BR112018014053B1 - POWER TRANSMITTER FOR TRANSFERRING POWER TO A POWER RECEIVER, WIRELESS POWER TRANSFER SYSTEM AND METHOD FOR OPERATING A POWER TRANSMITTER - Google Patents

Abstract

The present invention relates to a power transmitter (101) of a wireless power transfer system comprising a resonance including a transmitter coil (103) for generating a power transfer signal for transferring wireless power to a receiver. of power (105). Additionally, a driver (1303) generates a drive signal for the resonance circuit (201) and a message receiver (1305) is arranged to receive messages from the power receiver (105). A power circuit controller (1307) implements a power control loop by adapting the power of the drive signal in response to power control messages received from the power receiver (105). However, the regulation is subject to a restriction of at least one of a resonance circuit current or voltage and a drive signal power that is below a maximum limit. Additionally, the power transmitter (101) comprises an adapter (1309) that adapts the maximum limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver (105).

Description

Field of invention

[001] The invention relates to inductive power transfer and specifically, but not exclusively, to a power transmitter that provides inductive power transfer using elements compatible with the Qi Specifications for inductive power transfer systems.

Background of the invention

[002] Most current systems require a dedicated electrical contact to be powered from an external power source. However, this tends to be impractical and requires the user to physically insert connectors or otherwise establish physical electrical contact. Typically, power requirements also differ significantly, and today most devices are equipped with their own dedicated power supply, leaving a typical user with several different power supplies, each dedicated to a specific device. While using internal batteries can avoid the need for a wired connection to a power source during use, this only provides a partial solution since the batteries will need recharging (or replacement). The use of batteries can also substantially increase the weight and potentially the cost and size of devices.

[003] In order for the user to have a significantly better usage experience, it has been proposed to use a wireless power supply, in which power is inductively transferred from a transmitter coil in a power transmitting device to a receiving coil in the devices individual.

[004] Power transmission through magnetic induction is a well-known concept, applied mainly in transformers, which have a short-proximity coupling between a primary transmitting coil and a secondary receiving coil. By separating the primary transmitter coil and the secondary receiver coil into two devices, wireless power transfer between the devices becomes possible, based on the principle of a loosely coupled transformer.

[005] This type of arrangement allows wireless power transfer to the device without the need for wires or physical electrical connections. In fact, this may simply enable a device to be placed adjacent to or on top of the transmitter coil to be recharged or externally powered. For example, power transmitting devices may have a horizontal surface upon which a device may simply be placed to be powered.

[006] Furthermore, such arrangements for wireless power transfer can be advantageously designed so that the power transmitting device can be used with a range of power receiving devices. Specifically, a wireless power transfer approach, known as the Qi Specification, has been defined and is currently under further development. This approach enables power transmitting devices that meet the Qi Specification to be used with power receiving devices that also meet the Qi Specification, without them needing to come from the same manufacturer or be dedicated to each other. The Qi Specification additionally includes some functionality to enable operation to be tailored to the specific power receiving device (e.g. according to specific power drain).

[007] The Qi standard is a standard developed by the Wireless Power Consortium and more information can be found, for example, on the website: http://www.wirelesspowerconsortium.com/index.html , where specifically defined Specification documents can be found.

[008] An important aspect of wireless power transmission is controlling the operating point for power transfer and is particularly important for controlling the inductive power transfer signal to provide adequate power to the power receiver. To control power transfer, systems such as Qi implement a power control loop, whereby the power receiver, during the power transfer phase, continuously transmits power control messages back to the power transmitter requesting (or not) a change in the power of the power transfer signal. The power transmitter then reacts by increasing or decreasing the power of the power transfer signal in response to requests from the power receiver. This type of approach can provide effective power control in many situations.

[009] Generally, the power control operation is implemented so that the operating range is restricted to a range considered safe. For example, for systems like Qi, the power transfer signal strength can be limited to a given maximum value.

[010] Document WO 2014/060871 A1 describes such a system in which a power control circuit is based on power control messages requesting a power change as needed. Document EP 2958247 A1 describes a disconnection mechanism for protecting a load from any out-of-range power signals.

[011] However, although this approach may provide an adaptive system that is capable of adapting to variations in operating conditions, it may not perform optimal adaptation in all circumstances. For example, in some cases, it may not react quickly enough to adapt to sudden changes in operating conditions.

[012] Therefore, an improved power transfer system would be advantageous. In particular, an approach that enables optimized operation, better power transfer, greater flexibility, easier implementation, easier operation, better power control, faster response to variations in power transfer operating characteristics and/or better performance.

Summary of the invention

[013] Consequently, the invention preferably seeks to mitigate, alleviate or eliminate one or more of the disadvantages mentioned above, individually or in any combination.

[014] According to one aspect of the invention, a power transmitter is provided for transferring power to a power receiver, the power transmitter comprising: a resonance circuit comprising a capacitive impedance and an inductive impedance, wherein the inductive impedance comprises a transmitter coil for generating a power transfer signal to wirelessly transfer power to the power receiver; a trigger stops generating a trigger signal for the resonance circuit. a message receiver for receiving messages from the power receiver; a power circuit controller for adapting a drive signal power in response to power control messages received from the power receiver by the message receiver, the adaptation being subject to a restriction of at least one of a circuit current resonance circuit, a resonance circuit voltage and a drive signal power that is below a maximum limit; and an adapter arranged to adapt the upper limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver.

[015] The invention can provide improved power transfer in many scenarios. In particular, improved power control can be achieved. In many embodiments, the approach can provide greater reliability and can, in particular, provide more protection against overvoltage conditions that occur in the power receiver resulting from rapid changes in coupling factor that result from, for example, movement of the power receiver. relative to the power transmitter.

[016] In particular, the inventors have realized that many current power transfer systems (such as those following the Qi Specifications) include a power control loop that can, in some situations, result in overvoltage conditions occurring in receivers. of power due to sudden changes in the coupling between the power transmitter and power receiver. In particular, it has been discovered that many existing power control approaches, when extended to higher power levels can, when a rapid change in coupling occurs, result in induced voltages that exceed levels that are considered unsuitable for the power receiving circuit. power.

[017] Such situations can, in particular, be mitigated or avoided by the approach in which the limits of the power control operation are restricted to values that are dynamically modified in response to load indications in the power transfer signal provided by the power receiver. power. In particular, dynamically varying current, voltage and/or power limits can ensure that inductive voltage does not exceed unacceptable levels even for sudden changes in coupling while at the same time enabling higher power transfer values to be provided.

[018] The adapter can dynamically adapt the maximum limit and, specifically, can dynamically adapt the maximum limit during the power transfer phase. In this way, the adapter can enable a limitation of the resonance circuit current and/or the power of the drive signal to be changed during power transfer in line with changes in the loading of the power transmission signal by the power receiver.

[019] The resonance circuit current may specifically be an inductive impedance current and, in many embodiments, may be a current through the transmitter coil. In some embodiments, the current may be a drive signal current. In some embodiments, the resonance circuit may be a resonance circuit in series with the inductive impedance consisting of the transmitter coil. In such an embodiment, the current from/through the inductive impedance, the current from/through the transmitter coil and the drive signal current may be the same current.

[020] The current of the resonance circuit can generally be the current of the transmitting coil and, therefore, the power transmitter can be arranged to limit, directly or indirectly, the current of the transmitting coil.

[021] The resonance circuit voltage may specifically be an inductive impedance and/or capacitive impedance voltage and, in many embodiments, may be a voltage across the transmitter coil and/or a capacitor in series or in parallel with the coil. transmitter. In some embodiments, the voltage may be a drive signal voltage. In some embodiments, the resonance circuit may be a resonance circuit in parallel with the inductive impedance consisting of the transmitter coil. In such an embodiment, the voltage across the inductive impedance, the transmitter coil and the drive signal voltage can be the same voltage.

[022] In some embodiments, the power circuit controller can adapt the power of the drive signal subject to a restriction on both the current and the voltage of the resonance circuit.

[023] The voltage of the resonance circuit can generally be the voltage of the transmitter coil and, therefore, the power transmitter can be arranged to limit, directly or indirectly, the voltage of the transmitter coil.

[024] The current, voltage and/or power may be an average value for one (or more) cycles of the drive signal/oscillations. The current can, for example, be an RMS or average (absolute) current.

[025] The drive signal may be an output power signal that supplies power to the resonance circuit. The drive signal may comprise a current component and a voltage component, that is, the drive signal may comprise a drive signal voltage and a drive signal current.

[026] According to an optional feature of the invention, the adapter is arranged to dynamically adapt the maximum limit to reflect variations in the load supplied by the power receiver.

[027] The approach can enable efficient power control over a wide dynamic range while also avoiding or reducing, for example, overvoltage conditions resulting from sudden changes in operating conditions, such as a rapid increase in coupling between the power transmitter and the power receiver.

[028] The adapter can be arranged to determine the maximum limit as a function of the load (current) of the power transfer signal. The adapter may be arranged to determine the maximum limit as a function of (load indication). The function can be a monotonic function. In many embodiments, the function may be a monotonically increasing function.

[029] The maximum limit update rate may, in many embodiments, be greater than 0.1 Hz; 1 Hz or even 10 Hz.

[030] In some embodiments, the maximum limit may be determined as a value that exceeds, by a margin, the loading of the power transmission signal. In many embodiments, the margin may be determined as a function of the load/load indication.

[031] In some embodiments, the maximum limit may be determined to exceed the power transfer signal loading by a predetermined absolute or relative offset (e.g., the maximum limit may exceed the current loading by a predetermined percentage of the current loading). chain).

[032] According to an optional feature of the invention, the adapter is arranged to adapt the maximum limit during a power transfer phase.

[033] The approach can provide efficient power control during active power transfer while also avoiding or reducing, for example, overvoltage conditions resulting from sudden changes in operating conditions, such as a rapid increase in coupling between the power transmitter and energy and the power receiver.

[034] In the power transfer phase, power control can be done based on power control messages, that is, dynamic power control operation based on receiver power control messages can be active. In this way, the approach can allow variations in the maximum limit to occur during the time in which the power control based on the power control message is active.

[035] The adapter may be specifically arranged to adapt and change the maximum limit while the power is controlled by the power control messages (and therefore is not restricted by the maximum limit). In some embodiments/scenarios, received power control messages may result in a change in the power of the power transfer signal (and the power extracted by the power receiver). The load indication may vary as a result of changed power and therefore received power control messages may result in a change in the load indication and consequently a change in the maximum limit (and transfer signal power). power). Specifically, the power circuit controller may be arranged to adapt the power of the drive signal in response to power control messages and the adapter may be arranged to adapt the upper limit in response to power control messages. (directly or by changing the power of the drive signal).

[036] According to an optional feature of the invention, the driver is arranged to determine a power indication that is indicative of a drive signal strength, and the adapter is arranged to determine the load indication as a power indication function.

[037] This can provide advantageous dynamic adaptive limiting of current, voltage and/or power and can specifically, in many applications, reduce overvoltage conditions.

[038] The adapter may be arranged to determine the maximum limit as a function of the power indication.

[039] According to an optional feature of the invention, the power circuit controller is arranged to limit a current or voltage (or both) of at least one of the drive signal and the transmitter coil.

[040] In particular, in many embodiments, the adaptation of the power circuit controller may be subjected to a current (and/or voltage) of the drive signal/current (and/or voltage) of the transmitter coil below a maximum threshold the limit being adapted in response to the power indication. In this way, the current/voltage resulting from power control can be subject to a limit that is dynamically adapted in response to a power of the drive signal. Specifically, in many embodiments, the power control may be subject to a constraint that the drive signal current/voltage is below a threshold determined as a function of the drive signal power.

[041] This can provide particularly efficient power control that, in many situations, can avoid or reduce overvoltage conditions that occur in the power receiver caused by sudden changes in the coupling between the power transmitter and the power receiver.

[042] The power of the drive signal can be determined in response to, for example, measurements of the current and voltage of the drive signal that is fed to the resonance circuit from the driver. The power of the drive signal is indicative of the power extracted from the power transfer signal, and is therefore generally indicative of the power extracted by the power receiver, i.e., it is indicative of the loading of the power transmission signal by the power receiver. power. The power of the drive signal may, for example, be estimated or determined in response to, for example, measurements of the current and voltage supplied to the driver. Specifically, a power indication of the drive signal power may be determined as the input power to the driver (or an output circuit thereof).

[043] The transmitter coil current reflects the intensity of the magnetic field generated by the transmitter coil and, in this way, the approach can enable the maximum magnetic field intensity to be adapted based on the power that is extracted from the power transfer signal.

[044] According to an optional feature of the invention, the maximum limit is a monotonically increasing function of an energy load indicated by the load indication.

[045] This can provide improved power control operation and can, in many embodiments, reduce overvoltage conditions caused by sudden changes in coupling between the power transmitter and power receiver.

[046] Specifically, the maximum limit can be determined as a function of the energy loading of the power transmission signal, as indicated by the load indication. The function may be a monotonically increasing function. Thus, in many embodiments, as the power that is extracted from the power transmission signal by the power receiver increases, the maximum limit also increases.

[047] According to an optional feature of the invention, the adapter (1309) is arranged to increase the maximum limit above a first threshold only if the load indication is indicative of a drive signal strength that is above a second threshold.

[048] This can provide effective, low-complexity operation in many modalities and scenarios.

[049] In some embodiments, the power circuit controller is arranged to limit the power of the drive signal so that it is below the maximum limit.

[050] This can provide advantageous performance and can, in particular, reduce the risk of overvoltage conditions in the power receiver due to sudden changes in the coupling between the power receiver and the power transmitter.

[051] According to an optional feature of the invention, the adapter is arranged to determine the maximum limit to include both a maximum current limit of the resonance circuit current (and/or a maximum voltage limit of the circuit voltage). resonance circuit) and a maximum power limit for the drive signal power, and the adaptation is subjected to either the resonance circuit current that is below the maximum current limit (and/or the resonance circuit voltage that is below maximum voltage limit) for the power of the drive signal that is lower than the maximum power limit.

[052] This can provide improved operation in many embodiments, in particular, it can provide improved protections against overvoltage conditions in many scenarios. Indeed, it has been observed that in many practical systems it is possible to maintain overvoltage at an acceptably low level for an increasing operating range, and specifically at higher powers, when both power and current are limited (and with limits potentially many different).

[053] According to an optional feature of the invention, the adapter is arranged to determine the load indication in response to load data received in at least one message from the power receiver, the load data being indicative of a loading of the power transmission signal by the power receiver.

[054] This can provide optimized operation and/or performance in many modalities. This may enable greater control of the power transfer operation to reside in the power receiver. In many modalities, it can allow for less complexity and/or more precise adaptation. This can provide more reliable fitting with less need to estimate loading.

[055] In some embodiments, the load data comprises an indication of at least one of a load current and a load voltage for a power receiver load, and the adapter is arranged to determine the load indication in response to the indication of at least one of the load current and the load voltage.

[056] This can provide optimized operation in many situations. In particular, in many embodiments and applications, it can provide improved control and adaptation of the generated magnetic field potentially resulting in reduced overvoltage in the power receiver while at the same time enabling reduced complexity in the power receiver.

[057] According to an optional feature of the invention, the adapter is additionally arranged to change the maximum limit in response to detecting a change in a load of the power transfer signal.

[058] This can provide optimized performance in many modalities and can, in particular, enable a faster reaction to some possible changes. Specifically, the approach can, in many applications, enable more accurate and slower adaptation of the threshold based on information provided by the power receiver, while also enabling the power transmitter to independently detect and respond quickly to possible sudden changes. under operating conditions.

[059] Detection of a change in the loading of the power transfer signal can be done by detecting a change in a current, voltage and/or power of the drive signal.

[060] According to one aspect of the invention, there is provided a wireless power transfer system comprising a power receiver and a power transmitter for transferring power to the power receiver, the power transmitter comprising: a resonance circuit comprising a capacitive impedance and an inductive impedance, the inductive impedance comprising a transmitter coil for generating a power transfer signal for transferring power wirelessly to the power receiver, a driver for generating a drive signal for the resonance circuit, a receiver for receiving messages from the power receiver, a power circuit controller for adapting a drive signal power in response to power control messages received from the power receiver, the adaptation being subjected to a restriction that at least one of a resonance circuit current, a resonance circuit voltage, and a drive signal power is below a maximum limit, and an adapter configured to determine the maximum limit in response to an indication of load determined based on load data received in a message from the power receiver, the load data being indicative of a loading of the power transfer signal by the power receiver; and the power receiver comprising: a data generator for generating load data reflecting a load from the power receiver and a transmitter for transmitting at least one message comprising the load data to the power transmitter.

[061] According to an optional feature of the invention, the data generator is arranged to determine the charging of the power receiver in response to at least one of a measurement of a load current and a measurement of a load voltage for a power receiver load.

[062] This can provide efficient operation and a lower complexity power transmitter. This can also provide accurate information about the load conditions at the power receiver, which can enable more accurate adaptation of the upper limit to reflect likely overvoltage conditions in the event of a sudden change in coupling between the power transmitter and receiver. of power.

[063] According to an optional feature of the invention, the transmitter is arranged to transmit at least one message to the power transmitter in response to a detection that a change in a load of the power receiver satisfies a criterion power change load; the load data of the at least one message is indicative of the change that satisfies the power change load criterion; wherein the adapter is arranged to modify the upper limit in response to detecting that the at least one message comprises load data indicative of the change satisfying the power change load criterion.

[064] In many embodiments, this can provide particularly efficient operation. For example, it can, in many embodiments, reduce the number of messages that need to be communicated (and therefore the processing resource required to process and react to the messages).

[065] According to an optional feature of the invention, the adapter is additionally arranged to change the maximum limit in response to detecting a change in a power indication for the drive signal.

[066] This may provide advantageous operation in some embodiments and scenarios. Detecting a change in power indication for the drive signal may be (at least partially) by detecting a change in a current or voltage for the drive signal.

[067] According to one aspect of the invention, there is provided a method of operation for a power transmitter that transfers power to a power receiver, the power transmitter comprising a resonance circuit comprising a capacitive impedance and a inductive, wherein the inductive impedance comprises a transmitter coil for generating a power transfer signal for wirelessly transferring power to a power receiver; the method comprises: generating a drive signal for the resonance circuit; receive messages from the power receiver; adapt a power of the drive signal in response to power control messages received from the power receiver, the adaptation being subject to a constraint of at least one of a resonance circuit current, a resonance circuit voltage and a drive signal strength that is below a maximum threshold; and adapting the maximum limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver.

[068] These and other aspects, features and advantages of the invention will be evident and will be elucidated with reference to the embodiment described (or embodiments described) below.

Brief description of the drawings

[069] Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which:

[070] Figure 1 illustrates an example of elements of a power transfer system according to some embodiments of the invention;

[071] Figure 2 illustrates an example of elements of a power transfer system according to some embodiments of the invention;

[072] Figure 3 illustrates an example of elements of a half-bridge inverter of a power transmitter according to some embodiments of the invention;

[073] Figure 4 illustrates an example of elements of a full-bridge inverter of a power transmitter according to some embodiments of the invention;

[074] Figure 5 illustrates an example of an equivalent simulation circuit of a wireless power transfer system;

[075] Figure 6 illustrates an example of parameters of the equivalent simulation circuit of Figure 5;

[076] Figures 7 to 12 illustrate examples of signals in a wireless power transfer system;

[077] Figure 13 illustrates an example of some elements of an energy transmitter according to some embodiments of the invention;

[078] Figures 14 to 19 illustrate examples of signals in a wireless power transfer system;

[079] Figure 20 illustrates an example of some elements of a power receiver for a wireless power transfer system according to some embodiments of the invention and

[080] Figures 20 and 21 illustrate examples of load data messages that can be used in a wireless power transfer system according to some embodiments of the invention.

Detailed description of some embodiments of the invention

[081] The following description focuses on embodiments of the invention applicable to a wireless power transfer system using a power transfer approach, as known from the Qi Specification. However, those skilled in the art will understand that the invention is not limited to this application, but that it can be applied to many other wireless power transfer systems.

[082] Figure 1 illustrates an example of a power transfer system according to some embodiments of the invention. The power transfer system comprises a power transmitter 101 that includes (or is coupled to) a transmitter/inductor coil 103. The system further comprises a power receiver 105 that includes (or is coupled to) a receiver/inductor coil. inductor 107.

[083] The system provides a wireless inductive power transfer from the power transmitter 101 to the receiver 105. Specifically, the power transmitter 101 generates a wireless inductive power transfer signal (also called a power transfer signal or signal inductive power transfer signal), which is propagated as a magnetic flux through the transmitter or inductor coil 103. The power transfer signal may generally have a frequency between about 70 kHz and about 150 kHz, and often for systems Qi-compatible devices, typically in the 95 kHz to 115 kHz range. The transmitter coil 103 and the receiver coil 107 are loosely coupled, and in this way the receiver coil 107 captures (at least part of) the power transfer signal from the power transmitter 101. In this way, power is transferred from the power transmitter 101. power 101 to the power receiver 105 through a wireless inductive coupling from the transmitting coil 103 to the receiving coil 107. The term “power transfer signal” is mainly used to refer to the inductive signal/magnetic field between the transmitting coil 103 and the receiving coil 107 (the magnetic flux signal), but it should be considered that, by equivalence, the term can also be considered and used to refer to an electrical signal supplied to the transmitting coil 103 or picked up by the receiving coil 107 .

[084] The system is arranged to transfer substantial power levels, and specifically, the power transmitter can support power levels above 500 mW, 1, 5 or 50, in many embodiments. For example, for corresponding Qi applications, power transfers can generally be in the power range of 1 to 5 W for low-power applications, and above 100 W and even more than 1,000 W for high-power applications, such as, for example, kitchen applications.

[085] Figure 2 illustrates the system architecture of a specific example of the system in Figure 1 in a slightly more detailed way. In this example, the power transmitter output circuit 101 includes a resonance tank or resonance circuit 201 that includes the transmitter coil 103 (in Figure 2, the transmitter coil 103 is shown for clarity, external to the resonance circuit 201 , but is considered part of it). The resonance circuit 201 of the power transmitter 101 will also be called the transmitter resonance circuit 201 (or sometimes, for brevity, just the resonance circuit 201). The resonance circuit 201 may generally be a series or parallel resonance circuit, and may, in particular, consist of a resonance capacitor coupled in parallel or in series to the transmitter coil 103. The power transfer signal is generated by driving the output resonance circuit from a driver 203 that generates a drive signal with a suitable drive frequency (generally in the frequency range of 20 to 200 kHz).

[086] Similarly, the power receiver input circuit 105 includes a resonance circuit or resonance tank 205 that includes the receiver inductor 107 (in Figure 2, the receiver inductor 107 is shown for clarity , external to the resonance circuit 205, but is considered as part of it). The resonance circuit 205 of the power receiver 105 will also be called the receiver circuit 205 or the receiver resonance circuit. The receiver resonance circuit 205 may generally be a series or parallel resonance circuit, and may, in particular, consist of a resonance capacitor coupled in parallel (or in series) to the receiver inductor 107. The resonance circuit receiver 205 is coupled to a power converter 207 that converts the received power transfer signal, that is, the induced signal provided by the receiver resonance circuit 205, into a power that is supplied to an external load 209 (generally by running an AC/DC conversion, as is well known to those skilled in the art).

[087] The load may, for example, be a battery, and the power supply may be to charge the battery. As another example, the load may be a device, and the energy supply may be to power the device.

[088] The driver 203 of Figure 2 generates a variable voltage (and generally AC) drive signal that is applied to the resonance circuit 201 (and thus the resonance capacitor (not shown in Figure 2) and the coil transmitter 103). In some embodiments, the transmitter resonance circuit 201 may be a series resonance circuit, and the voltage drive signal may be applied across the capacitor and inductor. In some embodiments, the driver 203 may be coupled directly (or indirectly) to the transmitter coil 103 and the voltage drive signal may be provided to the transmitter coil 103.

[089] Thus, in the system, the driver 203 generates a drive signal, which is supplied to the transmitter 201/transmitter coil 103 resonance circuit, which causes the transmitter coil 103 to generate the power transfer signal that supplies power to the power receiver 105. The drive signal is generated to have a certain frequency called the drive frequency, that is, the drive frequency is the frequency of the drive signal.

[090] Driver 203 generates the current and voltage that are fed to the transmitter coil 103. Driver 203 is generally a drive circuit in the form of an inverter that generates an alternating signal from a DC voltage . The output of the driver 203 is generally a switch bridge that generates the trigger signal by properly switching the switch bridge. Figure 3 shows a half-bridge switch/inverter bridge. Switches S1 and S2 are controlled so that they are never closed at the same time. Alternatively, S1 is closed at the same time as S2 is opened, and S2 is closed at the same time as S1 is opened. The switches are opened and closed with the desired frequency, thus generating an alternating signal at the output. Generally, the inverter output is connected to the transmitter coil through a resonance capacitor. Figure 4 shows a full bridge switch/inverter bridge. Switches S1 and S2 are controlled so that they are never closed at the same time. Switches S3 and S4 are controlled so that they are never closed at the same time. Alternatively, switches S1 and S4 are closed while S2 and S3 are open, and then S2 and S3 are closed while S1 and S4 are open, thus generating a square wave signal at the output. The switches are opened and closed as often as desired.

[091] The above description corresponds to the case where the left and right bridges are 180° out of phase and provide the maximum output power or maximum duty cycle. However, in other scenarios, the bridge halves may be partially out of phase, resulting in the simultaneous closure of both S2 and S4 or both S1 and S3. In this state, the bridge voltage will be zero and thus the approach can be used to reduce the output power or duty cycle from maximum values.

[092] The driver 203 consequently generates a drive signal and applies this signal to the transmitter resonance circuit 201. The transmitter resonance circuit 201 is formed by an inductive impedance and a capacitive impedance.

[093] In the following, the operation of the power transmitter 101 and the power receivers 105, 107 will be described with specific reference to an embodiment in accordance with the Qi Specification (with the exception of modifications and improvements described (or consequential) herein). In particular, the power transmitter 101 and the power receivers 105, 107 may be substantially compatible with the Qi Specification version 1.0, 1.1 or 1.2 (except for the modifications and improvements described (or consequential) herein).

[094] To control power transfer, the system proceeds through different phases, in particular, a selection phase, a ping phase, an identification and configuration phase, and a power transfer phase are used in the Qi system. More information can be found, for example, in Chapter 5 of Part 1 of the Qi Wireless Power Transfer Specification.

[095] For example, when establishing communication with the first energy receiver 105, the energy transmitter 101 may initially be in the selection phase where it simply monitors the potential presence of an energy receiver. The power transmitter 101 may use a variety of methods for this purpose, for example, as described in the Qi Wireless Power Transfer Specification. If such a potential presence is detected, the power transmitter 101 enters the ping phase, where a power signal is temporarily generated. The first power receiver 105 may apply the received signal to power its electronic components. Upon reception of the power signal, the power receiver 105 transmits an initial packet to the power transmitter 101. Specifically, a signal strength packet is transmitted that indicates the degree of coupling between the power transmitter 101 and the first power receiver. power 105. More information can be found in Chapter 6.3.1 of Part 1 of the Qi Wireless Power Transfer Specification (or Section 5.2.3.1 of version 1.2). Thus, in the ping phase, it is determined whether a power receiver 105 is present at the power transmitter 101 interface.

[096] Upon receiving the signal strength message, the power transmitter 101 moves to the identification and configuration phase. In this phase, the power receiver 105 keeps its output load disconnected and communicates with the power transmitter 101 through the use of load modulation. The power transmitter provides a power signal with constant amplitude, frequency and phase for this purpose (except for the change caused by load modulation). The messages are used by the energy transmitter 101 to configure itself as requested by the energy receiver 105.

[097] After the identification and configuration phase, the system moves to the energy transfer phase, where the actual energy transfer occurs. Specifically, after having communicated its power requirement, the power receiver 105 connects the output load and supplies it with the received power. The power receiver 105 monitors the output load and measures the control error between the actual value and the desired value of a certain operating point. It communicates these control errors to the power transmitter 101 at a minimum frequency of, for example, every 250 ms to indicate the errors to the power transmitter 101, as well as the desire for a change, or no change, of the control signal. energy.

[098] Thus, to prepare and control the power transfer between the power transmitter 101 and the power receivers 105, 107 in the wireless power transfer system, the power receivers 105, 107 communicate information to the power transmitter energy 101. Such communication has been standardized in the Qi Specification, versions 1.0, 1.1 and 1.2.

[099] At the physical level, the communication channel from the power receiver 105 to the power transmitter 101 is implemented using the wireless inductive power signal as a communication vehicle. The power receivers 105 transmit data messages by modulating the load of the receiving coil 107. This results in corresponding variations in the power signal on the power transmitter side. Load modulation can be detected by a change in the amplitude and/or phase of the transmitter coil current or, alternatively or additionally, by a change in the voltage of the transmitter coil 103. Based on this principle, the power receiver 105 can modulate data which the power transmitter 101 can then demodulate. This data is formatted into bytes and packets. More information can be found in the publication “System Description, Wireless Power Transfer, Volume I: Low Power, Part 1: Interface Definition, version 1.0, July 2010, published by Wireless Power Consortium”, available at http://www.wirelesspowerconsortium .com/downloads/wireless- power-specification-part-1.html, also called the Qi Wireless Power Transfer Specification, in particular, chapter 6: Communications Interface (or later versions of the Specification).

[0100] In order to provide efficient, reliable and safe power transfer, the system is arranged to control the power of the generated power transmission signal by controlling a characteristic of the generated drive signal.

[0101] The power transfer to the power receiver 105 therefore occurs mainly in the power transfer phase. During this phase, the power receiver monitors the output load conditions and specifically measures the control error between the actual value and the desired value of a certain operating point. It communicates these control errors in control error messages to the power transmitter at a minimum rate, for example every 250 ms. This provides an indication of the continued presence of the energy receiver to the energy transmitter. Additionally, control error messages are used to implement closed-loop power control, where the power transmitter adapts the power signal to minimize the reported error. Specifically, if the actual operating point value is equal to the desired value, the power receiver reports a control error with a value of zero, resulting in no change in the power signal. In the event that the power receiver reports a non-zero control error, the power transmitter will adjust the power signal accordingly, that is, it will increase or decrease the power of the power transfer signal in response to feedback from the power receiver. power 106.

[0102] Actual power regulation may be different in different embodiments. In some systems, power can be adjusted by changing a voltage or current of the drive signal. However, in most practical applications, power can be adjusted by modifying a duty cycle or frequency of the drive signal. For example, the generated drive signal may be a square wave signal that has a given value (often alternatively positive and negative) during active time intervals with inactive time intervals, between which the voltage is zero. In this way, power is only supplied to the resonance circuit during active time intervals. The power level can be increased and decreased respectively by increasing and decreasing the duration of the active time interval. In this way, the duty cycle can be modified to change the power supplied to the transmitter communication inductor 209 and thus the power of the power transmission signal. In other embodiments, the drive frequency can be changed with the power being increased by moving the drive frequency toward the resonance frequency of the resonant circuit, and being decreased by moving the drive frequency in the opposite direction to the drive frequency. resonance.

[0103] Thus, during the power transfer phase, the system operates a power control loop based on power control error messages that are transmitted to the power transmitter from the power receiver. This power control loop adjusts the operating point to a desired value. Specifically, in many embodiments, the power receiver may transmit power control messages to control the power of the power transmission signal so as to result in a given voltage being induced in the power receiver for a given load.

[0104] In addition to the operation of the power control loop, the power transmitter may also adopt limits on the operating range for power transfer and thus restrictions within which the power control loop needs to operate. In particular, for power transmitters, the power that is supplied to the resonance circuit may be limited to be below a given threshold.

[0105] Qi originally defined wireless power transfer for low-power devices considered devices with a power drain of less than 5 W. However, the system is being expanded to higher power levels to support an increased range of power transfer devices and applications. However, increased power levels have resulted in new challenges, and it has been discovered that in some scenarios, approaches used for lower power applications are not suitable for higher power levels.

[0106] In particular, it has been discovered that increased power levels (such as those introduced by the expanded power profile of the Qi Specification of v1.2.1) may possibly result in damage to some power receiving devices in some situations. In particular, it has been realized that if the power receiving device is suddenly moved to increase the coupling between the power receiver and the power transmitter, an overvoltage condition may occur in the power receiver due to the fact that the power loop Power control is inherently relatively slow. Furthermore, increasing power levels require higher limits, which are not sufficient to prevent such overvoltage conditions from reaching possibly undesirable levels.

[0107] Specifically, it can be generally considered that the maximum input voltage to the power receiver coil of the power receiver/receiver resonance circuit should not exceed an amplitude of 20 V. In most practical implementations, voltages up to about 25 V do not tend to cause damage to electronic circuits (such as suitable integrated circuits). However, higher voltages can, in some scenarios and applications, possibly damage the circuit, resulting in failure and damage to the power receiver itself.

[0108] Generally, for low power applications, the power control and applied limits are such that the induced voltage does not exceed 20 V even for very sudden changes, for example, coupling between devices. However, for higher power levels it has been found that this cannot be guaranteed in all situations.

[0109] For example, the following scenario can be considered: - A user can place his phone with a wireless power receiver on a charger comprising a wireless power transmitter. It can place it in a position where the coupling between the two is inadequate but high enough to initiate power transfer. - After the initial steps in the communication protocol, the phone directs the charger to provide more power by sending appropriate control error packets. - The charger responds by increasing the transmitter coil current until the phone indicates that it is satisfied (by sending zero value control error packets) or until the charger reaches its power and/or current limit. This usually takes no more than a second or two after the charger and phone establish communication, and results in a large magnetic field. - Once the user discovers that the phone is charging at a low speed due to poor coupling, he quickly moves it to a position where the coupling is (much) better. - At this time, the charger's broad magnetic field generates a high voltage (possibly well above 20 V) on the phone, which can damage its electronic components.

[0110] One option for dealing with the possible overvoltage condition is to add protection circuits or voltage regulator circuits that can handle voltages above 20 V at the power receiver. However, this is generally undesirable or even impossible due to their design limitations. In particular, this generates an unacceptable increase in cost and complexity.

[0111] To consider the scenario in more detail, the simulation/equivalent circuit of Figure 5 can be considered. In the example, the signal generator 501 represents the driver, Cp corresponds to the transmitter resonance circuit capacitor, Lp represents the transmitter resonance circuit inductor, Rp represents transmitter power losses, Cs represents the receiver resonance circuit capacitor, Ls represents the inductor of the receiver resonance circuit, Rs represents the receiver power losses and kop represents the coupling between the transmitter and receiver inductors. ZL represents the complex-valued load fed by the power transfer signal (and may include both an internal power receiver circuit and an external load).

[0112] Figure 6 illustrates parameter values corresponding to an expanded power profile Qi (15 W). The restrictions on the operating point of the power transmitter are mentioned below the table. In particular, the power transmitter - it is possible to operate only at frequencies above the resonance peaks in the system transfer function; - has a current limit of 3 A (RMS); - it cannot drain more than 24 W (average) from your power supply and - it has to limit the voltage across its resonant capacitor to 120 V (RMS).

[0113] Figures 7 and 8 illustrate the complete operating space of the system of Figures 5 and 6 at a coupling factor of kop = 0.56, 0.448, 0.336, 0.224 and 0.112.

[0114] Figure 7 illustrates the input power that corresponds to the power supplied to the resonance circuit (and therefore the drive signal power) by the driver as a function of the current through the transmitter coil 103. Figure 7 shows the relationship of different coupling factors between the power of the drive signal and the coil current as the loading of the power transfer signal varies. As can be seen, the lower the coupling factor, the greater the coil current that is required to deliver a given power. This reflects that for lower coupling factors, an increased magnetic field strength is required for the power receiver to extract the required power. The strength of the magnetic field is given by the coil current and thus a higher coil current is required for a stronger magnetic field. The figures specifically illustrate the relationship between the power of the drive signal and the transmitter coil current after the power control has been adapted to the specific load supplied by the power receiver.

[0115] In the example, the drive signal power is limited to a maximum value of 24 W and the coil current (and therefore the drive signal current) is limited to a maximum value of 3A (as indicated in Figure 7).

[0116] Figure 8 illustrates the corresponding power receiver load voltage as a function of load current for different couplings. The different curves illustrate the maximum values that can be achieved for the different couplings under the restrictions indicated in Figure 7, that is, the curves show the maximum values that can be reached before the power or current limits are reached. Consequently, the curves delimit the possible operating points that can be achieved for different coupling values.

[0117] In this way, all points within a contour of a specific curve are reachable for the system in the associated coupling. Point 801 indicates the intended operating point of the power receiver in the specific example. The system can achieve the intended operating point at coupling factors up to about kop = 0.336 (the coupling factor of kop = 0.56 is assumed to be the maximum possible given a given physical finding). This range can be considered to provide the user with sufficient positioning tolerance. It can also be noted that the system can potentially operate with a load voltage well above uL = 30 V if the load impedance is above Z L = 50 Q. This possible high voltage can be problematic since most of the circuits is designed for a maximum voltage that preferably does not generally exceed 20 V in all possible circumstances.

[0118] It should be noted that the figure captions are shown associated with the upper limits of the curves. However, it should be noted that these are part of completely closed contours that represent the accessible states/operating points for a specific coupling factor. Thus, the contours that define the possible operating points for the coupling also include the power and current limits of Figure 7, as well as the illustrated lower limits (corresponding, for example, to the curves in the lower right part of Figure 7 and near to (0,0) in Figure 8. However, since these are very close to each other and do not differ significantly in the different couplings, the individual legends are, for reasons of clarity, not included in the figures. Furthermore, the following comments, description and basic principles apply to the effect of upper limits and operating point limits and therefore consideration of lower limits is not significant.

[0119] Figures 9 and 10 illustrate examples of how signals can change as systems control operating parameters toward target operating point 801 for different coupling values.

[0120] After the initialization phases of the power transfer protocol, the first power receiver controls its voltage to a level (us =12.6 V) just above its intended operating voltage (us =12.0 V). This is done at a relatively high load impedance (800 Q) and consequently the load current is very low. However, during this first phase, the power transmitter coil current is still relatively significant and increases with decreasing coupling. For example, as can be seen in Figure 9, the coil current for a 0.56 coupling is about 0.6 A and for kop =0.224 it is about 2.4 A. In fact, for kop =0.112 , the current would have to be above 3A for the power receiver voltage to reach 12.6 V and, therefore, even this operating point cannot be reached for this coupling value.

[0121] The power receiver then connects its load, which results in a load step of ZL = 800 Q to ZL = 8 Q. This significant load step causes the voltage at the power receiver to drop. The resulting immediate (intermediate) operating point depends on the coupling. In fact, as illustrated in Figure 10, for kop = 0.56, the voltage drops to about 6 V and the load current increases to about 0.75 A. For kop = 0.224, the voltage drops to about 10 V and the load current increases to about 1.2 A. On the power transmitter side, the coil current and drive signal power increase correspondingly. For example, for kop = 0.56, the input power increases to about 5 W and the coil current increases to about 0.12 A. For kop = 0.224, the input power increases to about 13 W and the coil current increases to 3 A where it is limited.

[0122] The system then proceeds to perform power control. Specifically, the power receiver continually requests that power be increased until the desired operating point 801 is reached. In Figure 10, this corresponds to the operating point that moves the linear path corresponding to an 8 Q resistor until the 12 V, 1.5 A operating point 801 is reached. On the power transmitter side, this results in increasing input power and coil current until the operating point is reached. This is only possible for the three highest coupling factors as limits are reached for the lowest coupling factors. The power/end controlled input power at the power transmitter is almost equal for the three main coupling factors (about 20 W with the difference being the power loss in the resistors indicating other losses). However, the coil current is different for different couplings. In particular, it is about 2.2 A for kop = 0.56 and 2.8 A for kop = 0.336.

[0123] In the figures, the following captions are used: Star: Initial operating point. Square: Final operating point after trying to reach the destination. Diamond: Operating point after moving to maximum coupling from the value indicated in the legend. Circle: Operating point after moving to zero coupling from the value indicated in the legend.

[0124] Figure 11 shows the effect on the instantaneous operating point if the coupling point is changed suddenly. Specifically, Figure 11 shows the change in operating point if the coupling is suddenly changed from the current coupling level to the maximum coupling level of kop = 0.56 before the load has increased (i.e., when the load impedance is still 800 Q and before it has dropped to ZL = 8 Q). As expected, the change is most significant for the largest step in the coupling, that is, for an initial coupling of kop = 0.112 where the high current (at the limit of 3 A) results in a large magnetic field and thus a high induced voltage. In fact, as can be seen, an overvoltage of more than 35 V is formed, thus causing possible damage.

[0125] Consequently, as can be seen, the system is susceptible to possible overvoltages due to the increased coil current required at lower coupling factors. This problem generally cannot be overcome by merely reducing the maximum limits, as this generally does not sufficiently reduce overvoltages without resulting in a restriction of the available operating range greater than acceptable (and will therefore directly reduce the amount of power that can be transferred). In fact, Figure 12 illustrates the effect of reducing the coil current limit from 3 A to 2.25 A. As can be seen, this can also cause overvoltages of up to 30 V. Additionally, analysis and simulations show that the desired operating point of 12 V, 1.5 can be supported only for the maximum coupling of kop = 0.56 if the current limit is reduced in this way. Therefore, restricting the current limit to 2.25 A does not prevent an overvoltage, but it does prevent the desired operating point from being reached by anything other than an ideal position of the power receiver. Further reducing current to reduce overvoltage would make it impossible to achieve the desired operating point.

[0126] However, it was additionally discovered that the overvoltage at full load, that is, with load impedance ZL = 8 Q, is lower. This is illustrated by point 1001 of Figure 10 showing the maximum deviation from the desired operating point 801 that occurs for a sudden change in coupling from the lowest value to the highest value. As can be seen, the temporary voltage rise is relatively low and in fact the maximum voltage is below 20 V and thus an overvoltage condition is avoided.

[0127] Figure 13 illustrates elements of the energy transmitter 101 in more detail. The power transmitter 101 comprises functionality that can provide improved power regulation and that can specifically, in many situations and applications, reduce or even avoid the risk of unacceptable overvoltage conditions.

[0128] In the example, the power transmitter 101 comprises an inductive impedance that, in the specific example, corresponds directly to the transmitter coil 103. However, it must be considered that, in other embodiments, the inductive impedance can be, for example, any element of a gate/two terminals that has at least partial inductive impedance, that is, that has an inductive reactance component or, in other words, that has a complex impedance with a positive imaginary part. Thus, the transmitter coil 103 of Figure 13 can be, more generally, considered an inductive impedance that is a circuit or component (equivalent) with two linear terminals for which the voltage at the terminals is at least partially dependent on a derivative of current through the component/circuit. In the following, the inductive impedance, for the sake of brevity, will be considered with reference to the specific example where it is equal to the transmitter coil 103.

[0129] The transmitter coil 103 is additionally coupled to a capacitive impedance which, together with the transmitter coil 103 (inductive impedance), forms a resonance circuit and, specifically, a series resonance circuit. In the specific example, the capacitive impedance corresponds directly to a single resonance circuit capacitor (called transmitter capacitor 1301), but it should be considered, in other embodiments, that the capacitive impedance can be, for example, any element of a gate /two terminals that have at least a partial capacitive impedance, that is, that have a capacitive reactance component or, in other words, that have a complex impedance with a negative imaginary part. Thus, more generally, the transmitter capacitor 1301 may be considered to represent a capacitive impedance that may be a circuit or component (equivalent) with two linear terminals for which the current through the circuit/component at the terminals is at least partially dependent of a voltage derivative across all terminals.

[0130] It should be considered that, in most embodiments, the resistive part of the inductive and capacitive impedances will generally be much smaller and often negligible compared to the reactance component. This will ensure that the oscillations are not relatively damped, i.e. provide a relatively high Q for the resonance circuit.

[0131] For purposes of clarity and brevity, the following description will focus on the inductive impedance that is an (ideal) inductor, and specifically the transmitter coil 103 of Figures 1 and 2, and the capacitive impedance that is an ideal capacitor, the namely, the transmitter capacitor 1301. However, it should be considered that any reference to the transmitter coil 103 may, as appropriate, be replaced by a reference to an inductive impedance or reactance, and that any reference to the transmitter capacitor 1301 may, as appropriate, be replaced by a reference to a capacitive impedance or reactance. For the sake of brevity, the pair of transmitter coil 103 and transmitter capacitor 1301 will also be referred to as “resonant components”.

[0132] The transmitter coil 103 and the transmitter capacitor 1301 are coupled/connected together in a resonant configuration. In the example, the transmitter coil 103 and the transmitter capacitor 1301 are coupled in series resonance, but it should be considered that, in other embodiments, they may be coupled in a parallel resonance configuration.

[0133] The resonance circuit formed by the transmitter coil 103 and the transmitter capacitor 1301 are coupled to a driver 1303 that may have an output stage that is described with reference to Figures 3 and 4 (and which corresponds to the driver 201 of Figure 2 ). In this way, driver 1303 generates a drive signal that drives the resonance circuit and which specifically induces oscillations in the resonance circuit. The drive signal is a power signal that supplies energy to the resonance circuit. The drive signal thus supplies a voltage and current to the resonance circuit. The drive signal current (the drive current) is, in the specific example, equal to the resonance circuit current and the current passing through the transmitter coil 103 (and the transmitter capacitor 1301). The drive signal voltage (the drive voltage) passes through the transmitter capacitor 1301 and the transmitter coil 103. Although the following description refers to a series resonance circuit, it should be understood that the principles described can also be applied to a parallel resonance circuit (bearing in mind the equivalence of these and especially the complementary nature of voltages and currents for series and parallel resonance circuits).

[0134] The power of the drive signal is, in the example of Figure 13, where the resonant components are considered ideal, equal to the power of the power transfer signal and equal to the power being extracted from the power transfer signal. In practical cases, part of the power supplied by the drive signal will be dissipated as losses, as represented by the loss resistance Rp in Figure 5. Therefore, in practice, the power of the drive signal may be slightly greater than the power extracted from the signal of power transfer.

[0135] The power extracted from the power transfer signal may be composed of various parasitic losses, such as losses resulting from the induction of eddy currents in metallic parts present in the magnetic field generated by the transmitter coil 103. These losses, including various parasitic losses in the receiver of power 105, are represented by the loss resistance Rs of Figure 5. These losses are, however, generally small compared to the maximum loading by a power receiver target load, i.e., by the intended target loading for transfer. of power.

[0136] The power transmitter 101 further comprises a message receiver 1305 which is arranged to receive messages from the power receiver 105. These messages may be specifically received by load modulation as will be known to those skilled in the art. Message receiver 1305 may be specifically arranged to receive power control error messages indicating whether power receiver 105 requests an increased, decreased, or unchanged power level of the power transmission signal.

[0137] The message receiver 1303 is coupled to a power circuit controller 1307 which is further coupled to the driver 1303. The power circuit controller 1307 is arranged to adapt a drive signal strength in response to message messages. power control (error) received from the power receiver 105. In this way, the power circuit controller 1307 implements the power control loop operation that enables the power of the power transmission signal to be dynamically controlled during, in particular , the power transfer phase.

[0138] Controlling the power of the power transmission signal is done by controlling the power of the drive signal and, thus, the power supplied to the resonance circuit. The power circuit controller 1307 thus controls the driver 1303 to adapt the power of the drive signal.

[0139] As previously mentioned, this control can be, for example, direct, by controlling the voltage or current component of the drive signal, but is often achieved by controlling a duty cycle or a frequency of the signal. (i.e., the further the frequency of the drive signal is from the resonant frequency, the lower the power).

[0140] The power circuit controller 1307 is further arranged to limit the operating range of the power transmitter 101 to ensure reliable and safe operation, and specifically the power circuit controller 1307 seeks to prevent, e.g. excessive signal values that could possibly damage components.

[0141] In particular, the power circuit controller 1307 is arranged to control the drive signal subject to a constraint that a current and/or voltage of the resonance circuit and a power of the drive signal are below a Maximum limit. In situations where both current and/or voltage and power are restricted, the maximum limit may, of course, comprise multiple different limits (e.g., one being a maximum power limit and the other being a maximum current limit). . Thus, the power circuit controller 1307 is arranged to control the power of the drive signal subject to at least one constraint that the resonance circuit current and/or voltage is below a maximum current limit and a restriction that the power of the drive signal is below a maximum power limit. In the following, the term maximum limit will be used to refer to both the maximum current/voltage limit(s) (for a current restriction) and the maximum power limit (for a power restriction), as appropriate. Thus, an indication that the maximum limit can be adapted can be considered to refer to the maximum current limit when restricting the current and refer to the maximum power limit when restricting the power.

[0142] The following description focuses on embodiments in which both power and current are limited, but it should be considered that this is not essential to the principles described. Additionally, embodiments will focus on embodiments in which the resonance circuit current is restricted or limited, while no specific limit is determined and applied to any resonance circuit voltage. However, it must be considered that the described principle can also be applied to voltage limits (alternatively or additionally to the current/power limit(s)).

[0143] The power and/or current limit can be achieved in different ways in different modalities. In some embodiments, the driver 1303 may comprise, for example, a current limiter that is controlled by the power circuit controller 1307. In other embodiments, the power transmitter 101 may, for example, implement a fast internal control loop. For example, the current through the transmitter coil 103 can be continuously monitored and, if it increases above the maximum current limit of the power circuit controller 1307, can immediately control the driver 1303 to change the amplitude/frequency/duty cycle of the signal. drive to reduce the current to below the maximum current limit. In some embodiments, the system may implement an external power control loop that controls the power transfer operating point with a faster internal control loop applying maximum limits.

[0144] The power transmitter 101 further comprises an adapter 1309 which is arranged to adapt the upper limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver. Thus, in the power transmitter 101 of Figure 13, the limits imposed on power control and, specifically, the maximum values or limits are not fixed, but are dynamically adapted to reflect variations in the loading provided by the power receiver 105. Thus, in the system of Figure 13, a limiter is implemented that applies a variable limit to the drive signal power, the resonance circuit current, or possibly both.

[0145] This approach can, in many scenarios and applications, solve the problem of overvoltages at higher power levels. The approach may reflect the realization that the overvoltage condition can often occur if the user moves the power receiver to a better position (higher coupling) when the power transmitter is operating with a high coil current (and therefore generating a strong magnetic field), but in which, despite the high current, the power transmitter only provides a small amount of power.

[0146] In this way, the system can specifically detect and avoid situations where the current is high while the power is low. Although such scenarios can be avoided, for example, with a fixed limit on the maximum current, such a fixed limit will generally limit the unacceptable operating range and specifically will not enable higher power levels to be achieved. For example, this could prevent the extension of the Qi Specifications to higher power levels. However, in some embodiments, the power transmitter 101 of Figure 13 may apply a maximum current value, that is, a current limit, which depends on the power supplied.

[0147] For example, the maximum current value/limit for the current through the transmitter coil 103, which in the example of Figure 13 is equal to the current supplied by the driver 1303 (i.e., the drive current), which can be restricted to a maximum value that depends on the power of the drive signal. The current limit (the maximum current limit) can be reduced to a low level for a low power corresponding to a low load by the power receiver 105. This will ensure that the magnetic field is kept relatively low (which is not a problem , since the power receiver loading is low). Consequently, if the user moves the power receiver by suddenly increasing the coupling, the induced voltage will still be maintained at lower levels and an overvoltage condition can be avoided. However, if the power increases, the current limit can also be increased and thus a higher magnetic field intensity will be possible. This enables support of higher power level operating points and reflects a greater power receiver load. Additionally, if the coupling is suddenly improved, for example, when the user moves the power receiver from a suboptimal position, the increased load on the power receiver results in a substantial reduction in the peak voltage.

[0148] Thus, in many embodiments, the power transmitter can limit the coil current depending on the amount of energy it is providing, with the limit being lower if the amount of energy is smaller. In this way, the maximum current limit can be determined as a monotonically increasing function of the drive signal power (and thus the energy supplied to the resonance circuit).

[0149] The operation can also be illustrated in Figures 14, 15 and 16 which correspond to Figures 7 to 12, but with a variable current limit that depends on the power of the drive signal and, specifically, with the current limit being current has a linear relationship with the power of the drive signal.

[0150] In the example, the power circuit controller 1307 ensures that the drive signal provides a minimum amount of power for currents above Ip = 1.5 A, that is, the current limit for zero power supplied is set to Ip = 1.5 A. As the power increases, the current limit also increases linearly. The current limit varies linearly from 1.5 A at a minimum power to 3 A at a maximum power of 24 W, that is, with a slope of about 62.5 mA per W. This is illustrated in Figure 14. The resulting operating ranges for different couplings are shown in Figure 15. Figure 16 illustrates the overvoltages that can occur when the coupling is suddenly changed from a lower level to the maximum coupling of kop = 0.56.

[0151] As can be seen, the problem of possible overvoltage is greatly reduced at the impedance of ZL = 800 Q. The analysis (and specifically the simulations) also shows that the increase in voltage at the highest current and power is still low and , in fact, the maximum voltage (for a step from the lowest to the highest coupling) is only around 13 V. Therefore, in this case, the voltage does not go above 20 V and no overvoltage condition occurs. The exact overshoot and maximum voltage can, of course, depend on several characteristics, including, in particular, the speed of current regulation of the power transmitter.

[0152] However, although the linear relationship between current limit and power may provide advantageous performance in many cases, in some scenarios it may not be ideal. For example, in the specific example, the maximum voltage still reaches about 22 V, which is above the preferred limit of 20 V. Furthermore, at a load impedance of just over ZL =50 Q, the gap peak operation at the power receiver still reaches a voltage level of uL > 35 V. One way to mitigate this is to design the system so that the coupling factor can never reach more than, for example, kop =0.336 (Figure 15) . However, if this approach is used, the intended operating point of the power receiver also needs to be adjusted, since the available operating range is substantially limited. Another problem with this approach is that it substantially reduces the positioning tolerance: if the coupling factor is reduced from kop = 0.336 to kop = 0.224, the system is not even capable of transferring a power of 5 W. Consequently, a Linear relationship between input power and coil current limit may not be ideal for all scenarios.

[0153] In some embodiments, it may be preferable to use a non-linear relationship. For example, Figures 17 through 19 correspond to Figures 14 through 16, but with the use of a second-order polynomial relationship between input power and coil current limit.

[0154] In the power transmitter 101 of Figure 13, the maximum value for the resonance circuit current is thus determined as a function of a load indication that reflects a loading of the power transmission signal by the power receiver. .

[0155] The load indication can be specifically determined by considering the energy supplied to the resonance circuit, that is, the power of the drive signal. The driver 1303 may specifically determine a power indication that is indicative of a drive signal strength. This can, for example, be determined by directly measuring, for example, the currents and voltages of the drive signal and then calculating the instantaneous power. This can then be low-pass filtered and, for example, the RMS power value can be determined.

[0156] However, in many embodiments, the power may be determined as the input power to the driver 1303. This may, in many embodiments, be easier and result in less complexity. In fact, the input voltage to the driver 1303 is often a DC voltage, and in this way the power can be determined directly from the input current to the driver 1303. Because the losses in the driver 1303 are generally relatively low compared to the power of the drive signal, the input power of the driver 1303 tends to be an accurate measure of the power of the drive signal and thus the power extracted from the power transmission signal. Accordingly, it is also an indication of the power extracted from the power transmission signal by the power receiver 105 and thus the charging of the power receiver 105.

[0157] The load indication can therefore be generated based on the power indication of the drive signal, that is, it can be generated from the input power to the driver 1303. For example, the losses in the driver 1303 and in the resonance circuit can be estimated and subtracted from the measured input power to generate a power transfer signal power estimate that can be used as an indication of load for the power receiver. In other embodiments, the determined input power can be directly used as the load indication.

[0158] In the example, the driver 1303 is arranged to restrict/limit the drive signal current and, as this is equal to the transmitter coil current, it inherently restricts/limits the transmitter coil current as well. In some embodiments, the drive signal current and the transmitter coil current may not be identical (e.g., if there are components in parallel with the transmitter coil 103). In such scenarios, the power transmitter 101 may specifically limit the transmitter coil current, for example, by a current limiter in series with the transmitter coil 103. In some embodiments, the transmitter coil path may include a current sensor to measure the transmitter coil current, and the drive signal can be controlled so that this measured current does not exceed the maximum current value.

[0159] In the specific example, the adapter 1309 determines the maximum limit as a function of the monotonic increase of a load indicated by the load indication and, specifically, the power indication, (e.g., it depends on the power/current/voltage of the signal drive). Specifically, the maximum current limit can be determined as a function of monotonically increasing drive signal power, for example, as estimated by the drive input power. This can reduce overvoltage conditions while enabling the system to support operating points at higher power levels.

[0160] In some embodiments, the function may be a linear function, but, as described above, the advantageous operation may, in many scenarios, be obtained with the use of a non-linear function.

[0161] In some embodiments, the adapter 1309 is arranged to increase the upper limit above a first threshold only if the load indication is indicative of a drive signal strength that is below a second threshold. For example, in the example of Figure 14, the adapter 1309 is arranged to only increase the current limit above the 1.5 A threshold if the drive signal power increases above the 0 W threshold. that, in other embodiments, other or, in fact, more thresholds may be included. For example, the current limit may only be increased above, for example, 2 A, if the power of the drive signal increases to, for example, more than 7 W. It should be considered that the exact values may depend on preferences and needs of the individual modality. In particular, they may depend on the various electrical properties of the power transmitter and power receiver, as well as the intended operating ranges.

[0162] In many embodiments, the adapter is arranged to determine the upper limit as a function of the loading (current) of the power transfer signal. The adapter may be arranged to determine the maximum limit as a function of (load indication).

[0163] In some embodiments, the maximum limit may be determined as a value that exceeds the loading of the power transmission signal by a margin, which, for example, may be determined as a function of the loading/charge indication. For example, the maximum limit may be determined by exceeding the power transfer signal loading by a predetermined absolute or relative offset (e.g., the maximum limit may exceed the current loading by a predetermined percentage of the current loading).

[0164] The examples above focused on a scenario where the current limit was adapted based on the load indication. However, as described, in some embodiments, adapter 1309 may alternatively or additionally be arranged to adapt the maximum power limit based on currently experienced load conditions. Thus, in some embodiments, the power control loop that is operating, for example, during the power transfer phase may be arranged to drive the system toward its desired operating point subject to maximum signal power. of drive without exceeding a threshold that is dynamically adapted based on the load indication that reflects the loading of the power transmission signal by the power receiver.

[0165] Threshold adaptation and modification can generally be slower than the rate at which load changes occur. For example, the system can operate at the desired operating point of 12 V and 1.5 A, that is, with an 18 W load. In response, the adapter 1309 can restrict the drive signal power to 20 W, e.g. example. In this case, the user now moves the power receiver, which results in a sudden increase in coupling between the power transmitter and the power receiver, which can result in inducing an increased voltage at the power receiver. However, this increased voltage can result in an increased current in the load impedance (e.g. if this is fed directly from the induced voltage) and thus in an increased power consumption by the power receiver. In this way, the loading of the power transfer signal is suddenly increased, but since threshold adaptation is generally relatively slow, the threshold will (at least during this time) be maintained at 20 W. Therefore, the power available for The receiver power is restricted by the maximum limit and consequently the power can only increase by a certain amount. This way, the initial overvoltage will be restricted to a low level. Additionally, the power control adapts relatively quickly to the higher coupling and restores the power transfer to be at the 12 V, 1.5 A operating point and thus the system will adapt to the desired operating point. with only a relatively low peak in power receiver voltage.

[0166] However, if instead the desired operating point were 12 V and 0.1 A, corresponding to a power transfer of 1.2 W, a power limit of 20 W would result in an overvoltage and potentially large currents generated in the power receiver. In fact, the power could temporarily (until corrected by the power control loop) increase by a factor of more than 16 times, thus causing a short-term increase in voltage of more than 50 V (for a constant resistive load fed directly from the induced voltage).

[0167] However, in the present case, the power limit would be adjusted to reflect the lower operating point. For example, the 1309 adapter may adapt the power limit to be, for example, 1.8 W. In this case, the peak overvoltage is less than 15 V and will then be regulated back to the operating point of 12 V, 0.1 A through the power control loop.

[0168] In this way, the power limit can be dynamically adapted resulting in a reduced peak in overvoltage that potentially arises from a sudden change in coupling factor.

[0169] It should be considered that different control and regulation may operate with different time constants in many embodiments. For example, in many embodiments, adaptation of the upper limit may be substantially slower than adaptation of the power control loop. In fact, in many embodiments, a power control loop regulation time constant may be at least five or ten times lower (faster) than a maximum limit regulation/adaptation time constant in response to a power indication. charge. The slower reaction may, for example, be caused by the load indication being determined with more averaging or low-pass filtering than that applied to the power control loop.

[0170] Furthermore, the application of the maximum limit can be done by a fast internal circuit in the energy transmitter. A limiting time constant can generally be at least five or ten times lower (faster) than a power control loop regulation time constant.

[0171] However, it must be considered that this is not always the case. For example, in the example where the current is limited by a value dependent on the power of the drive signal, the adaptation may, in some embodiments, have a corresponding time constant or even a smaller time constant than for the operation of the loop. power control.

[0172] The upper limit update rate may, in many embodiments, be greater than 0.1 Hz; 1 Hz or even 10 Hz.

[0173] In this way, maximum threshold adaptation may occur during a power transfer phase, and specifically during a time when power control operation based on power control messages is active (and specifically sometimes when restrictions are not active).

[0174] In some embodiments/scenarios, received power control messages may result in a change in the power of the power transfer signal (and the power extracted by the power receiver). The load indication may vary as a result of changed power and therefore received power control messages may result in a change in the load indication and consequently a change in the maximum limit. Specifically, the power circuit controller may be arranged to adapt the power of the drive signal in response to power control messages, and the adapter may be arranged to adapt the upper limit in response to power control messages. power (directly or by changing the power of the drive signal).

[0175] In the previously described examples, the load indication is determined by the energy transmitter based on the properties determined by the energy transmitter. However, in other embodiments, the load indication may be determined based on the load data that is received from the power receiver, with the load data being indicative of a loading of the power transmission signal by the power receiver.

[0176] As an example of low complexity, the power receiver can regularly transmit messages of the load value ZL and the power transmitter can directly use this value as the load indication, that is, it can directly set the maximum limit dependent on the payload value (for example, based on data stored in a lookup table).

[0177] The power transmitter can then adapt the current and/or power limit based on the load data received from the power receiver. For example, for the parameters in Figure 6, the power transmitter may set the coil current limit to 1.2 A at a load impedance of ZL = 800 and to 3 A at a load impedance of ZL = 10 Q .

[0178] An example of elements of a power receiver 105 arranged to provide load data to the power transmitter 101 is illustrated in Figure 20. The power receiver 105 comprises the power receiving coil 107 and a receiver capacitor 2001 which is coupled in series to provide a receive resonance circuit. The receive resonance circuit is coupled to a power receiver controller 2003 that comprises various functionalities for the operation of the power receiver 105, including voltage conversion, control, etc. The power receiver controller 2003 is additionally coupled to an external load 2005 corresponding to the ZL load. The operation of these elements may substantially correspond to the operation in conventional power receivers, as is known to those skilled in the art. It may employ the approaches previously described with reference to Figures 1 and 2.

[0179] The power receiver 105 further comprises a data generator 2007 that is arranged to generate load data that reflects the loading of the power receiver and, specifically in many embodiments, that directly indicates the value of the ZL load.

[0180] The data generator 2007 is coupled to a transmitter 2009 that is arranged to transmit load messages comprising the load data to the power transmitter. Messages comprising load data can be transmitted in the same way as power control error messages, that is, they can be communicated using load modulation and can, for example, be communicated periodically. In fact, in some embodiments, load data may be attached to power control error messages.

[0181] In some embodiments, the data generator 2007 may be arranged to determine the charging of the power receiver in response to a measurement of the load current, the load voltage, or, in fact, both the load current and from the load voltage to the power receiver load.

[0182] For example, the power receiver controller 2003 may comprise functionality for measuring the voltage over and current through the load 2005. These values may be fed to the data generator 2007 which proceeds to calculate the power (by multiplying the values) or the impedance (by dividing the voltage by the current) and transmitting this to the transmitter 2009 to be transmitted to the power transmitter 101.

[0183] In other embodiments, the data generator 2007 may be arranged to transmit the load voltage and/or current to the power transmitter 101, which may then proceed to generate, for example, power or impedance values. These can then be used as the load indication.

[0184] Thus, in some embodiments, the functionality to calculate the load indication may be in the power transmitter 101 while, in other embodiments, it may be in the power receiver 105.

[0185] The power receiver 105 may, for example, transmit information about the impedance of the load ZL to the power transmitter 101 using a structured data packet, as shown in Figure 21 (where the impedance value is provided in ohms). Alternatively (or additionally), a data packet, as illustrated in Figure 22, can be used to indicate the load voltage and current. Data values can be converted into current and voltage values using the relationships:

[0186] The Ack bit in these data packets indicates whether the power receiver requests an acknowledgment response from the power transmitter (ONE) or not (ZERO). The data packet format in Figure 21 is smaller, but requires the power receiver to calculate the load impedance. The data packet in Figure 22 shifts the load impedance calculation effort from the power receiver to the power transmitter.

[0187] In some embodiments, transmitter 2009 may be arranged to transmit a load message to the power transmitter in response to a detection that a change in load of the power receiver satisfies a power change load criterion. The energy change load criterion may, for example, be that the load has changed by more than a given amount since the last load that was reported or may, for example, indicate that the load exceeds a threshold. It should be considered that the exact criteria for when to transmit a payload message may depend on the individual modality.

[0188] The message may indicate that the criterion has been met, but may, in some embodiments, not include a specific load value. Adapter 1309 may then proceed to adapt the maximum limit based on the received message. For example, the message may simply indicate that the load has changed to be in a different category and the adapter 1309 may adapt, for example, the current limit to reflect the typical operating characteristics of that specific category.

[0189] For example, the power receiver may send a packet to the power transmitter to indicate whether the load is above or below a threshold that reflects whether it is safe to use a higher current limit or not. For example, if the power receiver has not connected to the external load, the impedance in search of its coil is generally high, and an overvoltage situation can easily occur. However, if the power receiver has connected external load, then the impedance in search of its coil may be low enough that an overvoltage situation does not easily occur. The load data may simply indicate whether the external load is connected or not, and the transmitter 2009 may be arranged to transmit a load message when the load is connected or disconnected. More specifically, a power receiver may, for example, send a packet to the power transmitter when the impedance seeking its coil falls below, for example, 15 Q, and when this impedance increases to a level above 15 Q. The power transmitter may then, for example, toggle the upper limit between two predetermined values depending on whether information is received indicating that the load is disconnected or whether it indicates that the load is connected.

[0190] As a specific example, the power transmitter may initially set its current and power limits to levels that are suitable for a basic Qi power profile device that corresponds to a transmitter that can transmit up to about 5 W of power . For these limits, the system can be such that it is ensured that an overvoltage will not exceed the desired value of uL = 20 V. As the power transmitter cannot supply more than about 5 W of power, the power receiver can , then first use the power control loop to establish an intermediate operating point at a power level restricted by the basic power profile (i.e., at a power of less than 5 W). After reaching this intermediate operating point, the power receiver can communicate to the power transmitter that the load impedance has reached a value below a critical threshold (e.g., Z L <15 Q). The power transmitter can, in response to receiving load data, indicate that the load impedance is below threshold, adjust current and power limits to levels that are suitable for an extended Qi power profile, providing power levels taller. You can also optionally confirm the new limits for the power receiver by sending an ACK response. The power receiver can subsequently increase its power demand to the intended operating point.

[0191] If the power receiver load impedance ZL subsequently increases to exceed the critical level (ZL > 15 Q), the power receiver generates a new message indicating this load and transmits it to the power transmitter. Upon receiving this, the power transmitter reduces the limits back to the base power profile limits.

[0192] In some embodiments, instead of merely informing the power transmitter when a load threshold is exceeded, the power receiver may transmit information to the power transmitter indicating the value of a suitable threshold and then proceed to transmit regularly simple charge messages indicating a current charge. The power transmitter can then compare the received values to the received threshold and adjust the limits accordingly. Therefore, with this approach, the comparison effort is shifted from the power receiver to the power transmitter.

[0193] Once every second or every few seconds may often be a suitable update rate for load information to be transmitted to the power transmitter for use in limit control. This way, the update rate is generally lower than for the power control loop.

[0194] In some embodiments in which limits are determined in response to messages from the power receiver, the power transmitter may also be arranged to autonomously adapt the maximum limit(s) in response to a detection of a change in power transfer signal loading/a change in drive signal power.

[0195] For example, if the system is operating at the desired operating point of 12 V and 1.5 A, the power limit can be set to, say, 20 W, and the current limit to, say, 3 A Additionally, the 1303 driver can output about 19 W (i.e., 1 W is lost to parasitic losses). The power receiver can transmit a load message every 2 seconds. However, the 1309 power adapter can continuously monitor the power of the drive signal, and if this suddenly drops to, say, 2 W, it is likely that a sudden and drastic change in the power receiver loading may have occurred. For example, a user may have simply removed or disconnected the external load from the power receiver.

[0196] However, the energy transmitter will not be informed of this until the next load message is received, which, in the last case, may take up to 2 seconds. If the user additionally moves the power receiver to increase coupling, an overvoltage condition may arise, and this may not be effectively mitigated by the upper current limits. This could cause damage, for example, to the power receiver circuit.

[0197] However, in the example, adapter 1309 can quickly detect the reduced power level and proceed to immediately reduce the levels. For example, the moment a drastic change in power is detected, the 1309 adapter can adjust levels accordingly. In the specific example, adapter 1309 may, in response to a detection of change in drive signal power, proceed to instantly reduce thresholds, e.g., 3 W and 1.5 A. Adapter 1309 may then wait for next load message (or load messages) and then adapt the thresholds in response to them. This way, in some examples, the power transmitter can implement an independent and very fast adaptation of the limits.

[0198] As another example, based on information received from the power receiver relating to load voltage and current, corresponding operating parameters for the transmitter can be determined. In this way, a relationship between the received load indication and the power transmitter parameters (specifically the drive signal properties) can be established during normal operation. For example, drive signal properties for a 5 W, 10 W, and 15 W load can be established and stored in a lookup table. Additionally, suitable limits can be identified for different operating points and stored in the lookup table.

[0199] In the event that the power receiver suddenly changes its load, this change may be detected at the power transmitter before the power receiver provides any information about the change. In response, the power transmitter may identify one of the stored operating points considered to more closely reflect the detected current conditions. It can then retrieve the stored operation values for that operation point and apply them, including the stored limits.

[0200] In this way, such approaches can enable accurate operation based on information from the power receiver while enabling the power transmitter to respond very quickly to sudden load changes, thereby reducing the risk of any overvoltage conditions.

[0201] In the examples described, the intensity of the magnetic fields, and thus the resistance of the power transfer signal, has been limited by an adaptive limit. The magnetic field strength depends directly on the current through the transmitter coil 103 and the description has focused on examples in which the transmitter coil current has been limited using an adaptive limit.

[0202] Current limiting can be performed directly or indirectly. For example, a current limiter can be introduced directly in series with the transmitter coil. A more indirect approach may be to limit the drive signal current by controlling the operating parameters for the driver, such as by controlling the duty cycle, drive signal frequency, driver output circuit voltage, or current. input to the trigger. In the example where the transmitter coil is in series with the capacitor and driver (i.e., the resonance circuit is a series resonance circuit coupled directly to the driver output and with no other parallel current paths), the drive current ( the driver output current) is equal to the transmitter coil current, and thus controlling and limiting the driver current is also a direct control and limiting of the transmitter coil current.

[0203] Similarly, determining the transmitter coil current to determine whether it exceeds the limit or not can be done directly or indirectly. For example, this can be achieved by a current sensor that directly senses the current through the transmitter coil (e.g., by a current sensor that provides an output that is a function of the magnetic field strength (e.g., by a coil measuring device positioned close to the transmitter coil)). Such an approach can be particularly efficient for situations where the transmitter coil current is not equal to the drive current, such as if the resonance circuit is a parallel resonance circuit or if there are parallel current paths to the driver output. .

[0204] In other embodiments, an indirect measurement of the transmitter coil current can be applied, for example, by measuring the input current to the driver output circuit.

[0205] It should also be considered that in many embodiments, limitation and measurement can be integrated. For example, the transmitter coil current can be measured and limited by the system by imposing an adjustable current limit for the input source to the driver output circuit. In other embodiments, different properties can be evaluated and controlled. For example, for a parallel resonance circuit, the current through the transmitter coil can be sensed directly by a separate current sense coil, and based on this value, a limit on the input current to the driver output circuit can be tax.

[0206] Therefore, to limit the intensity of the power transfer signal, the coil current is the parameter that is limited. For this, other related parameters can be measured and/or limited, such as, for example, the coil voltage or the resonance capacitor voltage. Although the driving current in the resonance circuit influences the coil current, the relationship between this current and the coil current may depend strongly on other parameters in some embodiments (such as, for example, the frequency of operation). In particular, if it is in parallel with the transmitter coil, the resonance capacitor requires only a very small drive current to obtain a high coil current when the quality factor of the resonance circuit is high and the drive frequency matches the frequency of resonance. In particular, for such embodiments, it may be advantageous, for example, to directly measure the transmitter coil current and, for example, limit it by reducing, for example, the drive signal voltage, if the measured current exceeds the limit .

[0207] It should also be considered that different measurements can be used for, for example, current. For example, the current limit can be a limit to an average, range, or RMS current value. Current and/or power values are therefore generally values that reflect the entire cycle and that do not vary due to variations within a single cycle. The values represent the properties of the entire cycle and are generally average values over at least one cycle (of the drive signal/resonance circuit).

[0208] In conclusion, the main approaches described refer to power control in a wireless power transfer system. Power control messages are received from a power receiver and the power of the power transfer signal is adapted according to these messages. However, instead of a conventional power circuit, the approach additionally introduces a constraint on this adaptation in response to power messages by the power controller that performs the adaptation, with the adaptation being below a maximum threshold. In this way, the power controller can adapt and modify the power of the power transfer signal, but it is limited by the maximum limit. In this way, the power control adaptation is simultaneously subjected to two considerations, namely, the received power control messages and the maximum limit.

[0209] Furthermore, the maximum limit is not a constant or fixed limit, but rather is adapted in response to the loading of the power transmission signal by the power receiver. In this way, the maximum limit imposed on the power of the power transfer signal as controlled by the power control loop is adjusted based on the loading of the power transfer signal (and is therefore related to the power of the power transfer signal). power).

[0210] The approach provides very flexible power control in a wireless power transfer signal, and the power control can provide very flexible and precise power control that covers a very large dynamic range, but at the same time avoids the overvoltage conditions that are experienced in traditional systems when, for example, the coupling factor is rapidly changed, for example due to displacement of the power receiver.

[0211] The approach can, in particular, provide a power control approach where power control is freely available over a wide dynamic range while, at the same time, ensuring that a safety limit is imposed to avoid damage under operating conditions. overvoltage that occurs. Significantly, the approach enables the safety limit to be within the dynamic range covered by the power control and thus enables it to be very close to the current operating point which, in practice, is necessary to avoid possibly harmful overvoltage conditions. . The approach provides a solution to the conflicting problems of how to avoid overvoltage conditions in case of sudden changes in coupling factor and how to provide efficient power control over a very wide dynamic range.

[0212] It should be considered that, for the sake of clarity, the above description described embodiments of the invention with reference to different functional circuits, units and processors. However, it will be evident that any suitable distribution of functionality between the different functional circuits, units or processors can be used without departing from the invention. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controllers. Therefore, references to specific functional units or circuits should be considered only as references to means suitable for providing the described functionality and not as indicative of a physical structure or strict logical or physical organization.

[0213] The invention may be implemented in any suitable form, including hardware, software, firmware or any combination thereof. The invention may optionally be implemented, at least partially, as computer software that runs on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be implemented physically, functionally and logically in any suitable manner. In fact, functionality can be implemented in a single unit, in a plurality of units, or as part of other functional units. Thus, the invention can be implemented in a single unit or can be physically and functionally distributed among different units, circuits and processors.

[0214] Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form presented here. Instead, the scope of the present invention is limited only by the appended claims. Additionally, although it may appear that a feature is described in connection with specific embodiments, one skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term “comprising” does not exclude the presence of other elements or other steps.

[0215] Furthermore, although individually mentioned, a plurality of means, elements, circuits or method steps may be implemented, for example by means of a single circuit, a single unit or a single processor. Additionally, although individual features may be included in different claims, they may be advantageously combined, and their inclusion in different claims does not imply that a combination of features is not viable and/or advantageous. Furthermore, the inclusion of a feature in a category of claims does not imply a limitation to that category, but rather indicates that the feature is equally applicable to other categories of claims, as appropriate. Furthermore, the order of the features in the claims does not imply any specific order in which the features need to be worked on, and in particular, the order of the individual steps in a method claim does not imply that the steps need to be performed in that order. The steps can actually be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to “one”, “one”, “first”, “second”, etc., do not exclude a plurality. Reference marks in the claims are provided merely as clarifying examples and should not be construed as limiting the scope of the claims in any way.

Claims (15)

1. POWER TRANSMITTER (101) FOR TRANSFERRING ENERGY TO A POWER RECEIVER (105), the energy transmitter (101) comprising: - a resonance circuit (201) comprising a capacitive impedance (1301) and a inductive impedance (103), wherein the inductive impedance (103) comprises a transmitter coil (103) for generating a power transfer signal for wirelessly transferring power to the power receiver (105); - a driver (1303) for generating a drive signal for the resonance circuit (201); - a message receiver (1305) for receiving messages from the power receiver (105); - a power circuit controller (1307) for adapting a drive signal power in response to power control messages received from the power receiver (105) by the message receiver (1305), characterized in that the adaptation is subject to a constraint of at least one of a resonance circuit current, a resonance circuit voltage (201) and a drive signal power that is below a maximum threshold; and - an adapter (1309) arranged to adapt the maximum limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver (105). 2. POWER TRANSMITTER (101), according to claim 1, characterized in that the adapter (1309) is arranged to dynamically adapt the maximum limit to reflect variations in the load provided by the power receiver. 3. POWER TRANSMITTER (101), according to claim 1 or 2, characterized in that the adapter (1309) is arranged so as to adapt the maximum limit during a power transfer phase. 4. POWER TRANSMITTER (101), according to claim 1, characterized in that the driver (1303) is arranged to determine a power indication that is indicative of a drive signal strength, and the adapter (1309) is arranged to determine the load indication as a function of the power indication. 5. POWER TRANSMITTER (101), according to claim 1, characterized in that the power circuit controller (1307) is arranged so as to limit at least one of a current and a voltage of at least one of the drive signal and the transmitter coil (1303). 6. ENERGY TRANSMITTER (101), according to claim 1, characterized in that the maximum limit is a function of monotonic increase of an energy load indicated by the load indication. 7. POWER TRANSMITTER (101), according to claim 1, characterized in that the adapter (1309) is arranged so as to increase the maximum limit above a first threshold only if the load indication is indicative of a power signal strength. triggering that is above a second threshold. 8. POWER TRANSMITTER (101), according to claim 1, characterized in that the adapter (1309) is arranged to determine the maximum limit to include both a maximum current limit for the drive signal current (201) and a maximum power limit for the power of the drive signal, and for the adaptation to be subject to both the resonance circuit current that is below the maximum current limit and the power of the drive signal that is below the maximum power limit. 9. POWER TRANSMITTER (101), according to claim 1, characterized in that the adapter (1309) is arranged to determine the load indication in response to load data received in at least one message from the power receiver (105 ), and the load data is indicative of a loading of the power transmission signal by the power receiver (105). 10. POWER TRANSMITTER (101), according to claim 9, characterized in that the adapter (1309) is additionally arranged to change the maximum limit in response to a detection of a change in a load of the power transfer signal. 11. WIRELESS POWER TRANSFER SYSTEM, comprising a power receiver (105) and a power transmitter (101) for transferring power to the power receiver (105), the power transmitter (101) comprising: - a resonance circuit (201) comprising a capacitive impedance (1301) and an inductive impedance (103), the inductive impedance (103) comprising a transmitter coil (103) for generating a power transfer signal to transfer mode wireless power to the power receiver (105), - a driver (203) for generating a drive signal for the resonance circuit (201), - a receiver (1305) for receiving messages from the power receiver (105), - a power circuit controller (1307) for adapting a power of the drive signal in response to power control messages received from the power receiver (105), characterized in that the adaptation is subject to a restriction of at least one of a current of the resonance circuit (201), a voltage of the resonance circuit (201) and a drive signal power that is below a maximum limit and - an adapter (1309) arranged so as to determine the maximum limit in response to a load indication determined based on load data received in a message from the power receiver (105), the load data being indicative of a loading of the power transmission signal by the power receiver (105); and the power receiver (105), which comprises: - a data generator (2007) for generating load data that reflects a load from the power receiver (105) and - a transmitter (2009) for transmitting at least one message that comprises the load data for the power transmitter (101). 12. WIRELESS POWER TRANSFER SYSTEM according to claim 11, characterized in that the data generator (2007) is arranged to determine the loading of the power receiver (105) in response to at least one of a power measurement. a load current and a measurement of a load voltage for a power receiver load (105). 13. WIRELESS POWER TRANSFER SYSTEM according to claim 11, characterized in that the transmitter (2009) is arranged to transmit at least one message to the power transmitter (101) in response to a detection that a change in a power receiver load (105) satisfies a power change load criterion; the load data of at least one message is indicative of the change that satisfies the power change load criterion; and wherein the adapter (1309) is arranged to modify the upper limit in response to detecting that the at least one message comprises load data indicative of the change satisfying the energy change load criterion. 14. WIRELESS POWER TRANSFER SYSTEM according to claim 11, characterized in that the adapter (1309) is further arranged to change the maximum limit in response to a detection of a change in a power indication for the signal. drive. 15. METHOD FOR OPERATING A POWER TRANSMITTER (101), which transfers power to a power receiver (105), the power transmitter (101) comprising a resonance circuit (201) comprising a capacitive impedance (1301 ) and an inductive impedance (103), wherein the inductive impedance (103) comprises a transmitter coil (103) for generating a power transfer signal for wirelessly transferring power to the power receiver (105); the method comprising: - generating a drive signal for the resonance circuit (201); - receive messages from the power receiver (105); - adapting a drive signal power in response to power control messages received from the power receiver (105), characterized in that the adaptation is subject to a restriction of at least one of a resonance circuit current, a resonance circuit voltage resonance (201) and a drive signal power that is below a maximum limit; and - adapting the maximum limit in response to a load indication indicative of a loading of the power transmission signal by the power receiver (105).