Improvements relating to inductive power transfer

Abstract

An inductive power transfer receiver. The receiver comprises: an inductive power input circuit comprising a tuning circuit having a receiver coil; and an electric energy control circuit for controlling the output electric energy. A controller is configured to control the power control circuit. The power control circuit includes at least one variable reactance component that can be varied to control the output power provided to the load.

Description

Technical Field

[0001] This specification relates to improvements in wireless power transfer (wireless power transfer for charging and real-time wireless power transfer). Background Art

[0002] As Figure 1 shown, a typical inductive power transfer system includes an inverter, a primary tuning network and a secondary tuning network, a primary coil and a secondary coil, a secondary rectifier, and a load (such as a battery). Electric power is wirelessly transmitted from the primary coil (transmitting) to a nearby secondary coil (receiving) via a magnetic field. This magnetic field is generated by injecting an alternating current (Ipt) into the primary coil, and this magnetic field induces an alternating voltage in series with the secondary coil for power transfer.

[0003] The load has power consumption requirements. These power consumption requirements may be constant or dynamic. The electric power provided by the primary side, received by the secondary side, and then provided to the load should meet these power consumption requirements. However, this may not occur due to changes in the transmitted power, received power, or power consumption requirements. Summary of the Invention

[0004] The object of the present invention is to provide power control in an inductive power transfer system or receiver.

[0005] In a first aspect, the present invention can be said to include an inductive power transfer receiver, which includes: an inductive power input circuit, which includes: a receiver coil tuning circuit, and a power control circuit for controlling the output power; and a controller configured to control the power control circuit, wherein the power control circuit includes at least one variable reactance component, which can be changed to control the output power provided to the load.

[0006] Optionally, the output power includes the power magnitude and the power factor, and controlling the output power includes controlling the power magnitude and / or the power factor.

[0007] Optionally, the power control circuit includes at least a first reactance component, which is connected in parallel with the receiver circuit coil for controlling the power magnitude.

[0008] Optionally, the power control circuit includes at least a first series reactance component and at least a second series reactance component, which are connected in parallel with the receiver circuit coil for controlling the power magnitude and / or the power factor.

[0009] Optionally, the electric energy control circuit includes a first series reactance component, a second series reactance component, and a third series reactance component. The first series reactance component, the second series reactance component, and the third series reactance component are connected in parallel with the receiver circuit coil. The first series reactance component and the second series reactance component are used to control the power factor, and the third series reactance component is used to control the magnitude of the electric energy.

[0010] Optionally, the electric energy control circuit forms part of the tuning circuit.

[0011] Optionally, the tuning circuit includes a first tuning sub-circuit and a second tuning sub-circuit, and the electric energy control circuit is located between the first tuning sub-circuit and the second tuning sub-circuit.

[0012] In a second aspect, the present invention can be said to include an inductive electric energy transmission receiver, which includes: an inductive electric energy input circuit having a topology that can be modeled as a constant current source connected in series with a variable reactance component, wherein the variable reactance component can be changed to control the output electric energy supplied to the load.

[0013] In a third aspect, the present invention can be said to include an inductive electric energy transmission receiver, which includes: an inductive electric energy input circuit and a controller. The inductive electric energy input circuit includes: a first tuning circuit having a receiver coil; a second tuning circuit coupled to a load or a rectifier coupled to the load; an electric energy control circuit for controlling the output electric energy coupled between the first tuning circuit and the second tuning circuit; the controller is configured to control the electric energy control circuit, wherein the electric energy control circuit includes: at least a first variable reactance component and a second variable reactance component, the first variable reactance component and the second variable reactance component are coupled between the first tuning circuit and the second tuning circuit; and at least one third variable reactance component, the third variable reactance component spans the first reactance component and the second reactance component, wherein the first reactance component, the second reactance component, and the third variable reactance component are coupled to the second tuning circuit, and the first reactance component, the second reactance component, and the third variable reactance component can be changed to control the output electric energy supplied to the load.

[0014] In a fourth aspect, the present invention can be said to include an inductive power transfer receiver, comprising: an inductive power input circuit and a controller, the inductive power input circuit comprising: a first tuning circuit having a receiver coil; a second tuning circuit coupled to the first tuning circuit and a load or a rectifier coupled to the load; a power control circuit for controlling the output power coupled between the first tuning circuit and the second tuning circuit; the controller being configured to control the power control circuit, wherein the power control circuit includes at least one variable reactance component spanning the coupling between the first tuning circuit and the second tuning circuit, and the first tuning circuit and the second tuning circuit can be changed to control the output power supplied to the load.

[0015] In a fifth aspect, the present invention can be said to include an inductive power transfer system, comprising an inductive power transfer transmitter and an inductive power transfer receiver according to any one of the preceding claims.

[0016] Optionally, the inductive power transfer receiver or the inductive power transfer system according to any of the above statements includes a rectifier for providing a DC output power to the load.

[0017] In a sixth aspect, the present invention can be said to include Figure 4 circuitry.

[0018] In a seventh aspect, the present invention can be said to include Figure 5A circuitry.

[0019] In an eighth aspect, the present invention can be said to include circuitry according to Figure 6 any one of the models of Figure 6 A to

[0020] F. Figure 7 circuitry.

[0021] The second, third, fourth, fifth, sixth, seventh, eighth, and ninth aspects may include any one or more of the features of the first aspect described above.

[0022] References to numerical ranges disclosed herein (e.g., 1 to 10) are intended to also include references to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), so all sub-ranges of all ranges explicitly disclosed herein are hereby explicitly disclosed. These are merely examples of specific intended uses, and all possible combinations of the values between the recited minimum and maximum values should be considered to be explicitly recited in this application in a similar manner.

[0023] As used in this specification, the term "comprising" means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", there may also be features other than the one or more features that begin with that term. Related terms such as "comprise" and "comprises" shall be interpreted in the same manner. Unless the context clearly requires otherwise, throughout the description and claims, the words "comprise" and "comprising" shall be interpreted in an inclusive sense, rather than an exclusive or exhaustive sense, that is, in the sense of "including but not limited to". Description of the Drawings

[0024] The embodiments will be described with reference to the following drawings, in which:

[0025] Figure 1 An inductive power transfer system is shown.

[0026] Figure 2A 、 Figure 2B Two example circuits of the primary side transmitter of the inductive power transfer system are shown.

[0027] Figure 3A 、 Figure 3B Two example circuits of the secondary side receiver of the inductive power transfer system are shown.

[0028] Figure 4 A general form of an inductive power transfer system having a power control circuit for power control is shown.

[0029] Figure 5A An inductive power transfer system having a power control circuit for power control according to a first embodiment is shown.

[0030] Figure 5B 、 Figure 5C Shows a diagram demonstrating power control using Figure 5A the power control circuit.

[0031] Figure 6 A through Figure 6 F show the Thevenin and Norton models of the power control circuit.

[0032] Figure 7 An inductive power transfer system having a power control circuit for power control according to a second embodiment is shown. Detailed Description of the Invention

[0033] 1. Overview of Inductive Power Transfer System

[0034] Referring to Figure 1 , electrical energy is transmitted from the transmitter (primary side) 35 of the inductive power transfer system 1 to the receiver (secondary side) 36. The electrical energy received at the receiver 36 is used to power the load 12, which can be any load that would benefit from inductive power transfer. For example, the load 12 can be a battery, and the transmitted electrical energy can be used to charge the battery. Alternatively, the load 12 can be a device that is powered in real time through the inductive power transfer system. The electrical energy mentioned can refer to the magnitude of the electrical energy (e.g., in watts) and / or the power factor (e.g., in θ).

[0035] The load 12 has an electrical energy consumption requirement. This electrical energy consumption requirement can be either constant or dynamic. The electrical energy provided by the primary side 35, received by the secondary side 36, and then supplied to the load 12 should meet this electrical energy consumption requirement. However, this may not happen due to changes in electrical energy influencing factors such as the transmitted electrical energy, the received electrical energy, the interaction between the primary side 35 and the secondary side 36 (e.g., mutual inductance), environmental factors (e.g., temperature), load impedance changes, and / or the load electrical energy consumption requirement (magnitude and / or power factor). For example:

[0036] - The transmitted electrical energy may be too high or too low for the load 12, so the received electrical energy does not meet the load electrical energy requirement.

[0037] - The transmitted electrical energy meets the electrical energy consumption requirement, but due to changes such as a change in coil alignment, the electrical energy received at the transmitter 36 and supplied to the load 12 does not meet the electrical energy consumption requirement.

[0038] - The electrical energy consumption requirement changes (e.g., during the charging cycle of the battery load 12), so the transmitted and received electrical energy does not meet the dynamic electrical energy consumption requirement.

[0039] These are just some examples, and there may be other examples as follows, where the inductive power transfer system 1 does not transmit, receive, and / or otherwise provide electrical energy that meets the electrical energy consumption requirement of the load.

[0040] The control provided in this embodiment enables the electrical energy received at the receiver and / or supplied to the load to meet the electrical energy consumption requirement of the load.

[0041] 1.1 Overview of Inductive Power Transfer System

[0042] First, an overview of the traditional inductive power transfer system 1 will be described to provide background information for the embodiments described herein. This provides context, however, the embodiments described herein can be used for various applications and not just for reference Figure 1The described inductive power transfer system. For example, the inductive power transfer system 1 (including the described embodiments and the sub - circuits that make up the inductive power transfer system) can be used for high - power applications, such as wireless charging of electric vehicles in an industrial / commercial environment or alternatively in a home environment. But it can also cover wireless charging or real - time power transfer for other electrical devices such as robots, industrial equipment, etc.

[0043] Figure 1 Shows an overview of the inductive power transfer system 1 for wirelessly transferring electrical energy from the power input section 10 to the load 12. The inductive power transfer system includes an inductive power transfer transmitter 35 (also referred to as "primary device", "primary side", "primary circuit", "transmitter circuit", "transmitter side", or "transmitter module") and an inductive power transfer receiver 36 (also referred to as "secondary device", "secondary side", "secondary circuit", "receiver circuit", "receiver side", or "receiver module"). The inductive power transfer transmitter 35 is the part of the inductive power transfer system 1 that wirelessly transmits electrical energy. The inductive power transfer receiver 36 is the part of the inductive power transfer system 1 that wirelessly receives electrical energy.

[0044] First, refer to the inductive power transfer transmitter 35. In the inductive power transfer transmitter 35, the inductive power transfer system 1 includes a power input section 10. The power input section 10 can be a voltage and / or current input section. For example, the power input section 10 can provide a DC voltage, which can be generated from a power factor correction (PFC) unit, a DC - DC converter, a battery, or other types of DC sources. In the inductive power transfer transmitter 35, the inductive power transfer system 1 also includes an inverter sub - circuit 14, which is used to convert the direct current of the power input section into an alternating - current output. The inverter sub - circuit 14 includes at least one inverter, but can have two or more inverters. The inverters that make up the inverter sub - circuit 14 can be half - bridges, full - bridges, another switching mechanism, or a combination of the above. The inverter sub - circuit 14 can be regarded as a modular independent component. Those skilled in the art will understand that if the power input section already has high - frequency alternating current, the inverter sub - circuit 14 is not required.

[0045] In the inductive power transfer transmitter 35, the inductive power transfer system 1 also includes a primary coil 18 (interchangeable with "transmitting coil"), which is used to wirelessly transmit electrical energy. The primary coil 18 can have multiple coils in series or parallel combinations, but can be collectively referred to as "primary coil 18". The primary coil 18 is tuned through a tuning sub - circuit 20 so that the primary coil 18 and the tuning sub - circuit 20 form a tuned circuit 22. The tuned circuit 22 can be regarded as modular. The tuned circuit 22 can be a series - tuned circuit (for example, see Figure 2A), wherein the tuning sub - circuit 20 has a capacitor for tuning the primary coil 18. Alternatively, the tuned circuit 22 may be a (parallel) LC tuned circuit, wherein the tuning sub - circuit 20 has a capacitor for providing tuning. However, preferably, the tuned circuit 22 is an LCL tuned circuit (for example, see Figure 2B ). In the LCL tuned circuit 22, the tuning sub - circuit 20 provides a capacitor and an inductor for the primary coil 18 to form an LCL tuned circuit. The capacitor for the LCL tuned circuit 22 is provided by the tuning sub - circuit 20. In addition to the primary coil 18, the inductor for the LCL tuned circuit 22 may be provided by the tuning sub - circuit 20.

[0046] Now refer to the inductive power transfer receiver 36. In the inductive power transfer receiver 36, the inductive power transfer system 1 further includes a secondary coil 24 (which may be interchangeable with the "receiving coil") for receiving the power wirelessly transmitted from the primary coil 18. The secondary coil 24 may have a plurality of coils in series or parallel combination, but may be collectively referred to as the "secondary coil 24". Similar to the primary coil 18, the secondary coil 24 is tuned by a tuning sub - circuit 26 to form a tuned circuit 28. The tuned circuit 28 may be regarded as modular. The tuned circuit 28 may be an LCL tuned circuit (for example, see Figure 3A ), wherein the tuning sub - circuit 26 has an inductor and a capacitor for providing tuning. Figure 3A The tuned circuit may be regarded as including two shown tuning sub - circuits, which are themselves tuned circuits. For example, the first part 28A may be a parallel LC tuned circuit, and the second part 28B may improve the power factor. Alternatively, the tuned circuit 28 may be a (parallel) LC tuned circuit, wherein the tuning sub - circuit 26 has a capacitor for providing tuning. However, the tuned circuit 28 may be a series tuned circuit (for example, see Figure 3B ). In the series tuned circuit 28, it is the tuning sub - circuit 26 that provides the capacitor for the series tuning of the secondary coil 24. In the inductive power transfer receiver 36, the inductive power transfer system 1 further includes a rectifier sub - circuit 32 for converting the AC input into a DC output (for DC). The rectifier sub - circuit 32 may be regarded as modular. In the inductive power transfer receiver 36, the inductive power transfer system 1 further includes a load 12. Those skilled in the art will understand that in the case where DC power needs to be provided to the load 12, having the rectifier sub - circuit 32 meets the need, but for example, when powering an AC load, it is unnecessary.

[0047] 1.2 The power received at the load does not meet the requirements.

[0048] The inductive power transfer system 1 as described above transmits electrical power from the primary transmitter side 35 to the secondary receiver side 36 in order to supply power to the load 12. The electrical power transmitted from the primary side, received at the secondary receiver side, and then supplied to the load should meet the power consumption required by the load (i.e., the "power consumption requirement", which is the amount of electrical power required by the load). This can be achieved by controlling the magnitude of the electrical power and / or the power factor provided. Meeting the power consumption requirement means that the electrical power supplied to the load 12 should be substantially the same as the electrical power required by the load. If the electrical power supplied to the load is higher or lower than the required load power consumption, the supplied electrical power will be considered not to meet the required load power consumption. (It will be understood that the mention of "meeting" the load power consumption requirement does not necessarily mean that the supplied electrical power needs to exactly meet the requirement, but alternatively is just within an adequate tolerance range for proper operation. "Meeting" can mean "meeting an appropriate tolerance range", for example, within a range of about + / -1%, or about + / -2%, or about + / -3%, or about + / -4%, or about + / -5%.)

[0049] However, as pointed out above, this does not always happen in practice. This may be due to variations in electrical power influencing factors such as the transmitted electrical power, the received electrical power, the interaction between the primary side 35 and the secondary side 36 (e.g., mutual inductance), environmental factors (e.g., temperature), load impedance changes, and / or load power consumption requirements. Some (non-exhaustive) reasons are briefly described below.

[0050] Due to a change in the misalignment / coupling coefficient (hereinafter referred to as k) of the coils, the power transfer to the load 12 may differ from the power consumption requirement. When the primary coil 18 and the secondary coil 24 are correctly aligned, the inductive power transfer system 1 transfers electrical power in an optimal manner. Alignment can place the secondary coil 24 within the optimal portion of the electromagnetic field generated by the primary coil 18. Misalignment between the primary coil 18 and the secondary coil 24 may result in non-optimal power transfer from the primary device 35 to the secondary device 36. This means that even if: a) the load power consumption requirement is constant, and b) the transmitter 35 provides sufficient electrical power to meet this power consumption requirement, due to such misalignment, sufficient electrical power may not be able to reach the receiver / load 12 from the transmitter 35. Misalignment can cover lateral misalignment (where the primary coil 18 and the secondary coil 24 do not have a coincident axis) and / or separation misalignment (where the gap between the primary coil 18 and the secondary coil 24 is too large or too small).

[0051] A brief description will be further given to misalignment. The wireless power transfer system operates within a wide range of coupling coefficient k. The change of k may be caused by physical changes in the alignment between the primary coil and the secondary coil. Since it may be difficult to achieve perfect alignment (in the lateral and / or separation directions) for both the transmitter coil and the receiver coil in practice, misalignment may occur, which may cause k to change, making it a value different from (e.g., greater than or less than) the optimal value (or outside the optimal range). In addition, the ground clearance of the vehicle may change (e.g., due to vehicle load, tire pressure, different vehicle types, etc.), which may also cause k to change due to the change in coil separation deviating from the optimal spacing (which can also be regarded as "misalignment"). For example, for electric vehicle charging applications, k may typically change by about 2.5 times, depending on the amount or degree of (mis)alignment.

[0052] For wireless power transfer, the primary circuit injects an alternating current (Ipt) into the transmitting coil Lpt to create a magnetic field, and the secondary coil should be placed in this magnetic field to wirelessly receive power.

[0053] More specifically, this magnetic field induces a voltage in series with the secondary coil. This voltage is usually measured when the secondary coil is open-circuited.

[0054] Therefore, this voltage is often referred to as the open-circuit voltage Voc of the secondary coil.

[0055]

[0056] Where ω = 2πf, and f is the operating frequency of the wireless power transfer system. Ipt is the primary coil current. Lpt and Lst are the self-inductances of the primary coil and the secondary coil respectively, and k is the coupling factor or coupling coefficient.

[0057] For a fixed passive secondary circuit, Voc determines the electrical energy transferred from the primary to the secondary. Therefore, if Voc can be kept constant for the change of k, the wireless system can operate at full power within the specified potential misalignment range.

[0058] For the sake of simplicity, we can assume that neither the inductance of the primary coil nor the inductance of the secondary coil changes when there is misalignment between the coils. In addition, we can assume that the frequency is fixed when used for a specific application (such as EV charging). Therefore, Voc can be directly controlled by the product of Ipt and k.

[0059] Therefore, in order to keep Voc constant for the change of k, Ipt should change in the opposite direction to k. For example, if k changes by 2.5 times, the primary coil current Ipt should change by the same multiple but in the opposite direction to keep Voc constant.

[0060] Alternatively, or in addition, due to a dynamic change in the power consumption requirement, the power transfer to the load may not meet the power consumption requirement. The inductive power transfer system 1 should also control the DC charging voltage and / or current during the charging cycle. More specifically, for example, when the charging percentage increases from 0% to 100%, the charging current should be controlled from its maximum allowable value to near zero. For a passive secondary circuit, where the DC charging current is proportional to Voc, this means that Voc should drop an additional amount, thus further expanding the required Voc range. Therefore, even though the power provided by the primary side 35 and received by the secondary side 36 may meet the power consumption requirement at the start of charging, as charging progresses, the power may exceed the load power consumption requirement that decreases over time, and thus the provided power no longer meets the requirement.

[0061] The ambient air temperature (or other environmental conditions) and / or the system can also change the operation of the system such that the power provided to the load 12 may not meet the load power consumption requirement.

[0062] In an example where a single primary side 35 transmits to multiple secondary side 36 receivers (each receiver powering a different load 12), the above may be further complicated. In these examples, the misalignment or k between the primary side 35 and the secondary side 36 may be different from the misalignment or k of other secondary side receivers. Among the multiple secondary side receivers, the charging cycle phases of each secondary side load may also be different.

[0063] Alternatively, or in addition, in some examples, due to a dynamic change in the load impedance, the power transfer to the load may not meet the power consumption requirement. For example, the load impedance may change and become overly inductive or capacitive, which may cause the power factor to become worse.

[0064] Differences in operating parameters caused by manufacturing tolerances can also be mitigated through power control.

[0065] Alternatively, or in addition, due to poor power factor at the transmitter (e.g., below about 0.7, or between 0.4 and 0.7, or below 0.4), the power transfer to the load may not meet the power consumption requirement, meaning that the transmitter cannot provide a sufficient amount of power magnitude to the receiver side to meet the power requirement.

[0066] 1.3 Control the Transmitter Power to Address Different Power Requirements

[0067] As described above (or for other reasons), the electrical energy provided by the inductive power transfer system 1 to the load 12 may not meet the load electrical energy consumption requirements. Conventionally, to solve this problem, the electrical energy on the primary side 35 can be controlled. For example, the primary side 35 controls the current Ipt of its primary coil 18 so that: a) compensate for the change in k caused by misalignment, and / or b) reduce the primary coil current to reduce the DC charging current when the battery is charged to 100%.

[0068] However, it may be challenging to rely solely on the primary side 35 to change its coil current over a wide range. In some examples, this is particularly difficult or even impossible when one primary side 35 transmits to multiple secondary side 36 receivers (each receiver powers a different load 12). In these examples, since the load electrical energy consumption requirements for each primary side are different, and / or the factors affecting the electrical energy received at each load in the load may be different, it may not be possible to fully control the electrical energy on the primary side 35 to provide the required electrical energy to all secondary sides 36 / loads 12.

[0069] 2 Secondary circuit electrical energy control solution

[0070] This embodiment provides secondary side control 46 of electrical energy (both magnitude and / or power factor) such that the electrical energy provided to the load 12 can meet the load electrical energy consumption requirements (i.e., the magnitude of the electrical energy required by the load). As described above, it will be understood that the mentioned "meeting" of the load electrical energy consumption requirements does not necessarily mean that the provided electrical energy needs to fully meet the requirements, but alternatively just within a sufficient tolerance range for good operation. As explained previously, "meeting" can mean "meeting an appropriate tolerance range", for example, such as within a range of about + / -1%, or about + / -2%, or about + / -3%, or about + / -4%, or about + / -5%. For example, in the case of slower charging, the accuracy of the current can have a greater tolerance, but the current may need to remain constant or have a smaller ripple to achieve this purpose.

[0071] In addition, it may be necessary to control the power factor to minimize losses in the tuning circuit and / or help improve the power factor and electrical energy control of the transmitter side inverter. Therefore, also for these reasons, this embodiment provides secondary side control 46 of the power factor.

[0072] Power factor and the amount of electrical energy are usually different requirements, and thus the drivers used to control each requirement can be different. The amount of electrical energy is controlled to meet the electrical energy consumption requirement, and the power factor is controlled for efficiency and stability. However, in practice, for practical reasons, there may be an interrelationship between the two. This is due to the following reasons. Poor power factor on the receiver side may require more current in the transmitter coil to meet the output electrical energy amount (load electrical energy consumption requirement), and thus poor power factor on the receiver side may impose stress on the transmitter side. Poor power factor may also cause a large amount of reactive current to circulate in the tuning circuit and in the secondary / receiver of the non-series tuned secondary / receiver coil, which may generate excessive heat and greater interference. This may limit the ability to safely and reliably provide the required electrical energy. Sometimes, to manage the heat problem, the amount of electrical energy delivered must be reduced, which may mean that the electrical energy consumption requirement cannot be met. Therefore, meeting the electrical energy consumption requirement may mean not only controlling the amount of electrical energy but also controlling the power factor.

[0073] This embodiment relates to secondary circuit 46 topologies that adjust secondary electrical energy (amount of electrical energy and / or power factor) to provide the required electrical energy at the load, even due to changes in electrical energy influencing factors. Examples of changes in electrical energy influencing factors include:

[0074] - Electrical energy provided on the primary side.

[0075] - Electrical energy received from the primary side, which may be different from the required electrical energy due to misalignment or other interference.

[0076] - Load electrical energy consumption requirement.

[0077] - Load impedance change.

[0078] - Interaction between the primary side and the secondary side.

[0079] - Environmental factors.

[0080] In fact, and in addition, due to changes in electrical energy influencing factors, the circuit topologies enable adjustment of the amount of electrical energy and / or power factor correction.

[0081] Figure 4Shows the general topology of the secondary circuit 46 (modified from the secondary circuit 36 discussed previously) of the inductive power transfer system 1 of the present embodiment. As in the example described previously, the secondary circuit 46 has a tuning circuit (inductive power input circuit) 56. The tuning circuit 56 can nominally be divided into a first tuning sub-circuit 56A and a second tuning sub-circuit 56B. Each tuning sub-circuit can be regarded as a tuning circuit individually, or can be regarded as a tuning circuit 56 together. The secondary circuit 46 further includes a secondary power control circuit 41, which is arranged between the first tuning sub-circuit 56A and the second tuning sub-circuit 56B. The power control circuit 41 can form part of the entire tuning circuit 56, or can be regarded as a circuit between the two tuning circuits 56A and 56B. The power control circuit 41 is used to control the power supplied to the load 12 (that is, control the magnitude of the power to the load and / or correct the power factor of the load), as will be further described below.

[0082] A controller 42 is provided, which receives an input 43 indicating the magnitude of the power on the load side 12 (output side) from the secondary circuit 46, and / or receives an input 44 indicating the power factor from the coil side (input side) of the secondary circuit 46. The controller 42 can send one or more control signals 45 to the power control circuit 41 to adjust the power (magnitude and / or power factor) so that the supplied power can meet the power consumption required by the load 12 (that is, the required power magnitude, and the power factor is the required power factor), usually 1 or close to 1, although this is not necessary.

[0083] The power control circuit 41 includes one or more variable reactance components (these can be, for example, variable capacitors or inductors (see Figure 5A and Figure 7 and the related descriptions of the examples)). The one or more variable reactance components can cooperate with the two tuning sub-circuits 56A and 56B to adjust the power magnitude and / or power factor. In the case where the power control circuit 41 controls the power factor and controls the power magnitude, the control of the power factor is independent of the control of the power magnitude and does not affect the control of the power magnitude. This will be described in more detail later.

[0084] 3 First Embodiment

[0085] Figure 5A Shows a non-limiting example of the secondary circuit 46 with the power control circuit 41. It should be noted that the described tuning sub-circuits 56A and 56B are not restrictive, but are provided only as examples. Moreover, the power control circuit 41 is only an example.

[0086] In this example, the first tuning sub-circuit 56A includes a secondary receiving coil 24, a first series capacitor C1A, a second series capacitor C1B coupled to the power control circuit, and a shunt capacitor C2. This forms a parallel LC tuning circuit. The second tuning sub-circuit 56B includes a first series inductor L5A, a second series inductor L5B coupled to the output of the power control circuit 41. The second tuning sub-circuit 56B may also optionally include a first series capacitor C5A and a second series capacitor C5B, which are in series with the first series inductor L5A and the second series inductor L5B respectively and are coupled to the rectifier. The rectifier on the output of the load, the shunt capacitor Cdc is as described above.

[0087] The power control circuit 41 may include two power factor correction reactance components X3A, X3B (in this example, the two power factor correction reactance components X3A, X3B are inductors, but in other examples they may be capacitors), and are connected in series between the first tuning sub-circuit 56A and the second tuning sub-circuit 56B. In other examples, there may be a single power factor correction reactance component. This may be referred to as X3 (as discussed below). Some such examples may involve X3A, X3B being combined into a single power factor correction reactance component. As in the previous example, the single power factor correction reactance component may be inductive or capacitive.

[0088] The power control circuit 41 further includes a power (magnitude) control reactance component X4 (in this example X4 is an inductor, but it can be understood that in other examples X4 may be a capacitor). The power (magnitude) control reactance component X4 is located between the power factor reactance components X3A, X3B and the inductors L5A, L5B.

[0089] Now will refer to Figure 5BAn example of the operation of the electrical energy control circuit is described. If the load 12 (in this case a battery) is being charged by the inductive electrical energy transfer system 1, the voltage will slowly increase from an initial value (which can be the minimum value if the battery is flat) to a maximum value (i.e., the battery is 100% charged). For example, an EV battery can change from 330V to 410V during charging. The charging current is typically controlled to remain constant at 10A during the first charging stage (when the battery voltage is below 400V) and slowly decrease to near zero during the second charging stage (e.g., when the battery voltage is above 400V). Such changes indicate that the charging power level may vary significantly during the charging cycle. Depending on the tuning parameters, the direction of change of the output electrical energy may be the same as the direction of change of the reactance of X4; increasing the reactance of X4 may cause an increase in the output electrical energy. In the example where X4 is an inductor, for the first charging stage, the inductance X4 can be slowly increased to match the increasing output electrical energy requirements. For the second charging stage, the inductance X4 can be decreased to match the decreasing charging electrical energy requirements. This is described below. The typical range of inductive X4 can be (but is not limited to) from about 5uH to about 100uH. The typical range of capacitive X4 can be (but is not limited to) from about 10nF to about 150nF.

[0090] The proposed topology 41 also acts as a low - pass filter. For example, where X4 is capacitive and / or X3A, X3B are inductive, they can all serve to filter or block higher - order harmonics from reaching the secondary coil 24. This improves the EMI performance of the system 1 compared to a conventional tuned secondary side.

[0091] In addition, the variable components X3A and X3B can be adjusted to improve the power factor of Voc (open - circuit induced voltage) during electrical energy delivery. The left side of X3 (representing both X3A and X3B) is an electrical energy source, which is Figure 5A the first tuning sub - circuit 56 in. Thus, X3 is used for power factor correction, so the "load of the electrical energy source" is largely real, where the "load of the electrical energy source" is the circuit to the right of the first tuning sub - circuit 56 (including X3). Due to changes in X4 and the load, the impedance of the load of the electrical energy source changes. A unified power factor helps to optimize / minimize the current in the primary and secondary coils, making the system more efficient. If the first tuning sub - circuit 56A is tuned to a current source, adjusting X3A and X3B will not affect the power level. This allows for independent control of the Voc power factor and the power level. For other types of the first tuning sub - circuit 56A, both the power level and the Voc power factor may change with X3A and X3B, which may make the control algorithm more complex.

[0092] Refer to Figure 5CAn example of the operation of a power factor control on an electrical energy control circuit is described. The variation of the electrical energy magnitude over time is similar to the variation described with respect to Figure 5B The nearly uniform power factor of Voc can be achieved by varying X3 during the charging cycle. A well-paralleled tuned circuit 56A can have the following condition: If the impedance of the combination of Lst, C1A, and C1B is jX, then C2 should be -jX or very close to -jX. By adjusting X3A and X3B such that the impedance on the right side of C2 (Imp_c2right) is jX, the power factor of Voc can become uniform or very close to uniform. The smaller the difference between Imp_c2right and jX, the better the power factor may be.

[0093] Components L5A, L5B, C5A, and C5B can also be tunable or adjustable. Changing the values of these components may also affect the power factor and power level of Voc. The exact impact of the change on these components may depend on the entire tuning network. Adjusting one or more of the components X3A, X3B, X4, L5A, L5B, C5A, and C5B may also change the impedance on the receiver side, which, by reflecting the adjusted impedance on the receiver side to the transmitter side, may help improve the power factor of the inverter in the transmitter and the transmitter electrical energy output.

[0094] 4. Thevenin and Norton Models

[0095] Using the Thevenin and Norton models, the concept of controlling the electrical energy magnitude using X4 as described in the first embodiment of Figure 5A is explained in Figure 6 A to Figure 6 F, and examples of how the circuit proposed in the first embodiment can be simplified and reduced to a series-tuned equivalent circuit are shown in Figure 6 A to Figure 6 F. Additionally, this can provide a model that can be used to determine alternative solution embodiments, some of which will be listed later.

[0096] Figure 6 A shows an example of the original or starting circuit A. In these examples, Voc represents the open-circuit induced voltage in series with the secondary coil. The combined impedance of Lst, C1A, and C1B is designed to be +X, and the impedance of C2 is designed to be -X, as shown in circuit B in Figure 6 Using the Norton transformation, Voc and +X can be transformed into a parallel connection of Isc (Isc = Voc / X) and +X, as shown in Figure 6The circuit shown in C is shown. Since the equivalent impedance is –X*X / (X-X), placing +X and -X in parallel results in an infinite impedance. (If the denominator is zero, the combined impedance is infinite.) In this example, X3A and X3B are in series with the current source and thus do not affect the current value, so they can be removed from circuit C. Thus, we obtain Figure 6 The circuit D shown in D.

[0097] The parallel connection of the current source Isc and X4 can be transformed into a voltage source Veq in series with X4 using Thevenin's transformation (as shown in circuit E in Figure 6 circuit E shown) and the following formula:

[0098] Veq = Isc*X_X4 = Voc / X*X_X4 (1).

[0099] where X_X4 is the reactance of component X4. If we assume no primary side control (Voc is fixed), we can see that changing the reactance of X4 (X_X4) changes Veq. If Veq drives a DC load through X4 and X5 in circuit F (where X5 is the combination of L5A, C5A, L5B, and C5B), it can be understood that the DC power can be controlled by changing the reactance X4 (X_X4). Generally speaking, reducing the reactance X4 (X_X4) will reduce the DC power, and vice versa. X4 and X5 can be fully or partially series-tuned to increase the output current.

[0100] In some examples, X3 can also be added for power factor control, as referenced in Figure 5A and 5B described. Equation (1) of Veq does not require X3, so the value of X3 does not affect Veq, which also means that X3 does not affect the power control of X4. That is, X3 is independent of X4, and X3 can be added and changed independently of X4, which can be changed to control the power, to control the power factor. This can be explained as follows:

[0101] The combined impedance on the right side of X3 (including X4, L5A, L5B, C5A, C5B, rectifier, Cdc, and load) can be expressed as:

[0102] R_load + jX_load (2).

[0103] The total impedance of Lst, C1A, and C1B is jX1, and the reactance of C2 is –jX1. Then, the reactance X3 (X_X3) can be expressed as:

[0104] j(X1 - X_load) (3).

[0105] Therefore, the combined impedance on the right side of the first tuning sub-circuit can be expressed as:

[0106] R_load + jX1(4).

[0107] Thus, as will be understood, the load of the open-circuit voltage becomes real, i.e., a unity power factor, which minimizes the current in the secondary / receiver coil 24. According to the above principle, by changing the reactance X3 (X_X3), a unified power factor can be maintained for variations in X4 and the load. More specifically, due to variations in X4 and / or the load 12, the change in the combined impedance to the right of X3 can be expressed as:

[0108] ΔR_load + jΔX_load(5).

[0109] Thus, the change in the reactance X3 (X_X3) may approximate the following equation:

[0110] j(X1 - ΔX_load)(6).

[0111] This can cancel out the change in reactance to the right of X3. Therefore, the change in impedance to the right of the first tuning sub-circuit is ΔR_load, which is only a real resistance change.

[0112] 5. Second Embodiment

[0113] Although the power factor reactance component X3 is preferred, as can be seen from Figure 6 A to Figure 6 F, the resulting model shows that the electrical energy delivered to the load is independent of the power factor reactance component X3. Therefore, using these reactance components to control the power factor does not affect the control of the magnitude of the electrical energy. Thus, for the control of the magnitude of the output electrical energy, X3 may not be necessary. For certain applications and examples where the secondary power factor does not change significantly (such as in low-power applications), or where a poor secondary power factor does not cause significant losses in the secondary coil, or where the secondary power factor is good but there is no X3, X3 can be omitted, as Figure 7 shown. In these applications or examples, only the magnitude of the electrical energy will be controlled.

[0114] 6. Variations

[0115] The above embodiments describe using a rectifier to power a DC load (with DC power requirements).

[0116] In examples utilizing an AC load (with AC power requirements), a rectifier may not be required. Thus, these examples can include any of the above embodiments, but without the rectifier.

[0117] In the above embodiments, the secondary-side circuit 46 is described as a receiving circuit for an inductive power transfer system. However, in some examples, it can be used as an input for any type of power system.

[0118] This embodiment makes the primary - side control easier. In a traditional system, if the coupling factor k or other influencing factors change, the primary side usually requires significant changes. This embodiment allows using the secondary - side control of the power requirement to achieve minor changes (including no changes in some embodiments) on the primary side.

[0119] Terms and Definitions

[0120] Unless the context otherwise requires, the phrase "computer - readable medium" or "machine - readable medium" as used in this specification and the claims shall be regarded as including a single medium or multiple media. Examples of multiple media include centralized or distributed databases and / or associated caches. These multiple media store one or more sets of computer - executable instructions. The phrase "computer - readable medium" or "machine - readable medium" shall also be regarded as including any medium that is capable of storing, encoding, or carrying a set of instructions for execution by a processor of a computing device and that causes the processor to execute any one or more of the methods described herein. A computer - readable medium can also store, encode, or carry data structures used by or associated with these sets of instructions. The phrase "computer - readable medium" or "machine - readable medium" includes, but is not limited to, portable to fixed storage devices, solid - state memories, optical media or optical storage devices, magnetic media, and / or various other media capable of storing, containing, or carrying one or more instructions and / or data. The "computer - readable medium" or "machine - readable medium" can be non - transient.

[0121] As used in this specification and the claims, the term "comprising" means "consisting at least in part of" or "including, but not limited to", and thus should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense. When interpreting each statement in this specification and the claims that includes the term "comprising", there may also be features other than the one or more features that begin with that term. Related terms such as "comprise" and "comprises" should be interpreted in the same way.

[0122] References to numerical ranges (e.g., 1 to 10) disclosed herein are intended to also include references to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and thus all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are merely examples of specific intended uses, and all possible combinations of the numerical values between the recited minimum and maximum values should be considered to be expressly recited in this application in a similar manner.

[0123] The term "and / or" means "and" and "or" or both.

[0124] The use of "(s)" after a noun means the plural and / or singular form of that noun.

[0125] Unless otherwise expressly stated, or otherwise interpreted in the context in which it is used, conditional language such as "can", "could", "may", or "might" generally is intended to convey that some embodiments include some features, elements, and / or steps, while other embodiments do not include some features, elements, and / or steps. Thus, such conditional language generally is not intended to imply that the features, elements, and / or steps are required in any way for one or more embodiments, or that one or more embodiments must include (regardless of user input or prompting) logic for determining whether these features, elements, and / or steps are included in any particular embodiment or are to be performed in any particular embodiment.

[0126] Degree language used herein, such as the terms "about", "approximately", "substantially", and "essentially" as used herein, means a numerical value, quantity, or characteristic that is close to the recited numerical value, quantity, or characteristic, and that still performs the desired function or achieves the desired effect. For example, the terms "about", "approximately", "substantially", and "essentially" may refer to a quantity within a range of less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the recited quantity.

[0127] In this specification, where reference is made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing context for discussing the features of the invention. Unless otherwise specifically stated, references to such external documents should not be construed as an admission that such documents, or such sources of information, are prior art in any jurisdiction, or form part of the common general knowledge in the art.

[0128] In the above description, specific details are given to provide a thorough understanding of the embodiments. However, those of ordinary skill in the art will understand that these embodiments may be practiced without these specific details. For example, software modules, functions, circuits, etc. may be shown in block diagrams so as not to obscure these embodiments with unnecessary details. In other cases, well-known modules, structures, and techniques may be shown without detail so as not to obscure these embodiments.

[0129] Moreover, it should be noted that these embodiments may be described as processes depicted in process drawings, flowcharts, structural diagrams, or block diagrams. Although a flowchart may describe operations as a sequential process, many operations may be performed in parallel or concurrently. Additionally, the order of the operations may be rearranged. When the operations of a process are completed, the process will terminate. A process may correspond to a method, function, step, subroutine, subprogram, etc. in a computer program. When a process corresponds to a function, its termination corresponds to the function returning to the calling function or the main function.

[0130] Aspects of the above-described systems and methods can operate or be implemented on any type of general-purpose computer system or computing device, including but not limited to desktop computers, laptop computers, notebooks, tablets, smart TVs, gaming consoles, or mobile devices. The term "mobile device" includes but is not limited to wireless devices, mobile phones, smartphones, mobile communication devices, user communication devices, personal digital assistants, mobile handheld computers, laptop computers, wearable electronic devices (such as smartwatches and head-mounted devices), e-book readers, and reading devices capable of reading electronic content, and / or other types of mobile devices that are typically carried by an individual and / or have some form of communication capability (e.g., wireless, infrared, short-range radio, cellular, etc.).

[0131] Aspects of the above-described systems and methods can operate or be implemented on any type of special-purpose or dedicated computer, or any machine or computer or server or electronic device having a microprocessor, processor, microcontroller, programmable controller, etc., or a cloud-based platform or other network of processors and / or servers (whether local or remote), or any combination of such devices.

[0132] In addition, embodiments can be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments for performing the necessary tasks can be stored in a machine-readable medium (such as a storage medium or other storage device). The processor can perform the necessary tasks. A code segment can represent any combination of steps, functions, subroutines, programs, routines, subroutines, modules, software packages, classes, or instructions, data structures, or program statements. By passing and / or receiving information, data, arguments, parameters, or memory contents, a code segment can be coupled to another code segment or a hardware circuit. The information, arguments, parameters, data, etc. can be passed, forwarded, or transmitted via any suitable means, including memory sharing, message passing, token passing, network transmission, etc.

[0133] In the above description, the storage medium can represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and / or other machine-readable media or computer-readable media for storing information.

[0134] The various illustrative logical blocks, modules, circuits, elements, and / or components described in connection with the examples disclosed herein can perform the functions described herein using a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic components, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general-purpose processor can be a microprocessor, but as an alternative, the processor can be any conventional processor, controller, microcontroller, circuit, and / or state machine. The processor can also be implemented as a combination of computer components, for example, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, a combination of one or more microprocessors and a DSP core, or any other such configuration.

[0135] The methods or algorithms described in connection with the examples disclosed herein can be implemented directly in hardware, in a software module executable by a processor, or in a combination thereof, in the form of a processing unit, programming instructions, or other directions, and can be included in a single device or distributed among multiple devices. The software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. The storage medium can be coupled to the processor such that the processor can read information from the storage medium and write information to the storage medium. In an alternative, the storage medium can be an integral part of the processor.

[0136] One or more of the components and functions shown in the figures may be rearranged and / or combined into a single component or implemented in multiple components without departing from the scope of the present disclosure. Other elements or components may be added without departing from the scope of the present disclosure. Additionally, the features described herein may be implemented in software, in hardware, as a business method, or a combination thereof.

[0137] In various aspects, embodiments of the present disclosure may be implemented in a computer-implemented process, a machine (such as an electronic device, or a general-purpose computer that provides a platform on which a computer program may be executed, or other devices), a process executed by such machines, or an article of manufacture. Such articles of manufacture may include computer program products or digital information products (wherein a computer-readable storage medium contains computer program instructions or computer-readable data stored thereon), as well as the processes and machines for forming and using these articles of manufacture.

[0138] Although the present disclosure has been described in the context of certain embodiments and examples, those skilled in the art will understand that the present disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses and their obvious modifications and equivalents. Additionally, although several variations of the embodiments of the present disclosure have been shown and described in detail, other modifications within the scope of the present disclosure will be readily apparent to those skilled in the art. It is contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made, and such combinations or sub-combinations remain within the scope of the present disclosure. For example, the features described above with respect to one embodiment may be used with different embodiments described herein, and such combination remains within the scope of the present disclosure. It should be understood that the various features and aspects of the disclosed embodiments may be combined with or substituted for one another to form different modes of the embodiments of the present disclosure. Therefore, the scope of the present disclosure should not be limited by the specific embodiments described above. Thus, unless otherwise stated, or unless clearly incompatible, each embodiment of the present disclosure may include one or more features from each other embodiment of the invention disclosed herein in addition to the basic features described herein.

[0139] The present disclosure may also be broadly said to include the parts, elements, and features individually or jointly mentioned or indicated in the present disclosure, and any or all combinations of any two or more of said parts, elements, or features, and where such specific integers mentioned herein have known equivalents in the art to which the present disclosure pertains, such known equivalents shall be deemed to be incorporated herein as if individually listed.

[0140] Features, materials, characteristics, or groups described in connection with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment, or example described in this section or elsewhere in this specification, unless an incompatibility is anticipated. All features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The protection is not limited to the details of any foregoing embodiment. The protection extends to any novel feature or any novel combination of features disclosed in this specification (including any accompanying claims, abstract, and drawings), or to any novel step, or any novel combination of steps, of any method or process so disclosed.

[0141] In addition, certain features described in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented separately in multiple implementations, or in any suitable sub-combination. Moreover, although the features may be described above as acting in certain combinations, in some cases, one or more features of a claimed combination may be deleted from the combination, and the combination may be claimed as a sub-combination or a variation of a sub-combination.

[0142] Moreover, while operations may be depicted in a particular order in the figures or described in the specification, such operations need not be performed in the particular order shown or in sequential order, nor do all operations need to be performed to achieve the desired result. Other operations not depicted or described may be incorporated into the example methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the described operations. Further, these operations may be rearranged or reordered in other implementations. Those skilled in the art will understand that in some embodiments, the actual steps taken in the processes shown and / or disclosed may differ from the steps shown in the figures. Depending on the embodiment, some of the steps described above may be deleted, and other steps may be added. In addition, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of this disclosure. Moreover, the separation of the various system components in the foregoing implementations should not be understood to be required in all implementations, and it should be understood that the described components and systems may generally be integrated together into a single product, or packaged into multiple products.

[0143] For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be practiced or carried out in a manner that achieves one advantage or a group of advantages as taught herein, without necessarily achieving other advantages that may be taught or suggested herein.

[0144] The scope of the disclosure should not be limited by the specific disclosure of embodiments in this or other portions of this specification, and may be defined by claims that are presented in this or other portions of this specification or that may be presented in the future. The language of the claims should be interpreted broadly based on the language employed in the claims and not limited to the examples described in this specification or the examples described during the prosecution of the application, which examples should be construed as non-exclusive.

Claims

1. An inductive power transfer receiver, comprising: An inductive power input circuit, comprising: A tuning circuit having a receiver coil, and A power control circuit for controlling the output power; And A controller configured to control the power control circuit, Wherein the power control circuit includes at least one variable reactance component that can be changed to control the output power supplied to the load.

2. The inductive power transfer receiver according to claim 1, wherein, The output power includes power magnitude and power factor, and controlling the output power includes controlling the power magnitude and / or the power factor.

3. The inductive power transfer receiver according to claim 1 or 2, wherein The power control circuit includes at least a first reactance component, which is connected in parallel with the receiver circuit coil for controlling the power magnitude.

4. The inductive power transfer receiver according to claim 1 or 2, wherein, The power control circuit includes at least a first series reactance component and at least a second series reactance component, the first series reactance component and the second series reactance component being connected in parallel with the receiver circuit coil for controlling the power magnitude and / or the power factor.

5. The inductive power transfer receiver according to claim 4, wherein, The power control circuit includes a first series reactance component, a second series reactance component and a third series reactance component, the first series reactance component, the second series reactance component and the third series reactance component being connected in parallel with the receiver circuit coil, the first series reactance component and the second series reactance component being used to control the power factor, and the third series reactance component being used to control the power magnitude.

6. The inductive power transfer receiver according to any one of the preceding claims, wherein, The power control circuit forms part of the tuning circuit.

7. The inductive power transfer receiver according to any one of claims 1 to 6, wherein, The tuning circuit includes a first tuning sub-circuit and a second tuning sub-circuit, and the power control circuit is located between the first tuning sub-circuit and the second tuning sub-circuit.

8. An inductive power transfer receiver, comprising: An inductive power input circuit having a topology that can be modeled as a constant current source in series with a variable reactance component, Wherein the variable reactance component can be changed to control the output power supplied to the load.

9. An inductive power transfer receiver, comprising An inductive power input circuit, comprising: A first tuning circuit having a receiver coil; A second tuning circuit coupled to A load, or A rectifier coupled to the load; A power control circuit for controlling the output power coupled between the first tuning circuit and the second tuning circuit; And A controller configured to control the power control circuit, Wherein the power control circuit includes: At least a first variable reactance component and a second variable reactance component, the first variable reactance component and the second variable reactance component being coupled between the first tuning circuit and the second tuning circuit; and At least one third variable reactance component spanning the first reactance component and the second reactance component, wherein the first reactance component, the second reactance component and the third variable reactance component are coupled to the second tuning circuit, The first reactance component, the second reactance component and the third variable reactance component can be changed to control the output power supplied to the load.

10. An inductive power transfer receiver, comprising an inductive power input circuit, comprising: a first tuning circuit having a receiver coil; a second tuning circuit coupled to the first tuning circuit and a load, or a rectifier coupled to the load; a power control circuit for controlling the output power coupled between the first tuning circuit and the second tuning circuit; and a controller configured to control the power control circuit, wherein the power control circuit includes at least one variable reactance component spanning a coupling portion between the first tuning circuit and the second tuning circuit, and the first tuning circuit and the second tuning circuit can be varied to control the output power supplied to the load.

11. An inductive power transfer system, comprising an inductive power transfer transmitter and the inductive power transfer receiver according to any one of the preceding claims.

12. The inductive power transfer receiver or inductive power transfer system according to any one of the preceding claims, further comprising a rectifier for providing a DC output power to a load.

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