Wireless power transfer

Abstract

A power transmitter (101) provides power to a power receiver (105) via an electromagnetic power transfer signal. The power transmitter (101) includes an output circuit (302, 103) having a transmitter coil (103) that generates the power transfer signal in response to a drive signal generated by a driver (301). A configuration controller (303) switches between power transfer configurations having different maximum power limits and voltage amplitudes for the drive signal. A transmitter (307) transmits a power configuration message to the power receiver (105) including data indicating a voltage amplitude for a first power transfer configuration. A receiver (305) receives a power transfer configuration change request message from the power receiver (105). The configuration controller (303) switches the power transmitter (101) to the first power transfer configuration in response to the power transfer configuration change request message. This method allows power transmitters and receivers to cooperate to change power transfer configurations that provide different maximum power limits.

Description

Technical Field

[0001] The present invention relates to the operation of a wireless power transmission system, and particularly, but not exclusively, to a method for supporting higher power levels in a wireless power transmission system (e.g., Qi). Background Technology

[0002] Most electronic devices today require dedicated electrical contacts to be powered from an external power source. However, this is often impractical and requires users to physically insert connectors or otherwise establish physical electrical contacts. Power requirements also vary considerably, and most devices are currently supplied with their own dedicated power supplies, resulting in a typical situation where users have a large number of different power supplies, each dedicated to a specific device. While using an internal battery can avoid the need for a wired connection to a power source during use, this only provides a partial solution, as the battery will require recharging (or replacement). Using a battery can also significantly increase the weight of the device and potentially increase its cost and size.

[0003] To provide a significantly improved user experience, the use of wireless power has been proposed, in which power is inductively transmitted from a transmitter coil in a power transmitter device to a receiver coil in an individual device.

[0004] Power transmission via magnetic induction is a well-known concept, primarily used in transformers where there is tight coupling between the primary transmitter inductor / coil and the secondary receiver coil. Wireless power transfer between two devices becomes possible based on the principle of loosely coupled transformers, by separating the primary transmitter coil and the secondary receiver coil between them.

[0005] This arrangement allows for wireless power transfer to the device without requiring any cabling or physical electrical connections. In fact, it can simply allow the device to be placed near or on top of the transmitter coil for external recharging or power supply. For example, the power transmitter device can be arranged on a horizontal surface, allowing the device to be easily placed on that surface to receive power.

[0006] Furthermore, such a wireless power transfer arrangement can be advantageously designed to allow power transmitter devices to be used with a range of power receiver devices. In particular, a wireless power transfer method known as the Qi specification has been defined and is currently under further development. This method allows power transmitter devices that comply with the Qi specification to be used with power receiver devices that also comply with the Qi specification, without requiring these devices to be from the same manufacturer or to be proprietary to each other. The Qi standard also includes features to allow operation adapted to specific power receiver devices (e.g., depending on specific power consumption).

[0007] The Qi specification was developed by the Wireless Power Consortium, and more information can be found on their website, for example: http: / / www.wirelesspowerconsortium.com / index.html, where the specification document can be found in detail.

[0008] Qi initially defined low-power wireless power transmission in version 1.0 as practically limited to lower power levels below 5W. This has been extended to higher power levels in subsequent versions and version 1.2 (e.g., providing compliance testing for power levels up to 15W).

[0009] However, there is a desire to support higher power levels, and in some cases, dedicated solutions have been introduced to meet this need. However, most proposed methods for supporting high-power-level wireless power transfer are often suboptimal and can introduce numerous challenges or undesirable effects. For example, supporting a wide power range is challenging. For instance, it may be difficult to control variations in the supplied power over a large range simply by adjusting or limiting the current supplied to the power transmitter coil. Another challenge is ensuring that the effects and consequences of changing operating parameters and conditions, for example, when the power level changes, are acceptable and can be handled, for example, by the power receiver. For example, substantial and rapid changes in the drive voltage can cause transients in the voltage induced at the power receiver, potentially leading to overvoltage (or undervoltage) conditions.

[0010] Therefore, it would be advantageous to improve the methods used for wireless power transfer, especially methods that allow for increased flexibility, reduced cost, reduced complexity, improved support for high power ranges, improved instantaneous power performance, improved adaptability, backward compatibility, improved power transfer operation, and / or improved performance. Summary of the Invention

[0011] Therefore, the present invention seeks to mitigate, alleviate, or eliminate one or more of the disadvantages mentioned above, preferably in a single manner or in any combination.

[0012] According to one aspect of the invention, a power transmitter is provided for wirelessly providing power to a power receiver via an electromagnetic power transmission signal; the power transmitter includes: a transmitter coil for generating the power transmission signal in response to a drive signal being applied to the transmitter coil; a driver for generating the drive signal; a configuration controller for switching between a set of power transmission configurations, the power transmission configurations in the set of power transmission configurations having different combinations of maximum power limits and voltage amplitudes for the drive signal; a transmitter for transmitting a power configuration message to the power receiver, the power configuration message including data indicating a voltage amplitude for a first power transmission configuration in the set of power transmission configurations; a receiver for receiving a power transmission configuration change request message from the power receiver; and wherein the configuration controller is arranged to switch the power transmitter to the first power transmission configuration in response to the power transmission configuration change request message.

[0013] In many scenarios, the present invention can provide improved performance and / or improved power delivery. In many embodiments, it can allow for improved and more efficient power delivery over a wide range of power levels. In many embodiments, the method can support, implement, improve, or facilitate high-power wireless power delivery.

[0014] In many embodiments, improved switching between different power delivery configurations can be achieved, and in particular, the effects of transient conditions and variations in power delivery parameters can often be mitigated. Specifically, in many embodiments and scenarios, improved transient undervoltage / overvoltage operation can be achieved.

[0015] For different power delivery configurations in this set of power delivery configurations, at least one of the maximum power limit and voltage amplitude is different in meaning; this set of power delivery configurations can have different combinations of maximum power limit and voltage amplitude for the drive signal.

[0016] The first power transmission configuration is a candidate power transmission configuration. The first power transmission configuration is different from the current power transmission configuration (which is the power transmission configuration in which the power transmitter is currently operating).

[0017] A configuration controller can be configured to switch a power transmitter from its current power transmission configuration to a first power transmission configuration in response to a power transmission configuration change request message. The configuration controller can be configured to switch a power transmitter to the first power transmission configuration in response to receiving a power transmission configuration change request message. The power transmission configuration change request message can request a change from the current power transmission mode to the first power transmission mode.

[0018] The output circuit may include, or primarily comprise, a resonant (or energy storage) circuit including a transmitter coil. The transmitter coil may be a resonant component of a resonant circuit. The resonant circuit may be a series resonant circuit or a parallel resonant circuit. The resonant circuit may include one or more capacitors.

[0019] The voltage amplitude can be, for example, the peak-to-peak voltage amplitude, the peak amplitude, and / or the half-amplitude amplitude. In some embodiments, and for some signals, the voltage amplitude can be, for example, the effective amplitude or the root mean square amplitude.

[0020] The voltage amplitude for a power transfer configuration can be a constant voltage amplitude for the drive signal. The power transmitter can be arranged to control the power level of the power transfer signal by changing at least one of the frequency, duty cycle, and current amplitude of the drive signal. For a given power transfer configuration, the voltage amplitude can be constant / fixed.

[0021] In some embodiments, the voltage amplitude for a power transmission configuration may be a range of voltage amplitudes for a drive signal. For example, the voltage amplitude for each power transmission configuration may be a maximum voltage amplitude limit and / or a minimum voltage amplitude limit. In some embodiments, the voltage amplitude provided in the power transmission configuration for a first power transmission configuration may be an indication of the voltage amplitude range and / or maximum / minimum voltage amplitude limits of the first power transmission configuration. In some embodiments, the voltage amplitude provided in the power configuration message for a first power transmission configuration may be an indication of the nominal or initial voltage amplitude for the drive signal after switching to the first power transmission configuration.

[0022] According to an optional feature of the invention, the data indicates the relative difference between the voltage amplitude for the first power transmission configuration and the voltage amplitude for the current power transmission configuration.

[0023] In many embodiments, this can provide improved performance. In many embodiments, it can allow for a more efficient trade-off between accuracy and communication bandwidth, and can provide particularly relevant information for transient performance when power delivery configurations are changed.

[0024] According to an optional feature of the invention, the data indicates the ratio between the voltage amplitude for the first power transmission configuration and the voltage amplitude for the current power transmission configuration.

[0025] In many embodiments, this can provide improved performance. In many embodiments, it can allow for a more efficient trade-off between accuracy and communication bandwidth, and can provide particularly relevant information for transient performance when power delivery configurations are changed.

[0026] According to an optional feature of the invention, the first power transmission configuration is a power transmission configuration in the set of power transmission configurations that has a maximum power limit of at least one of a next higher maximum power limit and a next lower maximum power limit for the current power transmission configuration.

[0027] In many embodiments, this can provide particularly efficient operation. It can particularly provide an efficient method for controlling dynamic power level variations that can support a wide range of power levels while maintaining low communication requirements. It can limit power level variations to reduce transient nature and / or reduce communication requirements, for example, by making it possible to provide no additional information beyond voltage amplitude for candidate power transfer configurations.

[0028] According to an optional feature of the invention, the power configuration message includes data indicating the voltage amplitude for a second power transmission configuration in the set of power transmission configurations, wherein the first power transmission configuration is a power transmission configuration in the set of power transmission configurations having a maximum power limit that is a next higher maximum power limit for the current power transmission configuration; and the second power transmission configuration is a power transmission configuration in the set of power transmission configurations having a maximum power limit that is a next lower maximum power limit for the current power transmission configuration.

[0029] In many embodiments, this can provide particularly efficient operation. Power mode messages can specifically provide information for the power transmitter that is closest in terms of power transmission configuration (in terms of maximum power limits) to increase and decrease power levels respectively.

[0030] According to an optional feature of the invention, a predetermined value of the data indicating the voltage amplitude indicates that the set of power transmission configurations does not include a power transmission configuration having a maximum power limit higher than the maximum power limit of the current power transmission configuration.

[0031] This allows for particularly efficient communication with the availability of power transmission configurations.

[0032] In some embodiments, a predetermined value of the data indicating the voltage amplitude indicates that the set of power delivery configurations does not include a power delivery configuration having a maximum power limit lower than the maximum power limit of the current power delivery configuration.

[0033] This allows for particularly efficient communication with the availability of power transmission configurations.

[0034] In some embodiments, a predetermined value of the data indicating voltage amplitude indicates that the voltage amplitude for a first power transmission configuration has not changed relative to the voltage amplitude for the current power transmission configuration.

[0035] According to an optional feature of the invention, the configuration controller is arranged to send the power configuration message in response to detecting that the operating characteristics of the power transmission meet the criteria.

[0036] In many embodiments, this can provide particularly advantageous performance and operation. The method can support changes to the power transmission configuration initiated by the power transmitter while ensuring that this is done in cooperation with the power receiver, thereby reducing the risk of undesirable effects at the power receiver.

[0037] The operating characteristics of power transfer can be parameters that indicate the current power level of the power transfer signal (for the current power transfer configuration), such as parameters indicating the frequency or current of the drive signal.

[0038] According to an optional feature of the invention, the configuration controller is arranged to send the power configuration message in response to detecting that the current power level of the power transmitter exceeds a threshold, the threshold depending on the maximum power limit of the current power transmission configuration.

[0039] In many embodiments, this can provide particularly advantageous performance and operation. The method can support changes to the power transmission configuration initiated by the power transmitter while ensuring that this is done in cooperation with the power receiver, thereby reducing the risk of undesirable effects at the power receiver.

[0040] According to an optional feature of the invention, the configuration controller is arranged to send the power configuration message in response to receiving a power configuration information request message from the power receiver.

[0041] In many embodiments, this can provide particularly advantageous performance and operation. The method can support power transmission configuration changes initiated by the power receiver while ensuring that this is done in cooperation with the power transmitter.

[0042] According to an optional feature of the invention, the configuration controller is arranged to switch the power transmitter to the first power transmission configuration after an acknowledgment message has been sent to the power receiver, the acknowledgment message confirming the request message received from the power receiver.

[0043] In many embodiments, this can provide particularly advantageous performance and operation.

[0044] According to one aspect of the invention, a power receiver is provided for wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the power receiver comprising: an input circuit including a power receiver coil arranged to extract power from the power transmission signal; a receiver for receiving a power configuration message from the power transmitter, the power configuration message including data indicating the voltage amplitude of a drive signal for at least a first power transmission configuration in a set of power transmission configurations, the power transmission configurations in the set of power transmission configurations having different combinations of maximum power limits and voltage amplitudes, and the drive signal being used for an output circuit of the power transmitter, the output circuit including a transmitter coil for generating the power transmission signal in response to the drive signal being applied to the output circuit; a configuration controller arranged to detect a power transmission configuration change bias for switching the power transmitter to the first power transmission configuration; and a transmitter for sending a power transmission configuration change request message to the power transmitter in response to detecting the power transmission configuration change bias, the power transmission configuration change request message including a request for switching the power transmitter to the first power transmission configuration.

[0045] According to an optional feature of the invention, the configuration controller is arranged to control the power transmission to change the voltage induced on the power receiver coil before the power transmission configuration is changed to the first power transmission configuration.

[0046] In many embodiments, this can provide particularly advantageous performance and operation. In many scenarios, it can compensate for or mitigate transient voltage changes and, for example, prevent undervoltage or overvoltage conditions.

[0047] According to an optional feature of the invention, the configuration controller is arranged to change the load impedance for the power receiver coil before the power transmission configuration is changed to the first power transmission configuration.

[0048] In many embodiments, this can provide particularly advantageous performance and operation.

[0049] According to one aspect of the present invention, a method of operating a power transmitter is provided, the power transmitter wirelessly providing power to a power receiver via an electromagnetic power transmission signal; the method includes: generating the power transmission signal in response to a drive signal being applied to the transmitter coil; generating the drive signal; switching between a set of power transmission configurations, the power transmission configurations in the set of power transmission configurations having different combinations of maximum power limits and voltage amplitudes for the drive signal; sending a power configuration message to the power receiver, the power configuration message including data indicating a voltage amplitude for a first power transmission configuration in the set of power transmission configurations; receiving a power transmission configuration change request message from the power receiver; and wherein the switching between the set of power transmission configurations is in response to the power transmission configuration change request message to switch the power transmitter to the first power transmission configuration.

[0050] According to one aspect of the present invention, a method of operating a power receiver is provided, the power receiver wirelessly receiving power from a power transmitter via an electromagnetic power transmission signal, the method comprising: a power receiver coil extracting power from the power transmission signal; receiving from the power transmitter a power configuration message, the power configuration message including data indicating the voltage amplitude of a drive signal for at least a first power transmission configuration in a set of power transmission configurations, the power transmission configurations in the set of power transmission configurations having different combinations of maximum power limits and voltage amplitudes, and the drive signal being used for an output circuit of the power transmitter, the output circuit including a transmitter coil for generating the power transmission signal in response to the drive signal being applied to the output circuit; detecting a power transmission configuration change bias for switching the power transmitter to the first power transmission configuration; and sending a power transmission configuration change request message to the power transmitter in response to detecting the power transmission configuration change bias, the power transmission configuration change request message including a request for the power transmitter to switch to the first power transmission configuration.

[0051] According to another aspect of the present invention, a wireless power transmission system is provided for wirelessly providing power from a power transmitter to a power receiver via an electromagnetic power transmission signal; the power transmitter includes: an output circuit including a transmitter coil for generating the power transmission signal in response to a drive signal being applied to the output circuit; a driver for generating the drive signal; a configuration controller for switching between a set of power transmission configurations having different combinations of maximum power limits and voltage amplitudes for the drive signal; a transmitter for transmitting a power configuration message to the power receiver, the power configuration message including data indicating a voltage amplitude for a first power transmission configuration in the set of power transmission configurations; and a receiver for receiving power from the power receiver. A power transmission configuration change request message; wherein the configuration controller is arranged to switch the power transmitter to the first power transmission configuration in response to the power transmission configuration change request message; and the power receiver includes: an input circuit including a power receiver coil arranged to extract power from the power transmission signal; a receiver for receiving the power configuration message from the power transmitter; a configuration controller arranged to detect a power transmission configuration change bias for switching the power transmitter to the first power transmission configuration; and a transmitter for sending the power transmission configuration change request message to the power transmitter in response to detecting the power transmission configuration change bias, the power transmission configuration change request message including a request for switching the power transmitter to the first power transmission configuration.

[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 with reference to the accompanying drawings, and by way of example only, in which:

[0054] Figure 1 Examples of elements of a power transmission system according to some embodiments of the present invention are illustrated;

[0055] Figure 2 The illustration shows an example of a set of power transmission configurations for a power transmitter according to some embodiments of the present invention;

[0056] Figure 3 Examples of elements of a power transmitter according to some embodiments of the present invention are illustrated;

[0057] Figure 4 The diagram illustrates an example of the components in the output stage of a power transmitter;

[0058] Figure 5 The diagram illustrates an example of the components in the output stage of a power transmitter;

[0059] Figure 6 Examples of elements of a power receiver according to some embodiments of the present invention are illustrated;

[0060] Figure 7 Examples of power configuration messages according to some embodiments of the present invention are illustrated;

[0061] Figure 8 An example of a power transmission configuration change request message according to some embodiments of the present invention is illustrated;

[0062] Figure 9 Examples of message exchange according to some embodiments of the present invention are illustrated; and

[0063] Figure 10 Examples of message exchange according to some embodiments of the present invention are illustrated. Detailed Implementation

[0064] The following description focuses on embodiments of the invention applicable to wireless power transmission systems utilizing, for example, power transmission methods known from the Qi specification. However, it will be appreciated that the invention is not limited to this application, but can be applied to many other wireless power transmission systems.

[0065] Figure 1 An example of a power transmission system according to some embodiments of the present invention is illustrated. The power transmission system includes a power transmitter 101, which includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105, which includes (or is coupled to) a receiver coil / inductor 107.

[0066] The system provides an 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 through a transmitter coil or inductor 103 (which is typically part of an output circuit in the form of a resonant circuit or energy storage circuit). The power transfer signal can correspond to an electromagnetic power transfer component representing the energy transfer from the power transmitter to the power receiver, and can be considered to correspond to the component in the generated electromagnetic field that transfers power from the power transmitter to the power receiver. For example, if there is no load on the receiver coil 107, the power receiver will not extract any power from the generated electromagnetic field (except for losses). In such a scenario, driving the transmitter coil 103 can generate an electromagnetic field with potentially high field strength, but the power level of the power transfer signal will be zero (except for losses). In some cases (the presence of a foreign object), the power transfer signal can be considered to include a component corresponding to the power transfer to the foreign object, and therefore can be considered to correspond to the power extracted from the electromagnetic field generated by the power transmitter.

[0067] The power transmission signal typically has a frequency between approximately 20 kHz and approximately 500 kHz, and often for Qi-compatible systems, the power transmission signal is typically in the range of 95 kHz to 205 kHz (or, for example, for high-power kitchen applications, the frequency may typically be in the range of 20 kHz to 80 kHz). The transmitter coil 103 and the power receiving coil 107 are loosely coupled, so that 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.

[0068] 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 (e.g., a metallic heating element), in which case the power transmission signal directly induces eddy currents, thereby causing direct heating of the element.

[0069] The system is configured to transmit a wide range of power levels, and in particular, the power transmitter in many embodiments 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 (baseline power distribution); for Qi specification version 1.2, power delivery is typically up to 15W; for higher-power applications (e.g., power tools, laptops, drones, robots, etc.), power delivery is typically up to 100W; and for very high-power applications (e.g., kitchen applications), power delivery is typically over 100W and up to 1000W or more.

[0070] In the following description, the operation of power transmitter 101 and power receiver 105 will be described with specific reference to embodiments generally based on the Qi specification (other than the modifications and enhancements described herein or subsequently thereafter) or embodiments suitable for use with the higher-power Qi specification developed by the Wireless Power Consortium. In particular, power transmitter 101 and power receiver 105 may follow or be substantially compatible with elements of Qi specification versions 1.0, 1.1, or 1.2 (other than the modifications and enhancements described herein or subsequently thereafter).

[0071] Figure 1 The system is configured to support power transmission over a wide range of power levels. This functionality is achieved through power transmitters capable of operating in multiple different power transmission configurations, each corresponding to a different power level.

[0072] Specifically, some power transmission configurations use different voltage amplitudes to drive the output circuit with transmitter coil 103. Typically, the output circuit is a series resonant circuit, where the transmitter coil forms an inductive resonant element, and where the series resonant circuit is driven by a drive signal with a constant voltage amplitude, and where the power level is determined and changed directly or indirectly by altering the current supplied to the output circuit (e.g., by changing the drive frequency or duty cycle of the drive signal). However, because the required current variation becomes difficult to achieve and control, it becomes difficult to support large power level variations in this manner. Therefore, Figure 1The system allows the power transmitter 101 to switch between different power transmission configurations, which may correspond to different maximum power limits and use different voltage amplitudes for the drive signal used for the transmitter coil 103. Specifically, for a given power transmission configuration, the voltage amplitude of the drive signal may be constant, but for different power transmission configurations, the voltage amplitude may be different. The maximum power limit may be an upper limit on the power of the power transmission signal supported in the current power transmission configuration. The power limit can be imposed by limiting the current supplied to the drive signal of the transmitter coil 103. Therefore, the maximum power limit may correspond to a maximum current limit.

[0073] The voltage amplitude can be the peak-to-peak, peak-to-peak, or half-amplitude of the drive signal, and in many embodiments, the drive signal can be a square wave or a rectangular wave. Specifically, the drive signal can be a signal with a value of +Va, -voltage amplitude, or 0, where Va is the (peak) voltage amplitude. The drive signal can have a mean of 0. In some embodiments, the drive signal can be different waveforms, such as a sine wave, a triangle wave, etc.

[0074] Therefore, the power transmitter 101 can be arranged to operate in one of a plurality of power transmission configurations, wherein each power transmission configuration may specifically correspond to a different combination of drive signal voltage amplitude and maximum power limit (and therefore maximum current limit). For example, as Figure 2 As shown, the power transmitter 101 can be arranged to operate in one of n different power transmission configurations, wherein each configuration has an associated maximum power limit and a fixed drive signal voltage amplitude. For example, the power transmitter 101 can be arranged to select the current power transmission configuration from a set of power transmission configurations having the following maximum power limit / maximum current limit and drive signal voltage amplitude (in this example, valid values ​​for the voltage amplitude and maximum current limit are provided):

[0075] · 5V, 1.5A (7.5W)

[0076] 9V, 1A (9W)

[0077] 5V, 2A (10W)

[0078] 12V, 1A (12W)

[0079] 9V, 2A (18W)

[0080] 12V, 1.5A (18W)

[0081] 19V, 1A (19W)

[0082] 12V, 2A (24W)

[0083] 19V, 2A (38W)

[0084] 19V, 3A (57W)

[0085] The power transmitter 101 can therefore be arranged to operate in one of a set of power transmission configurations with different voltage amplitudes, wherein a higher voltage amplitude is required to achieve a higher power level.

[0086] Figure 3 A more detailed illustration is provided. Figure 1 The power transmitter 101 is a component.

[0087] The power transmitter 101 includes a driver 301 capable of generating a drive signal that is fed to an output circuit, in this example, a resonant circuit formed by a transmitter coil 103 and a transmitter capacitor 302. In response to the drive signal, the transmitter coil 103 generates an electromagnetic field and thus an electromagnetic power transfer signal that provides power transfer to the power receiver 105. The power transfer signal is provided (at least) during the power transfer phase.

[0088] The driver 301 is typically a drive circuit in the form of an inverter that generates an AC signal based on a DC voltage. The output of the driver 301 is typically a switching bridge that generates a drive signal by appropriately switching its switches. Figure 4 A half-bridge switching inverter is shown. Switches S1 and S2 are controlled so that they never close simultaneously. Alternatively, S1 closes when S2 is open, and S2 closes when S1 is open. The switches open and close at a desired frequency, thereby generating an alternating signal at the output. Typically, the inverter output is connected to a transmitter inductor via a resonant capacitor. Figure 5 A full-bridge switched bridge / inverter is shown. Switches S1 and S2 are controlled so that they never close simultaneously. Switches S3 and S4 are also controlled so that they never close simultaneously. Alternatively, when S2 and S3 are open, switches S1 and S4 are closed, and then when S1 and S4 are open, S2 and S3 are closed, thereby creating a square wave signal at the output. The switches open and close at the desired frequency.

[0089] Driver 301 thus generates a drive signal for the output resonant circuit and therefore for the transmitter coil 103. For a given power transfer configuration, the drive signal has a (substantially) constant voltage amplitude. In this example, the constant voltage amplitude is achieved by setting a constant rail voltage for the driver's output circuit, i.e., for a given power transfer configuration, the drive signal for... Figure 4 and Figure 5The rail voltage V of the bridge is constant. For a half-bridge, the output voltage is switched between 0 and V by switching the bridge transistors accordingly, and for a full-bridge, the output voltage is switched between V and -V by switching the bridge transistors accordingly. Therefore, in this example, for any given power transmission configuration, the power transmitter can set the rail voltage to be constant, but the rail voltage may vary between power transmission configurations.

[0090] The power transmitter 101 also includes a power transmitter controller 303, which is arranged to control the operation of the power transmitter 101 according to a desired operating principle. In particular, the power transmitter 101 may include a number of functions required for performing power control in accordance with the Qi specification.

[0091] Specifically, the power transmitter controller 303 is arranged to control the generation of drive signals by the driver 301. Specifically, the power transmitter controller 303 can set a rail voltage for the drive corresponding to a specific power transmission configuration in which the power transmitter is currently operating.

[0092] The power transmitter controller 303 can also dynamically control the power level of the drive signal and thus the power level of the power transmission signal generated by the transmitter coil 103. Specifically, the power transmitter controller 303 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 a power control phase. Specifically, power level control can be achieved by controlling the current of the drive signal or, more typically, by controlling the duty cycle or frequency of the drive signal. In the latter example, the power level can be increased by shifting the frequency closer to the resonant frequency of the output resonant circuit including the transmitter coil 103 (and / or the resonant frequency of the resonant circuit including the receiver coil 107 of the power receiver 105), and decreased by shifting the frequency further away from said resonant frequency.

[0093] Additionally, for a given power delivery configuration, the power transmitter controller 303 can limit the power level to a maximum power level. This is typically accomplished by limiting the current of the drive signal. The current can be actively limited, or in some embodiments, the maximum power limit can be indirect (or even unintentional) and, for example, due to an actual limitation on the current that can be supplied to the driver by the power supply. In some embodiments, the maximum power limit can be a constraint imposed by a control algorithm, for example, to ensure that the thermal capability of the switching bridge transistor is not exceeded. For example, in a system where the power level is controlled by controlling the frequency and / or duty cycle of the drive signal / power delivery signal, the controller can continuously monitor the power level and adapt to frequencies subject to the requirement that the power level does not exceed the maximum power limit for the current power delivery configuration.

[0094] In order to receive data and messages from power receiver 105, power transmitter 101 includes a first receiver 305, which is arranged to receive data and messages from power receiver 105 (data messages may provide one or more bits of information, as those skilled in the art will appreciate). In this example, power receiver 105 is arranged to load modulate the power transmission signal generated by transmitter coil 103, and first receiver 305 is arranged to sense changes in voltage and / or current of transmitter coil 103 and demodulate the load modulation based on these changes. Those skilled in the art will understand the principles of load modulation, for example, used in Qi wireless power transmission systems, and therefore these will not be described in further detail.

[0095] The power transmitter 101 is also arranged to transmit data to the power receiver 105, and thus includes a first transmitter 307, which in particular is arranged to transmit data to the power receiver, for example, by modulating the drive signal and thus the power transmission signal using frequency, amplitude and / or phase modulation.

[0096] It will be appreciated that other methods for data communication between power transmitter 101 and power receiver 105 can be used in other embodiments. For example, in some embodiments, a separate communication channel can be used to perform communication, which can be implemented using a separate communication coil or actually using transmitter coil 103. For example, in some embodiments, near-field communication can be implemented, or a high-frequency carrier (e.g., with a carrier frequency of 13.56 MHz) can be superimposed on the power transmission signal.

[0097] The power transmitter 101 also includes a first configuration controller 309, which is arranged to control in which power transmission configuration the power transmitter 101 operates, and is therefore specifically arranged to switch the power transmitter 101 between different power transmission configurations in a set of possible power transmission configurations.

[0098] Figure 6 Some exemplary components of the power receiver 105 are illustrated.

[0099] Receiver coil 107 is coupled to power receiver controller 601, which couples receiver coil 107 to load 603. Power receiver controller 601 includes a power control path that converts the power extracted by receiver coil 107 into supply power suitable for use with the load. Additionally, power receiver controller 601 may include various power receiver controller functions required to perform power transfer, and in particular, functions required to perform power transfer according to the Qi specification.

[0100] The power receiver 105 also includes a second receiver 605, which is arranged to receive data transmitted from the power transmitter 101. In this example, the second receiver 605 is arranged to appropriately demodulate the amplitude, frequency, and / or phase modulation of the power transmission signal in order to recover the data transmitted from the power transmitter.

[0101] To support communication from power receiver 105 to power transmitter 101, power receiver 105 includes a second transmitter 607. The second transmitter 607 is arranged to transmit data to the power transmitter by changing the load of receiver coil 107 in response to data to be transmitted to power transmitter 101. The load change is then detected and demodulated by power transmitter 101, as those skilled in the art will appreciate.

[0102] As mentioned above, in other embodiments, other communication methods may be used, such as a separate and dedicated short-range communication method, for example, NFC.

[0103] The power receiver 105 also includes a second configuration controller 609, which is arranged to support the use of different power transmission configurations, and in particular, the second configuration controller 609 can support and control the switching of the power transmitter 101 between different power transmission configurations.

[0104] Therefore, in Figure 1In this system, a range of different power transmission configurations with varying maximum power levels can be used for power transmission, thereby providing a potentially wide range of supported power levels, including considerably high power levels. Additionally, the power transmitter and power receiver can be arranged to dynamically switch between different power configurations. For example, power transmission operation can initially begin at a low power level and then gradually increase the power level to increasingly higher levels. For instance, charging a large-capacity battery can begin at a low charging level for safety reasons and then increase to a potentially high level with a high charging current once it is ensured that the battery charging can be safely supported (e.g., ensuring there are no metallic foreign objects nearby). Similarly, in many embodiments, load 603 can be a variable load with highly variable power consumption. For example, the load can be a device comprising an engine that operates only intermittently. Therefore, in many cases, it may be desirable to change between different power transmission configurations, where the changes can be unpredictable and can occur in both the power increase and power decrease directions.

[0105] However, while this may allow for improved performance over a wider power range in many embodiments, the inventors have further recognized the potential risks and difficulties of changing between different power delivery configurations with different drive voltages for the drive signal.

[0106] In particular, changes in the voltage of the drive signal can cause step-like / transient changes in the induced voltage at the receiver coil 107. Therefore, switching from one power transmission configuration to another may cause undervoltage or overvoltage conditions at the power receiver. For some power receivers, and in some cases, such undervoltage or overvoltage conditions may be perfectly acceptable and have no significant impact on operation. However, for other power receivers and / or in other scenarios, undervoltage and / or overvoltage may have a significant impact and may cause suboptimal or even erroneous operation. In fact, in some cases, it is even conceivable that overvoltage conditions could damage the power receiver if appropriate precautions are not taken.

[0107] As a specific example, a power transmitter might operate in a 10W (5V, 2A) configuration, where a power receiver controls its operating point to 8V, 1A. When the power transmitter switches to a higher configuration (e.g., 12W (12V, 1A)), the power receiver will initially see a voltage of 12 / 5*8 = 19.5V, 2.4A, far exceeding the capability of the power transmitter in that configuration. Therefore, power delivery may fail due to the generation of overvoltage or overpower conditions.

[0108] A similar situation can occur when switching to a lower power configuration. For example, if the power transmitter is operating at 12V, 1A and the power receiver is only receiving 4W (e.g., 5V, 0.8A), switching to the next lower configuration on the power transmitter (e.g., 5V, 1.5A) might be more advantageous. If this switch is made before the power receiver is ready, it will experience a voltage drop of 5 / 12*5 = 2.1V after the switch, which may be too low to sustain its operation (i.e., undervoltage). Therefore, this will also lead to a breakdown in power delivery.

[0109] exist Figure 1 The method implements specific techniques for switching between power transmission configurations, which in many embodiments can provide improved performance. This method allows the power transmitter and power receiver to operate interactively to carefully control the switching of power transmission configurations, and in particular, enables the power receiver to be aware of and generally have complete control over the switching from one power transmission configuration to another, thereby preventing unpredictable undervoltage or overvoltage conditions.

[0110] This method is based on the exchange of information between the power transmitter and the power receiver to control and coordinate changes to the power transmission configuration. In particular, message exchange can allow the power receiver to control changes to the power transmission configuration used by the power transmitter, enabling this operation to continue without changes that would cause unacceptable effects at the power receiver (it can, for example, allow the power receiver to compensate for such effects).

[0111] Therefore, in this example, the power transmitter 101 includes a first configuration controller 309 arranged to control the power transmitter 101 to operate from a set of multiple power transmission configurations, each of which may represent a different combination of a (substantially) constant voltage amplitude for a drive signal used in the output circuitry including the transmitter coil 103 and a maximum power limit for the power transmission signal / drive signal. The power transmitter 101 is also arranged to send a power configuration message to the power receiver 105, the power configuration message including data indicating the voltage amplitude of the drive signal for one or more of these power transmission configurations.

[0112] Specifically, the power configuration message may include data describing the voltage amplitude of a power transmission configuration for which the power transmitter 101 can potentially switch. In particular, in many embodiments, the power configuration message may provide voltage amplitude information for the next higher and / or next lower power transmission configuration in a given (e.g., predetermined or previously communicated) sequence of power transmission configurations in which the power transmitter 101 may operate. For example, the power transmission configurations may be ordered by maximum power limits (and by voltage amplitude if some power transmission configurations have the same maximum power limit), and the power configuration message may indicate the values ​​of the next higher and lower power transmission configurations based on this sequence. The power configuration message may accordingly provide voltage amplitudes for the immediately following higher maximum power limit and the immediately following lower maximum power limit.

[0113] Voltage indication can be given in absolute form or, for example, in relative form, relative to the voltage amplitude of the current power transmission configuration.

[0114] In this method, the power receiver 105 may be provided with information on the power transmission configuration that the power transmitter can switch to.

[0115] The second receiver 605 of the power receiver 105 can receive power configuration messages and accordingly inform the power receiver 105 of potential changes in the power transmission configuration and the resulting changes in voltage amplitude. Therefore, the power receiver has information that allows it to evaluate the results of subsequent changes to the power transmission configuration.

[0116] Additionally, the power receiver 105 includes a second configuration controller 609, which is arranged to detect a power transmission configuration bias that the power transmitter is about to switch to (one or more) power transmission configurations indicated by a power configuration message.

[0117] The desired / requested / biased change of power transmission configuration can be detected in any suitable manner and using any suitable algorithm / criteria. This method is independent of any particular method or requirement, or where the bias is actually determined, by which function, or by which device or apparatus. Therefore, this method is based on the second configuration controller 609 detecting the presence of a bias for changing the power transmission configuration, but is independent of where, why, and how the bias originates.

[0118] In many embodiments, the bias can be determined in the power receiver 105, and particularly by the second configuration controller 609. For example, the second configuration controller 609 can determine that power transmission is operating close to the maximum power limit for the current power transmission configuration, and that there is a demand for increased power and therefore a bias to switch to a power transmission configuration with a higher maximum power limit.

[0119] In some embodiments, the bias toward switching to a different power transmission configuration may be determined, for example, by the power transmitter, and the second configuration controller 609 may detect this bias, for example, in response to the nature of the power transmission signal or communication from the power transmitter. For example, when the power transmitter determines that such a switch would be desirable, the power transmitter may send a request for a change in the power transmission configuration to the power receiver. In fact, in many embodiments, the power transmitter may be arranged to send a power configuration message in response to the power transmitter determining that there is a bias toward changing the power transmission configuration, and therefore the power configuration message itself may be a power transmission configuration change request message.

[0120] The second transmitter 607 can be arranged to send a power transmission configuration change request message to the power transmitter in response to detecting a power transmission configuration change bias. In many embodiments, the sending can be conditional, for example, specifically conditional on the voltage amplitude of the corresponding power transmission configuration to meet certain criteria.

[0121] For example, the second configuration controller 609 may, in response to detecting an expectation of changing the power transmission configuration to a given candidate power transmission configuration, evaluate whether a change to that candidate power transmission configuration would result in an unacceptable undervoltage or overvoltage condition at the power receiver due to switching. As a simple example, the second configuration controller 609 may simply determine whether the ratio between the voltage amplitude of the current power transmission configuration and the voltage amplitude of the candidate power transmission configuration exceeds a threshold considered acceptable (in a specific case) for a particular power receiver. If so, the second transmitter 607 may continue to send a power transmission configuration change request message to the power transmitter; otherwise, it may not send a power transmission configuration change request message.

[0122] In other embodiments, the second transmitter 607 may be arranged to always send a power transmission configuration change request message to the power transmitter 101 if a power transmission configuration change bias is detected. In such embodiments, the power receiver 105 may be arranged to adapt its operation or configuration in response to the voltage amplitude of the requested power transmission configuration and generally in response to the relationship between the voltage amplitude of the requested power transmission configuration and the voltage amplitude of the current power transmission configuration.

[0123] For example, if the voltage amplitude change is small enough, problematic undervoltage or overvoltage conditions will not occur, and therefore no change in operation or configuration may be required. However, if the voltage amplitude change is large enough, this can cause unacceptable transient performance and, for example, lead to transient overvoltages until the power control loop can adapt to the power level, etc. In this case, the operation of the power receiver 105 can be adapted by the second configuration controller 609 to prepare for changes in the power delivery configuration. For example, the input circuitry can be isolated from sensitive circuitry that may be susceptible to overvoltage conditions. In particular, in many embodiments, the load 603 can be disconnected.

[0124] The first receiver 305 may receive a power transmission configuration change request message from the power receiver 105, and in response to receiving the power transmission configuration change request message, the first configuration controller 309 may continue to switch the power transmitter 101 to a new candidate power transmission configuration. In some embodiments, the power transmission configuration change request message may indicate the power transmission configuration, such as whether the power transmitter 101 is requested to switch to a higher or lower maximum power limit. In other embodiments, this may be implicit, for example, by having only one candidate power transmission configuration.

[0125] In this system, changes to the power transmission configuration are not exclusively performed by the power transmitter 101, but rather collaboratively between the power transmitter and the power receiver. The power receiver is not only informed of the potential impact of the power transmission configuration change, but also controls whether the change occurs. Therefore, while a change to the power transmission configuration can theoretically be initiated by either the power transmitter or the power receiver, this method allows the power receiver to control whether the change proceeds.

[0126] Therefore, this method allows for a flexible approach that effectively supports a wide range of power levels by employing a range of different power delivery configurations with varying voltages and maximum power limits. This method allows for use with a wide range of power transmitters and receivers without the risk of, for example, unacceptable overvoltage or undervoltage conditions. Conversely, this method ensures that changes to a given power delivery configuration occur in a specific way and only if such a change is acceptable to a particular power receiver. Therefore, this method allows for operational adaptation to the specific power transmitters and receivers involved.

[0127] This method also provides improved backward compatibility and, for example, allows for its introduction into systems where some power receivers do not support different power transmission configurations. Such a power receiver would not include functionality for generating and sending power transmission configuration change request messages, and therefore the power transmitter would not switch power transmission configurations, even if it would consider doing so advantageous.

[0128] In some embodiments, the power configuration message may also provide an indication of the maximum power level for one or more power delivery configurations that provide voltage indications therefor. For example, the power configuration message may explicitly indicate the maximum power level using dedicated data, such as giving a value in watts or providing a reference to one of a set of predetermined levels.

[0129] However, in many embodiments, the power configuration message may not include any data defining the maximum power limit for one or more power transfer configurations. In some such embodiments, the power configuration message itself may (implicitly) indicate some information about the maximum power level. For example, as indicated above, the power configuration message itself may indicate whether a higher maximum power limit and / or a lower maximum power limit actually exist. In some embodiments, the maximum power limit for this set of power transfer configurations is predetermined and is known to the power receiver (or, for example, communicated to the power receiver during power transfer initialization). In this case, the power receiver will know the maximum power limit for the next higher power transfer configuration and the next lower power transfer configuration, and therefore the power configuration message also implicitly provides an indication of the maximum power limit by providing a voltage indication.

[0130] In particular, in many embodiments, the power configuration message may provide a voltage amplitude for a power transmission configuration having a maximum power limit that is at least one of a next higher maximum power limit or a next lower maximum power limit relative to the maximum power limit of the current power transmission configuration; or, in many embodiments, advantageously, the power configuration message may provide a voltage amplitude for a power transmission configuration having a maximum power limit that is at least one of a next higher maximum power limit and a next lower maximum power limit relative to the maximum power limit of the current power transmission configuration (therefore, voltage amplitudes may be provided for both the next higher power transmission configuration and the next lower power transmission configuration).

[0131] Therefore, in many embodiments, the power configuration message may include information about two power transmission configurations corresponding to the next lower power limit and the next higher power limit available. This can provide an efficient system where power levels can be flexibly changed while maintaining low complexity and communication bandwidth. For example, once the power transmission configuration changes, only the new data needs to be communicated, and only the data needs to be used for one or two power transmission configurations. In particular, communication is limited by very few parameters and does not need to communicate data for all power transmission configurations supported by the power transmitter. This is a substantial advantage in practice because communication from the power transmitter to the power receiver is very slow in wireless power transmission systems such as Qi.

[0132] This method can also accommodate situations where voltage step changes tend to be limited to smaller steps. For example, large power level changes will tend to be broken down into multiple smaller steps, resulting in smaller transients.

[0133] In this example, the power transmitter informs the power receiver of the next higher or lower voltage configuration available from the set of power delivery configurations supported by the power transmitter. The power receiver can then request to switch to the available lower or higher configuration. Since the power receiver requires higher or lower power, it can proceed step-by-step through the configuration. This avoids the power transmitter changing the configuration without prior notice (which could cause difficulties) or even potentially damage the power receiver.

[0134] In many embodiments, the indication of voltage amplitude can advantageously be provided as the relative difference between the voltage amplitude of a candidate power transmission configuration and the voltage amplitude of the current power transmission configuration, and particularly as a ratio between them. This is particularly advantageous in embodiments that indicate only adjacent power transmission configurations, as it allows for standardization of the values ​​to be conveyed, thereby allowing for a more accurate representation of a given number of bits. For example, if the maximum step of the voltage amplitude between adjacent power transmission configurations is, for example, a factor of 2, although this set of power transmission configurations covers, for example, a voltage amplitude range with a factor of 10, the indication of the ratio only needs to cover, for example, the range from 1 to 2.

[0135] exist Figure 7The diagram illustrates an example of a possible power configuration message. In this example, the power configuration message is referred to as a Power Supply Configuration (PSC) packet sent from the power transmitter to the power receiver. In this example, the PSC packet includes two fields, each 8 bits long. The first field includes voltage sag data values, and the second field includes voltage ramp data values, wherein the first field indicates the relative change in the voltage amplitude of the driving signal when the power transmitter switches to the next lower power transmission configuration, and the second field indicates the relative change in the voltage amplitude of the driving signal when the power transmitter switches to the next higher power transmission configuration. As a specific example, values ​​may be provided according to the following protocol:

[0136] Voltage step When the next lower power transmission configuration is activated, the load voltage will be reduced by 1 / 64 of this factor (values ​​range from 64 to 255).

[0137] Voltage step-up When the next higher power transmission configuration is activated, the load voltage will increase by 1 / 64 of this factor (the value is in the range of 64…255).

[0138] In some embodiments, a predetermined value of a data field that includes data indicating the voltage magnitude of a candidate power transfer configuration can be used to indicate that the current power transfer configuration is an extreme power transfer configuration in the sense that it is the highest or lowest power level power transfer configuration.

[0139] Therefore, a predetermined value in the voltage amplitude data field of the power configuration message can be used to indicate to the power receiver that this set of power transmission configurations supported by the power transmitter does not include any power transmission configuration with a higher maximum power limit. Similarly, another predetermined value in the voltage amplitude data field of the power configuration message can be used to indicate to the power receiver that this set of power transmission configurations supported by the power transmitter does not include any power transmission configuration with a higher maximum power limit.

[0140] For example, for Figure 7 In the PSC field, a value of 0 can indicate that there is no next higher or lower configuration available (i.e., 0 in the voltage step-down field indicates that there is no lower power transfer configuration, and 0 in the voltage step-up field indicates that there is no higher power transfer configuration).

[0141] In some embodiments, a predetermined value of the data indicating voltage amplitude indicates that the voltage amplitude of the candidate power transmission configuration has not changed relative to the voltage amplitude of the current power transmission configuration. For example, for Figure 7 The PSC message with a value of 64 indicates that the voltage amplitude will not change (but the maximum power limit can be changed).

[0142] It will also be recognized that the power transmission configuration change message request message can be in any suitable format or using any suitable protocol. Figure 8 An example is provided. In this example, the power transmission configuration change request message is referred to as a Specific Request / Next Configuration (SRQ / nc) packet sent from the power receiver to the power transmitter. In this example, the SRQ / nc message includes an 8-bit data field, but only one data bit, b0, is used. This data bit indicates the direction of the request, i.e., whether the request is for a power transmission configuration with an increased or decreased maximum power limit.

[0143] In many embodiments, the power transmitter may further respond to a power transmission configuration change request message, and may specifically acknowledge the request in the response. Specifically, the response message may indicate the timing of the power transmission configuration change. In particular, the response message may indicate the time of the change, or the timing of the response message itself may be an indication of the timing of the power transmission configuration change. For example, the power transmitter may continue to change the power transmission configuration after a predetermined time following the sending of the response message.

[0144] As a specific example, the response message could be one of the following:

[0145] ACK After the SRQ / en packet is confirmed, the requested new power transfer configuration becomes active within TBD ms.

[0146] NAK The power transmitter has rejected the request and continues to use the current power transmission configuration (e.g., because switching would cause the power supply capacity to be exceeded at the current operating point).

[0147] In some embodiments, the power transmitter can initiate potential changes to the power transmission configuration.

[0148] For example, the first configuration controller 309 may be arranged to send a power configuration message in response to detecting that the operating characteristics of the power transmission meet the criteria and, in particular, in response to detecting that the current power level of the power transmitter exceeds a threshold, wherein the threshold depends on the maximum power limit of the current power transmission configuration.

[0149] For example, the first configuration controller 309 can continuously monitor the power level of the drive signal and compare it with the maximum power limit of the current power transmission configuration. If the power level of the drive signal (e.g., low-pass filtered) exceeds, for example, 90% of the maximum power limit, the first configuration controller 309 can consider that it is likely appropriate to switch to a power transmission configuration with a higher maximum power limit, and can continue to send power configuration messages accordingly.

[0150] As another example, the first configuration controller 309 can monitor the frequency of the drive signal, and if this deviates too much from the given resonant frequency of the resonant circuit including the transmitter coil 103 (indicating that the drive signal is essentially detuned from the nominal operating point in order to reduce the power of the power transmission signal for the current voltage amplitude), the power transmitter can continue to send power configuration messages.

[0151] In this context, the transmission of the power configuration message provides not only information about the voltage amplitude of the candidate power transmission configuration but also an indication that the power transmitter expects / requests a change in the power transmission configuration. For example, in the two examples above, the power configuration message could indicate an expectation to switch to a higher maximum power limit power transmission configuration and an expectation to switch to a lower maximum power limit power transmission configuration, respectively. In some such embodiments, the power configuration message may also include an indication of an expected switch to a higher or lower maximum power limit.

[0152] In some embodiments, the power receiver can initiate a change in the power transmission configuration. For example, similar to the method described for the power transmitter, the second configuration controller 609 can determine the currently extracted power level and compare it to a threshold reflecting a maximum power limit of the current power transmission configuration. Alternatively or additionally, it can measure the frequency of the power transmission signal and detect whether this deviates too far from a nominal value.

[0153] The detection of such operational characteristics could be the detection of a power transmission configuration change bias, and in response, the power receiver could send a power configuration information request message to the power transmitter. In some embodiments, this message could be a request for the power transmitter to send a power configuration message, and thus the power transmitter could send a power configuration message to provide the power receiver with information about the possibilities of changing the power transmission configuration and the associated voltage amplitude.

[0154] exist Figure 9 The diagram illustrates a specific example of possible message exchanges for a power receiver-initiated change in power transmission configuration, and... Figure 10 The diagram illustrates possible message exchanges for a power receiver-initiated change to power transmission configuration. Examples include the following messages:

[0155] CE (power) control error is used by the power receiver to control its power and voltage levels to the appropriate target point.

[0156] RP / 0 receives power packets, which are used by the power receiver to inform the power transmitter of the amount of power it has received.

[0157] ACK confirmation; used by the power transmitter to indicate that it accepts the request.

[0158] NEGO negotiation request; used by the power receiver to initiate a negotiation sequence.

[0159] GRQ / psc is a general request / power configuration; it is used by the power receiver to request the power transmitter to send a PSC message.

[0160] PSC power configuration; parameters used by the power transmitter to communicate the next higher power configuration and the next lower power configuration.

[0161] SRQ / nc Specific Request / Next Configuration; used by the power receiver to request the next higher configuration or the next lower configuration.

[0162] SRQ / en Specific Request / Terminate Negotiation; used by the power receiver to terminate the negotiation sequence and indicate that the negotiation configuration should become active within TBD milliseconds.

[0163] In some embodiments, the power receiver may determine, as previously mentioned, whether a change in voltage amplitude associated with a switching of power transmission configuration will cause an unacceptable overvoltage or undervoltage condition, and if not, simply continue sending power transmission configuration change request messages.

[0164] In some embodiments, the power receiver may be arranged to compensate for the operation of the power receiver prior to switching in the power transmission configuration, such that the resulting voltage variation becomes acceptable, even if there is no change in operation.

[0165] For example, prior to a change in the power transmission configuration, the second configuration controller 609 can be arranged to modify the power transmission operation to change the induced voltage in the opposite direction to the voltage change that would occur in a subsequent change in the power transmission configuration.

[0166] For example, in the event of a change in the voltage amplitude of the drive signal, and thus a change in the instantaneous voltage induced in the receiver coil 107 when a change in the power transfer configuration occurs, the second configuration controller 609 can continue to reduce the induced voltage on the receiver coil 107 before the change. Then, when the change occurs, the voltage on the receiver coil 107 will increase, but due to the previous voltage reduction, this increase can be acceptable and will not lead to, for example, a destructive overvoltage condition.

[0167] In some embodiments, the second configuration controller 609 may be arranged to change the load impedance prior to the switching of the power transmission configuration, and in particular, such change of load impedance may be accomplished together with a change in the induced voltage.

[0168] For example, power transfer can occur under load conditions where the power transfer signal is close to the maximum power limit of the current power transfer configuration. Therefore, there may be a bias towards switching to the next higher maximum power limit, and this can be detected by the second configuration controller 609 (e.g., based on receiving a power configuration message or based on its own evaluation of power transfer characteristics). Therefore, it can send a power transfer configuration change request message to the power transmitter while simultaneously continuing to reduce impedance / resistance, resulting in a lower voltage and higher current providing the same power level at a lower voltage. After the power transfer configuration change, the impedance can be adjusted again to accommodate the new conditions.

[0169] As a specific example, consider the previously described scenario where the power transmitter operates in a 10W (5V, 2A) configuration, and the power receiver controls its operating point to 8V, 1A. When the power transmitter switches to a higher configuration (e.g., 12W (12V, 1A)), the power receiver will initially see a voltage of 12 / 5*8 = 19.5V, 2.4A, which is far beyond the capability of the power transmitter in that configuration. Therefore, power delivery may fail due to the generation of an overvoltage or overpower condition. To prevent this, the power receiver must control its power level back to, for example, 4V, 0.5A before switching. In the latter case, after the switch, the power receiver operates at 12* / 5*4 = 9.6V, 1.2A (i.e., 11.5W, assuming no losses).

[0170] A similar example of switching to a lower power configuration could be a situation where the power transmitter operates at 12V, 1A and the power receiver only uses 4W (e.g., 5V, 0.8A). The system could then switch to an even lower configuration on the power transmitter, such as 5V, 1.5A. If this switch occurs before the power receiver is ready, it will experience a voltage of 5 / 12*5 = 2.1V after the switch, which may be too low to sustain its operation (i.e., undervoltage). This would also lead to a breakdown in power delivery. However, this problem can be solved by increasing the induced voltage to prepare for the switch.

[0171] The previous examples focused on embodiments in which the voltage amplitude of the drive signal fed from the driver to the output circuit is constant for any given power delivery configuration. However, the method can also be adapted for embodiments in which the voltage amplitude is not constant when the power transmitter operates in a given power delivery configuration.

[0172] For example, in some embodiments, the power transmitter can be arranged to operate within a given voltage amplitude range for each power transmission configuration. For example, for each power transmission configuration, there may be a given maximum voltage amplitude, and therefore each power transmission configuration may be associated with different combinations of maximum power limits and maximum voltage amplitudes (limits) for the drive signal.

[0173] In this scenario, the voltage amplitude indication conveyed by the power configuration message can indicate the maximum voltage amplitude (limit) of the corresponding candidate power transmission configuration. Therefore, the power receiver can be configured to determine the maximum voltage transients or steps that may occur when switching from the current power transmission configuration to a candidate power transmission configuration. For example, when switching to a new power transmission configuration, the power transmitter can always start with the maximum voltage amplitude, and the power receiver tracking the current voltage amplitude (e.g., by comparing the current induced voltage with the voltage immediately after the power transmitter switched to the current power transmission configuration) can determine the induced voltage amplitude immediately after switching to the new power transmission configuration.

[0174] Similarly, the voltage amplitude of a given power transmission configuration can have a minimum limit, and the power configuration message can additionally or alternatively indicate the minimum voltage amplitude limit of a candidate power transmission configuration. This can accordingly allow the power receiver to determine the lowest induced voltage it will experience immediately after a change in the power transmission configuration.

[0175] In some embodiments, the voltage amplitude indicated in the power configuration message may not be a maximum voltage amplitude limit and / or a minimum voltage amplitude limit, but may be, for example, a nominal voltage amplitude or an initial voltage amplitude. For example, when switching power transmission configurations, the power transmitter may be arranged to initiate a new power transmission configuration using a given voltage amplitude for the drive signal, and this initial voltage amplitude may be sent to the power receiver in the power configuration message. Therefore, the power receiver can determine the induced voltage immediately after the power transmission configuration switch, for example by considering the initial voltage amplitude of candidate power transmission configurations related to the current voltage amplitude or the initial voltage amplitude of the current power transmission configuration. After the switch, the voltage amplitude may subsequently be modified by the power transmitter, but this is typically so slow that the power receiver will not experience transients or steps.

[0176] Voltage amplitude can be indicated, for example, in a power configuration message as a relative value to, for example, the initial voltage amplitude of the current power transmission configuration. In some embodiments, the voltage amplitude of a candidate power transmission configuration can be provided as a relative indication of the current voltage amplitude. For example, the ratio between the initial voltage amplitude of a candidate power transmission configuration and the current voltage amplitude can be included in the power configuration message. This facilitates the power receiver in determining the voltage step when switching power transmission configurations (e.g., it does not need to track changes in voltage amplitude), and is generally feasible because changes in voltage amplitude are very slow.

[0177] Methods with variable voltage amplitudes can particularly allow or support implementations in which the power level of a power transfer signal is controlled (at least in part) by changing the voltage amplitude of the drive signal. For example, it can allow methods that adapt the voltage amplitude of the drive signal based on power control error messages from the power receiver.

[0178] It will be appreciated that, for clarity, embodiments of the invention have been described above with reference to various functional circuits, units, and processors. However, it will be apparent that any suitable functional distribution can be used among different functional circuits, units, or processors 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 units used to provide the described functions and do not indicate a strict logical or physical structure or organization.

[0179] This invention can be implemented in any suitable form, including hardware, software, firmware, or any combination of these. Optionally, the invention can 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.

[0180] While the invention has been described in conjunction with some embodiments, it is not intended to limit the invention to the specific forms set forth herein. Rather, the scope of the invention is limited only by the claims. Furthermore, although it may appear that features have been 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, terms include but do not exclude the presence of other elements or steps.

[0181] It will be appreciated that the reference to the preferred value does not imply any limitation other than that it is a value determined in the foreign object detection initialization configuration, i.e., it is preferred by virtue of its determination during the adaptation process. The reference to the preferred value can be replaced by a reference to, for example, the first value.

[0182] Furthermore, although listed separately, multiple units, elements, circuits, or method steps can be implemented, for example, by a single circuit, unit, or processor. Additionally, while individual features may be included in different claims, these features may be advantageously combined, and inclusion in different claims does not imply that the combination of features is infeasible and / or disadvantageous. Including a feature in a claim of one type does not imply a limitation on that type, but rather indicates that the feature is equally applicable to other claim classes where appropriate. Furthermore, the order of features in a claim does not imply that the features must operate in any particular order, and in particular, the order of steps in a method claim does not imply that the steps must be performed in that order. Rather, the steps can be performed in any suitable order. Additionally, 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 only as clarifying examples and should in no way be construed as limiting the scope of the claims.

Claims

1. A power transmitter (101) for wirelessly providing power to a power receiver (105) via an electromagnetic power transfer signal; the power transmitter (101) comprising: an output circuit comprising a transmitter coil (103) for generating the power transfer signal in response to a drive signal being applied to the output circuit; a driver (301) for generating the drive signal; a configuration controller (309) for switching between a set of power transfer configurations, a power transfer configuration of the set of power transfer configurations having a different combination of maximum power limit and voltage amplitude for the drive signal; a transmitter (307) for transmitting a power configuration message to the power receiver (105), the power configuration message comprising data indicative of a voltage amplitude for a first power transfer configuration of the set of power transfer configurations; a receiver (305) for receiving a power transfer configuration change request message from the power receiver (105); and wherein the configuration controller (309) is arranged to switch the power transmitter (101) to the first power transfer configuration in response to the power transfer configuration change request message, such that the power receiver is aware of and fully controls the switching to the first power transfer configuration, thereby preventing the occurrence of unpredictable under-voltage or over-voltage conditions.

2. The power transmitter of claim 1, wherein, the data is indicative of a relative difference between the voltage amplitude for the first power transfer configuration and a voltage amplitude for a current power transfer configuration.

3. The power transmitter of claim 2, wherein, the data is indicative of a ratio between the voltage amplitude for the first power transfer configuration and a voltage amplitude for the current power transfer configuration.

4. The power transmitter of any preceding claim, wherein, the first power transfer configuration is a power transfer configuration of the set of power transfer configurations having a maximum power limit that is at least one of a next higher maximum power limit and a next lower maximum power limit than a maximum power limit for a current power transfer configuration.

5. The power transmitter of any one of claims 1-3, wherein, the power configuration message comprises data indicative of a voltage amplitude for a second power transfer configuration of the set of power transfer configurations, the first power transfer configuration is a power transfer configuration of the set of power transfer configurations having a maximum power limit that is a next higher maximum power limit than a maximum power limit for a current power transfer configuration, and the second power transfer configuration is a power transfer configuration of the set of power transfer configurations having a maximum power limit that is a next lower maximum power limit than the maximum power limit for the current power transfer configuration.

6. The power transmitter of any one of claims 1-3, wherein, a predetermined value of the data indicative of the voltage amplitude indicates that the set of power transfer configurations does not include a power transfer configuration having a maximum power limit that is higher than a maximum power limit of a current power transfer configuration.

7. The power transmitter of any one of claims 1-3, wherein, the configuration controller (309) is arranged to transmit the power configuration message in response to detecting that an operating characteristic of the power transfer satisfies a criterion.

8. The power transmitter of any one of claims 1-3, wherein, The configuration controller (309) is arranged to transmit the power configuration message in response to detecting that a current power level of the power transmitter exceeds a threshold value, the threshold value depending on a maximum power limit of a current power transfer configuration.

9. The power transmitter of any one of claims 1-3, wherein, The configuration controller (309) is arranged to transmit the power configuration message in response to receiving a power configuration information request message from the power receiver.

10. The power transmitter of any one of claims 1-3, wherein, The configuration controller (309) is arranged to switch the power transmitter to the first power transfer configuration after having transmitted an acknowledgement message to the power receiver, the acknowledgement message acknowledging a request message received from the power receiver.

11. A power receiver for wirelessly receiving power from a power transmitter (101) via an electromagnetic power transfer signal, the power receiver (105) comprising: an input circuit comprising a power receiver coil (107) arranged to extract power from the power transfer signal; a receiver (605) for receiving a power configuration message from the power transmitter (101), the power configuration message comprising data indicative of a voltage amplitude of a drive signal for at least a first power transfer configuration of a set of power transfer configurations, the power transfer configurations of the set of power transfer configurations having different combinations of maximum power limits and voltage amplitudes, and the drive signal being for an output circuit of the power transmitter (101), the output circuit comprising a transmitter coil (103) for generating the power transfer signal in response to the drive signal being applied to the output circuit; a configuration controller (609) arranged to detect a power transfer configuration change bias for the power transmitter to switch to the first power transfer configuration; and a transmitter (607) for transmitting a power transfer configuration change request message to the power transmitter in response to detecting the power transfer configuration change bias, such that the power receiver is aware of and fully controls the switch to the first power transfer configuration, thereby preventing the occurrence of unpredictable under- or over-voltage conditions, the power transfer configuration change request message comprising a request for the power transmitter to switch to the first power transfer configuration.

12. The power receiver of claim 11, wherein, The configuration controller (609) is arranged to control power transfer to change a voltage induced on the power receiver coil before a power transfer configuration is changed to the first power transfer configuration.

13. The power receiver of claim 11 or 12, wherein, The configuration controller (609) is arranged to control power transfer to change a load impedance for the power receiver coil before a power transfer configuration is changed to the first power transfer configuration.

14. A method of operating a power transmitter (101) that wirelessly provides power to a power receiver (105) via an electromagnetic power transfer signal; the method comprising: a transmitter coil (103) of an output circuit generating the power transfer signal in response to a drive signal being applied to the output circuit; generating the drive signal; switching between a set of power transfer configurations, the power transfer configurations in the set of power transfer configurations having different combinations of maximum power limit and voltage amplitude for the drive signal; sending a power configuration message to the power receiver (105), the power configuration message including data indicating a voltage amplitude for a first power transfer configuration in the set of power transfer configurations; receiving a power transfer configuration change request message from the power receiver (105); and wherein the switching between the set of power transfer configurations switches the power transmitter (101) to the first power transfer configuration in response to the power transfer configuration change request message, such that the power receiver knows of and fully controls the switching to the first power transfer configuration, thereby preventing the occurrence of unpredictable under-voltage or over-voltage conditions.

15. A method of operating a power receiver that wirelessly receives power from a power transmitter (101) via an electromagnetic power transfer signal, the method comprising: a power receiver coil (107) extracting power from the power transfer signal; receiving a power configuration message from the power transmitter (101), the power configuration message including data indicating a voltage amplitude of a drive signal for at least a first power transfer configuration in a set of power transfer configurations, the power transfer configurations in the set of power transfer configurations having different combinations of maximum power limit and voltage amplitude, and the drive signal being for an output circuit of the power transmitter (101), the output circuit including a transmitter coil (103) for generating the power transfer signal in response to the drive signal being applied to the output circuit; detecting a power transfer configuration change bias for the power transmitter to switch to the first power transfer configuration; and in response to detecting the power transfer configuration change bias, sending a power transfer configuration change request message to the power transmitter, such that the power receiver knows of and fully controls the switching to the first power transfer configuration, thereby preventing the occurrence of unpredictable under-voltage or over-voltage conditions, the power transfer configuration change request message including a request for the power transmitter to switch to the first power transfer configuration.

16. A wireless power transfer system for wirelessly providing power from a power transmitter (101) to a power receiver (105) via an electromagnetic power transfer signal; the power transmitter (101) comprising: an output circuit including a transmitter coil (103) for generating the power transfer signal in response to a drive signal being applied to the output circuit; a driver (301) for generating the drive signal; a configuration controller (309) for switching between a set of power transfer configurations, the power transfer configurations in the set of power transfer configurations having different combinations of maximum power limit and voltage amplitude for the drive signal; a power receiver coil (107) extracting power from the power transfer signal; receiving a power configuration message from the power transmitter (101), the power configuration message including data indicating a voltage amplitude of a drive signal for at least a first power transfer configuration in a set of power transfer configurations, the power transfer configurations in the set of power transfer configurations having different combinations of maximum power limit and voltage amplitude, and the drive signal being for an output circuit of the power transmitter (101), the output circuit including a transmitter coil (103) for generating the power transfer signal in response to the drive signal being applied to the output circuit; detecting a power transfer configuration change bias for the power transmitter to switch to the first power transfer configuration; and in response to detecting the power transfer configuration change bias, sending a power transfer configuration change request message to the power transmitter, such that the power receiver knows of and fully controls the switching to the first power transfer configuration, thereby preventing the occurrence of unpredictable under-voltage or over-voltage conditions, the power transfer configuration change request message including a request for the power transmitter to switch to the first power transfer configuration. a transmitter (307) for transmitting a power configuration message to the power receiver (105), the power configuration message comprising data indicative of a voltage amplitude for a first power transfer configuration of the set of power transfer configurations; a receiver (305) for receiving a power transfer configuration change request message from the power receiver (105); and wherein the configuration controller (309) is arranged to switch the power transmitter (101) to the first power transfer configuration in response to the power transfer configuration change request message, such that the power receiver is aware of and fully controls the switch to the first power transfer configuration, thereby preventing the occurrence of unpredictable under- or over-voltage conditions; and the power receiver (105) comprises: an input circuit comprising a power receiver coil (107) arranged to extract power from the power transfer signal; a receiver (605) for receiving the power configuration message from the power transmitter (101), a configuration controller (609) arranged to detect a power transfer configuration change bias for the power transmitter to switch to the first power transfer configuration; and a transmitter (607) for transmitting the power transfer configuration change request message to the power transmitter in response to detecting the power transfer configuration change bias, such that the power receiver is aware of and fully controls the switch to the first power transfer configuration, thereby preventing the occurrence of unpredictable under- or over-voltage conditions, the power transfer configuration change request message comprising a request for the power transmitter to switch to the first power transfer configuration.

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