power receiver mode for receiving power from a wireless power transmitter and a wireless power transmitter mode for transmitting power to an accessory, the electronic device comprising: a wireless power transmission coil; a rectifier coupled to the wireless power transmission coil and operable, in the wireless power receiver mode, to convert an AC voltage induced in the wireless power transmission coil by a wireless power transmitter into a DC voltage for use by the electronic device; an inverter coupled to the wireless power transmission coil, the inverter operable in the wireless power transmitter mode to convert a DC voltage to an AC voltage applied to the wireless power transmission coil; a controller and communication circuit that activates the wireless power receiver mode in response to detecting one or more object detection pings from a wireless power transmitter; An electronic device comprising:

2. The controller and the communication circuitry further include: detecting an object in proximity to the electronic device by transmitting a plurality of low power object detection pulses using the wireless power transmission coil and detecting responses to the low power object detection pulses associated with the object, the low power object detection pulses being generated by the controller and communication circuitry without using the rectifier or the inverter; In response to detecting the object, identifying the object as at least one of a wireless power receiver and a wireless power transmitter by performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter; activating the wireless power transmitter mode in response to identifying the object as a wireless power receiver; The electronic device of claim 1 , wherein the electronic device activates the wireless power receiver mode in response to identifying the object as a wireless power transmitter.

3. The electronic device of claim 2 , wherein the response to the low-power object detection pulse associated with the object is a change in one or more electrical or magnetic parameters of a circuit including the wireless power transmission coil.

4. 3. The electronic device of claim 2, wherein the low power object detection pulse is generated by a low power object detection pulse injection circuit separate from the inverter and coupled to the wireless power transfer coil.

5. The electronic device of claim 4 , wherein the low-power object detection pulse injection circuitry includes a detection circuit that responds to changes in one or more electrical or magnetic parameters of a circuit that includes the wireless power transmission coil.

6. The electronic device of claim 2 , wherein the one or more frequency sweeps are continuous frequency sweeps over a frequency range of interest.

7. The electronic device of claim 2 , wherein the one or more frequency sweeps are a plurality of discrete frequencies across a frequency range of interest.

8. 3. The electronic device of claim 2, wherein performing one or more frequency sweeps to identify one or more resonant frequencies of the object comprises driving the wireless power transmission coil with the inverter.

9. 3. The electronic device of claim 2, wherein performing one or more frequency sweeps to identify one or more resonant frequencies of the object comprises driving the wireless power transmission coil with an auxiliary circuit.

10. The wireless power transmitter is characterized by a first resonant frequency, the first resonant frequency being: a frequency associated with a compatible wireless power transmitter intended to operate with the electronic device; or and a frequency different from a resonant frequency of a wireless power receiver intended to operate with the electronic device.

11. The wireless power receiver is characterized by a second resonant frequency and a third resonant frequency, a valley is located between the second resonant frequency and the third resonant frequency, the valley is at a frequency higher than the first resonant frequency, and one or more of the second resonant frequency and the third resonant frequency and the valley are a frequency associated with a compatible wireless power receiver intended to operate with the electronic device; or 11. The electronic device of claim 10, wherein the resonant frequency is different from the resonant frequency of a wireless power transmitter intended to operate with the electronic device.

12. The electronic device of claim 1 , wherein the wireless power transmission coil is a single coil.

13. The electronic device of claim 1 , wherein the rectifier and the inverter are constructed from the same switching device.

14. 10. The electronic device of claim 1, wherein at least one of activating the wireless power transmitter mode and activating the wireless power receiver mode includes loading additional firmware corresponding to one of the respective modes.

15. 10. The electronic device of claim 1, wherein activating the wireless power transmitter mode comprises transmitting one or more object detection pings, wherein an interval between at least two of the one or more object detection pings is randomized.

16. 1. A method performed by a wireless power transfer controller and communications circuitry of an electronic device operable in a wireless power receiver mode for receiving power from a wireless power transmitter or in a wireless power transmitter mode for transmitting power to an accessory, the method comprising: Detecting one or more object detection pings from a wireless power transmitter; and activating the wireless power receiver mode in response to detecting one or more object detection pings from a wireless power transmitter.

17. detecting an object proximate to the electronic device, wherein detecting the object proximate to the electronic device includes transmitting a plurality of low power object detection pulses using a wireless power transfer coil of the electronic device, and detecting a response to the low power object detection pulse associated with the object, the low power object detection pulse being generated by the controller and the communication circuitry without the use of a rectifier or inverter of a wireless power transfer system of the electronic device; In response to detecting the object, identifying the object as at least one of a wireless power receiver and a wireless power transmitter, where identifying the object as at least one of a wireless power receiver and a wireless power transmitter includes performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter; In response to identifying the object as a wireless power receiver, activating the wireless power transmitter mode and transmitting power to the accessory using wireless power transmission circuitry of the electronic device; 17. The method of claim 16, further comprising: in response to identifying the object as a wireless power transmitter, activating the wireless power receiver mode and receiving power from the wireless power transmitter using the wireless power transmission circuitry of the electronic device.

18. 20. The method of claim 17, wherein the response to the low-power object detection pulse associated with the object is a change in one or more electrical or magnetic parameters of a circuit including the wireless power transmission coil.

19. The wireless power transmitter is characterized by a first resonant frequency, the first resonant frequency being: a frequency associated with a compatible wireless power transmitter intended to operate with the electronic device; or and a frequency that is different from a resonant frequency of a wireless power receiver intended to operate with the electronic device.

20. The wireless power receiver is characterized by a second resonant frequency and a third resonant frequency, a valley is located between the second resonant frequency and the third resonant frequency, the valley is at a frequency higher than the first resonant frequency, and one or more of the second resonant frequency and the third resonant frequency and the valley are a frequency associated with a compatible wireless power receiver intended to operate with the electronic device; or 20. The method of claim 19, wherein the frequency is different from a resonant frequency of a wireless power transmitter intended to operate with the electronic device.

21. 20. The method of claim 17, wherein activating the wireless power transmitter mode includes transmitting one or more object detection pings, wherein an interval between at least two of the one or more object detection pings is randomized.

22. 1. A controller and communication circuit for a wireless power transmission system for an electronic device, the electronic device being selectively operable in a wireless power receiver mode to receive power from a wireless power transmitter and in a wireless power transmitter mode to transmit power to an accessory, the controller and communication circuit comprising: Detecting one or more object detection pings from the wireless power transmitter; A controller and communication circuit configured to activate the wireless power receiver mode in response to detecting one or more object detection pings from a wireless power transmitter.

23. using a wireless power transfer coil of the electronic device to detect an object proximate to the electronic device and transmit a plurality of low power object detection pulses; and detecting a response to the low power object detection pulses associated with the object, the low power object detection pulses being generated by the controller and the communication circuitry without using a rectifier or inverter of a wireless power transfer system of the electronic device; In response to detecting the object, identifying the object as at least one of a wireless power receiver and a wireless power transmitter by performing one or more frequency sweeps to identify one or more resonant frequencies of the object that characterize the object as a wireless power receiver or a wireless power transmitter; activating the wireless power transmitter mode in response to identifying the object as a wireless power receiver; 23. The controller and communications circuit of claim 22, further configured to activate the wireless power receiver mode in response to identifying the object as a wireless power transmitter.

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