Wireless power transfer

Abstract

A wireless power transfer system comprises a power transmitter (101) that provides power to a power receiver (105) via an electromagnetic power transfer signal. The power receiver (105) comprises a circuit (107, 601, 613) comprising a receiver coil (107) as part of a resonant circuit having first and second resonances formed by the receiver coil (107) and at least first and second capacitors (601). The resonant frequencies differ substantially. A power path (607, 605) provides power from the receiver coil (107) to the load (603) and comprises a protection element (607) arranged to operate in a protected state in which a constraint is applied to power transfer from the receiver coil (107) and a non-protected state in which the constraint is not applied. The protection element (607) switches to a protection state in response to detecting the fault condition. The power receiver is arranged such that a resonance characteristic of the second resonance differs for the protection element (607) when in the protected state than when in the non-protected state.

Description

TECHNICAL FIELD

[0001] The present application relates to wireless power transfer, in particular but not exclusively to the operation of a wireless power transfer system and the provision of inductive power transfer by a power receiver to high power devices such as kitchen appliances. BACKGROUND

[0002] Most electrical products currently require dedicated electrical contacts in order to be powered from an external power source. However, such designs are often impractical, requiring the user to manually plug in a connector or otherwise establish physical electrical contact. Often, power requirements also vary significantly, with most current devices being provided with their own dedicated power supply, resulting in the average user needing to carry a large number of different power supplies, each dedicated to a particular device. Although the use of internal batteries can avoid the need for wired connection to a power source during use, this only provides a partial solution as the batteries need to be charged (or replaced). The use of batteries also significantly increases the weight, and potentially the cost and size, of the device.

[0003] In order to provide a significantly improved user experience, it has been proposed to use wireless power sources, in which power is inductively transferred from a transmitter inductor in a power transmitter device to a receiver coil in each device.

[0004] Power transfer via magnetic induction is a well-known concept, primarily applied in transformers with a tight coupling between a primary transmitter inductor / coil and a secondary receiver coil. By separating the primary transmitter coil and the secondary receiver coil between two devices, wireless power transfer between these devices becomes possible based on the principle of loosely coupled transformers.

[0005] Such an arrangement allows wireless power transfer to a device without the need for any wires or physical electrical connections. Indeed, it can simply allow a device to be placed near or on top of a transmitter coil in order to be externally charged or powered. For example, a power transmitter device can be arranged with a horizontal surface on which a device can simply be placed in order to be powered.

[0006] Furthermore, such wireless power transfer arrangements can advantageously be designed so that a power transmitter device can be used with a range of power receiver devices. In particular, a wireless power transfer method has been defined, known as the Qi specification, which is currently being further developed. This method allows a power transmitter device that complies with the Qi specification to be used with power receiver devices that also meet the Qi specification, without having to come from the same manufacturer or having to be dedicated to each other. The Qi standard also includes some functionality for allowing operation to be adapted to a particular power receiver device (e.g. depending on a particular power consumption).

[0007] The Qi specification is developed by the Wireless Power Consortium, more information can be found on its website: http: / / www.wirelesspowerconsortium.com / index.html, among others the specification document defining the specification can be found.

[0008] The Wireless Power Consortium develops the Qi specification based on the Ki specification (also known as the Wireless Power Kitchen specification), which aims to provide safe, reliable and efficient wireless power transfer to kitchen appliances. Ki supports higher power levels up to 2.2 kW.

[0009] A key issue for wireless power transfer is that it can be performed safely and reliably.

[0010] For example, a potential issue for wireless power transfer is that power can be unintentionally transferred to e.g. metal objects that happen to be in the vicinity of the power transmitter. For example, if a foreign object (e.g. a coin, a key, a ring, etc.) is placed on the power transmitter platform that is arranged to receive a power receiver, the magnetic flux generated by the transmitter coil will induce eddy currents in the metal object, which will cause the object to heat up. The heat increase can be very significant and can be very detrimental.

[0011] To reduce the risk of such a situation occurring, wireless power transfer systems include foreign object detection, where the power transmitter can detect the presence of a foreign object and reduce the transmit power and / or generate a user alert when a foreign object is detected. For example, the Qi system includes functionality for detecting foreign objects as well as for reducing power when a foreign object is detected. In particular, section 11 of the Qi specification version 1.2.1 describes various methods of detecting foreign objects.

[0012] A particularly challenging issue is to ensure safe and controllable operation even if the relevant devices and functionality malfunctions. For example, if a malfunction occurs in the power receiver (such as a component failure), it is important to ensure that the malfunction is handled appropriately, e.g. does not lead to further malfunctions or damage, in particular to ensure that no unsafe situations arise.

[0013] Hence, it would be desirable for a system to be arranged to cope with various malfunctioning and abnormal operating situations. However, such approaches are inherently difficult to adapt to, as they can be unpredictable and the consequences thereof extend beyond the specific location of the malfunction. Conventional wireless power transfer tends to be less than optimal in handling malfunctions, often the impact of the malfunction leads to undesirable operating scenarios and conditions.

[0014] Hence, an improved power transfer method / system would be advantageous, and in particular a method allowing increased flexibility, reduced cost, reduced complexity, improved operation, improved handling of malfunctions, better control of power transfer operation, increased robustness of power transfer and / or increased performance would be advantageous. SUMMARY

[0015] The present application therefore seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

[0016] According to an aspect of the present application, there is provided a power receiver for wirelessly receiving power from a power transmitter via an electromagnetic power transfer signal, the power receiver comprising: a circuit comprising a receiver coil as part of a resonant circuit, the resonant circuit having a first resonance and a second resonance formed by the receiver coil and at least a first capacitor and a second capacitor, the first resonance having a first resonance frequency and the second resonance having a second resonance frequency, the first resonance frequency being no more than twice the frequency of the power transfer signal and the second resonance frequency being at least twice different from the first resonance frequency; a power path coupling the receiver coil to a load and arranged to provide power from the receiver coil to the load, the power path comprising: a protection element arranged to operate in a protected state in which a constraint is imposed on power transfer from the receiver coil and an unprotected state in which the constraint is not imposed, the protection element being arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver; and wherein a resonant characteristic of the second resonance is different for the protection element being in the protected state than for the protection element being in the unprotected state.

[0017] The present application can in many embodiments allow for improved performance and can in particular in many embodiments allow for improved operation and handling of scenarios where a fault can have occurred. The approach can provide for improved circuit protection and / or prevent undesired operation and effects in case of a fault. The approach can in particular allow that fault detection can not only trigger protection of the power receiver but also that a fault can be reliably, accurately and / or with low complexity detected by the power transmitter, allowing the power transfer operation to be adapted to reflect the fault. The approach can for example be particularly suitable for detecting whether a power receiver is in a fault mode before starting power transfer, only proceeding with power transfer if the power receiver is not in a fault mode.

[0018] The approach can advantageously allow for detecting whether a protection element is in a protected state without requiring any data transfer or in fact without requiring the power receiver to be powered or activated in many embodiments.

[0019] The approach can in many embodiments allow for such functionality and effects while only having a negligible impact on normal power transfer operation, in fact the impact on the power transfer resonant operation (supported by the first resonance) can be negligible.

[0020] In many embodiments, the protection element can be arranged to irreversibly switch from the non-protected state to the protected state, and thus can not be able to switch from the protected state to the non-protected state. In other embodiments, the switching of the protection element can be reversible, and the protection element can also be able to switch from the protected state to the non-protected state, for example in response to a user interaction / reset or in response to detecting that the fault condition no longer exists.

[0021] The resonance characteristic can in particular be a resonance frequency or mass indication, in particular including whether or not a second resonance is present. In some embodiments, the second resonance can only be present when the power receiver is in the non-protected state.

[0022] According to an optional feature of the present application, the protection element comprises a current limiter arranged to limit current through the protection element when the protection element is in the protected state relative to when the protection element is in the non-protected state.

[0023] This can provide particularly advantageous operation and / or allow a simplified and / or reduced complexity implementation.

[0024] Current from the receiver coil to the load can flow through the protection element. The current limiter can be arranged to limit current from the receiver coil to the load. In some cases, the current limiter can limit the current to substantially zero when in the protected state and / or can not limit the current when in the non-protected state. The current limiter can implement a switching function that is an open circuit when in the protected state and a short circuit when in the non-protected state.

[0025] According to an optional feature of the present application, the protection element is coupled in series between the receiver coil and the load, and the second capacitor is coupled to a connection in the protection element that is also coupled to the load.

[0026] This can provide particularly advantageous operation and / or allow a simplified and / or reduced complexity implementation. The protection element can be in series with the receiver coil 107 and the load, such that current from the receiver coil flows through the protection element to the load. The second capacitor can be coupled to a side of the protection element that is also coupled to the load, rather than the receiver coil. The second capacitor can be coupled to the receiver coil only via the protection element.

[0027] According to an optional feature of the present application, the first capacitor is in series with the receiver coil and the load, and the second capacitor is in parallel with the receiver coil and the load.

[0028] This can provide particularly advantageous operation and / or allow a simplified and / or less complex implementation. The first resonance can be a series resonance and the second resonance can be a parallel resonance. The method can facilitate determination of a resonance characteristic of the second resonance.

[0029] According to an optional feature of the application, the protection element is arranged to decouple the second capacitor from the receiver coil when in the protected state.

[0030] This can provide particularly advantageous operation and / or allow a simplified and / or less complex implementation. The second capacitor can be coupled to the receiver coil when in the unprotected state.

[0031] According to an optional feature of the application, the input circuit comprises a third capacitor and the second resonance is formed by the receiver coil and at least the second capacitor and the third capacitor, the third capacitor being coupled to the receiver coil both when the protection element is in the protected state and when in the unprotected state.

[0032] This can provide particularly advantageous operation and / or allow a simplified and / or less complex implementation.

[0033] According to an optional feature of the application, the power receiver further comprises a communicator for transmitting data to the power transmitter, the communicator being arranged to transmit configuration data, the configuration data being indicative of a dependence of the resonance characteristic on the protection element being in the protected state or in the unprotected state.

[0034] This can provide particularly advantageous operation and / or allow a simplified and / or less complex implementation.

[0035] In many embodiments, the configuration data can comprise an indication of a component arrangement of at least part of the power receiver.

[0036] According to an optional feature of the application, the power receiver further comprises a load switch arranged to switch the load and a fourth capacitor between being coupled to the receiver coil and being decoupled from the receiver coil, the second resonance being formed by at least the second capacitor and the fourth capacitor when the fourth capacitor is coupled to the receiver coil.

[0037] This can provide particularly advantageous operation and / or allow a simplified and / or less complex implementation.

[0038] According to an optional feature of the application, the protection element is an electrical fuse and the second capacitor is disconnected from the power receiver coil if the electrical fuse is open.

[0039] This can provide particularly advantageous operation and / or allow a simplified and / or reduced complexity implementation.

[0040] According to an optional feature of the application, the protection element is a sacrificial component.

[0041] This can provide particularly advantageous operation and / or allow a simplified and / or reduced complexity implementation.

[0042] According to another aspect of the application, there is provided a wireless power transfer system comprising a power receiver according to the above description and a power transmitter comprising: a transmitter coil arranged to couple to the receiver coil; a driver arranged to generate a drive signal for the transmitter coil to generate the electromagnetic power transfer signal; a measurer arranged to determine a measured resonance characteristic of the transmitter coil when coupled to the receiver coil, the measured resonance characteristic being for a frequency which differs from a frequency of the power transfer signal by at least a factor of two; and a controller arranged to control power transfer to the power receiver in dependence on the measured resonance characteristic.

[0043] According to an optional feature of the application, the power controller is arranged to inhibit power transfer in response to detecting that the measured resonance characteristic satisfies a criterion indicative of the power receiver being in the protected state.

[0044] This can provide particularly advantageous operation in many embodiments.

[0045] According to an optional feature of the application, the measurer is arranged to determine the measured resonance characteristic by comparing a measure of loading of the transmitter coil at at least two different frequencies.

[0046] This can provide particularly advantageous operation in many embodiments.

[0047] A wireless power transfer system can comprise a power receiver as described above and a power transmitter comprising: a transmitter coil arranged to couple to the receiver coil; a driver arranged to generate a drive signal for the transmitter coil to generate the electromagnetic power transfer signal; a measurer arranged to determine a measured resonance characteristic of the transmitter coil when coupled to the receiver coil, the measured resonance characteristic being for a frequency which differs from a frequency of the power transfer signal by at least a factor of two; and a controller arranged to control power transfer to the power receiver in dependence on the measured resonance characteristic.

[0048] According to an optional feature of the application, the power controller is arranged to inhibit power transfer in response to detecting that the measured resonance characteristic satisfies a criterion indicative of the power receiver being in the protected state.

[0049] According to an optional feature of the invention, the measuring instrument is arranged to determine the measured resonant characteristics by comparing load measures of the transmitter coil at at least two different frequencies.

[0050] According to another aspect of the invention, an operating method for a power receiver is provided, the power receiver wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the power receiver comprising: a circuit including a receiver coil as part of a resonant circuit having a first resonance and a second resonance formed by the receiver coil and at least a first capacitor and a second capacitor, the first resonance having a first resonant frequency and the second resonance having a second resonant frequency, the first resonant frequency not exceeding twice the frequency of the power transmission signal, and the second resonant frequency differing from the first resonant frequency by at least twice; a power path coupling the receiver coil to a load and arranged to provide power from the receiver coil to the load, the power path including: a protection element arranged to operate in a protected state and an unprotected state, the protection state imposing a constraint on power transmission from the receiver coil and the unprotected state not imposing the constraint, the protection element being arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver; and the method comprising, relative to when the protection element is in the unprotected state, changing the resonant characteristics of the second resonance when the protection element is in the protected state.

[0051] According to another aspect of the invention, a method of operating a wireless power transmission system includes a wireless power transmitter that provides power to a power receiver via an electromagnetic power transmission signal, wherein the power receiver includes: a circuit comprising a receiver coil as part of a resonant circuit having a first resonance and a second resonance formed by the receiver coil and at least a first capacitor and a second capacitor, the first resonance having a first resonant frequency and the second resonance having a second resonant frequency, the first resonant frequency not exceeding twice the frequency of the power transmission signal, and the second resonant frequency differing from the first resonant frequency by at least twice; a power path coupling the receiver coil to a load and arranged to provide power from the receiver coil to the load, the power path including: a protection element arranged to operate in a protected state and an unprotected state, wherein in the protected state... The method involves applying a constraint to power transmission from the receiver coil, while not applying the constraint in the unprotected state; the protection element is arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver; and the power transmitter includes a transmitter coil coupled to the receiver coil; the method includes: relative to when the protection element is in the unprotected state, the power receiver changing the resonant characteristics of the second resonance; and the power transmitter performing the steps of: generating a drive signal for the transmitter coil to generate the electromagnetic power transmission signal; determining a measured resonant characteristic of the transmitter coil coupled to the receiver coil, the measured resonant characteristic for a frequency that differs from the frequency of the power transmission signal by at least twice; and controlling the power transmission to the power receiver based on the measured resonant characteristic.

[0052] These and other aspects, features, and advantages of the invention will become apparent and will be elucidated with reference to one or more embodiments described below. Attached Figure Description

[0053] Embodiments of the invention will be described by way of example only with reference to the accompanying drawings, in which: Figure 1 Examples of elements of a power transmission system according to some embodiments of the present invention are shown; Figure 2 An example of the electrical equivalent diagram of the power transfer function is shown; Figure 3 Examples of elements of a power transmitter according to some embodiments of the present invention are shown; Figure 4 An example of a half-bridge inverter for a power transmitter is shown; Figure 5 An example of a full-bridge inverter for a power transmitter is shown; Figure 6 Examples of elements of a power receiver according to some embodiments of the present invention are shown; Figure 7 An example of resonance of a power transmitter coil in a wireless power transmission system is shown; Figure 8 An example of resonance of the power transmitter coil of a power receiver according to some embodiments of the present invention is shown; Figure 9 Examples of elements of a power transmission circuit for a power receiver according to some embodiments of the present invention are shown; Figure 10 Examples of elements of a power transmission circuit for a power receiver according to some embodiments of the present invention are shown; and Figure 11 Examples of elements of a power transmission circuit for a power receiver according to some embodiments of the present invention are shown. Detailed Implementation

[0054] The following description focuses on embodiments of the invention applicable to wireless power transmission systems utilizing power transmission methods known, for example, from the Qi or Ki specifications. However, it should be understood that the invention is not limited to this application, but can be applied to many other wireless power transmission systems.

[0055] Figure 1 An example of a power delivery system according to some embodiments of the present invention is shown. The power delivery system includes a power transmitter 101 that includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105 that includes (or is coupled to) a receiver coil / inductor 107.

[0056] The system provides an induced electromagnetic power transfer signal that can inductively transfer power from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal that propagates as a magnetic flux via a transmitter coil or inductor 103. During power transfer, the electromagnetic signal transfers power to the power receiver 105 (and specifically to the receiver coil 107), and will be referred to hereinafter as the power transfer signal.

[0057] The frequency of the power transmission signal is typically between about 20 kHz and about 500 kHz, typically in the range of 95 kHz to 205 kHz for Qi-compatible systems, or typically in the range of 20 kHz to 80 kHz for Ki-compatible systems. The transmitter coil 103 and the power receiving coil 107 are loosely coupled, so the power receiving coil 107 picks up (at least a portion) of the power transmission signal from the power transmitter 101. Therefore, power is transmitted from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the power receiving coil 107. The term power transmission signal is primarily used to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107; however, it should be understood that, by equivalent means, it can also be considered and used as a reference to the electrical signal provided to the transmitter coil 103 or picked up by the power receiving coil 107.

[0058] In this example, power receiver 105 is specifically a power receiver that receives power via receiver coil 107. However, in other embodiments, power receiver 105 may include a metallic element, such as a metallic heating element, in which case the power transmission signal directly induces eddy currents, resulting in direct heating of the element.

[0059] The system is configured to transmit large power levels; specifically, in many embodiments, the power transmitter can support power levels exceeding 500mW, 1W, 5W, 50W, 100W, or 500W. For example, for Qi-compliant applications, power delivery is typically in the 1-5W range for low-power applications (basic power distribution), up to 15W for Qi specification version 1.2, up to 100W for higher-power applications such as power tools, laptops, drones, and robots, and up to 100W for very high-power applications such as Ki kitchen applications, exceeding 100W and reaching up to 2000W.

[0060] Figure 2 An example electrical equivalent diagram of the power transfer function of power transmitter 101 and power receiver 105 is shown. Various power transmitters and receivers may exist in a given system, and they can have fundamentally different properties and parameters. For example, coil size, inductance, and load can vary considerably. Therefore, as... Figure 2As specifically stated, system parameters can vary significantly in practice across different devices, mechanical configurations, and positioning. In particular, the placement of the power receiver, and therefore the relative positions of the receiver coil 107 and the transmitter coil 103, substantially affects the coupling between the coils (i.e., the primary (power transmitter side) inductor Lp and the secondary (power transmitter side) inductor Ls), and may therefore significantly alter the system behavior.

[0061] In the following description, the operation of the power transmitter 101 and the power receiver 105 will be described with specific reference to embodiments generally in accordance with the Qi or Ki specifications (in addition to the modifications and enhancements described herein (or correspondingly)).

[0062] Many wireless power transfer systems utilize resonant power transfer, where the transmitter coil 103 is part of a resonant circuit, and typically the receiver coil 107 is also part of a resonant circuit. In many embodiments, the resonant circuit can be a series resonant circuit, so the transmitter coil 103 and receiver coil 107 can be coupled in series with corresponding resonant capacitors. The use of resonant circuits tends to provide more efficient power transfer.

[0063] In most power transmission systems, a communication channel is established between the power transmitter 101 and the power receiver 105 before power transmission is initiated. Once communication has been established and the two devices have been identified, the power transmitter 101 can begin transmitting power to the power receiver 105.

[0064] Typically, wireless power delivery systems employ a power control loop to guide the system to an appropriate operating point. This power control loop modifies the amount of power transmitted from the power transmitter to the power receiver. The received power (or voltage or current) can be measured and, along with the setpoint power value, can generate an error signal. The power receiver transmits this error signal to the power control function in the power transmitter to ideally reduce the static error to zero.

[0065] Figure 3 Showing more details Figure 1 An exemplary component of the power transmitter 101.

[0066] The power transmitter 101 includes a driver 301 that generates a drive signal fed to a transmitter coil 103, which in turn generates an electromagnetic power transfer signal to provide power transfer to a power receiver 105. The transmitter coil 103 is part of an output resonant circuit that includes the transmitter coil 103 and a capacitor 303. In this example, the output resonant circuit is a series resonant circuit; however, it should be understood that in other embodiments, the output resonant circuit may be a parallel resonant circuit. It should be understood that any suitable resonant circuit can be used, including resonant circuits using multiple inductors and / or capacitors.

[0067] As is well known, the use of a resonant circuit including transmitter coil 103 provides more efficient power transfer in many cases and allows power transfer to be controlled by the frequency of the drive signal. Furthermore, having a power receiver that also employs a resonant circuit (i.e., receiver coil 107 is part of the resonant circuit) can result in resonant power transfer that achieves efficient power transfer.

[0068] Driver 301 generates current and voltage that are fed to the output resonant circuit and thus to the transmitter coil 103. Driver 301 is typically a drive circuit in the form of an inverter, which generates an AC signal from a DC voltage. The output of driver 301 is typically a switching bridge, and a drive signal is generated by appropriately switching the switches of this switching bridge. Figure 4 A half-bridge switching inverter is shown. Switches S1 and S2 are controlled so that they are not closed simultaneously. Alternatingly, S1 is closed while S2 is open, and S2 is closed while S1 is open. The switches open and close at a desired frequency, thereby generating an AC signal at the output. Typically, the inverter output is connected to the transmitter inductor via a resonant capacitor. Figure 5 A full-bridge switched bridge / inverter is shown. Switches S1 and S2 are controlled such that they do not close simultaneously. Switches S3 and S4 are controlled such that they do not close simultaneously. Alternatingly, switches S1 and S4 are closed while S2 and S3 are open, and then S2 and S3 are closed while S1 and S4 are open, thereby generating a square wave signal at the output. The switches open and close at a desired frequency.

[0069] The power transmitter 101 also includes a power transmitter controller 305, which is arranged to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 may include many functions required to perform power control according to Qi or Ki specifications.

[0070] The power transmitter controller 305 is specifically arranged to control the generation of drive signals by the driver 301, and it can specifically control the power level of the drive signals, and thus control the level of the resulting power transmission signal. The power transmitter controller 305 includes a power loop controller that controls the power level of the power transmission signal in response to a power control message received from the power receiver 105 during the power transmission phase.

[0071] The power transmitter also includes functionality for communicating with the power receiver 105. Figure 3 In the example of the power transmitter, the power transmitter 101 includes a first communicator 307, which is arranged to receive data and messages from the power receiver 105 and to transmit data and messages to the power receiver 105 (as those skilled in the art will understand, the data message may provide one or more bits of information).

[0072] In this method, communication is performed by modulating a separate communication carrier. The communication carrier signal is typically chosen to have a frequency significantly different from the power transmission drive signal / power transmission signal. In many embodiments, the frequency of the communication carrier signal can be at least 10, 100, or 500 times higher than the frequency of the power transmission signal. In many embodiments, the frequency of the communication drive signal / communication carrier signal can be at least 500 kHz, 1 MHz, or 10 MHz.

[0073] In some embodiments, the communication may be based on near-field communication (NFC) specifications, and the power transmitter and power receiver may specifically include NFC functionality. In these embodiments, the communicator may respectively implement the functions of an NFC reader and / or writer. Thus, in some embodiments, the communication drive signal / communication carrier signal is a constant-level (excluding modulation) 13.56 MHz signal.

[0074] Figure 6 Some exemplary components of the power receiver 105 are shown.

[0075] The power receiver 105 includes circuitry arranged to extract power from the power transmission signal to generate an induced power signal. This circuitry includes a receiver coil 107 arranged to extract power from the power transmission signal by induction, i.e., the magnetic field of the power transmission signal induces a signal in the receiver coil. In this example, the receiver coil 107 is coupled to a first capacitor 601, which together with the receiver coil 107 forms a first resonance. Therefore, the receiver coil 107 can form a resonant circuit with the first capacitor 601, and the power transmission can be a resonant power transmission between the resonant circuits.

[0076] The power receiver 105 also includes a power path that provides transmitted power from the receiver coil 107 to the load 603. The load 603 represents the target load for power transmission. The load 603 may be, for example, an external device, a battery, or a charging function. The load 603 may also represent a load of internal circuitry, such as control, support, and auxiliary circuitry that supports power transmission. The power path couples the power receiver 105 to the load 603, thereby providing the load 603 with the power extracted from the power transmission signal by the receiver coil 107.

[0077] In this example, the power path includes a power delivery circuit 605, which may include various functions that can be used to control and / or modify the power supplied to the load 603.

[0078] In many embodiments, the power delivery circuit 605 may include a rectifier and may include a smoothing capacitor to provide (smoothed) DC voltage and / or current. In many embodiments, the power delivery circuit 605 may include a voltage and / or current regulator. For example, in many embodiments, the power delivery circuit 605 may include a rectifier, a smoothing capacitor, and a voltage regulator to provide a regulated DC voltage to the load 603.

[0079] In many embodiments, the power delivery circuit 605 may also include a load switch that can switch the load 603 between coupling to and decoupling from the receiver coil 107. The load switch may specifically be formed of a switching element, such as a relay, an electrical switch, or a transistor, which can connect or disconnect the load 603 from the power path.

[0080] The power path also includes a protection element 607, which can operate in both protected and unprotected states, imposing a constraint on power transfer from the receiver coil in the protected state and no constraint in the unprotected state. This constraint can typically be a constraint / limitation on current and / or voltage, particularly on the current and / or voltage of the load 603. In many cases, the constraint can be an absolute constraint. Specifically, in many embodiments, the protection element can be arranged to prevent any current and / or voltage from being supplied to the load (from the receiver coil 107) when the protection element 607 is in the protected state. Furthermore, in many embodiments, the protection element 607 can be arranged not to impose any constraint or limitation on the current or voltage of the load 603 (from the receiver coil 107) when the protection element 607 is in the unprotected state.

[0081] The protection element 607 is arranged to switch from a non-protected state to a protected state in response to the detection of a fault condition in the power receiver. Therefore, if a fault occurs in the power receiver, this may cause the protection element 607 to change from not constraining the power of the load 603 to constraining the power. Specifically, the protection element 607 may be arranged to terminate power supply to the load 603 upon the occurrence / detection of a fault.

[0082] In many embodiments, the protection element 607 may be a series element that includes current limiting when in a protected state and does not include current limiting when in an unprotected state. In many examples, it may include a switch connected in series with the receiver coil 107 and the load 603, and the switch is open when in a protected state and short-circuited when in an unprotected state (or in some embodiments, it has a resistance higher than a first threshold when in a protected state and a resistance lower than a second threshold when in an unprotected state, wherein the second threshold is lower than the first threshold).

[0083] In many embodiments, the protection element 607 may be a parallel element that includes voltage limiting when in a protected state and does not include voltage limiting when in an unprotected state. In many examples, it may include a switch connected in parallel with the receiver coil 107 and the load 603, and the switch is short-circuited when in a protected state and open-circuited when in an unprotected state (or in some embodiments, it has a resistance higher than a first threshold when in an unprotected state and a resistance lower than a second threshold when in a protected state, wherein the second threshold is lower than the first threshold).

[0084] In some embodiments, fault detection can be based on a potentially complex evaluation of operating parameters, such as using appropriate detection circuitry or procedures. For example, multiple parameters and measurements may be considered, and if a fault criterion is met, the protection element 607 can switch from a non-protected state to a protected state. In some cases, the criterion may include alternative requirements, such as considering a fault detected if any of the multiple measurements are outside the permissible operating range. Alternatively or additionally, the criterion may include conditional requirements, such as considering a fault detected if all of the multiple measurements are outside the permissible operating range.

[0085] In different embodiments, fault detection can be based on different parameters. In many embodiments, current, particularly the power transmission current (e.g., the current across receiver coil 107 and / or load 603), can be measured, and if this exceeds a threshold (e.g., over a given duration), a fault is considered to have occurred. Similarly, in many embodiments, voltage, particularly the power transmission voltage (e.g., the voltage across receiver coil 107 and / or load 603), can be measured, and if this exceeds a threshold (e.g., over a given duration), a fault is considered to have occurred. In many embodiments, fault detection can alternatively or additionally consider, for example, the temperature of components of the power receiver or external components or the load. Specifically, if the temperature of a component of, for example, the power receiver or load, exceeds a given threshold indicating a normal or acceptable value, a fault can be considered to have occurred.

[0086] Therefore, in many embodiments, the protection element 607 can be arranged to switch from a non-protected state to a protected state in response to the detection of overcurrent, overvoltage, and / or overheating conditions.

[0087] Fault detection can be active detection based on measurement or evaluation methods. Similarly, switching from a non-protected state to a protected state can be an active switching performed, for example, by appropriate circuitry or procedures, in response to fault detection.

[0088] However, in many other embodiments, fault detection, and indeed the switching from a non-protected state to a protected state, can be passive detection and switching. In practice, in many cases, the protection element 607 can be arranged to automatically and inherently change from one state to another based on its characteristics. For example, the protection element 607 can be arranged to open when the current across it exceeds a given threshold, and / or can be arranged to short-circuit when the voltage across it exceeds a given threshold.

[0089] In some embodiments, the protection element 607 may be arranged to switch from a protected state to a non-protected state, for example, in response to detecting that a fault condition no longer exists (or, for example, in response to a different criterion). For example, if an overvoltage condition has already triggered a transition to a protected state, a voltage drop (e.g., the voltage on receiver coil 107) below a given threshold (typically below the threshold required to switch to a protected state) may cause the protection element 607 to switch from a protected state to a non-protected state.

[0090] However, in many embodiments, the protection element 607 may be arranged to perform irreversible operation when switching from a non-protected state to a protected state. Therefore, the protection element 607 may only be able to switch from a non-protected state to a protected state, and not vice versa. Consequently, in this case, the protection element 607 may be a one-time circuit or component that may need to be replaced after fault detection and switching to the protected state.

[0091] In practice, in many embodiments, the protection element 607 can be a sacrificial component. The protection element 607 can be designed to fail, for example, due to mechanical (e.g., thermal) or electrical stress, thereby protecting other parts of the power receiver (or actually the load 603).

[0092] In particular, in many embodiments, the protection element 607 may be implemented by a single passive component. For example, in some embodiments, the protection element 607 may be a thermal switch that disconnects the circuit at high temperatures. In many embodiments, the protection element 607 may be specifically implemented as (or include) an electric fuse. In some cases, the electric fuse may be resettable, but in many embodiments, the protection element 607 may simply be a one-time electric fuse. The following description will focus on examples where the protection element 607 is indeed implemented as a conventional electric fuse connected in series with the receiver coil 107 and the load 603.

[0093] Therefore, the protection element 607 can be an electronic component or circuit that provides protection for the power receiver and load 603, and specifically prevents damage or undesirable operation even in the event of a fault (such as component failure).

[0094] The power receiver also includes a power receiver controller 609, which includes various power receiver controller functions required to perform power transfer, particularly those required to perform power transfer according to the Qi or Ki specifications.

[0095] The power receiver also includes a communicator referred to as a second communicator 611, which is arranged to communicate with the first communicator 307 of the power transmitter. The second communicator 611 may specifically be an NFC communication function capable of exchanging data (in both directions) with the complementary power transmitter communicator 307.

[0096] Therefore, the power receiver 105 is arranged to transmit data to the power transmitter 101. Such data may specifically include power control loop error messages for implementing a feedback power loop used to control the power level of the power transmission signal during power transmission, as will be known to those skilled in the art. In many embodiments, as known to those skilled in the art, the power receiver is capable of transmitting a series of different messages serving different purposes. For example, a series of different messages may be transmitted, such as those specified in the Qi or Ki specifications.

[0097] A key requirement for wireless power transfer is that it can be established in a safe and controlled manner. Therefore, the system can implement multiple control and safety procedures and functions. As previously mentioned, including the protective element 607 can provide improved protection and operation in many situations. For example, in conventional cookware, it is common practice to introduce a protective element in series with the load. Examples of such a protective element can be any fuse, circuit breaker, or other unit that prevents current from flowing from the power source to the load. This approach can also be advantageously used in wireless power transfer systems.

[0098] However, the inventors have recognized that if the power transmitter is not adapted to the protective element 607 in a protected state, undesirable operating conditions may occur in some scenarios.

[0099] For example, if the series protection element 607 switches to an open-circuit state during or before power transfer, the power transfer parameters, particularly the resonant characteristics, will change. For instance, depending on operating conditions, the operating point of the power transmitter may shift closer to resonance, and therefore the primary current may reach an increased value, or even, in some cases, such a value, that could be destructive to some components of the system. Figure 7 An example is shown where the primary current (the current through transmitter coil 103) can reach values ​​of hundreds of amperes. Such a large resonant current often shortens the lifespan of the switching components and the field lifespan of the power transmitter.

[0100] The inventors have recognized that it would be advantageous for the power transmitter to know the state of the protection element 607 at the power receiver. However, they also recognize that a direct method of data transmission from the power receiver to the power transmitter may not be advantageous in all cases. For example, during power transmission initialization, the power transmitter has no means to detect whether the protection element 607 is in a protected state because communication at the power receiver and, in practice, suitable detection circuitry are typically inactive before power transmission is initialized, thus allowing the power receiver to be powered.

[0101] In some cases, power receivers can be configured to extract power from communication carriers to support control functions. However, even in such cases, determining the state of protective elements (such as fuses) is often practically difficult and requires additional complexity and / or components.

[0102] In the described method, the power receiver is arranged to change the resonant characteristics of the circuit including the receiver coil 107 depending on whether the power receiver is in an unprotected state or a protected state. When the transmitter coil 103 is coupled to the receiver coil 107, the power transmitter can perform a measurement of the resonant behavior, and based on this resonant behavior, the power transmitter can determine whether the protection element 607 of the power receiver is in an unprotected state or a protected state.

[0103] The power transmitter is arranged to control / modify / adjust power transmission operation based on measured resonant characteristics, particularly based on whether the power receiver is in an unprotected or protected state. Specifically, in many embodiments, the power transmitter may be arranged to disable power transmission when the measured resonant characteristics meet a criterion indicating that protection element 607 is considered to be in a protected state. In many embodiments, a check may be performed during power transmission initialization, and the power transmitter may prevent power transmission initialization from causing power transmission. Therefore, in many embodiments, if the measured resonant characteristics indicate that the power receiver is in a protected state, the power transmitter may terminate power transmission initialization. In some embodiments, a check may be performed during an ongoing power transmission phase, and the power transmitter may be arranged to terminate power transmission when the measured resonant characteristics indicate that the power receiver is in a protected state.

[0104] Specifically, the power receiver includes a second capacitor 613, which is arranged to form a second resonance with the receiver coil 107. Therefore, the arrangement of the receiver coil 107, the first capacitor 601, and the second capacitor 613 forms a resonant arrangement with two resonances, and thus two resonant frequencies. In practice, in some embodiments, more capacitors may be included, and more resonant frequencies may exist.

[0105] In this method, a first capacitor 601 forms a resonance with a resonant frequency generally close to that of the power transmission signal, and this resonant frequency provides resonance for resonant power transmission from the power transmitter to the power receiver. The first resonant frequency of the resonant circuit is arranged not to exceed twice the (maximum) frequency of the power transmission signal. In many embodiments, the power transmitter may be arranged to generate a power transmission signal with frequencies within a given frequency range, and the first resonant frequency may be at most twice the maximum frequency of that frequency range. In many embodiments, the first resonant frequency may be higher than the maximum frequency of the power transmission signal, but it should be understood that in some cases, the first resonant frequency may be selected to be lower than the (minimum) frequency of the power transmission signal. In this case, the first resonant frequency may generally be no less than half the minimum frequency of the power transmission signal.

[0106] Therefore, in many embodiments, the first resonant frequency may be close to, but may be outside, the operating frequency range of the power transmission signal. This approach allows for resonant power transmission but allows for frequency variation to control the amount of power transmitted. Specifically, the power transmitter may be arranged to change the frequency of the power transmission signal toward the first resonant frequency to increase the level of power transmission, and to change it away from the first resonant frequency to decrease the level of power transmission.

[0107] In many embodiments, the first resonant frequency may not exceed twice the resonant frequency of the output resonant circuit of the power transmitter, or may be less than half the resonant frequency of the output resonant circuit of the power transmitter.

[0108] In this example, the first capacitor 601 forms a series resonance with the receiver coil 107.

[0109] The second resonant frequency is arranged to be significantly different from the first resonant frequency, specifically differing from the first resonant frequency by at least a factor of two, or even by a factor of three, five, or even ten in many embodiments. Therefore, the second resonant frequency is not less than twice the first resonant frequency or not greater than half the first resonant frequency. In most embodiments, the second resonant frequency can be higher than the first resonant frequency, as this typically facilitates detection and measurement at the power transmitter and allows for smaller, cheaper components (e.g., lower capacitance of the second capacitor).

[0110] In this example, the second capacitor 613 forms a series resonance with the receiver coil 107.

[0111] In many embodiments, the first frequency is higher than 10 kHz or 20 kHz, and / or lower than 40 kHz, 50 kHz, or 100 kHz. The first resonant frequency may specifically have a resonant frequency according to the Ki specification. In many embodiments, the second resonant frequency is above 200 kHz.

[0112] In this method, the power receiver accordingly has two resonances in the receiver coil 107, where the resonant frequencies are significantly different (at least twice the difference). The greater the difference, the easier it is to detect frequencies visible in the circuit. For example, due to load damping, the effect of the second resonance on resonant power transfer operation based on the first resonant frequency can remain small, and in most embodiments may be practically negligible. Similarly, the effect of the first resonance on the second resonance can be ignored. Therefore, in this system, operations based on the first and second resonances can be considered and performed separately, and other resonances are typically not considered in practice.

[0113] Furthermore, due to the difference in resonant frequencies, the first resonance can be considered to be formed by the receiver coil 107 and the first capacitor 601, and therefore the first resonant frequency can be considered to be determined by the inductance of the receiver coil 107 and the capacitance of the first capacitor 601. Similarly, the second resonance can be considered to be formed by the receiver coil 107 and the second capacitor 613, and therefore the second resonant frequency can be considered to be determined by the inductance of the receiver coil 107 and the capacitance of the second capacitor 613. In reality, the resonant frequency may be slightly shifted or modified due to the presence of other capacitors, but this effect is generally negligible, and in fact, the described principle does not depend on or is sensitive to such effects.

[0114] The power receiver is configured to alter the resonant characteristics of the second resonance depending on whether the power receiver is in an unprotected or protected state. The resonant characteristics can typically be the resonant frequency or quality factor of the second resonance, or simply the presence or absence of a second resonance.

[0115] In practice, in many embodiments, the power receiver can be arranged to suppress and / or eliminate the second resonance when in a protected state; that is, the second resonance may exist when the power receiver is in an unprotected state, rather than when it is in a protected state. Specifically, in some embodiments where the second capacitor 613 is connected in parallel with the receiver coil 107, the power receiver can be arranged to disconnect the second capacitor 613 from the circuit when it enters a protected state. Correspondingly, in some embodiments where the second capacitor 613 is connected in series with the receiver coil 107, the power receiver can be arranged to short-circuit the second capacitor 613 from the circuit when it enters a protected state.

[0116] In some embodiments, the protection element 607 may be arranged to change the resonant frequency of the second resonant frequency when entering a protected state. For example, the second resonance may be determined by two capacitors (equivalent to the second capacitor 613 being formed by two capacitors), and one of these capacitors may be switched on or off in the protected state relative to the unprotected state. For example, a fixed capacitor may be coupled (e.g., in parallel or series) to a switchable capacitor that switches depending on whether the protection element 607 is in the unprotected or protected state.

[0117] Alternatively or additionally, in some embodiments, the protection element 607 may be arranged to change the quality of the second resonant frequency when entering a protected state. For example, a switchable resistor may be coupled in series or parallel with the second capacitor 613 and turn on (or off) when the protection element 607 switches from a non-protected state to a protected state.

[0118] As previously mentioned, the power transmitter can be arranged to determine resonant characteristics, such as a specific resonant frequency or quality factor (including the presence of a second resonance), and based on this, can be arranged to modify the power transmission operation.

[0119] The power transmitter may specifically include a resonance measurement circuit 309, which is arranged to determine the measured resonance characteristics of the transmitter coil 103 when coupled to the receiver coil 107. The resonance characteristics are determined for frequencies (particularly a frequency range) that differ from the frequency of the power transmission signal by at least twice. The resonance measurement circuit 309 is specifically arranged to determine the measured resonance characteristics within a frequency range where a second resonant frequency may exist.

[0120] The resonance measurement circuit 309 can identify the resonant characteristics of the power receiver in a variety of ways. One example of its implementation could be a frequency sweep, during which the power transmitter applies a low-amplitude signal with varying frequencies (e.g., 20 kHz…500 kHz) to the transmitter coil 103 while simultaneously measuring the current through the power coil. The envelope of this measurement (derived, for example, by Hilbert transform) is essentially a Bode plot depicting the resonance of the series and parallel systems.

[0121] The resonance measurement circuit 309 can specifically perform a frequency scan within the frequency range where a second resonance might exist. It can then determine whether any resonance exists, and / or the frequency of any resonance and / or the quality factor of any resonance. Figure 8 Examples of frequency sweep measurements are shown for cases with and without a second resonance.

[0122] Alternatively, instead of scanning, the resonance measurement circuit 309 can measure the impedance of the transmitter coil 103 at a predetermined frequency and detect the presence of secondary resonance by measuring the impedance at that frequency / at these frequencies. In some such embodiments, multiple measurements may be performed to reflect that the second resonant frequency may depend on the coupling between the transmitter coil 103 and the receiver coil 107.

[0123] As a specific example, when the power receiver is in an unprotected state, the second resonant frequency can be predetermined to have a specific value. The resonance measurement circuit 309 can then perform an impedance measurement at this frequency; if the obtained impedance meets a given requirement (such that it is, for example, substantially resistive), resonance can be determined to exist; otherwise, resonance can be determined not to exist. The power transmitter can then determine that the protection element 607 is in an unprotected state (if the second resonance exists) and otherwise in a protected state (if the second resonance does not exist).

[0124] Resonance measurement circuit 309 is coupled to power controller 311, which is arranged to control power transfer to power receiver based on the measured resonance characteristics. Specifically, power controller 311 is arranged to control power transfer to power receiver based on whether the measured resonance characteristics indicate that protection element 607 is in a non-protected or protected state. Power controller 311 can be arranged to modify power transfer operation when the measured resonance characteristics meet the criteria for protection element 607 to be in a protected state. For example, if no resonance is detected at (or near) the expected second resonant frequency (e.g., because it has shifted to a different resonant frequency, has been attenuated by reducing the quality factor (e.g., by coupling to a resistor), or has been completely removed by disconnecting the load), it can be determined that protection element 607 is in a protected state.

[0125] In many embodiments, the power controller 311 is arranged to disable power transmission in response to detecting that the measured resonant characteristics meet the criteria indicating that the protective element 607 is in a protected state. In the event that this occurs during power transmission operation, the power controller 311 can continue to control the transmitter controller 305 to immediately terminate power transmission.

[0126] However, in many embodiments, the evaluation can typically be performed during the power initialization process. Specifically, as part of power transfer initialization, the transmitter controller 305 may control the resonance measurement circuit 309 to perform a measurement of the resonance characteristics and control the power controller 311 to determine whether the result matches a criterion for the protection element 607 to be in a protected state. If so, the power controller 311 will control the transmitter controller 305 to terminate the power transfer initialization, preventing power transfer from starting.

[0127] As previously described, in different embodiments, the power receiver can implement the protection element 607 in different ways. In many embodiments, the protection element 607 is a series protection element 607 coupled in series between the receiver coil 107 and the load 603, and the protection element 607 is arranged to increase the impedance, for example, by at least 2, 5, 10, 100 times or more. Specifically, the protection element 607 can be a series protection element 607 arranged to disconnect the circuit when entering a protected state.

[0128] In this configuration, the second capacitor 613 can be located on one side of the load 603. Specifically, the protection element 607 can have a first connector and a second connector, wherein the first connector is coupled to and typically connected to the receiver coil 107, and the second connector is coupled to and typically connected to the load 603. In the unprotected state, the resistance between the first and second connectors may be significantly lower (e.g., 10 times lower) than in the protected state. Specifically, the protection element 607 can provide a short circuit between the first and second connectors in the unprotected state and an open circuit in the protected state. In this configuration, the second capacitor 613 can be coupled to the second connector, i.e., it is coupled to the same connector as the load 603.

[0129] As a result, in the unprotected state, the second capacitor 613 is also coupled to the receiver coil 107 through the protection element 607, thus providing a second resonance. However, in the protected state, the second capacitor 613 is not coupled to the receiver coil 107 (or is coupled through a larger resistance), so there is no second resonance (or it is essentially suppressed and has a low quality factor).

[0130] This approach may be particularly suitable when the protection element 607 is a current-limiting element. It allows for reduced complexity, especially when the protection element 607 also switches between states based on the current from the receiver coil 107 to the load 603. For example, the protection element 607 could have a current-sensing function that measures the current from the first connector to the second connector and switches to a protected state if the current exceeds a level (e.g., momentarily or exceeding the level for a given duration). This function can be implemented with a simple latching current-limiting circuit. In fact, in many embodiments, this approach can even advantageously be implemented using an electric fuse as the protection element 607. Indeed, this implementation can provide excellent performance in many embodiments with an electric fuse of low complexity and low cost, for example, providing a high level of safety using sacrificial components. Furthermore, simply coupling the second capacitor 613 to the load side of the fuse will allow it to disconnect when the fuse blows (corresponding to its transition from an unprotected state (where the normally operating fuse provides a short circuit) to a protected state (where the blown fuse provides an open circuit).

[0131] Figure 9 An advantageous example of this embodiment is shown, wherein L s Indicator receiver coil 107, C S Indicates the first capacitor 601, C d Indicates the second capacitor 613, Z 负载 The load is indicated as 603, and F s The protective element 607 is indicated; in this specific example, it is implemented by an electric fuse. During normal operation in the unprotected state, the fuse is short-circuited, and the circuit exhibits resonance of a second resonance form determined by the second capacitor 613 (assuming the load provided by the power transmission circuit 605 has sufficiently high ohms to not suppress the second resonance). However, when the fuse blows, the second capacitor 613 is disconnected from the receiver coil 107 and does not exhibit the second resonance. Therefore, the power transmitter can detect the state of the fuse by measuring the presence of the second resonance. This method provides a simple yet robust detection method if the series protective element in the power receiver opens.

[0132] In some cases, and indeed in many practical situations, the load impedance Z 负载 The second resonance can be effectively suppressed / prevented because its ohms are so low that they dominate performance. However, in many practical embodiments, the power transfer circuit 605 includes a load switch that disconnects the load, for example, outside the power transfer phase (Z). 负载 The described operation can be performed when the load impedance is disconnected, for example, during the initialization phase before the power transfer phase.

[0133] In many scenarios and embodiments, detecting the second resonance at a frequency much higher than the first resonant frequency and the operating frequency of the power transmission signal may be substantially more accurate and reliable than, for example, attempting to detect the presence of the first resonant frequency. In fact, changes in the first resonance are typically at much lower frequencies and may not be sufficiently reflected on the primary side. This is especially true because in many cases the power transmitter also implements a resonant circuit with a resonant frequency close to the first resonant frequency and the operating frequency of the power transmission signal. This power transmitter-based resonance can often be very strong, and the effect of the first resonance at the power receiver may be difficult to detect at the power transmitter because it is masked by the power transmitter's own resonance.

[0134] In many cases, the first resonance is significantly suppressed by the load during operation, making it difficult to detect. When the load is disconnected (e.g., during power transfer initialization), the second resonance can often be arranged with a no-load path, thus allowing for improved detection.

[0135] In some embodiments, the power receiver can be arranged to exhibit a second resonance in both the unprotected and protected states, but with the second resonant frequency varying between the two states. This can be specifically achieved by a third capacitor that forms the second resonance together with the second capacitor 613 when the protection element 607 is in the unprotected state, and forms the second resonance without the second capacitor 613 when the protection element 607 is in the protected state. This can be specifically achieved by coupling the third capacitor and specifically connecting it to the receiver coil 107 when the protection element 607 is in both the unprotected and protected states.

[0136] Figure 10 An example of this method is shown in the figure, in which a parallel resonant capacitor C is connected. d The resonant characteristics of the second resonance are modified by dividing the resonance into two physical instances: one before protection element 607 and one after protection element 607; specifically, one physical instance is before the fuse and one is after the fuse. In this case, if the fuse is closed / short-circuited in the unprotected state, the parallel resonant frequency is changed by L. s C s and C d1 +C d2 Confirmed. If the fuse blows and breaks the circuit, then L... s C s and C d1 Given that, under protected conditions, a lower capacitance results in a higher parallel resonant frequency. A particular advantage is the fixed value for the parallel resonant frequency, allowing the power transmitter to clearly identify the power receiver with open-circuit series protection.

[0137] In many embodiments, the power receiver may include a load switch arranged to switch load 603 between coupling to and decoupling from the receiver coil. Figure 6 In the example, such a switch can be implemented as part of a power transfer circuit 605. This load switch can be used, for example, to couple a load only when conditions are suitable for the load (e.g., a properly regulated voltage is available to supply the load, such as after power transfer initialization). For example, a load isolation switch in the power receiver is typically open before power transfer is initiated.

[0138] In some embodiments, the second resonance may also depend on the state of the load switch. Specifically, the power receiver may include a load switch capacitor that is coupled to the receiver coil 107 when the power receiver is in an unprotected state and when the load switch couples the load 603 to the receiver coil 107, and decoupled from the receiver coil 107 when the load switch decouples the load 603 from the receiver coil 107.

[0139] Specifically, the load switch can be a series switch connected in series with the receiver coil 107 and the load 603, and the load switch capacitor can be located on the load side of the load switch. Figure 11 The text shows the relationship with... Figure 9 and Figure 10 The example is modified to correspond to the example, where C d3 SW1 indicates the load switch capacitor and is shown separately from the rest of the power transmission circuit 605.

[0140] In this scenario, the power transmitter can detect the state of the load switch based on whether the second resonance indicates that the load switch capacitor is affecting the second resonance. For example, a frequency scan can be performed to determine the second resonant frequency and matched against expected values ​​for the power receiver in a protected state, an unprotected state with the load switch open, and an unprotected state with the load switch closed, respectively.

[0141] The power transmitter can then be configured to adjust power delivery based on the state of the load switch.

[0142] As described above, power receivers can alter their resonant characteristics in different ways in different embodiments and scenarios, such as by changing the resonant frequency or resonant properties. In some cases, different power receivers in the same system can use different methods.

[0143] In this configuration, the power receiver can be arranged to transmit configuration data indicating the dependence of the characteristics of the second resonance (specifically, the second resonant frequency) on whether the protection element is in a protected or unprotected state.

[0144] In some embodiments, the configuration data may directly indicate different values ​​for the resonant frequency, such as the resonant frequencies for the unprotected state and the protected state, respectively, or in some embodiments, it may indicate the component arrangement of at least a portion of the power receiver. The configuration data may, for example, describe the component or circuit topology, or it may, for example, describe the effect of the protection element 607 switching to the protected state on the effective circuitry of the power receiver.

[0145] Then, the power transmitter can continue to determine the desired values ​​of the resonant characteristics in the unprotected and protected states, and the power controller 311 can continue to adjust the decision criteria accordingly.

[0146] In some cases, a power receiver can, for example, transmit instructions on the topology or circuit layout of the power receiver. For instance, data can be transmitted to indicate whether a connection has been implemented in the power receiver. Figure 9 , 10 Or the circuit layout corresponding to circuit layout 11.

[0147] It should be understood that, for clarity, the above description has referenced various functional circuits, units, and processors to describe embodiments of the invention. However, it will be apparent that any suitable functional distribution among different functional circuits, units, or processors can be used without departing from the invention. For example, a function shown to be performed by a separate processor or controller may be performed by the same processor or controller. Therefore, references to specific functional units or circuits are to be considered merely as references to suitable means for providing said function, and not as indications of a strict logical or physical structure or organization.

[0148] This invention can be implemented in any suitable form, including hardware, software, firmware, or any combination thereof. The invention can optionally be implemented, at least in part, as computer software running on one or more data processors and / or digital signal processors. The elements and components of embodiments of the invention can be implemented physically, functionally, and logically in any suitable manner. In practice, functionality can be implemented in a single unit, in multiple units, or as part of other functional units. Therefore, the invention can be implemented in a single unit or can be physically and functionally distributed among different units, circuits, and processors.

[0149] Although the invention has been described in conjunction with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is defined only by the claims. Furthermore, although features may appear to be described in conjunction with specific embodiments, those skilled in the art will recognize that various features of the described embodiments can be combined according to the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0150] Furthermore, although listed separately, multiple devices, elements, circuits, or method steps can be implemented, for example, by a single circuit, unit, or processor. Additionally, although individual features may be included in different claims, these features can be advantageously combined together, and inclusion in different claims does not imply that such a combination of features is infeasible and / or disadvantageous. Moreover, including a feature in a class of claims does not imply a limitation on that class, but rather indicates that the feature is equally applicable to other claim classes. Including a feature in a dependent claim of an independent claim does not imply a limitation on that independent claim, but rather indicates that the feature is equally applicable to other appropriate independent claims. Furthermore, the order of features in a claim does not imply that these features must operate in any particular order; in particular, the order of steps in a method claim does not imply that the steps must be performed in that order. Rather, these steps can be performed in any suitable order. Furthermore, singular references do not exclude plural. Therefore, references to “a,” “an,” “first,” “second,” etc., do not exclude plural. Reference numerals in the claims are provided as clarifying examples only and should not be construed as limiting the scope of the claims in any way.

Claims

1. A power receiver (105) for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, the power receiver (105) comprising: The circuit (107, 601, 613) includes a receiver coil (107) as part of a resonant circuit having a first resonance and a second resonance formed by the receiver coil (107) and at least a first capacitor (601) and a second capacitor (613), the first resonance having a first resonant frequency and the second resonance having a second resonant frequency, the first resonant frequency not exceeding twice the frequency of the power transmission signal, and the second resonant frequency differing from the first resonant frequency by at least twice; Power paths (607, 605) that couple the receiver coil (107) to a load (603) and are arranged to provide power from the receiver coil (107) to the load, the power paths comprising: A protection element (607) is arranged to operate in a protected state and an unprotected state, in which a constraint is imposed on power transmission from the receiver coil (107) in the protected state and the constraint is not imposed in the unprotected state. The protection element (607) is arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver (105). The resonant characteristics of the second resonance are different for the protection element (607) when it is in the protected state and when it is in the unprotected state.

2. The power receiver according to claim 1, wherein, The protection element (607) includes a current limiter arranged to limit the current through the protection element (607) when the protection element is in the protected state relative to when the protection element is in the unprotected state.

3. The power receiver according to claim 2, wherein, The protection element (607) is coupled in series between the receiver coil (107) and the load (603), and the second capacitor (613) is coupled into the protection element (607) and also coupled into the load (603).

4. The power receiver according to any of the preceding claims, wherein, The first capacitor (601) is connected in series with the receiver coil (107) and the load (603), and the second capacitor (613) is connected in parallel with the receiver coil (107) and the load (603).

5. The power receiver according to any of the preceding claims, wherein, The protection element (607) is arranged to decouple the second capacitor (613) from the receiver coil (107) when the protection state is in effect.

6. The power receiver according to claim 4, wherein, The input circuit includes a third capacitor, and the second resonance is formed by the receiver coil (107) and at least the second capacitor (613) and the third capacitor, wherein the third capacitor is coupled to the receiver coil (107) when the protection element (607) is in the protected state and when it is in the unprotected state.

7. The power receiver according to any of the preceding claims further includes a communicator (611) for transmitting data to the power transmitter (101), the communicator (611) being arranged to transmit configuration data indicating the dependence of the resonant characteristics on whether the protection element (607) is in the protected state or the unprotected state.

8. The power receiver according to any of the preceding claims further includes a load switch arranged to switch the load and the fourth capacitor between coupling to and decoupling from the receiver coil (107), wherein when the fourth capacitor is coupled to the receiver coil (107), the second resonance is formed by at least the second capacitor and the fourth capacitor.

9. The power receiver according to any of the preceding claims, wherein, The protective element (607) is an electric fuse, and if the electric fuse is open, the second capacitor (613) is disconnected from the power receiver coil (107).

10. The power receiver according to any of the preceding claims, wherein, The protective element (607) is a sacrificial component.

11. A wireless power transmission system comprising a power transmitter (101) and a power receiver (105) according to any one of the preceding claims, the power transmitter comprising: A transmitter coil (103) is arranged to be coupled to the receiver coil (107); A driver (301) is arranged to generate a drive signal for the transmitter coil (103) to generate the electromagnetic power transmission signal; A measuring instrument (309) is arranged to determine the measurement resonance characteristics of the transmitter coil (103) when coupled to the receiver coil (107), the measurement resonance characteristics being for a frequency that differs from the frequency of the power transmission signal by at least two times; as well as A controller (311) is arranged to control the power transmission to the power receiver (105) based on the measured resonant characteristics.

12. The wireless power transmission system according to claim 11, wherein, The power controller (311) is arranged to disable power transmission in response to detecting that the measured resonant characteristics meet the criteria indicating that the power receiver is in the protection state.

13. The wireless power transmission system according to claim 11 or 12, wherein, The measuring instrument (309) is arranged to determine the measured resonance characteristics by comparing load measures of the transmitter coil (103) at at least two different frequencies.

14. A method of operating a power receiver (105) for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transmission signal, the power receiver (105) comprising: The circuit (107, 601, 613) includes a receiver coil (107) as part of a resonant circuit having a first resonance and a second resonance formed by the receiver coil (107) and at least a first capacitor (601) and a second capacitor (613), the first resonance having a first resonant frequency and the second resonance having a second resonant frequency, the first resonant frequency not exceeding twice the frequency of the power transmission signal, and the second resonant frequency differing from the first resonant frequency by at least twice; Power paths (607, 605) that couple the receiver coil (107) to a load (603) and are arranged to provide power from the receiver coil (107) to the load, the power paths comprising: A protection element (607) is arranged to operate in a protected state and an unprotected state, in which a constraint is imposed on power transmission from the receiver coil (107) in the protected state and the constraint is not imposed in the unprotected state. The protection element (607) is arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver (105). The method includes changing the resonant characteristics of the second resonance when the protection element (607) is in the protected state, relative to when the protection element (607) is in the unprotected state.

15. A method of operating a wireless power transmission system, the wireless power transmission system comprising a wireless power transmitter that provides power to a power receiver via an electromagnetic power transmission signal, wherein, The power receiver (105) includes: The circuit (107, 601, 613) includes a receiver coil (107) as part of a resonant circuit having a first resonance and a second resonance formed by the receiver coil (107) and at least a first capacitor (601) and a second capacitor (613), the first resonance having a first resonant frequency and the second resonance having a second resonant frequency, the first resonant frequency not exceeding twice the frequency of the power transmission signal, and the second resonant frequency differing from the first resonant frequency by at least twice; Power paths (607, 605) that couple the receiver coil (107) to a load (603) and are arranged to provide power from the receiver coil (107) to the load, the power paths comprising: A protection element (607) is arranged to operate in a protected state and an unprotected state, wherein in the protected state, it imposes a constraint on power transmission from the receiver coil (107), and in the unprotected state, it does not impose the constraint; the protection element (607) is arranged to switch from the unprotected state to the protected state in response to detecting a fault condition of the power receiver (105); and the power transmitter includes: Transmitter coil (103) coupled to receiver coil (107); And the method includes: Compared to when the protective element is in the unprotected state, the power receiver changes the resonant characteristics of the second resonance when the protective element is in the unprotected state; and the power transmitter performs the following steps: A drive signal is generated for the transmitter coil (103) to generate the electromagnetic power transmission signal; The measured resonant characteristics of the transmitter coil (103) coupled to the receiver coil (107) are determined, the measured resonant characteristics being for a frequency that differs from the frequency of the power transmission signal by at least twice; and The power transmission to the power receiver (105) is controlled based on the measured resonance characteristics.

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