Power transmission disable switch in wireless power receiving device

Abstract

The present disclosure provides systems, methods, and devices for preventing power transfer in a secondary coil of a wireless power receiving device. Some implementations generally relate to the use of one or more switches. In some implementations, the one or more switches may be coupled in series to one or both ends of the secondary coil. The one or more switches may be controlled based on handshake communication between the wireless power receiving device and a corresponding wireless power transmitting device. The one or more switches may be controlled using bias power from a wireless communication interface separate from the power receiving circuit including the secondary coil. The one or more switches may disable power transfer in the secondary coil to protect one or more components of the wireless power receiving device or to enable measurement of a coupling coefficient during a measurement period.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to Indian Provisional Patent Application No. 202111007255, entitled "POWER TRANSFER DISABLEMENT SWITCH IN A WIRELESS POWER RECEPTION APPARATUS," filed on February 19, 2021, and assigned to the assignee of the present application. The disclosure of the prior application is deemed to be a part of this patent application and is incorporated by reference into this patent application. [Technical field]

[0002] This disclosure relates generally to wireless power. More specifically, this patent application relates to a power transfer disable switch in a wireless power receiving device. [Background technology]

[0003] Technologies have been developed that allow for wireless transmission of power from a wireless power transmission device to a wireless power receiving device. Examples of wireless power receiving devices may include several types of mobile devices, small electronic devices, computers, tablets, gadgets, appliances (such as cordless blenders, water kettles, mixers, etc.), and several types of larger electronic devices, among other examples. Wireless power transmission may be referred to as contactless power transmission or non-contact power transmission. Wireless power may be transmitted using inductive or resonant coupling between a primary coil of the wireless power transmission device and a secondary coil of the wireless power receiving device. For example, the wireless power transmission device may include a primary coil that generates an electromagnetic field. The electromagnetic field may induce an electromotive force in the secondary coil of the wireless power receiving device when the secondary coil is placed in close proximity to the primary coil. In this configuration, the electromagnetic field may wirelessly transmit power to the secondary coil.

[0004] In some conventional wireless power systems, the primary coil can transmit wireless energy to the secondary coil up to a rating predetermined by the wireless standard. For example, a low-power wireless power signal may transmit five watts (5W), 9W, 12W, or 15W. Low-power wireless power systems may deliver up to 15 watts of energy, suitable for many electronic devices. Higher-power wireless systems are being developed to support wireless power transmission to appliances or devices that require higher power. For example, a high-power cordless kitchen transmitter may deliver as much as 2.2 kW. Some inductive systems may generate energy for purposes other than wireless power transmission (such as induction-based heating). Unintentional power transmission may damage the electronics in the wireless power receiving device. Summary of the Invention

[0005] The systems, methods, and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of the subject matter described in this disclosure can be implemented as a wireless power receiving device. The wireless power receiving device can include a secondary coil configured to receive power from a wireless power signal of a wireless power transmission device. The wireless power receiving device can include a receiving circuit configured to utilize the received power. The wireless power receiving device can include one or more switches disposed between the secondary coil and the receiving circuit. The one or more switches can be configured to connect the secondary coil and the receiving circuit based on communication from the wireless power transmission device.

[0007] Another innovative aspect of the subject matter described in this disclosure can be implemented as a wireless power receiving device. The wireless power receiving device may include a secondary coil configured to receive power from a wireless power signal of a wireless power transmitting device. The wireless power receiving device may include a receiving circuit configured to utilize the received power. The wireless power receiving device may include one or more switches disposed between the secondary coil and the receiving circuit. The one or more switches are configured to disconnect the secondary coil from the receiving circuit during a coupling coefficient (k-factor) measurement period and connect the secondary coil to the receiving circuit during a power transmission period.

[0008] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method. The method can include controlling one or more switches disposed between a secondary coil and a receiving circuit of a wireless power receiving device based on a communication from a wireless power transmitting device. The secondary coil can be configured to receive power from a wireless power signal of the wireless power transmitting device. The receiving circuit can be configured to utilize the received power.

[0009] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method. The method may include disconnecting a secondary coil of a wireless power receiving device from a power receiving circuit of the wireless power receiving device using one or more switches disposed between the secondary coil and the power receiving circuit during a coupling coefficient (k-factor) measurement period. The secondary coil may be configured to receive power from a wireless power signal of a wireless power transmission device. The power receiving circuit may be configured to utilize the received power. The method may include connecting the secondary coil to the power receiving circuit using one or more switches during a power transmission period. [Brief description of the drawings]

[0010] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the following specification. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. It should be noted that the relative dimensions of the following figures may not be drawn to scale.

[0011] [Figure 1] 1 shows a block diagram of an exemplary wireless power transfer system.

[0012] [Diagram 2] 1 shows a block diagram of an exemplary wireless power transmission device.

[0013] [Diagram 3] 1 shows a block diagram of an exemplary wireless power receiving device having a switch connected in series between a secondary coil and a rectifier.

[0014] [Figure 4] 1 shows a block diagram of an exemplary wireless power receiving device having a switch connected in series between a secondary coil and a load.

[0015] [Diagram 5] 1 shows a block diagram of an exemplary wireless power receiving device having multiple switches connected in series between a secondary coil and a rectifier.

[0016] [Figure 6] 1 shows a block diagram of an exemplary wireless power receiving device having a switch connected as a shunt across a secondary coil.

[0017] [Figure 7] 1 shows a block diagram of an example wireless power receiving device having a switch that allows disconnection of the secondary coil during measurements to determine the coupling coefficient.

[0018] [Figure 8] 1 illustrates a flowchart of an example process according to some implementations.

[0019] [Figure 9] 1 illustrates a flowchart diagram of another example process according to some implementations.

[0020] [Figure 10] 1 shows a block diagram of an exemplary apparatus for use in a wireless power transfer system.

[0021] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A wireless power transmission (WPT) system may include a wireless power transmission device and a wireless power receiving device. The wireless power transmission device may include one or more primary coils that transmit wireless energy (as a wireless power signal) to one or more corresponding secondary coils in the wireless power receiving device. The primary coil refers to a source of wireless energy (such as induction or magnetic resonance energy that generates an electromagnetic field) in the wireless power transmission device. The secondary coil located in the wireless power receiving device may receive the wireless energy via the electromagnetic field.

[0023] Some types of wireless power receiving devices (such as cordless kitchen appliances, among other examples) may be intended to operate on a wireless power transmission surface configured by one or more primary coils. As an example, a kitchen countertop or range top (sometimes called a cooktop or hob) may include one or more induction coils. The induction coils may be operated as burners for heating kitchen gadgets or as primary coils for wireless power transmission to cordless kitchen appliances. Some induction hobs may implement different capabilities or combinations of capabilities for different induction coils. For example, a subset of induction coils may be dedicated to heating and another subset of induction coils may be capable of heating or wireless power transmission. A conventional induction hob may support induction heating but not wireless power transmission. Unintentional placement of a cordless kitchen appliance intended for wireless power on the surface of a conventional induction bob may result in unintentional power transmission to the cordless kitchen appliance. This may raise dangerous safety concerns and may damage the conventional induction hob or cordless kitchen appliance, among other concerns. Furthermore, when the power generated by the induction coil reaches higher levels (compared to conventional wireless charging), the high power may damage electrical components of the cordless kitchen appliance. Additionally or alternatively, there may be times when induction of wireless power in the secondary coil is undesirable.

[0024] The present disclosure provides systems, methods, and devices for preventing power transfer in a secondary coil of a wireless power receiving device. Some implementations generally relate to the use of one or more switches coupled to a secondary coil to prevent power transfer to the secondary coil when placed on a conventional induction fob that does not support wireless power transfer. In some implementations, the one or more switches may be coupled in series to one or both ends of the secondary coil. The one or more switches may be controlled based on communication (such as handshake communication, sometimes referred to as digital handshake) between the wireless power receiving device and a corresponding wireless power transmitting device. Although a conventional induction fob does not have a communication system, a wireless power transmitting device may require handshake communication according to a wireless power protocol. Thus, the techniques of the present disclosure prevent a wireless power receiving device from being inadvertently powered by a conventional induction fob.

[0025] In some implementations, the one or more switches may be normally open so that the secondary coil is disconnected from the receiving circuit. The receiving circuit may include a load, a rectifier, or both. After establishing one-to-one communication with the wireless power transmission device, the one or more switches may be closed to enable power transmission through the secondary coil. In some implementations, the one or more switches may be closed using bias power from a wireless communication interface. The wireless communication interface may be separate from the receiving circuit including the secondary coil. In some implementations, the one or more switches may be kept open (to disable power transmission from the secondary coil) during a measurement period to determine the coupling between the secondary coil and the primary coil.

[0026] In some implementations, the one or more switches may be a first series switch connected to one side or leg of the secondary coil. Alternatively or additionally, the one or more switches may include a second series switch connected to the other side or leg of the secondary coil. In some implementations, the one or more switches may include a static or electromagnetic relay or other type of switch that can interrupt the voltage when the switch is open. The one or more switches may be capable of conducting electricity in both positive and negative polarities such that alternating current (AC) power can be induced in the secondary coil when the switch is closed. In some implementations, the one or more switches may include a shunt switch that shorts the two sides or legs of the secondary coil to protect one or more other components or during a measurement period.

[0027] In some implementations, a wireless communication interface (such as a short-range radio frequency interface using Bluetooth™ or Near Field Communication (NFC), among other examples) may collect bias power via a communication signal. The bias power is used by the wireless powered device to control one or more switches connected to the secondary coil. Thus, the one or more switches may be operated independently of a wireless power signal that would otherwise be received via the secondary coil.

[0028] In some implementations, the one or more switches may be referred to as protection switches. The protection switch may be disposed between the secondary coil and one or more other components of the wireless power receiving device. For example, in some implementations, the protection switch may be disposed between the secondary coil and a rectifier of the wireless power receiving device. In some implementations, the protection switch may be disposed between the secondary coil and a load associated with the wireless power receiving device. The protection switch may remain open (thus disabling power transfer from the secondary coil) if the wireless power receiving device is disposed over an incompatible induction coil (such as one that does not support wireless power transfer but rather is used for induction-based heating).

[0029] In some implementations, the one or more switches may enable coupling factor measurement. The coupling factor (sometimes referred to as k-factor) may be an indication of how well the secondary coil and the primary coil can transmit wireless power. For example, the k-factor may be a measure of the potential magnetic flux coupling of wireless power transmission between the primary coil and the secondary coil. In some implementations, the k-factor may depend on, among other things, the number of turns in the primary coil (n1), the number of turns in the secondary coil (n2), the voltage transmitted by the primary coil (v1), and the voltage induced in the secondary coil (v2) during the measurement period. In some implementations, it is desirable to disconnect the secondary coil from other components of the wireless power receiving device during the measurement period to determine the k-factor. Thus, in some implementations, the one or more switches described in the present disclosure may enable the secondary coil to be disconnected from one or more other components (such as a rectifier, a load, or both) during the k-factor measurement period.

[0030] Particular implementations of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages: The one or more switches may protect components of a wireless powered device when the wireless powered device is placed on an incompatible induction coil. For example, the one or more switches may improve the safety of a cordless kitchen appliance that may be inadvertently placed on an induction coil that is not configured for wireless power transmission. Additionally or alternatively, the one or more switches may improve the accuracy of the k-factor measurement by disconnecting the secondary coil from one or more other components during the k-factor measurement period.

[0031] The following description refers to specific implementations for purposes of illustrating the innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented in any means, device, system, or method for wireless power transmission.

[0032] FIG. 1 illustrates a block diagram of an exemplary wireless power transmission system 100. The wireless power transmission system may include a wireless power transmitter 102 and a wireless power receiver 118. The wireless power transmitter includes a primary coil 110. The primary coil 110 may be associated with a power signal generator 106. The primary coil 110 may be a wire coil that transmits wireless power (also referred to as wireless energy). The primary coil 110 may transmit wireless energy using induction or magnetic resonance fields. The power signal generator and the primary coil together may generate a primary magnetic field during wireless power transmission. The power signal generator 106 may include components (not shown) that provide power to the primary coil 110 to cause the primary coil 110 to generate a wireless power signal 155. For example, the power signal generator 106 may include one or more switches, drivers, series capacitors, rectifiers, or other components. The wireless power transmitter 102 may also include a transmission controller 108 that controls the components of the power signal generator 106. For example, the transmission controller 108 may determine an operating point (such as a voltage or current) and control the power signal generator 106 according to the operating point.

[0033] In some implementations, the power signal generator 106, the transmission controller 108, and other components (not shown) may be collectively referred to as a power transmission circuit. Some or all of the power transmission circuit may be embodied as an integrated circuit (IC) that implements features of the present disclosure for controlling and transmitting wireless power to one or more wireless powered devices. The transmission controller 108 may be implemented as a microcontroller, a special purpose processor, an integrated circuit, an application specific integrated circuit (ASIC), or any other suitable electronic device.

[0034] The power source 112 may provide power to the power transmission circuitry within the wireless power transmission apparatus 102. The power source 112 may convert alternating current (AC) power to direct current (DC) power. For example, the power source 112 may include a converter that receives AC power from an external power source (such as a power mains) and converts the AC power to DC power used by the power signal generator 106.

[0035] In some implementations, the first communication unit 142 may be coupled to components of the power signal generator 106 or the primary coil 110 to transmit or receive communications via the wireless power signal 155. The first communication unit 142 may include logic for controlling one or more switches and other components that cause communication signals to be transmitted and received via the wireless power signal 155. For example, the first communication unit 142 may include a modulator or demodulator that converts information into a modulated signal added to the wireless power signal 155. In one example, the first communication unit 142 may convert data from the transmission controller 108 into a frequency shift key (FSK) modulated signal that is combined with the wireless power signal 155 for communication from the wireless power transmitting device 102 to the wireless power receiving device 118. In another example, the first communication unit 142 may detect a load modulated amplitude shift key (ASK) signal from the power signal generator 106 or the primary coil 110 and demodulate the ASK signal to obtain data that the first communication unit 142 provides to the transmission controller 108. Communication signals transmitted or received via wireless power signal 155 may be referred to as in-band communications because they are carried using wireless power signal 155. In contrast, out-of-band communications may be carried as wireless communication signals 175 using a wireless or wired communication channel that is separate and distinct from wireless power signal 155. For example, wireless communication signals 175 may include out-of-band communications via short-range radio frequency communications (such as Bluetooth™) or near field communication (NFC).

[0036] The wireless power transmitting device 102 may include a wireless communication interface 114 configured to communicate with the wireless power receiving device 118 using wireless communication signals 175. The wireless communication interface 114 may be connected to a first communication coil 116 (which may be a coil or a loop antenna, among other examples). The wireless communication interface 114 may include logic to control one or more switches and other components that cause wireless communication signals to be transmitted and received through the first communication coil 116. In some implementations, the wireless communication interface 114 may support short-range radio frequency communication or NFC. NFC is a technology that transfers data at a carrier frequency of 13.56 MHz. The wireless communication interface 114 may also support any suitable communication protocol.

[0037] The transmission controller 108 may detect the presence or proximity of the wireless power receiving device 118. In some implementations, the presence or proximity of the wireless power receiving device 118 may be detected based on a load change in response to a periodic low-power signal generated by the power signal generator 106 and the primary coil 110. In some implementations, the presence or proximity of the wireless power receiving device 118 may occur during a periodic ping process of the wireless communication interface 114 in the wireless power transmitting device 102. Alternatively or additionally, the wireless power transmitting device 102 may detect the presence or proximity of the wireless power receiving device 118 based on communication via the wireless communication signal 175. For example, the wireless power transmitting device 102 may periodically or continuously transmit a communication or polling signal via the wireless communication signal 175. In some implementations, the wireless communication signal 175 may include a small amount of power (sometimes referred to as communication bias power or bias power) for powering the wireless communication interface 132 of the wireless power receiving device 118. Upon receiving a response from the wireless power receiving device 118 via the wireless communication signal 175, the wireless power transmitting device 102 may perform further communications to verify the compatibility and power requirements of the wireless power receiving device 118.

[0038] The transmission controller 108 may control the characteristics of the wireless power that the wireless power transmitter 102 supplies to the wireless power receiver 118. After detecting the wireless power receiver 118, the transmission controller 108 may receive information from the wireless power receiver 118 (either via the wireless communication interface 114 or the first communication unit 142). For example, the transmission controller 108 may receive information as part of a handshake communication with the wireless power receiver 118. A handshake communication (sometimes referred to as a digital handshake) refers to a one-to-one communication between the wireless power receiver 118 and the wireless power transmitter 102. During the handshake communication, the wireless power transmitter 102 may transmit a first communication signal, and the wireless power receiver 118 may respond to the first communication signal by transmitting information (such as a power rating, manufacturer, model, or parameters of the receiver when operating with a standard transmitter, among other examples). For example, the transmission controller 108 and the receiver controller 128 may communicate information with each other via their respective wireless communication interfaces. The transmission controller 108 may use the information received from the receiver controller 128 to determine at least one operational control parameter (such as frequency, duty cycle, voltage, etc.) for the wireless power to supply to the wireless powered device 118. To configure the wireless power, the transmission controller 108 may vary the frequency, duty cycle, voltage, or any other suitable characteristic of the power signal generator 106.

[0039] The wireless powered device 118 may include a secondary coil 120 and a receiver controller 128. In some implementations, the wireless powered device 118 may include a rectifier 126. The wireless powered device may include or be connected to a load 130. In some implementations, the load 130 may be external to the wireless powered device 118 and coupled via a wire from the secondary coil 120 or the rectifier 126 (if present). The rectifier 126, the load 130, or both may be referred to as a powered circuit. The powered circuit may be configured to utilize the received power. The secondary coil 120 is configured to receive power (based on an induced voltage) via a wireless power signal 155. The secondary coil 120 may provide the received power to the powered circuit. When the secondary coil 120 is aligned with the primary coil 110, the secondary coil 120 may generate an induced voltage based on the wireless power signal received from the primary coil 110. In some implementations, a capacitor (not shown) may be in series between the secondary coil 120 and the rectifier 126 (if present) or the load 130 (if the rectifier 126 is not present). If present, the rectifier 126 may rectify the induced voltage and provide the rectified voltage to the load 130.

[0040] The receiver controller 128 may control one or more components of the wireless power receiving device 118. In some implementations, the receiver controller 128 may be connected to a second communication unit 152 for in-band communication via wireless power signals. For example, the second communication unit 152 may be coupled to components of the secondary coil 120 or the rectifier 126 to transmit or receive communications via wireless power signals. The second communication unit 152 may include logic for controlling one or more switches (not shown) and other components that cause communication signals to be transmitted and received via wireless power signals.

[0041] The wireless power receiving device 118 may include a wireless communication interface 132. The wireless communication interface 132 may include modulation and demodulation circuitry for wireless communication via a second communication coil 134 (which may be a coil or a loop antenna, among other examples). Thus, the receiver controller 128 may wirelessly communicate with the transmission controller 108 via the wireless communication interface 132 and the wireless communication signal 175. In some implementations, the wireless communication interface 132 may be configured to communicate using NFC or Bluetooth technology. In some implementations, the wireless communication interface 132 may be powered by harvesting energy from the wireless communication signal 85. For example, the wireless communication interface 132 may harvest energy from the wireless communication signal 175 via the second communication coil 134 in the form of bias power. The bias power may be sufficient to power the wireless communication interface 132 but less than the amount required to power the load 130. In some implementations, the bias power may be used by other components of the wireless power receiving device 118, such as the receiver controller 128. After the secondary coil 120 and the power receiving circuit are connected, they may begin receiving the wirelessly transmitted power. In some implementations, once the wireless power receiving device 118 begins receiving the wirelessly transmitted power, the bias power may be derived from the wirelessly transmitted power.

[0042] As described herein, the wireless power signal 155 may be used to wirelessly transmit power using electromotive forces in the secondary coil 120. The electromotive forces may generate voltages and currents in the secondary coil 120 when the secondary coil 120 is connected to other components in the wireless powered device 118 (such as the rectifier 126 or the load 130). However, there may be cases when the wireless powered device 118 is not ready to use the power or when the power may damage other components of the wireless powered device 118. Furthermore, the secondary coil 120 may unexpectedly receive energy from an induction coil used for heating (rather than wireless power transmission). To prevent damage to other components or to disable unintended wireless power transmission, a switch 150 may be connected to one or both ends of the secondary coil 120. Thus, even if a magnetic field is induced near the secondary coil 120, the secondary coil 120 does not conduct current because the secondary coil 120 is disconnected from the power receiving circuit. Thus, the switch 150 may prevent induced voltage from flowing through the secondary coil 120 to the power receiving circuit. The present disclosure includes several options for the placement, construction, and operation of switch 150. For example, switch 150 may be a switch connected in series between secondary coil 120 and rectifier 126 (or load 130), as shown in Figure 1. Other possible configurations of switch 150 are described herein.

[0043] The switch 150 may also be used to disconnect the secondary coil 120 from the power receiving circuit (such as the rectifier 126, the load 130, or both) during the k-factor measurement period. The k-factor measurement period may be different from the power transfer period. In some implementations, the k-factor measurement period may precede the power transfer period. Alternatively or additionally, multiple k-factor measurement periods may interleave multiple power transfer periods in an alternating pattern. The power transfer period may include powering the load 130 using power received by the secondary coil 120. In contrast, the k-factor measurement period may be used to measure a coupling coefficient between the secondary coil 120 and the primary coil 110. During the k-factor measurement period, the wireless power transmitting device 102 may transmit a k-factor measurement signal to the wireless power receiving device 118. The wireless power receiving device 118 may measure the voltage of the k-factor measurement signal during the k-factor measurement period. During the k-factor measurement period, it may be desirable to disconnect the receiving circuit to prevent the receiving circuit from interfering with the k-factor measurement signal or to improve the accuracy of the measurement. The receiver controller 128 may control the switch 150 to disconnect the rectifier 126 from the secondary coil 120 during the k-factor measurement period. The receiver controller 128 may send feedback to the wireless power transmission device 102 (e.g., via the wireless communication interface 132) based on measurements taken during the k-factor measurement period.

[0044] FIG. 2 illustrates a block diagram of an exemplary wireless power transmission device 102. The wireless power transmission device 102 may include a power source 112, a power signal generator 106, and a primary coil 110. The power signal generator 106 is illustrated by a half-bridge circuit that converts DC power from the power source 112 into an AC signal that is applied to the primary coil 110. Although not illustrated in FIG. 2, the power source 112 may include a conversion unit that converts AC mains power into DC power of the power source 112. Furthermore, the power signal generator 106 may be any type of power conversion circuit that can provide an AC signal to the primary coil 110. For example, the power signal generator 106 may include a half-bridge circuit with a parallel capacitor as shown in FIG. 2. Alternatively, the power signal generator 106 may include a full-bridge circuit.

[0045] The wireless power transmission device 102 may also include a wireless communication interface 114 and a first communication coil 116 described with reference to FIG. 1. The wireless communication interface 114 may be configured to transmit or receive a communication signal via the first communication coil 116. The wireless communication interface 114 may implement a Bluetooth or NFC protocol, or any other type of short-range radio frequency communication protocol. The wireless communication interface 114 may be included in the wireless power transmission device 102 because the wireless power transmission device 102 is constructed according to a wireless power transfer (WPT) protocol.

[0046] As described herein, some induction-based systems for transmitting energy may use induction for purposes other than wireless power transmission. For example, the induction-based heating element of a conventional induction hob may include a power source, a power signal generator, and an induction coil that operate very similarly to the power source 112, the power signal generator 106, and the primary coil 110, respectively. Because of the similarity, these induction-based systems may inadvertently induce a voltage in the secondary coil of the wireless power receiving device. However, a conventional induction hob that does not support the WPT protocol may not include the wireless communication interface 114 required by the technical standard of the WPT protocol. The wireless power receiving device may determine whether the induced voltage in its secondary coil is from a wireless power transmitting device 102 that supports the WPT protocol based on the presence of handshake communication from the wireless communication interface 114. In the absence of handshake communication, the wireless power receiving device may disconnect the secondary coil from the power receiving circuit to prevent damage to the power receiving circuit.

[0047] A conventional induction-based system (such as a conventional induction hob) may send a ping or "pan detect" signal. When a pan or non-WPT device is placed on the hob, the hob may measure the change in impedance to detect that a pan or non-WPT device is placed over an induction-based heating element. If the measured impedance is within acceptable limits, the hob changes operation to an induction-based heating mode that uses induction to transmit energy. Thus, pan detection is based on the impedance provided by the pan / appliance. In the case of a wireless power receiving device (such as those described herein), one or more switches may cause the impedance of the secondary coil to be outside of acceptable limits. For example, a series switch (such as described with reference to Figures 1, 3, 4, 5, and 7) may cause the impedance measured by a conventional induction-based hob to be higher than acceptable limits. A shunt switch (such as described with reference to Figure 6) may cause the impedance measured by a conventional induction-based hob to be lower than acceptable limits. Thus, the conventional induction-based hob does not change to an induction-based heating mode.

[0048] FIG. 3 illustrates a block diagram of an exemplary wireless power receiving device 300 having a switch 350 connected in series between the secondary coil 120 and the rectifier 126. The components of the wireless power receiving device 300 may include components with similar numbers as the wireless power receiving device 118 described with reference to FIG. 1. The wireless power receiving device 300 may include a load 130, or the load 130 may be an external component connected to the wireless power receiving device 300. The exemplary rectifier 126 illustrated in FIG. 3 is a full-bridge rectifier configured to convert the received power from an AC signal to DC power used by the load 130. In some implementations, the wireless power receiving device 300 may not include the rectifier 126. Other types of rectifiers or power conversion units may be used in various implementations. Furthermore, the wireless power receiving device 300 illustrates an optional capacitor 226 connected between two legs of the rectifier 126. In some implementations, the wireless power receiving device 300 may not include the optional capacitor 226. 3 also shows a capacitor 162 that may be coupled to one or more legs of the secondary coil 120. A switch 350 may be connected in series between one leg of the secondary coil 120 and the rectifier 126. The switch 350 may be connected before or after the capacitor 162 when the capacitor 162 is present on that leg.

[0049] The wireless power receiving device 300 includes a second communication coil 134, a wireless communication interface 132, and a receiver controller 128, as described with reference to FIG. 1. The wireless communication interface 132 may be configured to receive a communication signal from a wireless power transmitting device. For example, the wireless communication interface 132 may receive a communication signal from a corresponding wireless communication interface 114, as described with reference to FIGS. 1 and 2. The receiver controller 128 may detect a state of the load 130 using the detection signal 331. The receiver controller 128 may control the switch 350 (labeled "S1") using the control signal 351. According to an aspect of the present disclosure, the receiver controller 128 may operate the control signal 351 based on the presence or absence of a handshake communication. For example, the receiver controller 128 may cause the switch 350 to connect the secondary coil 120 to the rectifier 126 (or the load 130) when a handshake communication is established between the wireless power receiving device 300 and a wireless power transmitting device implementing a WPT protocol. Alternatively or additionally, the receiver controller 128 may cause the switch 350 to disconnect the secondary coil 120 from the rectifier 126 (or the load 130) if there is no handshake communication or if the wireless communication interface 132 receives a communication signal that is not compatible with the wireless power receiving device 300.

[0050] In some implementations, the second communication coil 134 may be configured to harvest energy from the communication signal to power the wireless communication interface 132 and the receiver controller 128. For example, the communication signal may provide sufficient energy to generate bias power for the startup and operation of the wireless communication interface 132 prior to the power transfer stage via the secondary coil 120. In some implementations, the bias power may be used to operate the switch 350. In some implementations, the switch 350 may be normally open (NO) such that the secondary coil 120 is disconnected from the rectifier 126 until the switch 350 is closed. In some implementations, the switch 350 may be closed using bias power obtained from the wireless communication interface 132 or from a battery (not shown) included in the wireless power receiving device 120.

[0051] In some implementations, the second communication coil 134 (such as an NFC coil) may potentially have an induced voltage from a conventional induction-based fob. However, the impedance caused by the second communication coil 134 may be outside the acceptable limits of the conventional induction-based fob. Furthermore, the second communication coil 134 typically has fewer turns or coils that limit the amount of induced voltage. Thus, the second communication coil 134 and the wireless communication interface 132 are less susceptible to overvoltage or unintended power transfer from a conventional induction-based fob.

[0052] FIG. 4 illustrates a block diagram of an exemplary wireless powered device 400 having a switch 450 connected in series between the secondary coil 120 and a load 430. The components of the wireless powered device 400 may include similarly numbered components as the wireless powered device 118 described with reference to FIG. 1. However, the wireless powered device 400 may not include a rectifier (not shown) because the load 430 is configured to operate using an AC signal captured by the secondary coil 120. In this example, the load 430 may be a powered circuit configured to utilize the power captured by the secondary coil 120. The switch 450 may be connected in series between the secondary coil 120 and the load 430 to prevent the load 430 from being damaged by an unexpected voltage induced in the secondary coil 120, such as when the wireless powered device 400 is located near a non-WPT induction-based system. Similar to the wireless powered device 300 described with reference to FIG. 3, the receiver controller 128 may be configured to manage the switch 450 based on the presence or absence of a communication signal captured by the wireless communication interface 132.

[0053] 5 illustrates a block diagram of an example wireless power receiving device 500 having multiple switches connected in series between the secondary coil 120 and the rectifier 126. Components of the wireless power receiving device 500 may include similarly numbered components as the wireless power receiving device 300 described with reference to FIG. 3. Instead of a single series switch (such as the switch 350 described with reference to FIG. 3), the wireless power receiving device 500 may include series switches 551 and 552 connected between a leg of the secondary coil 120 and the rectifier 126. A first series switch 551 (labeled "S1") may be connected in series with a first leg of the secondary coil 120. A second series switch 552 (labeled "S2") may be connected in series with a second leg of the secondary coil 120.

[0054] FIG. 6 illustrates a block diagram of an exemplary wireless power receiving device 600 having a switch 650 connected as a shunt between both ends of the secondary coil 120. The components of the wireless power receiving device 600 may include components with similar numbers as the wireless power receiving device 118 described with reference to FIG. 1. The switch 650 may be referred to as a shunt switch. The switch 650 may short the ends of the secondary coil 120 to prevent or reduce the induced voltage of the secondary coil 120 from reaching the rectifier 126. In this example, the shunt switch 650 may be normally closed (to short the secondary coil 120) in the absence of a communication signal from a corresponding wireless power transmission device. When the wireless communication interface 132 receives a communication signal from a corresponding wireless power transmission device, the receiver controller 128 may open the switch 650 to allow the transfer of power from the secondary coil 120 to the rectifier 126.

[0055] 7 illustrates a block diagram of an example wireless power receiving device 700 having a switch 750 for enabling disconnection of the secondary coil 120 during a measurement period for determining the coupling coefficient. The components of the wireless power receiving device 700 may include similarly numbered components as the wireless power receiving device 118 and the wireless power receiving device 300 described with reference to FIGS. 1 and 3, respectively. Note that the switch 750 is shown as a series switch on one leg of the secondary coil 120. However, in some implementations, the switch 750 may be similar to any configuration of the switches 350, 450, 551, 552, or 650 described with reference to FIGS. 3, 4, 5, or 6, respectively.

[0056] The wireless power receiving device 700 may also include a voltage sensor 720 coupled to the secondary coil 120. The receiver controller 128 may cause the switch 750 to disconnect the secondary coil 120 and the voltage sensor 720 from the power receiving circuit (such as the rectifier 126 and the load 130) during the k-factor measurement period. The receiver controller 128 may cause the switch 750 to connect the secondary coil 120 to the power receiving circuit during a power transfer period (different from the k-factor measurement period).

[0057] During the k-factor measurement period, the wireless power transmission device (not shown) may transmit a k-factor measurement signal to the wireless power receiving device. The k-factor measurement signal may be at a lower power than that transmitted during the power transfer period. In some implementations, the k-factor measurement signal may be transmitted using a known or predetermined voltage (v1) and frequency (fp). The voltage sensor 720 may allow the receiver controller 128 to measure the received voltage (v2) of the secondary coil 120 during the k-factor measurement period. The receiver controller 128 may communicate feedback to the wireless power transmission device via the wireless communication interface 132. The feedback may be based on v2 measured during the k-factor measurement period. The wireless power transmission device may utilize the feedback to determine a coupling coefficient (k-factor). The k-factor may be used by the wireless power transmission device to determine an operating point of the wireless power signal that the wireless power transmission device transmits during the power transfer period. For example, the operating point may be based on a calculation that considers the ratio between v1 and v2.

[0058] In some implementations, a communication from the wireless power transmitting device to the wireless power receiving device may precede the k-factor measurement signal. For example, the wireless communication interface 132 may receive a communication from the wireless power transmitting device to set the k-factor measurement period before receiving the k-factor measurement signal. In some implementations, the communication may indicate the start or duration of the k-factor measurement period. Alternatively or additionally, the communication may include an instruction to start the k-factor measurement period or may indicate that the wireless power transmitting device is transmitting the k-factor measurement signal. In some implementations, the communication (such as based on a WPT protocol) may infer that the k-factor measurement signal will be transmitted and cause the wireless power receiving device to start the k-factor measurement period. Alternatively or additionally, the communication may be an indication that the wireless power transmitting device supports the WPT protocol. The wireless power receiving device may determine the k-factor measurement period based on the WPT protocol.

[0059] FIG. 8 illustrates a flow chart diagram of an example process 800 according to some implementations. The operations of the process 800 may be implemented by a wireless power receiving device described herein. For example, the operations of the process 800 may be implemented by any of the wireless power receiving devices 118, 300, 400, 500, 600, or 700 described with reference to FIG. 1, FIG. 2, FIG. 4, FIG. 5, FIG. 6, FIG. 7, or FIG. 7, respectively. For brevity, the operations are described as being performed by the device. In block 810, the device may control one or more switches disposed between a secondary coil and a receiving circuit of the wireless power receiving device based at least in part on a communication from the wireless power transmitting device. The secondary coil may be configured to receive power from a wireless power signal of the wireless power transmitting device. The receiving circuit may be configured to utilize the received power.

[0060] FIG. 9 illustrates a flow chart diagram of another exemplary process 900 according to some implementations. The operations of the process 900 may be implemented by a wireless power receiving device described herein. For example, the operations of the process 900 may be implemented by any of the wireless power receiving devices 119, 300, 400, 500, 600, or 700 described with reference to FIG. 1, FIG. 2, FIG. 4, FIG. 5, FIG. 6, FIG. 7, or FIG. 7, respectively. For brevity, the operations are described as being performed by the device. In block 910, the device may disconnect the secondary coil of the wireless power receiving device from the receiving circuit of the wireless power receiving device using one or more switches disposed between the secondary coil and the receiving circuit during a coupling coefficient (k-factor) measurement period. The secondary coil may be configured to receive power from a wireless power signal of the wireless power transmitting device. The receiving circuit may be configured to utilize the received power. In block 920, the device may connect the secondary coil to the receiving circuit using one or more switches during a power transmission period.

[0061] FIG. 10 illustrates a block diagram of an exemplary apparatus 1000 for use in a wireless power transmission system. In some embodiments, the apparatus 1000 may be a wireless power receiving device, such as any of the wireless power receiving devices described herein. The apparatus 1000 may include a processor 1002 (possibly including multiple processors, multiple cores, multiple nodes, or multi-threading, etc.). The apparatus 1000 may also include a memory 1006. The memory 1006 may be a system memory or any one or more of the possible implementations of the computer-readable media described herein. The apparatus 1000 may also include a bus 1011 (PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.).

[0062] The apparatus 1000 may include one or more controllers 1062 configured to manage one or more switches 1064. The one or more switches 1064 may connect or disconnect a power transmission coil 1066 (such as a secondary coil) to a rectifier or a load (not shown). In some implementations, the controller 1062 may be distributed within the processor 1002, the memory 1006, and the bus 1011. The controller 1062 may perform some or all of the operations described herein. For example, the controller 1062 may implement features of a driver controller described herein.

[0063] The memory 1006 may include computer instructions executable by the processor 1002 to implement the functionality of the implementations described with reference to Figures 1-9. Any of these functions may be implemented partially (or entirely) in hardware or in the processor 1002. For example, the functions may be implemented by an application specific integrated circuit, logic implemented in the processor 1002, a co-processor on a peripheral device or card, etc. Furthermore, an implementation may include fewer or additional components not shown in Figure 10. The processor 1002, the memory 1006, and the controller 1062 may be coupled to a bus 1011. Although shown as being coupled to the bus 1011, the memory 1006 may be coupled to the processor 1002.

[0064] 1-10 and the operations described herein are examples intended to aid in understanding example implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some different operations.

[0065] The foregoing disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practicing the aspects. Although aspects of the present disclosure have been described with respect to various examples, any combination of aspects from any example is within the scope of the present disclosure. The examples of the present disclosure are provided for educational purposes. Alternatively, or in addition to other examples described herein, the examples include any combination of the following implementation options (identified as clauses for reference):

[0066] Terms Clause 1. A wireless power receiving device comprising: a secondary coil configured to receive power from a wireless power signal of a wireless power transmission device; a receiving circuit configured to utilize the received power; and one or more switches disposed between the secondary coil and the receiving circuit, the one or more switches configured to connect the secondary coil and the receiving circuit based at least in part on communication from the wireless power transmission device.

[0067] Clause 2. A wireless power receiving device as described in clause 1, wherein the receiving circuit includes a rectifier, and the one or more switches include a first switch connected in series between a first end of the secondary coil and the rectifier.

[0068] Clause 3. A wireless power receiving device as described in clause 2, wherein the one or more switches include a second switch connected in series between a second end of the secondary coil and the rectifier.

[0069] Clause 4. A wireless power receiving device as described in Clause 1, wherein the received power is alternating current (AC) power, the receiving circuit includes a load configured to utilize the AC power from the secondary coil, and the one or more switches include a switch connected in series between a first end of the secondary coil and the load.

[0070] Clause 5. A wireless power receiving device as described in clause 4, wherein the one or more switches include a second switch connected in series between the second end of the secondary coil and the load.

[0071] Clause 6. A wireless power receiving device described in any one of clauses 1 to 5, wherein the one or more switches are normally open to disconnect the secondary coil from the receiving circuit in the absence of communication from the wireless power transmission device.

[0072] Clause 7. A wireless power receiving device described in any one of clauses 1 to 6, wherein one or more switches are operated to connect the secondary coil and the receiving circuit when communication from the wireless power transmission device complies with a wireless charging protocol.

[0073] Clause 8. A wireless power receiving device described in any one of clauses 1 to 6, further comprising a wireless communication interface configured to receive communications from the wireless power transmitting device, and a receiver controller configured to control one or more switches based at least in part on the communications.

[0074] Clause 9. A wireless power receiving device as described in clause 8, wherein the one or more switches are operated, at least initially, using bias power obtained by a communication coil of the wireless communication interface.

[0075] Clause 10. A wireless power receiving device as described in clause 9, wherein after the one or more switches connect the secondary coil and the power receiving circuit, the one or more switches are subsequently operated using the received power.

[0076] Clause 11. A wireless power receiving device according to any one of clauses 9 to 10, wherein the communication coil of the wireless communication interface is electrically isolated from the secondary coil and the power receiving circuit.

[0077] Clause 12. A wireless power receiving device described in any one of clauses 8 to 11, wherein the wireless communication interface is a short-range radio frequency interface configured to receive and process wireless communication signals from a corresponding wireless communication interface of the wireless power transmission device.

[0078] Clause 13. A wireless power receiving device as described in any one of clauses 1 to 12, wherein the one or more switches include a protection switch configured to protect the receiving circuit from damage when the secondary coil is placed near an inductive source that is not a wireless power transmission device.

[0079] Clause 14. A wireless power receiving device as described in Clause 1, wherein the one or more switches include a shunt switch connected across both ends of the secondary coil, the shunt switch configured to prevent or reduce an induced voltage on the secondary coil from reaching the receiving circuit when the secondary coil is placed near an inductive source that is not a wireless power transmission device.

[0080] Clause 15. A wireless power receiving device as described in clause 14, wherein in the absence of communication from the wireless power transmitting device, the shunt switch is normally closed to prevent or reduce induced voltage from reaching the receiving circuit.

[0081] Clause 16. A wireless power receiving device comprising: a secondary coil configured to receive power from a wireless power signal of a wireless power transmission device; a receiving circuit configured to utilize the received power; and one or more switches arranged between the secondary coil and the receiving circuit, the one or more switches configured to disconnect the secondary coil from the receiving circuit during a coupling coefficient (k coefficient) measurement period and to connect the secondary coil to the receiving circuit during a power transmission period.

[0082] Clause 17. The wireless power receiving device of clause 16, further comprising a receiver controller configured to control one or more switches based at least in part on the k-factor measurement period and the power transfer period.

[0083] Clause 18. The wireless power receiving device of clause 17, wherein a k-factor measurement period precedes a power transfer period, and an operating point of the wireless power signal is based, at least in part, on a coupling factor determined during the k-factor measurement period.

[0084] Clause 19. A wireless power receiving device described in any one of clauses 17 to 18, wherein the secondary coil is further configured to receive a k-factor measurement signal from the wireless power transmission device, and the k-factor measurement period enables measuring the voltage of the secondary coil based on the k-factor measurement signal while the secondary coil is disconnected from the receiving circuit.

[0085] Clause 20. The wireless power receiving device according to any one of clauses 16 to 19, further comprising a wireless communication interface configured to receive communication from a wireless power transmitting device.

[0086] Clause 21. A wireless power receiving device as described in any one of clauses 16 to 20, wherein the communication includes at least one member of the group consisting of an indication of the start or duration of the k-factor measurement period, an instruction to start the k-factor measurement period, communication inferred by the wireless power receiving device to start the k-factor measurement period, and an indication that the wireless power transmission device supports a wireless power transmission protocol that specifies the k-factor measurement period.

[0087] Clause 22. A wireless power receiving device as described in any one of clauses 16 to 19, wherein the one or more switches include at least one member of the group consisting of a switch connected in series between a first end of the secondary coil and the receiving circuit, a switch connected in series between a second end of the secondary coil and the receiving circuit, a switch connected in series between at least one end of the secondary coil and a load configured to utilize the received power alternating current (AC), and a shunt switch connected between both ends of the secondary coil.

[0088] Clause 23. A method, comprising: controlling, based at least in part on communication from a wireless power transmission device, one or more switches disposed between a secondary coil and a receiving circuit of a wireless power receiving device, the secondary coil being configured to receive power from a wireless power signal of the wireless power transmission device, and the receiving circuit being configured to utilize the received power.

[0089] Clause 24. The method of clause 23, wherein controlling the one or more switches includes disconnecting the secondary coil from the receiving circuit in the absence of communication from the wireless power transmission device.

[0090] Clause 25. A method according to any one of clauses 23 to 24, wherein controlling the one or more switches includes connecting the secondary coil and the receiving circuit if communication from the wireless power transmission device complies with a wireless charging protocol.

[0091] Clause 26. The method of any one of clauses 23 to 25, further comprising receiving communication from a wireless power transmitting device via a wireless communication interface of the wireless power receiving device.

[0092] Clause 27. The method of clause 26, further comprising collecting bias power via a communication coil of the wireless communication interface, and at least initially using the bias power to control one or more switches.

[0093] Clause 28. The method of clause 27, further comprising subsequently controlling the one or more switches using the received power after the one or more switches connect the secondary coil and the receiving circuit.

[0094] Clause 29. The method according to any one of clauses 26 to 28, wherein the wireless communication interface is a short-range radio frequency interface configured to receive and process wireless communication signals from a corresponding wireless communication interface of a wireless power transmission device.

[0095] Clause 30. A method according to any one of clauses 23 to 29, wherein controlling the one or more switches includes operating one or more switches to protect the receiving circuit from damage when the secondary coil is placed near an inductive source that is not a wireless power transmission device.

[0096] Clause 31. A method, comprising: disconnecting a secondary coil from a receiving circuit using one or more switches disposed between a secondary coil of a wireless power receiving device and a receiving circuit of the wireless power receiving device during a coupling coefficient (k-factor) measurement period, wherein the secondary coil is configured to receive power from a wireless power signal of a wireless power transmission device and the receiving circuit is configured to utilize the received power; and connecting the secondary coil to the receiving circuit using the one or more switches during a power transmission period.

[0097] Clause 32. The method of clause 31, further comprising controlling, by the receiver controller, one or more switches based at least in part on the k-factor measurement period and the power transfer period.

[0098] Clause 33. A method according to any one of clauses 31 to 32, further comprising receiving, by the secondary coil, a k-factor measurement signal from the wireless power transmission device during a k-factor measurement period, and measuring a voltage of the secondary coil based on the k-factor measurement signal with the secondary coil disconnected from the receiving circuit during the k-factor measurement period.

[0099] Clause 34. The method of any one of clauses 31 to 33, further comprising receiving a communication from a wireless power transmission device via a wireless communication interface.

[0100] Clause 35. The method of any one of clauses 31 to 34, wherein the communication includes at least one member of the group consisting of an indication of the start or duration of the k-factor measurement period, an instruction to start the k-factor measurement period, a communication inferred by the wireless power receiving device to start the k-factor measurement period, and an indication that the wireless power transmission device supports a wireless power transmission protocol that specifies the k-factor measurement period.

[0101] Clause 36. The method of clause 33, further comprising providing feedback to the wireless power transmission device based on a voltage of the secondary coil measured during the k-factor measurement period.

[0102] The diagrams, operations, and components described herein are examples intended to aid in understanding example implementations and should not be used to limit potential implementations or to limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some different operations.

[0103] As used herein, phrases referring to "at least one of" or "one or more of" a list of items refer to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover the possibilities of a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a, b, and c.

[0104] The various example components, logic, logic blocks, modules, circuits, operations and algorithmic processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed herein and structural equivalents thereof. Interoperability of the hardware, firmware, and software has been generally described in terms of functionality and illustrated in the various example components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the particular application and design constraints imposed on the overall system.

[0105] The hardware and data processing devices used to implement the various example components, logic, logic blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed using general purpose single-chip or multi-chip processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices (PLDs), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration. In some implementations, certain processes, operations, and methods may be performed by circuitry specific to a given function.

[0106] As mentioned above, some aspects of the subject matter described herein can be implemented as software. For example, various functions of components disclosed herein, or various blocks or steps of methods, operations, processes or algorithms disclosed herein, can be implemented as one or more modules of one or more computer programs. Such computer programs can include non-transitory processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by or to control the operation of a data processing device, including components of the device described herein. By way of example and not limitation, such storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0107] Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of the present disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but should be accorded the widest scope consistent with the present disclosure, the principles, and novel features disclosed herein.

[0108] Moreover, various features described herein in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Thus, although features may be described above as acting in a particular combination and initially claimed as such, one or more features from a claimed combination can, in some cases, be deleted from the combination, and the claimed combination may be directed to a partial combination or a variation of the partial combination.

[0109] Similarly, although operations are shown in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or in any sequential order, or that all of the operations shown be performed, to achieve desirable results. Additionally, the figures may generally depict one or more exemplary processes in the form of a flowchart or flow diagram. However, other operations not shown may be incorporated into the exemplary process depicted in the schematic. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the depicted operations. In some circumstances, multitasking and parallel processing may be advantageous. Additionally, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products.

Claims

1. A wireless power receiving device, a secondary coil configured to receive power from a wireless power signal of a wireless power transmission device; A power receiving circuit configured to utilize the received power; one or more switches disposed between the secondary coil and the power receiving circuit, the one or more switches configured to connect the secondary coil and the power receiving circuit based at least in part on a handshake communication between the wireless power receiving device and the wireless power transmission device; a wireless communication interface configured to receive the handshake communication from the wireless power transmission device; a receiver controller configured to control the one or more switches based at least in part on the handshake communication; Equipped with A wireless power receiving device, wherein the one or more switches are, at least initially, operated using bias power obtained by a communication coil of the wireless communication interface.

2. The wireless power receiving device of claim 1 , wherein the one or more switches include a first switch connected in series between a first end of the secondary coil and the power receiving circuit.

3. 3. The wireless power receiving device according to claim 2, wherein there are multiple switches arranged between the secondary coil and the power receiving circuit, including a second switch connected in series between a second end of the secondary coil and the power receiving circuit.

4. 2. The wireless power receiving device of claim 1, wherein the received power is alternating current (AC) power, the power receiving circuit includes a load configured to utilize the AC power from the secondary coil, and the one or more switches include a switch connected in series between a first end of the secondary coil and the load.

5. The wireless power receiving device according to any one of claims 1 to 4, wherein the one or more switches are normally open to disconnect the secondary coil from the receiving circuit in the absence of the handshake communication from the wireless power transmission device.

6. The wireless power receiving device according to any one of claims 1 to 5, wherein the one or more switches are operated to connect the secondary coil and the receiving circuit when the handshake communication from the wireless power transmission device complies with a wireless charging protocol.

7. The wireless power receiving device of claim 1 , wherein after the one or more switches connect the secondary coil and the power receiving circuit, the one or more switches are subsequently operated using the received power.

8. The wireless power receiving device according to any one of claims 1 to 7, wherein the communication coil of the wireless communication interface is electrically isolated from the secondary coil and the power receiving circuit.

9. The wireless power receiving device according to any one of claims 1 to 8, wherein the wireless communication interface is a short-range radio frequency interface configured to receive and process wireless communication signals from a corresponding wireless communication interface of the wireless power transmission device.

10. The wireless power receiving device according to any one of claims 1 to 9, wherein the one or more switches include a protection switch configured to protect the receiving circuit from damage when the secondary coil is placed near an inductive source that is not a wireless power transmission device.

11. the one or more switches include a shunt switch connected across both ends of the secondary coil, the shunt switch configured to prevent or reduce an induced voltage in the secondary coil from reaching the power receiving circuit when the secondary coil is placed near an inductive source that is not a wireless power transmission device; the shunt switch is normally closed to prevent or reduce the induced voltage from reaching the power receiving circuit when there is no handshake communication from the wireless power transmission apparatus. The wireless power receiving device according to claim 1 .

12. The wireless power receiving device according to any one of claims 1 to 11, wherein the power receiving circuit includes a rectifier between the secondary coil and a load.

13. The wireless power receiving device according to claim 1 , wherein the handshake communication includes at least a first one-to-one communication from the wireless power transmitting device to the wireless power receiving device.

14. A wireless power receiving device, a secondary coil configured to receive power from a wireless power signal of a wireless power transmission device; A power receiving circuit configured to utilize the received power; one or more switches disposed between the secondary coil and the power receiving circuit, During a coupling coefficient (k-factor) measurement period, the secondary coil is disconnected from the power receiving circuit; and one or more switches configured to connect the secondary coil and the power receiving circuit during a power transfer period.

15. a receiver controller configured to control the one or more switches based at least in part on the k-factor measurement period and the power transfer period. The wireless power receiving device according to claim 14 , further comprising:

16. 16. The wireless power receiving device of claim 15, wherein the k-factor measurement period precedes the power transfer period, and an operating point of the wireless power signal is based, at least in part, on a coupling factor determined during the k-factor measurement period.

17. the secondary coil is further configured to receive a k-factor measurement signal from a wireless power transmission device; the k-factor measurement period permits measuring a voltage of the secondary coil based on the k-factor measurement signal while the secondary coil is disconnected from the power receiving circuit. The wireless power receiving device according to any one of claims 15 to 16.

18. a wireless communication interface configured to receive communications from the wireless power transmission device; The wireless power receiving device according to any one of claims 14 to 17, further comprising:

19. The communication, an indication of the start or duration of said k-factor measurement period; instructions to initiate the k-factor measurement period; communication inferred by the wireless power receiving device to initiate the k-factor measurement period; and 20. The wireless power receiving device of claim 18, wherein the k-factor measurement period is incremented by 100.degree. ...

20. the one or more switches being: a switch connected in series between a first end of the secondary coil and the power receiving circuit; a switch connected in series between a second end of the secondary coil and the power receiving circuit; a switch connected in series between at least one end of the secondary coil and a load configured to utilize the received alternating current (AC); and A shunt switch connected across both ends of the secondary coil.

21. 1. A method comprising: controlling, based at least in part on a handshake communication between a wireless power transmission device and a wireless power receiving device, one or more switches disposed between a secondary coil and a receiving circuit of the wireless power receiving device, the secondary coil being configured to receive power from a wireless power signal of the wireless power transmission device, and the receiving circuit being configured to utilize the received power; receiving the handshake communication from the wireless power transmission device via a wireless communication interface of the wireless power receiving device; collecting bias power via a communication coil of the wireless communication interface; and at least initially using the bias power to control the one or more switches.

22. 22. The method of claim 21, wherein controlling the one or more switches comprises disconnecting the secondary coil from the power receiving circuit in the absence of the handshake communication from the wireless power transmitting device.

23. The method according to any one of claims 21 to 22, wherein controlling the one or more switches comprises connecting the secondary coil and the power receiving circuit when the handshake communication from the wireless power transmission device complies with a wireless charging protocol.

24. subsequently controlling the one or more switches using the received power after the one or more switches connect the secondary coil and the power receiving circuit.

22. The method of claim 21 further comprising:

25. The method according to any one of claims 21 to 24, wherein the wireless communication interface is a short-range radio frequency interface configured to receive and process wireless communication signals from a corresponding wireless communication interface of the wireless power transmission device.

26. The method of any one of claims 21 to 25, wherein controlling the one or more switches includes operating the one or more switches to protect the receiving circuit from damage when the secondary coil is placed near an inductive source that is not a wireless power transmission device.

27. 1. A method comprising: During a coupling coefficient (k-factor) measurement period, disconnecting a secondary coil of a wireless power receiving device from a power receiving circuit using one or more switches disposed between the secondary coil and a power receiving circuit of the wireless power receiving device, the secondary coil being configured to receive power from a wireless power signal of a wireless power transmission device and the power receiving circuit being configured to utilize the received power; and connecting the secondary coil to the power receiving circuit using the one or more switches during a power transfer period.

28. controlling, by a receiver controller, the one or more switches based at least in part on the k-factor measurement period and the power transfer period.

28. The method of claim 27, further comprising:

29. receiving, by the secondary coil, a k-factor measurement signal from a wireless power transmission device during the k-factor measurement period; measuring a voltage of the secondary coil based on the k-factor measurement signal while the secondary coil is disconnected from the power receiving circuit during the k-factor measurement period; The method of any one of claims 27 to 28, further comprising:

30. Receiving communication from the wireless power transmission device via a wireless communication interface. The method of any one of claims 27 to 29, further comprising:

31. The communication, an indication of the start or duration of said k-factor measurement period; instructions to initiate the k-factor measurement period; communication inferred by the wireless power receiving device to initiate the k-factor measurement period; and and an indication that the wireless power transmission device supports a wireless power transmission protocol that specifies the k-factor measurement period.

32. providing feedback to the wireless power transmission apparatus based on the voltage of the secondary coil measured during the k-factor measurement period; 30. The method of claim 29, further comprising:

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