Improvements in inductive power transfer

Abstract

This application provides an inductive power transfer receiver including an inductive power input circuit including a tuning circuit having a receiver coil and a power control circuit for controlling output power. The inductive power transfer receiver includes a controller 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 delivered to a load.

Description

[Technical Field]

[0001] The present invention relates to improvements in wireless power transfer (either for charging or real-time wireless power transfer). [Background technology]

[0002] A typical inductive power transfer system, shown in Figure 1, includes an inverter, primary and secondary tuning networks, primary and secondary coils, a secondary rectifier, and a load (such as a battery). Power is transmitted wirelessly from the primary (transmitting) coil to a nearby secondary (receiving) coil via a magnetic field. The magnetic field transmits an alternating current (I) through the primary coil. pt ), the magnetic field induces an AC voltage in series with the secondary coil for power transfer.

[0003] A load has a power draw requirement, which may be constant or dynamic. The power supplied by the primary side, received by the secondary side, and then supplied to the load must meet the power draw requirement. However, due to fluctuations in transmit power, receive power, or power draw requirement, the power draw requirement may not be met. Summary of the Invention

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

[0005] In a first aspect, the present invention may be considered to include an inductive power transfer receiver, the inductive power transfer receiver comprising: 1. An inductive power input circuit, comprising: a tuning circuit having a receiver coil; a power control circuit for controlling the output power; an inductive power input circuit; a controller 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 delivered to a load.

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

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

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

[0009] Optionally, the power control circuit includes a first series reactance component, a second series reactance component, and a third series reactance component in parallel with the receiver coil, the first series reactance component and the second reactance component controlling the power factor, and the third reactance component controlling the magnitude of the power.

[0010] Optionally, the power 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 power control circuit is between the first tuning sub-circuit and the second tuning sub-circuit.

[0012] In a second aspect, the present invention may be considered to include an inductive power transfer receiver, the 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; The variable reactance component can be varied to control the output power delivered to a load.

[0013] In a third aspect, the present invention may be considered to include an inductive power transfer receiver, the inductive power transfer receiver comprising: 1. An inductive power input circuit, the inductive power input circuit comprising: a first tuned circuit having a receiver coil; a second tuned circuit coupled to a load or to a rectifier coupled to a load; a power control circuit for controlling an output power coupled between the first tuning circuit and the second tuning circuit; an inductive power input circuit; a controller configured to control the power control circuit; The power control circuit includes: at least a first variable reactance component and a second variable reactance component coupled between the first tuning circuit and the second tuning circuit; and at least one third variable reactance component between the first variable reactance component and the second variable reactance component that can be varied to control the output power delivered to the load, the first variable reactance component and the second variable reactance component being coupled to the second tuned circuit.

[0014] In a fourth aspect, the present invention may be considered to include an inductive power transfer receiver, the inductive power transfer receiver comprising: 1. An inductive power input circuit, the inductive power input circuit comprising: a first tuned circuit having a receiver coil; a second tuning circuit coupled to the first tuning circuit; a load or a rectifier coupled to the load; a power control circuit for controlling an output power coupled between the first tuning circuit and the second tuning circuit; an inductive power input circuit; a controller configured to control the power control circuit; The power control circuit is across a coupling between the first tuned circuit and the second tuned circuit and includes at least one variable reactance component that can be varied to control the output power delivered to the load.

[0015] In a fifth aspect, the present invention may be considered to include an inductive power transfer system including an inductive power transfer transmitter and an inductive power transfer receiver according to any one of the aspects described above.

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

[0017] In a sixth aspect, the present invention may be considered to include the circuit of FIG.

[0018] In a seventh aspect, the present invention may be considered to include the circuit of FIG. 5A.

[0019] In an eighth aspect, the present invention may be considered to include a circuit according to any one of the models of Figures 6A to 6F.

[0020] In a ninth aspect, the present invention may be considered to include the circuit of FIG.

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

[0022] Reference to a range of numerical values ​​disclosed herein (e.g., 1 to 10) is also intended to encompass reference to all fractional numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10), and to encompass reference to any range of fractional numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and therefore all subranges of every range explicitly disclosed herein are hereby expressly disclosed. These are merely examples of ranges specifically intended, and all possible combinations of numerical values ​​between the minimum and maximum values ​​recited should be considered to be expressly set forth in this application in a similar manner.

[0023] The word "comprising" as used in this specification means "consisting at least in part of." When interpreting each statement in this specification containing the word "comprising," there may be features different from those that follow the word. Related words such as "comprise" and "comprises" should be interpreted in a similar manner. Unless the context clearly requires, throughout the specification and claims, words such as "comprise," "comprising," and the like should be interpreted in an inclusive sense, i.e., "including, but not limited to," rather than in an exclusive or exhaustive sense.

[0024] Several embodiments will be described with reference to the following drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 illustrates an inductive power transfer system. [Figure 2A]1 shows two exemplary circuits of a primary side transmitter for an inductive power transfer system. [Figure 2B] 1 shows two example circuits of a primary transmitter for an inductive power transfer system. [Figure 3A] 1 shows two exemplary circuits of a secondary side receiver for an inductive power transfer system. [Figure 3B] 1 shows two example circuits of a secondary side receiver for an inductive power transfer system. [Figure 4] 1 illustrates, in general form, an inductive power transfer system having a power control circuit for controlling power. [Figure 5A] 1 illustrates an inductive power transfer system using a first embodiment of a power control circuit for power control. [Figure 5B] 5B shows a graph demonstrating power control using the power control circuit of FIG. 5A. [Figure 5C] 5B shows a graph demonstrating power control using the power control circuit of FIG. 5A. [Figure 6] 1 shows a Thevenin and Norton model of a power control circuit. [Figure 7] 1 illustrates an inductive power transfer system using a second embodiment of a power control circuit for power control. DETAILED DESCRIPTION OF THE INVENTION

[0026] 1. Overview of Inductive Power Transfer System

[0027] Referring to FIG. 1 , power is transmitted from a (primary) transmitter 35 to a (secondary) receiver 36 of an inductive power transfer system 1. The power received at receiver 36 is used to power a load 12, which may be any load that would benefit from inductive power transfer. For example, load 12 may be a battery, and the transmitted power may be used to charge the battery. Alternatively, load 12 may be a device that is powered in real time by the inductive power transfer system. References to power may refer to the magnitude of the power, for example, in watts, and / or a power factor, for example, θ.

[0028] The load 12 has a power draw requirement, which may be constant or dynamic. The power provided by the primary side 35, received by the secondary side 36, and then delivered to the load 12 must meet the power draw requirement. However, this power draw requirement may not be met due to variations in power influencing factors, such as power transmitted, power received, interaction between the primary side 35 and the secondary side 36 (e.g., mutual induction), ambient factors (e.g., temperature), load impedance changes, and / or load power draw requirements (e.g., magnitude and / or power factor). For example, The transmitted power may be either too high or too low for the load 12, so that the received power does not meet the power consumption requirements of the load. The transmitted power meets the power consumption requirement, but due to variations such as changes in coil alignment, the power received by the transmitter 36 and delivered to the load 12 does not meet the power consumption requirement. The power consumption requirements change (eg, during a charging cycle of the battery load 12), so the transmit power and receive power do not meet the dynamic power consumption requirements.

[0029] These are just a few of several examples, and there may be other examples in which the inductive power system 1 does not transmit, receive, and / or provide power that meets the power consumption requirements of the load.

[0030] This embodiment provides control such that the power received at the receiver and / or the power delivered to the load can meet the power consumption requirements of the load.

[0031] 1.1 Overview of inductive power transfer systems

[0032] First, an overview of a conventional inductive power transfer system 1 is provided to provide background information for the embodiments described herein. This assumes that the embodiments described herein may be used in a variety of applications beyond just the inductive power transfer system described with reference to FIG. 1. For example, inductive power transfer system 1 (including the sub-circuits that make up the inductive power transfer system and the described embodiments) may be used in high power applications, such as wireless charging of electric vehicles in industrial / commercial environments, or alternatively, in domestic environments. Inductive power transfer system 1 may also be used for wireless charging or real-time power transfer to other electric devices, such as robots, industrial equipment, etc.

[0033] 1 shows an overview of an inductive power transfer system 1 that wirelessly transfers power from a power input 10 to power a load 12. The inductive power transfer system includes an inductive power transfer transmitter 35 (also referred to as a "primary device," "primary side," "primary circuit," "transmitter circuit," "transmitter side," or "transmitter module") and an inductive power transfer receiver 36 (also referred to as a "secondary device," "secondary side," "secondary circuit," "receiver circuit," "receiver side," or "receiver module"). The inductive power transfer transmitter 35 is the portion of the inductive power transfer system 1 that wirelessly transfers power. Inductive power transfer receiver 36 is the part of inductive power transfer system 1 that wirelessly receives power.

[0034] First, the inductive power transfer transmitter 35 will be described. In the inductive power transfer transmitter 35, the inductive power transfer system 1 includes a power input 10. The power input 10 may be a voltage input and / or a current input. For example, the power input 10 may provide a DC voltage generated from a power factor correction (PFC) unit, a DC-DC converter, a battery, or another type of DC power source. In the inductive power transfer transmitter 35, the inductive power transfer system 1 also includes an inverter subcircuit 14 used to convert the DC component of the power input to an AC output. The inverter subcircuit 14 includes at least one inverter, but may also include two or more inverters. The inverters that make up the inverter subcircuit 14 may be a half-bridge, a full-bridge, other switching mechanisms, or a combination thereof. The inverter subcircuit 14 may be considered a modular standalone component. Those skilled in the art will appreciate that if the power input already has high frequency alternating current, then inverter subcircuit 14 is not necessary.

[0035] In the inductive power transfer transmitter 35, the inductive power transfer system 1 also includes a primary coil 18 (which can be referred to as a "transmitting coil") used to wirelessly transmit power. The primary coil 18 may include multiple coils combined in series or parallel, collectively referred to as the "primary coil 18." The primary coil 18 is tuned by a tuning sub-circuit 20, whereby the primary coil 18 and tuning sub-circuit 20 form a tuned circuit 22. The tuning circuit 22 may be considered modular. The tuning circuit 22 may be a series tuned circuit (e.g., as shown in FIG. 2A ), in which the tuning sub-circuit 20 includes capacitors to tune the primary coil 18. Alternatively, the tuning circuit 22 may be a (parallel) LC tuned circuit, in which the tuning subcircuit 20 has capacitors to provide tuning. However, the tuning circuit 22 is preferably an LCL tuned circuit (e.g., as shown in FIG. 2B ). In the LCL tuned circuit 22, the tuning subcircuit 20 provides capacitors and inductors to the primary coil 18, resulting in an LCL tuned circuit. The capacitors used in the LCL tuned circuit 22 are provided by the tuning subcircuit 20. In addition to the primary coil 18, the inductors used in the LCL tuned circuit 22 may be provided by the tuning subcircuit 20.

[0036] Next, the inductive power transfer receiver 36 will be described. In the inductive power transfer receiver 36, the inductive power transfer system 1 also includes a secondary coil 24 (which can be referred to as a "receiving coil") for receiving power wirelessly transmitted from the primary coil 18. The secondary coil 24 may include multiple coils combined in series or in parallel, collectively referred to as the "secondary coil 24." Like the primary coil 18, the secondary coil 24 is tuned by a tuning subcircuit 26 to form a tuning circuit 28. The tuning circuit 28 may be considered modular. The tuning circuit 28 may be an LCL tuning circuit (e.g., as shown in FIG. 3A), in which the tuning subcircuit 26 includes an inductor and a capacitor to provide tuning. The tuning circuit of FIG. 3A may be considered to include two tuning subcircuits, as shown, each of which is a separate tuning circuit in its own right; for example, first portion 28A may be a parallel LC tuning circuit, and second portion 28B may improve power factor. Alternatively, tuning circuit 28 may be a parallel LC tuning circuit, in which tuning subcircuit 26 has a capacitor to provide tuning. However, tuning circuit 28 may also be a series tuning circuit (e.g., as shown in FIG. 3B). In a series tuning circuit 28, it is tuning subcircuit 26 that provides a capacitor to secondary coil 24, which is to be series tuned. Inductive power transfer system 1 also includes a rectifier sub-circuit 32 within inductive power transfer receiver 36 for converting an alternating current input to a direct current output (for a DC load). Rectifier sub-circuit 32 may be considered modular. Inductive power transfer system 1 also includes a load 12 within inductive power transfer receiver 36.Those skilled in the art will appreciate that it is desirable to have rectifier subcircuit 32 in situations where it is desirable to supply DC current to load 12, but that it is not essential to have rectifier subcircuit 32, such as when an AC load is being powered.

[0037] 1.2 Power received at the load does not meet requirements

[0038] The inductive power transfer system 1 described above transmits power from the primary transmitter side 35 to the secondary receiver side 36 to supply power to a load 12. The power transmitted from the primary side, received at the secondary receiver side, and then supplied to the load must meet a power draw required by the load (i.e., the "power draw requirement," which is the power magnitude required by the load). This may be achieved by controlling the magnitude and / or power factor of the power supplied by the system. Meeting the power draw requirement means that the power supplied to the load 12 must be substantially the same as the power required by the load. If the power supplied to the load is above or below the required load power draw, the supplied power will be considered to not meet the required load power draw. (Of course, a reference to "meeting" a load's power consumption requirements does not necessarily mean that the power supplied must exactly meet the load's power consumption requirements, but rather that it must be within a tolerance sufficient for successful operation. "Meet" may also mean "meet within a suitable tolerance," such as within about + / - 1%, about + / - 2%, about + / - 3%, about + / - 4%, about + / - 5%, etc.)

[0039] However, as explained above, in practice this is not necessarily the case. This may be due to variations in factors affecting power, such as transmitted power, received power, interactions between the primary side 35 and secondary side 36 (e.g., mutual induction), ambient factors (e.g., temperature), changes in load impedance, and / or power consumption requirements of the load. Some of the multiple (non-exhaustive) reasons are briefly discussed below.

[0040] Power transfer to the load 12 may vary from the power draw requirement due to coil misalignment or changes in the coupling factor (hereinafter referred to as k). The inductive power transfer system 1 optimally transfers power when the primary coil 18 and secondary coil 24 are properly aligned. Alignment may be achieved so that the secondary coil 24 is within the optimal portion of the electromagnetic field produced by the primary coil 18. Misalignment between the primary and secondary coils 18, 24 may result in less than optimal power transfer from the primary device 35 to the secondary device 36. This means that even if (a) the power consumption requirement of the load is constant and (b) the transmitter 35 is providing enough power to meet that power consumption requirement, such misalignment may cause the transmitter 35 to not provide enough power to the receiver / load 12. The misalignment may include lateral misalignment (the axes of the primary coil 18 and secondary coil 24 are not aligned) and / or separation misalignment (the gap between the primary coil 18 and secondary coil 24 is too large or too small).

[0041] Further, a brief description of misalignment is provided. Wireless power transfer systems operate over a wide range of coupling coefficients k. Changes in k may be due to physical changes in the misalignment between the primary and secondary coils. In practice, it may be difficult to perfectly align both the transmitter and receiver coils (laterally and / or separation-wise), resulting in misalignment, which may cause a change in k, thereby changing it to a value different from the optimal value (e.g., a value greater than or less than the optimal value) (or a value outside the optimal range). In addition, vehicle ground clearance may change (e.g., due to vehicle load, tire pressure, vehicle model, etc.), which may also contribute to a change in k due to changes in coil separation away from the optimal spacing (which may also be considered “misalignment”). For example, in the case of electric vehicle charging applications, k typically changes by a factor of about 2.5 depending on the amount or degree of misalignment (alignment).

[0042] To supply power wirelessly, the primary circuit includes the transmitting coil L pt AC current (I pt ) to generate a magnetic field, and then place a secondary coil within this field to receive power wirelessly.

[0043] More specifically, the magnetic field induces a voltage in series with the secondary coil. That voltage is usually measured with the secondary coil open circuited. Therefore, that voltage is often referred to as the secondary coil open circuit voltage, V oc It is known as.

number

[0044] In the case of a fixed passive secondary circuit, V oc determines the amount of power transferred from the primary to the secondary. Therefore, V oc If it is possible to keep σ constant, the wireless system can operate at maximum power over a designated range of potential misalignment.

[0045] For simplicity, we assume that the inductance of both the primary and secondary coils does not change when there is a misalignment between the primary and secondary coils. In addition, we assume that the frequency is constant when used in a specific application such as EV charging. As a result, V oc I pt and k.

[0046] Therefore, for a change in k, V oc To keep constant, I pt must change opposite to k. For example, if k changes by a factor of 2.5, V oc To keep the primary coil current I constant, pt must vary by the same factor and in opposite directions.

[0047] Alternatively or additionally, power transfer to the load may not meet the power consumption requirements due to dynamic changes in the power consumption requirements. The inductive power transfer system 1 also needs to control the DC charging voltage and / or current during the charging cycle. More specifically, the charging current needs to be controlled from its maximum allowed value to near zero as the percentage of charge increases from 0% to 100%, as one example. When the DC charging current Voc In the case of a passive secondary circuit where the current is proportional to V oc must be decreased by some additional amount, V oc Therefore, even though the power supplied by primary side 35 and received by secondary side 36 may meet the power consumption requirements at the beginning of charging, as charging progresses the power may exceed the time-decreasing load power draw requirement, such that the supplied power no longer meets the load power consumption requirements.

[0048] The ambient air temperature (or other ambient conditions) and / or the temperature of the system may also change the operation of the system, such that the power supplied to the load 12 may not meet the power consumption requirements of the load.

[0049] The above may be further complicated in instances where a single primary 35 transmits to multiple secondary 36 receivers, each powering a different load 12. In these instances, the offset, i.e., k, between the primary 35 and secondary 36 may be different from the offset of the other secondary receivers. The stage of the charge cycle of each secondary load may also be different among the multiple secondary receivers.

[0050] Alternatively or additionally, in some examples, power delivery to the load may not meet power consumption requirements due to dynamic changes in the load impedance, for example, the load impedance may change to become excessively inductive or capacitive, which may result in a poor power factor.

[0051] Variations in operating parameters due to manufacturing tolerances may also be mitigated by power control.

[0052] Alternatively or additionally, the power transfer to the load may not meet the power consumption requirements due to a poor power factor at the transmitter (e.g., below about 0.7, or between 0.4 and 0.7, or below 0.4), which means that the transmitter cannot provide a sufficient amount of power to the receiver side to meet the power requirements.

[0053] 1.3 Controlling transmitter power to accommodate changing power requirements

[0054] As explained above (or for other reasons), the power supplied to load 12 by inductive power transfer system 1 may not meet the power consumption requirements of the load. Conventionally, primary side power supply 35 may be configured to address this issue. For example, primary side 35 may be configured to reduce primary coil current 18I of primary side 35 to (a) compensate for changes in k due to misalignment, and / or (b) reduce the primary coil current as the battery charges toward 100%, thereby reducing the DC charging current. pt Control.

[0055] However, it is difficult or even impossible to vary the coil current over a wide range relying solely on the primary 35. Varying the coil current over a wide range relying solely on the primary 35 can be particularly difficult or even impossible when one primary 35 transmits to multiple secondary 36 receivers, each providing power to a different load 12. In these instances, when each secondary load has different power consumption requirements and / or when factors affecting the received power at each of the multiple loads are different, it may not be possible to sufficiently control the power of the primary 35 to provide the required power to all of the secondaries 36 / loads 12.

[0056] 2. Secondary circuit power control solution

[0057] This embodiment provides secondary-side control 46 of power (both magnitude and / or power factor), thereby enabling the power delivered to the load 12 to meet the load's power consumption requirements (i.e., the magnitude of power needed by the load). As explained above, it should be understood that reference to "meeting" the load's power consumption requirements does not necessarily mean that the delivered power needs to exactly meet the load's power consumption requirements, but instead means that it only needs to be within a tolerance sufficient for successful operation. As explained above, "meet" may also mean "meeting within an appropriate tolerance," such as within about + / - 1%, about + / - 2%, about + / - 3%, about + / - 4%, or about + / - 5%, for example. For example, when charging is slower, the current accuracy may have a greater tolerance, and the current may need to be constant or have a small ripple to achieve this.

[0058] Additionally, it may be desirable to control the power factor to help minimize losses in the tuned circuit and / or improve the power factor of the inverter on the transmitter side and power control. Therefore, this embodiment also provides for power factor control 46 on the secondary side for these reasons.

[0059] Power factor and power magnitude are generally separate requirements, so the drivers for controlling each may be different. Power magnitude is controlled to meet power consumption requirements, and power factor is controlled for efficiency and stability. However, in practice, for practical reasons, there may be an interrelationship between the two. This is because: A poor power factor at the receiving end may require more current in the transmitter coil to meet the output power magnitude (load power consumption requirement), and therefore a poor power factor at the receiver may place a load on the transmitter. A poor power factor may also cause large reactive currents to flow in the tuning circuit and secondary / receiver for a non-series tuned secondary / receiver coil, which may cause excessive heat and greater interference. This may limit the ability to safely and reliably deliver the required power. In some cases, the delivered power magnitude must be reduced to manage thermal issues, and reducing the delivered power may mean not meeting the power consumption requirements. Therefore, meeting power consumption requirements may mean controlling not only the power magnitude but also the power factor.

[0060] This embodiment relates to a topology of a secondary circuit 46 that regulates the secondary power (power magnitude and / or power factor) to supply the power required at the load despite variations in factors affecting the power. Examples of variations in factors affecting the power include: - power supplied by the primary side, - the power received from the primary side, which may deviate from the required power due to deviations or other disturbances; - power consumption requirements of the load, - Changes in load impedance, - Interaction between the primary and secondary sides, and - ambient factors, Includes.

[0061] In practice, the circuit topology, among other things, allows for power magnitude and power factor correction due to variations in factors affecting power.

[0062] FIG. 4 shows, in general topology, several embodiments of a secondary circuit 46 (modified from the secondary circuit 36 ​​described above) for the inductive power transfer system 1. Similar to the examples described above, the secondary circuit 46 includes a tuning circuit (inductive power input circuit) 56. The tuning circuit 56 may be nominally divided into a first tuning subcircuit 56A and a second tuning subcircuit 56B. Each tuning subcircuit may be considered to be a tuning circuit in its own right, or together they may be considered to be the tuning circuit 56. The secondary circuit 46 also includes a secondary power control circuit 41 located between the first tuning subcircuit 56A and the second tuning subcircuit 56B. The power control circuit 41 may form part of the overall tuning circuit 56, or may be considered to be a circuit between the two tuning circuits 56A and 56B. Power control circuit 41 is a power control circuit for controlling the power supplied to load 12 (i.e., controlling the magnitude of power to the load and / or correcting the power factor of the load), as described further below.

[0063] The controller 42 receives an input 43 from the load side 12 (output side) of the secondary circuit 46 indicative of the magnitude of the power at the load side, and / or an input 44 from the coil side (input side) of the secondary circuit 46 indicative of the power factor. The controller 42 sends 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 meets the required draw power for the load 12 (the required draw power is the magnitude of the power required, and the power factor is the desired power factor), which is typically or close to unity, but not necessarily unity.

[0064] Power control circuit 41 includes one or more variable reactance components (which may be, for example, variable capacitors and / or variable inductors (shown in FIGS. 5A and 7 and related description)). The one or more variable reactance components may operate in combination with two tuning subcircuits 56A and 56B to adjust the power magnitude and / or power factor. If power control circuit 41 controls both the power factor and the power magnitude, the power factor control is independent of and does not affect the power magnitude control. This will be explained in more detail below.

[0065] 3. First Embodiment

[0066] 5A shows one non-limiting example of a secondary circuit 46 having a power control circuit 41. It should be noted that the tuning subcircuits 56A and 56B illustrated are not limiting and are provided by way of example only. Similarly, power control circuit 41 is provided by way of example only.

[0067] In this example, the first tuning subcircuit 56A includes the secondary receiving coil 24, a first series capacitor C1A, a second series capacitor C1B coupled to the power control circuit, and a parallel capacitor C2, which form a parallel LC tuning circuit. The second tuning subcircuit 56B includes a first series inductor L5A and a second series inductor L5B coupled to the output of the power control circuit 41. Optionally, the second tuning subcircuit 56B may further include a first series capacitor C5A and a second series capacitor C5B connected in series with the first series inductor L5A and the second series inductor L5B, respectively, and coupled to the rectifier. The parallel capacitor Cdc at the output of the rectifier and the load is as described above.

[0068] The power control circuit 41 includes two power factor correction reactive components X3A and X3B (in this example, the two power factor correction reactive components X3A and X3B are inductors, but in other examples they may be capacitors) connected in series between the first tuning subcircuit 56A and the second tuning subcircuit 56B. In other examples, there may be a single power factor correction reactive component, which may be referred to as X3 (as described below). Such an example may include X3A and X3B combined into a single power factor correction reactive component. As with the previous example, this single power factor correction reactive component may be either inductive or capacitive.

[0069] The power control circuit 41 also includes a power (magnitude) control reactance component X4 (in this example, X4 is an inductor, but it will be understood that in other examples it may be a capacitor). The power (magnitude) control reactance component X4 is located between the power factor reactance components X3A and X3B and the inductors L5A and L5B.

[0070] Referring to FIG. 5B, an example of the operation of the power control circuit is described. When load 12 (in this case, a battery) is being charged by inductive power transfer system 1, the voltage slowly rises from an initial value (which may be a minimum value if the battery is empty) to a maximum value (i.e., when the battery is 100% charged). For example, an EV battery may vary from 330 V to 410 V during charging. The charging current is typically controlled to a constant 10 A during the first stage of charging (when the battery voltage is less than 400 V) and slowly decreases to near zero during the second stage of charging (e.g., when the battery voltage exceeds 400 V). Such a change indicates that the charging power level may vary significantly during a charging cycle. Depending on the tuning parameters, the output power may change in the same direction as the reactance of X4 changes; an increase in the reactance of X4 may increase the output power. In an example where X4 is an inductor, during the first stage of charging, the inductance X4 may be slowly increased to match the increasing output power demand. During the second stage of charging, the inductance X4 may be decreased to match the decreasing charging power demand. This is explained below. A typical range for inductive X4 may be (but is not limited to) about 5 uH to about 100 uH. A typical range for capacitive X4 may be (but is not limited to) about 10 nF to about 150 nF.

[0071] The proposed topology 41 also functions as a low pass filter, for example, when X4 is capacitive and / or X3A and X3B are inductive, the proposed topology 41 functions to filter or block high order harmonics from reaching the secondary coil 24. This improves the EMI performance of the system 1 compared to conventional tuned secondary coils.

[0072] Additionally, variable components X3A and X3B can be adjusted to adjust V oc The power factor (open-circuit induced voltage) may be improved. To the left of X3 (representing both X3A and X3B) is the power supply, which is the first tuning subcircuit 56 in FIG. 5A. Therefore, since X3 is the variable component for power factor correction, the "load of the power supply" is approximately real, and the "load of the power supply" is the circuit to the right of the first tuning subcircuit 56, including X3. Variations in X4 and the load cause the impedance of the load of the power supply to change. A power factor of unity helps optimize / minimize the current in both the primary and secondary coils, resulting in a more efficient system. When tuning the first tuning subcircuit 56A as a current source, adjusting X3A and X3B does not affect the power level. This means that V oc In the case of other types of first tuning sub-circuits 56A, the power level and V oc Both power factors may vary with X3A and X3B, making the control algorithm more complex.

[0073] One example of the operation of the power control circuit with respect to power factor control is described with reference to FIG. 5C. The variation of power magnitude over time is similar to that described with reference to FIG. 5B. By varying X3 during the charging cycle, V ocA suitable parallel tuned circuit 56A can be used to st , C1A, and C1B is jX, then C2 is -jX or very close to -jX. By adjusting X3A and X3B, the impedance on the right side of C2 (Imp_c2right) becomes jX, so that V oc The power factor of can be 1 or very close to 1. The smaller the difference between Imp_c2right and jX, the better the power factor.

[0074] Components L5A, L5B, C5A, and C5B may also be tunable or adjustable. Changing the values ​​of these components also affects V oc The exact effect of changes to these components may depend on the overall 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, and adjusting such components can help improve the power factor of the inverter at the transmitter and the transmitter's power delivery by mirroring the adjusted impedance on the receiver side.

[0075] 4. Thevenin and Norton models

[0076] Using the Thévenin and Norton models, the concept of power magnitude control using X4 as described in the first embodiment of Figure 5A is explained with reference to Figures 6A-6F, which show several examples of how the proposed circuit of the first embodiment can be simplified and reduced to a series tuned equivalent circuit. Furthermore, this makes it possible to provide a model that can be used to determine alternative solution embodiments, which will be described in detail later.

[0077] FIG. 6A shows one example of an original or starting circuit A. In these examples, V oc represents the open-circuit induced voltage in series with the secondary coil. As shown by circuit B in Figure 6B, L st The combined impedance of C1A, C1B, and C1B is designed to be +X, and the impedance of C2 is designed to be -X. Using a Norton transformation, V oc and +X is I sc (I sc =V oc 6B. Circuit C may be transformed into a parallel connection of +X (-X / X) and +X. Placing +X and -X in parallel creates an infinite impedance because the equivalent impedance is -X*X / (XX). (The combined impedance is infinite when the denominator is zero.) In this example, X3A and X3B are in series with the current source and therefore do not affect the value of the current and may be removed from circuit C. This results in circuit D, shown in FIG. 6D.

[0078] Using the Thévenin transform, we can calculate the current source I as shown in circuit E in Figure 6E. sc and X4 in parallel, and the voltage source V eq can be converted to V eq is the expression V eq =I sc *X_X4=V oc / X*X_X4 (1) In the above equation, X_X4 is the reactance of component X4. If there is no primary side control (V oc is fixed), the change in reactance of X4 (X_X4) is V eq In circuit F, V eqIt will be appreciated that because L5A drives a DC load through X4 and X5 (X5 being the combination of L5A, C5A, L5B, and C5B), it is possible to control the magnitude of the DC power by changing the reactance of X4 (X_X4). Generally, decreasing the reactance of X4 (X_X4) decreases the magnitude of the DC power, and vice versa. X4 and X5 may be fully or partially tuned in series to increase the output current.

[0079] In some examples, X3 may also be added for power factor control, as described with reference to Figures 5A and 5B. eq Since equation (1) for does not require X3, the value of X3 is V eq This also means that X3 does not affect the power magnitude control by X4. That is, X3 is independent of X4, and X3 may be added and changed to control the power factor independently of changing X4 to control the power magnitude. This may be explained as follows: (X4, L5A, L5B, C5A, C5B, rectifier, C dc The combined impedance on the right side of X3 (including the load) is given by the formula R_load+jX_load (2) It may be expressed as:

[0080] L st The total reactance of C1A and C1B is jX1, and the reactance of C2 is -jX1. Then, the reactance of X3 (X_X3) is expressed by the formula j(X1-X_load) (3) Therefore, the composite impedance on the right side of the first sub-tuned circuit is expressed as R_load+jX1 (4) It may be expressed as:

[0081] Therefore, as can be seen, a load with the open-circuit voltage becomes real, a unit power factor, and such a load minimizes the current in the secondary / receiver coil 24. By varying the reactance of X3 (X_X3) according to the principles explained above, it is possible to maintain unit power factor with variations in X4 and the load. More specifically, variations in the combined impedance to the right of X3 due to changes in X4 and / or the load 12 are expressed as ΔR_load+jΔX_load (5) It may be expressed as: Therefore, the variation of reactance (X_X3) of X3 is expressed as follows: j(X1-ΔX_load) (6) You may approach.

[0082] This allows the reactance change from the right side of X3 to be cancelled out. In this way, the change in impedance on the right side of the first sub-tuned circuit becomes ΔR_load, and the change in impedance is due to the real resistance change only.

[0083] 5. Second Embodiment

[0084] While a power factor reactance component X3 is preferred, it can be seen from FIGS. 6A-6F that the resulting model indicates that the delivered power to the load is independent of the power factor reactance component X3, and therefore, using those reactance components to control the power factor does not affect the control of the power magnitude. Therefore, X3 may not be essential only for controlling the magnitude of the output power. In certain applications or 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 without X3, X3 may be omitted as shown in FIG. 7. In those applications or examples, only the power magnitude would be controlled.

[0085] 6. Fluctuation

[0086] The above embodiments have been described using a rectifier to provide a DC load (having DC power requirements). In examples utilizing an AC load (having AC power requirements), a rectifier may not be necessary. As such, these examples may include any of the above embodiments, but do not use a rectifier.

[0087] Although in the above embodiments, the secondary circuit 46 has been described as a receiver circuit for an inductive power transfer system, in some examples, the secondary circuit 46 may be used as an input for any type of power system.

[0088] These embodiments allow for easier control of the primary side. In conventional systems, large changes are typically required by the primary side when the coupling factor k and other influencing factors change. These embodiments allow for control of power requirements on the secondary side, allowing for fewer (and sometimes no) changes on the primary side.

[0089] Terms and Definitions

[0090] The phrases "computer-readable medium" or "machine-readable medium" as used in this specification and claims should be interpreted to include a single medium or multiple media, unless the context indicates otherwise. Examples of multiple media include centralized or distributed databases and / or associated caches, which store one or more sets of computer-executable instructions. The phrases "computer-readable medium" or "machine-readable medium" should also be interpreted to include any medium capable of storing, encoding, or carrying sets of instructions executed by a processor of a computing device and causing the processor to perform one or more of the methodologies described herein. A computer-readable medium can also store, encode, or carry data structures used by or associated with those sets of instructions. The phrases "computer-readable medium" and "machine-readable medium" include, but are not limited to, fixed storage devices, solid-state memory, optical media or optical storage devices, magnetic media, and / or various other media capable of storing, containing, or carrying instructions and / or data. A "computer-readable medium" or "machine-readable medium" may also be a non-transitory medium.

[0091] The word "comprising" as used in this specification and the claims means "consisting at least in part of" or "including, but not limited to," and is thereby to be interpreted in an inclusive sense as opposed to an exclusive or exhaustive sense thereafter. When interpreting each statement in this specification and the claims that includes the word "comprising," there may also be other features or features following the word "comprising." Related words such as "comprise" and "comprises" are to be interpreted in a similar manner.

[0092] Reference to a numerical range disclosed in this specification (e.g., 1 to 10, etc.) is also intended to encompass reference 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, etc.), and to encompass reference to any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7, etc.), and accordingly, all subranges of all ranges explicitly disclosed in this specification are hereby expressly disclosed. They are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the minimum and maximum values ​​recited should be considered to be expressly disclosed in this application in the same manner.

[0093] The term "and / or" means "and," "or," or both.

[0094] When "(s)" is used following a noun, it refers to the plural and / or singular of that noun.

[0095] Conditional language such as "can," "could," "potential," "may," and the like, unless specifically stated otherwise or understood in the context in which it is used, is generally intended to indicate that certain embodiments include certain features, elements, and / or steps, while other embodiments do not. As such, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required by one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps are included or performed in any particular embodiment, with or without user input or prompting.

[0096] As used herein, terms of degree such as "approximately," "about," "generally," and "substantially" further describe a value, amount, or characteristic that approximates a stated value, amount, or characteristic that performs a desired function or achieves a desired result. For example, the terms "approximately," "about," "generally," and "substantially" may refer to an amount that is within a range of less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount.

[0097] Where this specification refers to patent specifications, other external documents, or other sources of information, such references are generally intended to provide a context for discussing features of the present invention. Unless otherwise expressly stated, a reference to such external documents should not be construed as an admission that such documents or such sources are prior art in any jurisdiction or form part of the common general knowledge in the art of the present invention.

[0098] In the above description, specific details are provided to provide a thorough understanding of several embodiments. However, those skilled in the art will understand that the 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 the embodiments with unnecessary detail. In other instances, well-known modules, structures, and techniques may not be shown in detail so as not to obscure the embodiments.

[0099] It should also be noted that embodiments may be described as a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. While a flowchart may describe operations as a sequential process, many of the operations may be performed in parallel or simultaneously. In addition, the order of operations may be rearranged. A process terminates when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a 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.

[0100] Aspects of the systems and methods described above may be operable on any type of general-purpose computer system or computing device, including, but not limited to, a desktop, laptop, notebook, tablet, smart television, game console, or mobile device. 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 smart watches and head-mounted devices, e-readers, and reading devices capable of reading electronic content, and / or any other type of mobile device typically carried by an individual and / or having some form of communication capability (e.g., radio, infrared, short-range radio, cellular, etc.).

[0101] Aspects of the systems and methods described above may be operable or implementable by any type of purpose-built or specialized computer, or any machine, computer, server, or electronic device having a microprocessor, processor, microcontroller, programmable controller, or the like, or a cloud-based platform, or other network of processors and / or servers, whether local or remote, or any combination of such devices.

[0102] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof. When implemented by software, firmware, middleware, or microcode, program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a storage medium or other storage device. A processor may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted by any suitable means, including memory sharing, message passing, token passing, network transmission, etc.

[0103] In the above description, a storage medium may 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- or computer-readable media for storing information.

[0104] The various illustrative logic blocks, modules, circuits, elements, and / or components described in connection with the examples disclosed herein may be implemented or performed by 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 component, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, circuit, and / or state machine. A processor may also be implemented as a combination of computing components, such as, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or other such configuration.

[0105] The methods or algorithms described in connection with the examples disclosed herein may be embodied directly in hardware, in software modules executable by a processor, or in a combination of both, in the form of processing units, programming instructions, or other instructions, whether contained within a single device or distributed across multiple devices. A software module may 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 may be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor.

[0106] One or more of the components and functions illustrated in the figures may be rearranged and / or combined into a single component or embodied in multiple components without departing from the scope of the disclosure. Also, additional elements or components may be added without departing from the scope of the disclosure. Additionally, features described in this specification may be implemented by software, hardware, business methods, and / or combinations thereof.

[0107] In various aspects, embodiments of the present disclosure may be embodied as a computer-implemented process, a machine (such as, for example, an electronic device, or a general-purpose computer, or other device that provides a platform on which a computer program can run), a process performed by such a machine, or an article of manufacture. Such articles of manufacture may include computer program products or digital information products, including computer program instructions or computer-readable data stored on a computer-readable storage medium, and processes and machines for making and using such products.

[0108] While this disclosure has been described in connection with specific embodiments and examples, those skilled in the art will recognize that the disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and / or applications, and obvious modifications and equivalents thereof. Additionally, while several variations of the embodiments of the present disclosure have been shown and described in detail, other modifications within the scope of this disclosure will be readily apparent to those skilled in the art. It is also contemplated that various combinations or subcombinations of specific features and aspects of the embodiments fall within the scope of the present disclosure. For example, features described above in connection with one embodiment may also be used with different embodiments described herein, and such combinations would still fall within the scope of the present disclosure. It should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another to form varying forms of the embodiments of the present disclosure. Thus, it is not intended that the scope of the disclosure herein be limited by the specific embodiments described above. Thus, unless otherwise specified or clearly contradicted, each embodiment of this disclosure may include, in addition to its essential features described herein, one or more of the features described herein from each of the other embodiments of the invention disclosed herein.

[0109] This disclosure may also be considered broadly to consist of the parts, elements, and features referred to or shown in this disclosure, and any or all combinations of any two or more parts, elements, or features, individually or collectively, and where a specific integer having a known equivalent in the art to which this disclosure pertains is referred to in this specification, such known equivalent is considered to be incorporated into this specification as if individually set forth.

[0110] It should be understood that features, materials, properties, or groups described in connection with a particular aspect, embodiment, or example are applicable to any other aspect, embodiment, or example described in this section or elsewhere in this specification, unless inconsistent therewith. All features disclosed in this specification (including the accompanying claims, abstract, and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of the features and / or steps are mutually exclusive. Protection is not limited to the details of the embodiments described above. Protection extends to any novel feature or any novel combination of features disclosed in this specification (including the accompanying claims, abstract, and drawings), or to any novel feature or any novel combination of methods or processes so disclosed.

[0111] Furthermore, certain features described in this disclosure 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 in multiple implementations separately or in any suitable subcombination. Furthermore, although features may be described above as acting in a particular combination, one or more features of a claimed combination may, in some cases, be deleted from that combination, and the combination may be claimed as a subcombination or a variation of that subcombination.

[0112] Furthermore, while operations may be shown in the figures or described herein in a particular order, such operations need not be performed in the particular order shown or in sequential order to achieve desirable results, nor need all of the operations be performed. Other operations not shown 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 a described operation. Furthermore, operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some of the embodiments, the actual steps performed in the illustrated and / or disclosed process may differ from those shown in the figures. Depending on the embodiment, some of the steps described above may be eliminated, and other steps may be added. Furthermore, the features and attributes of the specific embodiments disclosed above may be combined in various ways to form additional embodiments, all of which are within the scope of the present disclosure. It should also be understood that the separation of various system components in the implementations described above should not be understood to require such separation in all implementations, and that the components and systems described may generally be integrated together into a single product or packaged into multiple products.

[0113] For purposes of this disclosure, certain aspects, advantages, and novel features have been described in this specification. Not all such advantages may necessarily be achieved in accordance with any particular embodiment. Thus, for example, one skilled in the art will understand that the present disclosure may be embodied or performed to achieve one advantage or group of advantages taught in this specification, but not necessarily achieve other advantages that may be taught or suggested in this specification.

[0114] The scope of the present disclosure is not intended to be limited by the specific disclosure of embodiments in this section or elsewhere in this specification, but may be defined by the claims presented in this section or elsewhere in this specification, or claims presented in the future. Claim language should be interpreted broadly based on the language used in the claims, and not limited to the examples described in this specification or during the prosecution process of the application, which examples should be construed as non-exclusive.

Claims

1. 1. An inductive power transfer receiver, comprising:

1. An inductive power input circuit, the inductive power input circuit comprising: a tuning circuit having a receiver coil; a power control circuit for controlling the output power; an inductive power input circuit; a controller 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 delivered to a load; Inductive power transfer receiver.

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

3. 3. The inductive power transfer receiver of claim 2, wherein the power control circuit includes at least a first reactive component in parallel with the receiver coil to control the magnitude of the power.

4. 3. The inductive power transfer receiver of claim 2, wherein the power control circuit includes at least a first series reactive component and at least a second series reactive component in parallel with the receiver coil to control the magnitude of the power and / or the power factor.

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

6. 6. An inductive power transfer receiver as claimed in any preceding claim, wherein the power control circuit forms part of the tuning circuit.

7. 7. An inductive power transfer receiver as claimed in 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 between the first tuning sub-circuit and the second tuning sub-circuit.

8. 1. 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; the variable reactance component can be varied to control the output power delivered to a load; Inductive power transfer receiver.

9. 1. An inductive power transfer receiver, comprising:

1. An inductive power input circuit, the inductive power input circuit comprising: a first tuned circuit having a receiver coil; a second tuning circuit coupled to a load or to a rectifier coupled to a load; a power control circuit for controlling an output power coupled between the first tuning circuit and the second tuning circuit; an inductive power input circuit; a controller configured to control the power control circuit; The power control circuit includes: at least a first variable reactance component and a second variable reactance component coupled between the first tuning circuit and the second tuning circuit; at least one third variable reactance component between the first variable reactance component and the second variable reactance component, the third variable reactance component being variable to control the output power delivered to the load, the first variable reactance component and the second variable reactance component being coupled to the second tuned circuit; Inductive power transfer receiver.

10. 1. An inductive power transfer receiver, comprising:

1. An inductive power input circuit, the inductive power input circuit comprising: a first tuned circuit having a receiver coil; a second tuning circuit coupled to the first tuning circuit; a load or a rectifier coupled to the load; a power control circuit for controlling an output power coupled between the first tuning circuit and the second tuning circuit; an inductive power input circuit; a controller configured to control the power control circuit; the power control circuit includes at least one variable reactance component located across a coupling between the first tuned circuit and the second tuned circuit and that can be varied to control the output power delivered to the load; Inductive power transfer receiver.

11. An inductive power transfer system comprising an inductive power transfer transmitter and an inductive power transfer receiver according to any one of claims 1 to 10.

12. 12. An inductive power transfer receiver or system according to any preceding claim, further comprising a rectifier for providing DC output power to a load.

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