HK1196475B - Wireless energy transfer for implantable devices - Google Patents

Description

Wireless energy transfer for implantable devices

Cross Reference to Related Applications

This application claims priority from the following U.S. patent applications, each of which is hereby incorporated by reference in its entirety: U.S.13/154,131 filed 6/2011; U.S.13/222,915 filed on 8/31/2011; and U.S.13/232,868 filed on 9/14/2011.

The following U.S. patent applications are also incorporated by reference in their entirety: U.S. patent application No.12/789,611 filed on 28/5/2010; U.S. patent application No.12/770,137 filed on 29/4/2010; U.S. provisional application No.61/173,747 filed on 29/4/2009; U.S. application No.12/767,633 filed on 26/4/2010; U.S. provisional application No.61/172,633 filed on 24/4/2009; U.S. application No.12/759,047 filed on 13/4/2010; U.S. application No.12/757,716 filed on 9/4/2010; U.S. application No.12/749,571 filed 3/30/2010; U.S. application No.12/639,489 filed on 12, 16, 2009; U.S. application No.12/647,705 filed on 12/28/2009; and U.S. application No.12/567,716 filed on 9, 25, 2009; U.S. application No.61/100,721 filed on 27/9/2008; U.S. application No.61/108,743 filed on 27/10/2008; U.S. application No.61/147,386 filed on 26.1.2009; U.S. application No.61/152,086 filed on 12.2.2009; U.S. application No.61/178,508 filed on 5/15/2009; U.S. application No.61/182,768 filed on 6/1/2009; U.S. application No.61/121,159 filed on 9.12.2008; U.S. application No.61/142,977 filed on 7/1/2009; U.S. application No.61/142,885 filed on 6.1.2009; U.S. application No.61/142,796 filed on 6.1.2009; U.S. application No.61/142,889 filed on 6.1.2009; U.S. application No.61/142,880 filed on 6.1.2009; U.S. application No.61/142,818 filed on 6.1.2009; U.S. application No.61/142,887 filed on 6.1.2009; U.S. application No.61/156,764 filed on 3/2/2009; U.S. application No.61/143,058 filed on 7/1/2009; U.S. application No.61/163,695 filed on 3/26/2009; U.S. application No.61/172,633 filed on 24/4/2009; U.S. application No.61/169,240 filed on 14/4/2009; U.S. application No.61/173,747 filed on 29/4/2009; U.S. application No.12/721,118 filed on 10/3/2010; U.S. application No.12/705,582 filed on 13/2/2010; U.S. provisional application No.61/152,390 filed on day 2, 13, 2009; U.S. provisional application No.61/351,492 filed on 6/4/2010; and U.S. provisional application No.61/326,051 filed on 20/4/2010.

Technical Field

The present disclosure relates to wireless energy transmission, methods, systems and apparatus for enabling such transmission, and applications.

Background

Energy or power may be wirelessly transmitted using various techniques as disclosed in commonly owned U.S. patent APPLICATION No.12/789,611, entitled "RESONATOR ARRAYS FOR WIRELESS ENERGY TRANSFER," published as U.S. patent publication No. 2010/0237709 at 23/2010 and U.S. patent APPLICATION No.12/722,050, entitled "WIRELESSENERGY TRANSFER FOR regenerative APPLICATION," published as U.S. patent publication No. 2010/0181843 at 22/2010, the contents of which are incorporated in their entirety as if fully set forth herein. Prior art wireless energy transfer systems are limited by various factors including concerns over user safety, low energy transfer efficiency, and limited physical proximity/alignment tolerances to the energy supply and absorbing components.

Implantable devices, such as Mechanical Circulatory Support (MCS) devices, Ventricular Assist Devices (VADs), implantable cardioverter-defibrillators (ICDs), etc., may require an external energy source for operation over extended periods of time. In some patients and situations, implantable devices require constant or near constant operation and have considerable power requirements requiring connection to an external power source, requiring percutaneous cables or cables that pass through the patient's skin to an external power source, increasing the likelihood of infection and reducing patient comfort.

There is therefore a need for methods and designs for delivering energy to an implantable device without the need for direct wire connections.

Disclosure of Invention

In various embodiments, various systems and processes provide wireless energy transfer using coupled resonators. In some embodiments, the resonator structure may require or benefit from thermal management of the components of the resonator. The resonator components may require cooling to prevent their temperature from exceeding a critical temperature. The features of such embodiments are generic and applicable to a wide range of resonators, regardless of the specific examples discussed herein.

In an embodiment, the magnetic resonator may include some combination of inductors and capacitors. Additional circuit elements (e.g., capacitors, inductors, resistors, switches, etc.) may be interposed between the magnetic resonator and the power source and/or between the magnetic resonator and the power load. In this disclosure, the conductive coil of the high Q inductive loop including the resonator may also be referred to as an inductor and/or an inductive load. An inductive load may also be referred to as an inductor when it is wirelessly coupled (through mutual inductance) to other systems or foreign objects. In this disclosure, circuit elements other than an inductive load may be referred to as part of an impedance matching network or IMN. It should be understood that all, some, or none of the elements referred to as part of the impedance matching network may be part of the magnetic resonator. Which elements are part of the resonator and which elements are separate from the resonator will depend on the particular magnetic resonator and wireless energy transfer system design.

In embodiments, the wireless energy transfer described herein can be used to deliver power to an implantable device without the need for percutaneous wiring. In embodiments, wireless power transfer may be used to periodically or continuously power or recharge an implanted rechargeable battery, supercapacitor, or other energy storage component.

In embodiments, the wireless energy transfer described herein uses repeater resonators that may be internal or external to the patient to improve the range and allowable bias of the source and device resonators.

In embodiments, the source and device resonators may control the distribution of heat and energy dissipation by tuning the elements of the source and device.

Unless otherwise indicated, the present disclosure may use the terms wireless energy transmission, wireless power transfer, and the like interchangeably. Those skilled in the art will appreciate that various system architectures may be supported by the wide range of wireless system designs and functions described in the present application.

In the wireless energy transfer system described herein, power may be wirelessly exchanged between at least two resonators. The resonator may supply, receive, hold, transmit, and distribute energy. The source of wireless power may be referred to as a source or supplier, while the receiver of wireless power may be referred to as a device, a receiver, and a power load. The resonator may be a source, a device, or both, or may change from one function to another in a controlled manner. Resonators configured to hold or distribute energy without a wired connection to a power supply or power consumption may be referred to as repeaters.

The resonator of the wireless energy transfer system of the present invention is capable of transferring power over a distance greater than the size of the resonator itself. That is, the wireless energy transfer system of the present invention can transfer power over a distance greater than the characteristic dimension of the resonator if the resonator dimension is characterized by a radius of the smallest sphere that can enclose the resonator structure. The system is capable of exchanging energy between resonators, where the resonators have different characteristic sizes, and where the inductive elements of the resonators have different sizes, different shapes, are composed of different materials, and so forth.

The wireless energy transfer system of the present invention can be described as having a coupling region, a powered region or volume, all of which can transfer energy between resonant objects separated from each other by energy, which can have a variable distance from each other, and which can be described as being moveable relative to each other. In some embodiments, the region or volume through which energy may be transmitted is referred to as an active field region or volume. Further, the wireless energy transfer system may include more than two resonators, each of which may be coupled to the power source, the power load, both, or none.

The wirelessly supplied energy may be used to power an electrical or electronic device, recharge a battery, or charge an energy storage unit. Multiple devices may be charged or powered simultaneously, or power delivery to multiple devices may be serialized such that one or more devices receive power for a period of time after which power delivery may be switched to other devices. In various embodiments, multiple devices may share power from one or more sources with one or more other devices simultaneously, or in a time multiplexed manner, or in a frequency multiplexed manner, or in a spatial multiplexed manner, or in an orientation multiplexed manner, or in any combination of time and frequency and spatial and orientation multiplexing. Multiple devices may share power with each other while at least one device is continuously, intermittently, periodically, occasionally or temporarily reconfigured to operate as a wireless power source. One of ordinary skill in the art will appreciate that there are various ways to power and/or charge devices that may be applied to the techniques and applications described herein.

The present disclosure refers to certain individual circuit components and elements such as capacitors, inductors, resistors, diodes, transformers, switches, etc.; these elements as a combination of networks, topologies, circuits, and the like; and objects with intrinsic characteristics, such as "self-resonant" objects with capacitance or inductance distributed throughout the object (or partially distributed as opposed to merely clustered). Those of ordinary skill in the art will appreciate that adjusting and controlling variable components within a circuit or network may adjust the performance of the circuit or network, and that those adjustments are generally described as tuning, adjusting, matching, correcting, etc. Other methods may be used to tune or adjust the operating point of the wireless power transfer system, either alone or in addition to adjusting the tunable components (e.g., inductors and capacitors or a combination of inductors and capacitors). Those skilled in the art will recognize that the particular topologies discussed in this disclosure may be implemented in a variety of other ways.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict with the publications, patent applications, patents, and other references mentioned or incorporated by reference herein, the present specification, including definitions, will control.

Any of the features described above may be used alone or in combination without departing from the scope of the present disclosure. Other features, objects, and advantages of the systems and methods disclosed herein will be apparent from the detailed description and drawings that follow.

Drawings

Fig. 1 is a system block diagram of a wireless energy transfer arrangement.

Fig. 2A-2E are exemplary structures and schematic diagrams of a simple resonator structure.

Fig. 3 is a block diagram of a wireless source with a single-ended amplifier.

Fig. 4 is a block diagram of a wireless source with a differential amplifier.

Fig. 5A and 5B are block diagrams of sensing circuits.

Fig. 6A, 6B, and 6C are block diagrams of wireless sources.

Fig. 7 is a graph showing the effect of duty cycle on the parameters of the amplifier.

Fig. 8 is a simplified circuit diagram of a wireless power supply with a switching amplifier.

Fig. 9 shows a graph of the effect of a change in a parameter of the wireless power supply.

Fig. 10 shows a graph of the effect of a change in a parameter of a wireless power supply.

Fig. 11A, 11B, and 11C are graphs showing the influence of changes in parameters of the wireless power supply.

Fig. 12 shows a graph of the influence of a change in a parameter of the wireless power supply.

Fig. 13 is a simplified circuit diagram of a wireless energy transfer system including a wireless power supply with a switching amplifier and a wireless power device.

Fig. 14 shows a graph of the influence of a change in the parameter of the wireless power supply.

Fig. 15 is a diagram of a resonator showing a possible inhomogeneous magnetic field distribution due to irregular spacing between tiles of magnetic material.

Fig. 16 is a resonator with an arrangement of tiles in a block of magnetic material that can reduce hot spots in the block of magnetic material.

Fig. 17A is a resonator with a block of magnetic material comprising smaller individual tiles, while fig. 17B and 17C are resonators with additional strips of heat conducting material for thermal management.

Fig. 18 is an embodiment of a surgical robot and hospital bed with a wireless energy source and apparatus.

Fig. 19 is an embodiment of a surgical robot and hospital bed with a wireless energy source and apparatus.

Fig. 20A is a medical cart with a wireless energy transfer resonator. Fig. 20B is a computer locomotive with a wireless energy transfer resonator.

Fig. 21A and 21B are block diagrams of wireless power transfer systems of implantable devices.

Fig. 22A, 22B, 22C, and 22D are diagrams depicting source and device configurations of wireless energy transmission of an implantable device.

Detailed Description

As described above, the present disclosure relates to wireless energy transfer using coupled electromagnetic resonators. However, such energy transfer is not limited to electromagnetic resonators, and the wireless energy transfer systems described herein are more general and can be implemented using a wide variety of resonators and resonant objects.

As will be appreciated by those skilled in the art, important considerations for resonator-based power transfer include resonator efficiency and resonator coupling. A broad discussion of such problems (e.g., Coupling Mode Theory (CMT), coupling coefficients and factors, quality factors (also referred to as Q factors), and impedance matching) is provided in, FOR example, U.S. patent APPLICATION 12/789,611, published as US 20100237709 at 23/2010 and entitled "RESONATOR arrys FOR WIRELESS ENERGY TRANSFER," and U.S. patent APPLICATION 12/722,050, published as US20100181843 at 22/2010 and entitled "WIRELESS ENERGY TRANSFER forrrer APPLICATION," which are all incorporated herein by reference as if fully set forth herein.

A resonator may be defined as a resonant structure that can store energy in at least two different forms and where the stored energy oscillates between the two forms. The resonant structure will have a specific mode of oscillation with a resonant (modal) frequency f and a resonant (modal) field. The angular resonance frequency ω may be defined as ω =2 π f, the resonance period T may be defined as T =1/f =2 π/ω, and the resonance wavelength λ may be defined as λ = c/f, where c is the velocity of the relevant field wave (light for an electromagnetic resonator). Without a loss mechanism, coupling mechanism or external energy supply or consumption mechanism, the total amount W of energy stored by the resonator will remain fixed, but the form of energy will oscillate between the two forms supported by the resonator, one of which will be maximum when the other is minimum, and vice versa.

For example, the resonator may be configured such that the two forms of stored energy are magnetic energy and electrical energy. Furthermore, the resonator may be configured such that the electrical energy stored by the electric field is confined primarily within the structure, while the magnetic energy stored by the magnetic field is primarily in the region surrounding the resonator. In other words, the total electrical and magnetic energy will be equal, but their positioning (localization) will be different. With such a structure, the exchange of energy between the at least two structures may be transferred by the resonant magnetic near fields of the at least two resonators. These types of resonators may be referred to as magnetic resonators.

An important parameter of a resonator used in a wireless power transfer system is the quality factor or Q-factor or Q of the resonator, which is characterized by energy attenuation and is inversely proportional to the energy loss of the resonator. It may be defined as Q = ω W/P, where P is the time-averaged power lost in steady state. That isThat is, resonators with high Q have relatively low intrinsic losses and can store energy over a relatively long period of time. Since the resonator loses energy at its intrinsic decay rate 2, its Q (also referred to as its intrinsic Q) is given by Q = ω/2. The quality factor also represents the number of oscillation periods T that consider the energy in the resonator as attenuated by e^-2πMultiples of (a). Note that the quality factor or intrinsic quality factor or Q of the resonator is due to the intrinsic loss mechanism only. The Q of a resonator connected or coupled to the power generator g or load l may be referred to as the "loaded quality factor" or "loaded Q". The Q of a resonator in the absence of a foreign object intended to be part of the energy transfer system may be referred to as a "perturbation quality factor" or "perturbation Q".

Resonators coupled through any part of the resonator's near field may interact and exchange energy. The efficiency of this energy transfer can be significantly improved if the resonators are operated at substantially the same resonance frequency. By way of example, and not limitation, imagine having Q_sAnd a source resonator having Q_dThe device resonator of (1). High Q wireless energy transfer systems may utilize high Q resonators. The Q of each resonator may be high. Geometric averaging of resonator QMay also or alternatively be high.

The coupling factor k is a number between 0 ≦ k ≦ 1, and it may be independent of (or nearly independent of) the resonant frequencies of the source and device resonators (when those are placed at sub-wavelength distances). Instead, the coupling factor k may be determined primarily by the relative geometry and distance between the source and device resonators, with the laws of physical attenuation of the fields that convey their coupling being taken into account. Coupling coefficient for use in CMTMay be a strong function of the resonant frequency as well as other properties of the resonator structure. Application to wireless energy transfer in the near field using resonatorsIn use, it is desirable to have a resonator size that is much smaller than the resonator wavelength, so that the power lost through radiation is reduced. In some embodiments, the high Q resonator is a sub-wavelength structure. In some electromagnetic embodiments, the high Q resonator structure is designed to have a resonant frequency above 100 kHz. In other embodiments, the resonant frequency may be less than 1 GHz.

In an exemplary embodiment, the power radiated into the far field by these sub-wavelength resonators may be further reduced by lowering the resonant frequency of the resonators and the operating frequency of the system. In other embodiments, far-field radiation may be reduced by arranging for the far-fields of two or more resonators to destructively interfere in the far-fields.

In a wireless energy transfer system, the resonator may be used as a wireless energy source, a wireless energy capture device, a repeater, or a combination thereof. In embodiments, the resonator may alternate between transmitting energy, receiving energy, or transferring energy. In a wireless energy transfer system, one or more magnetic resonators may be coupled to an energy source and energized to generate an oscillating magnetic near field. Other resonators within the oscillating magnetic near-field can capture these fields and convert the energy into electrical energy that can be used to power or charge a load, thereby enabling wireless transfer of useful energy.

So-called "useful" energy in a useful energy exchange is energy or power that must be delivered to a device in order to power or charge it at an acceptable rate. The transmission efficiency corresponding to the useful energy exchange may be system or application dependent. For example, high power vehicle charging applications that transmit several kilowatts of power may need to be at least 80% efficient in order to supply a useful amount of power, achieve a useful exchange of energy sufficient to recharge the vehicle battery, without significantly heating the various components of the transmission system. In some consumer electronics applications, a useful energy exchange may include any energy transfer efficiency greater than 10%, or any other amount acceptable to keep a rechargeable battery "full" and running for a long period of time. In implantable medical device applications, a useful energy exchange may be any exchange that does not harm the patient but extends the life of the battery or wakes up the sensor or monitor or stimulator. In such applications, 100mW or less of power may be useful. In distributed sensing applications, power transmission of microwatts may be useful, and transmission efficiencies may be well below 1%.

Useful energy exchange for wireless energy transfer in powering or recharging applications may be efficient, highly efficient, or sufficiently efficient, so long as the wasted energy level, heat dissipation, and associated field strength are within acceptable limits and appropriately coordinated with relevant factors (e.g., cost, weight, size, etc.).

The resonator may be referred to as a source resonator, a device resonator, a first resonator, a second resonator, a repeater resonator, etc. Embodiments may include three (3) or more resonators. For example, a single source resonator may transfer energy to multiple device resonators or multiple devices. Energy may be transferred from a first device to a second device, and then from the second device to a third device, and so on. Multiple sources may transfer energy to a single device or to multiple devices connected to a single device resonator or to multiple devices connected to multiple device resonators. The resonators may alternately or simultaneously function as sources, devices, and/or they may be used to transfer power from a source at one location to a device at another location. The intermediate electromagnetic resonator may be used to extend the range of the wireless energy transfer system and/or to create a region of concentrated magnetic near-field. Multiple resonators may be daisy chained together, exchanging energy over extended distances and with various sources and devices. For example, a source resonator may transfer power to a device resonator via several repeater resonators. Energy from the source may be transferred to a first repeater resonator, the first repeater resonator may transfer power to a second repeater resonator, and the second repeater resonator may transfer power to a third repeater resonator, and so on until the last repeater resonator transfers its energy to the device resonator. In this aspect, the range or distance of wireless energy transfer may be extended and/or adjusted by adding repeater resonators. The high power level may be distributed among multiple sources, transmitted to multiple devices and recombined at a remote location.

The resonator may be designed using a coupling mode theoretical model, a circuit model, an electromagnetic field model, and the like. The resonator may be designed with tunable feature sizes. The resonators may be designed to handle different power levels. In an exemplary embodiment, a high power resonator may require larger conductors and higher current or voltage rated components than a lower power resonator.

Fig. 1 shows a diagram of an exemplary configuration and arrangement of a wireless energy transfer system. The wireless energy transfer system may include at least one source resonator (R1) 104 (optionally R6, 112) coupled to an energy source 102 and optionally to a sensor and control unit 108. The energy source may be any type of source of energy that can be converted into electrical energy that can be used to drive the source resonator 104. The energy source may be a battery, a solar panel, an electric mains, a wind or water turbine, an electromagnetic resonator, a generator, etc. The electrical energy used to drive the electromagnetic resonator is converted by the resonator into an oscillating magnetic field. The oscillating magnetic field may be captured by other resonators, which may be device resonators (R2) 106, (R3) 116 optionally coupled to energy consumers 110. The oscillating field may optionally be coupled to a repeater resonator (R4, R5) configured to expand or adjust the wireless energy transfer region. The device resonator may capture magnetic fields in the vicinity of the source resonator, repeater resonator, and other device resonators and convert them into electrical energy that may be used by the energy consumer. Energy consumer 110 may be an electrical, electronic, mechanical, or chemical device configured to receive electrical energy, or the like. The repeater resonator may capture the magnetic field in the vicinity of the source, device, and repeater resonator and continue to transfer energy to other resonators.

The wireless energy transfer system may include a single source resonator 104 coupled to the energy source 102 and a single device resonator 106 coupled to the energy consumer 110. In embodiments, a wireless energy transfer system may include a plurality of source resonators coupled to one or more energy sources, and may include a plurality of device resonators coupled to one or more energy consumers.

In an embodiment, energy may be transferred directly between the source resonator 104 and the device resonator 106. In other embodiments, energy may be transferred from one or more source resonators 104, 112 to one or more device resonators 106, 116 via any number of intermediate resonators, which may be device resonators, source resonators, repeater resonators, or the like. Energy may be transferred via a network or arrangement of resonators 114 that may include sub-networks 118, 120, the sub-networks 118, 120 being arranged in any combined topology (e.g., token ring, mesh, ad hoc, etc.).

In an embodiment, the wireless energy transfer system may include a centralized sensing and control system 108. In embodiments, parameters of the resonator, energy source, energy consumer, network topology, operating parameters, etc. may be monitored and adjusted in accordance with the control processor to meet specific operating parameters of the system. The central control processor may adjust parameters of the individual components of the system to optimize global energy transfer efficiency, optimize the amount of power transferred, and the like. Other embodiments may be designed with a substantially distributed sensing and control system. Sensing and control may be incorporated into each resonator or group of resonators, energy sources, energy consumers, etc., and may be configured to adjust parameters of individual components in the group to maximize the power transmitted, maximize the efficiency of energy transfer in the group, etc.

In embodiments, components of a wireless energy transfer system may have wireless or wired data communication links to other components (e.g., devices, sources, repeaters, power sources, resonators, etc.) and may send or receive data that may be used to implement distributed or centralized sensing and control. The wireless communication channel may be separate from the wireless energy transmission channel, or it may be the same. In one embodiment, the resonators used for energy exchange may also be used to exchange information. In some cases, information may be exchanged by modulating components in the source or device circuitry and sensing the change using port parameters or other monitoring devices. The resonators may signal each other by tuning, changing, altering, dithering, etc. the resonator parameters (e.g., the impedance of the resonator), which may affect the reflected impedance of other resonators in the system. The systems and methods described herein may enable simultaneous transmission of power and communication signals between resonators in a wireless power transfer system, or it may enable transmission of power and communication signals using the same magnetic field used during wireless energy transfer during different time periods or at different frequencies. In other embodiments, wireless communication may be accomplished using separate wireless communication channels (e.g., WiFi, Bluetooth, infrared, etc.).

In embodiments, the wireless energy transfer system may include multiple resonators, and overall system performance may be improved by control of various elements in the system. For example, a device with lower power requirements may tune its resonant frequency away from the resonant frequency of a high power source that supplies power to the device with higher power requirements. In this way, low and high power devices may be safely operated or charged from a single high power source. Furthermore, multiple devices in the charging region may find their available Power adjusted according to any of various consumption control algorithms, such as First-Come First-Serve (First-Come First-Serve), best effort (BestEffort), Guaranteed Power (guarded Power), etc. The power consumption algorithm may be hierarchical in nature, giving priority to certain users or certain types of devices, or it may support any number of users by equally sharing the power available in the source. Power may be shared through any of the multiplexing techniques described in this disclosure.

In embodiments, electromagnetic resonators may be implemented or realized using a combination of shapes, structures, and configurations. The electromagnetic resonator may comprise an inductive element, a distributed inductance or a combination of inductances with a total inductance L and a capacitive element, a distributed capacitance or a combination of capacitances with a total capacitance C. A minimal circuit model of an electromagnetic resonator including capacitance, inductance, and resistance is shown in fig. 2F. The resonator may include an inductive element 238 and a capacitive element 240. Provided with initial energy (e.g., electric field energy stored in the capacitor 240), the system will oscillate as the capacitor discharges, converting the energy into magnetic field energy stored in the inductor 238, which in turn converts the energy back into electric field energy stored in the capacitor 240. Intrinsic losses in these electromagnetic resonators include losses due to resistance in inductive and capacitive elements and due to radiation losses and are represented by resistor R242 in fig. 2F.

Fig. 2A shows a simplified diagram of an exemplary magnetic resonator structure. The magnetic resonator may comprise a loop of conductors that act as an inductive element 202 and a capacitive element 204 at the end of the conductor loop. The inductor 202 and capacitor 204 of the electromagnetic resonator may be bulk circuit elements, or the inductance and capacitance may be distributed and may result from the manner in which the conductors are formed, shaped, or positioned in the structure.

For example, inductor 202 may be implemented by shaping a conductor to enclose a surface area, as shown in fig. 2A. This type of resonator may be referred to as a capacitively loaded loop inductor. Note that we can use the term "loop" or "coil" to generically indicate a conductive structure (wire, tube, strip, etc.) that surrounds a surface of any shape and size with any number of turns. In fig. 2A, the enclosed surface area is circular, but the surface may be of any of a variety of other shapes and sizes and may be designed to achieve certain system performance specifications. In embodiments, inductance may be implemented using inductor elements, distributed inductance, networks, arrays, series and parallel combinations of inductors and inductances, and so forth. The inductance may be fixed or variable and may be used to vary the impedance matching and resonant frequency operating conditions.

There are various ways to achieve the capacitance required to reach the desired resonant frequency of the resonator structure. The capacitor plates 204 may be formed and utilized as shown in fig. 2A, or capacitance may be distributed or realized between adjacent windings of a multi-turn conductor. Capacitance may be implemented using capacitor elements, distributed capacitance, networks, arrays, series and parallel combinations of capacitance, and the like. The capacitance may be fixed or variable and may be used to vary the impedance matching and resonant frequency operating conditions.

The inductive element used in a magnetic resonator may comprise more than one turn and may spiral inward or outward or upward or downward or in some combination of directions. In general, magnetic resonators can have various shapes, sizes, and number of turns, and they can be composed of various electrically conductive materials. The conductor 210 may be, for example, a wire, Litz wire, tape, tube, trace formed from conductive ink, paint, gel, or the like, or trace formed from a single or multiple traces printed on a circuit board. An exemplary embodiment of a trace pattern on a substrate 208 forming a conductive loop is depicted in fig. 2B.

In embodiments, the inductive element may be formed using magnetic materials having any size, shape thickness, etc., and materials having a wide range of permeability and loss values. These magnetic materials may be solid blocks that may enclose a hollow volume, they may be formed from many smaller pieces of magnetic material laid and/or stacked together, and they may be integrated with conductive sheets and housings made of highly conductive materials. The conductor may be wrapped around the magnetic material to generate a magnetic field. These conductors may be wound around one or more axes of the structure. Multiple conductors may be wrapped around the magnetic material and combined in parallel or series or via switches to form a customized near-field pattern and/or orient the dipole moment of the structure. Examples of resonators comprising magnetic material are depicted in fig. 2C, 2D, 2E. In fig. 2D, the resonator includes a coil of conductor 224 wrapped around a core of magnetic material 222, resulting in a structure having a magnetic dipole moment 228 parallel to the axis of the coil of conductor 224. The resonator may include multiple turns of conductors 216, 212 wound around the magnetic material 214 in orthogonal directions, forming a resonator with magnetic dipole moments 218, 220 that may be oriented in more than one direction (depending on how the conductors are driven) as shown in fig. 2C.

An electromagnetic resonator may have a characteristic frequency, a natural frequency, or a resonant frequency determined by its physical properties.The resonant frequency is the electric field W of the energy stored in the resonator_E（W_E=q²/2C, where q is the charge on the capacitor C) and the magnetic field W_B（W_B=Li²Where i is the current through the inductor L) at which the stored energy oscillates. The frequency at which this energy is exchanged may be referred to as the characteristic frequency, natural frequency or resonant frequency of the resonator, and is given by omega,

the resonance frequency of the resonator can be changed by adjusting the inductance L and/or the capacitance C of the resonator. In one embodiment, the system parameters are dynamically adjustable or tunable to achieve optimal operating conditions as close as possible. However, based on the above discussion, a sufficiently efficient energy exchange can be achieved even if some system parameters are not variable or the components cannot be dynamically adjusted.

In an embodiment, the resonator may comprise an inductive element coupled to more than one capacitor arranged in a network of capacitors and circuit elements. In an embodiment, a coupling network of capacitors and circuit elements may be used to define more than one resonant frequency of the resonator. In embodiments, the resonator may be resonant or partially resonant at more than one frequency.

In an embodiment, the wireless power supply may include at least one resonator coil coupled to a power supply, which may be a switching amplifier, such as a class D amplifier or a class E amplifier, or a combination thereof. In this case, the resonator coil is actually the power load of the power supply. In an embodiment, a wireless power device may include at least one resonator coil coupled to a power load, which may be a switching rectifier, such as a class D rectifier or a class E rectifier, or a combination thereof. In this case, the resonator coil is actually the power supply for the power load, and the impedance of the load is also directly related to the work-drain rate (work-drain rate) of the load from the resonator coil. The efficiency of power transfer between a power supply and a power load may be affected by how closely the output impedance of the power supply is matched to the input impedance of the load. When the input impedance of the load is equal to the complex conjugate of the internal impedance of the power supply, power can be delivered to the load with the maximum possible efficiency. Designing the impedance of a power supply or power load to achieve maximum power transfer efficiency is often referred to as "impedance matching" and may also be referred to as optimizing the ratio of useful power to lost power in the system. Impedance matching may be performed by adding a network or collection of elements (e.g., capacitors, inductors, transformers, switches, resistors, etc.) to form an impedance matching network between the power supply and the power load. In embodiments, mechanical adjustments and variations in component positioning may be used to achieve impedance matching. For varying loads, the impedance matching network may include variable components that are dynamically adjusted to ensure that the impedance at the power supply terminals and the characteristic impedance of the power supply, as viewed toward the load, remain substantially complex conjugates of each other, even in dynamic environments and operating conditions.

In embodiments, impedance matching may be achieved by tuning the duty cycle and/or phase and/or frequency of the drive signal of the power supply, or by adjusting physical components (e.g., capacitors) within the power supply. Such a tuning mechanism may be advantageous because it may allow impedance matching between the power supply and the load without the use of a tunable impedance matching network, or with the use of a simplified tunable impedance matching network (e.g., an impedance matching network with fewer tunable components). In embodiments, tuning the duty cycle and/or frequency and/or phase of a drive signal for a power supply may result in a dynamic impedance matching system with extended tuning range or accuracy, with higher power, voltage, and/or current capability, with faster electronic control, with fewer external components, and/or the like.

In some wireless energy transfer systems, parameters of the resonator (e.g., inductance) may be affected by environmental conditions (e.g., surrounding objects, temperature, orientation, number, and location of other resonators), and so forth. Changes in the resonator's operating parameters may change certain system parameters, such as the efficiency of the transmitted power in the wireless energy transfer. For example, a highly conductive material located near a resonator may shift the resonant frequency of the resonator and detune it from other resonant objects. In some embodiments, a resonator feedback mechanism is used that corrects its frequency by changing a reactive element (e.g., an inductive element or a capacitive element). To achieve acceptable matching conditions, at least some of the system parameters may need to be dynamically adjustable or tunable. All system parameters may be dynamically adjustable or tunable to substantially achieve optimal operating conditions. However, a sufficiently efficient energy exchange can be achieved even if all or some of the system parameters are not variable. In some examples, at least some of the devices may not be dynamically adjusted. In some examples, at least some of the sources may not be dynamically adjusted. In some examples, at least some of the intermediate resonators may not be dynamically adjusted. In some examples, none of the system parameters may be dynamically adjusted.

In some embodiments, variations in parameters of a component may be mitigated by selecting a component having a characteristic that changes in a complementary or opposite manner or direction when subject to differences in operating environments or operating points. In embodiments, the system may be designed with components (e.g., capacitors) having opposing dependencies or parameter fluctuations due to temperature, power level, frequency, etc. In some embodiments, the component values as a function of temperature may be stored in a look-up table in the system microcontroller, and readings from the temperature sensor may be used in a system control feedback loop to adjust other parameters to compensate for temperature-induced component value changes.

In some embodiments, an active tuning circuit including a tunable component may be used to compensate for variations in parameter values of the component. Circuits that monitor the operating environment and operating points of the components and systems may be incorporated into the design. The monitoring circuit may provide the signals necessary to actively compensate for changes in the parameters of the component. For example, the temperature readings may be used to calculate an expected change in capacitance of the system or to indicate a previously measured value of the capacitance of the system, allowing compensation over a range of temperatures by switching into other capacitors or tuning capacitors to maintain a desired capacitance. In an embodiment, the RF amplifier switching waveform may be adjusted to compensate for component values or load variations in the system. In some embodiments, active cooling, heating, active environmental conditioning, and the like may be used to compensate for changes in parameters of the component.

Parameter measurement circuitry may measure or monitor certain power, voltage and current, signals in the system, and a processor or control circuitry may adjust certain settings or operating parameters based on those measurements. In addition, the amplitude and phase of the voltage and current signals and the amplitude of the power signals throughout the system can be accessed to measure or monitor system performance. The measured signals referred to throughout this disclosure may be port parameter signals as well as any combination of voltage signals, current signals, power signals, temperature signals, and the like. These parameters may be measured using analog or digital techniques, they may be sampled and processed, and they may be digitized or converted using several known analog and digital processing techniques. In an embodiment, certain measured quantity preset values are loaded into a system controller or memory location and used in various feedback and control loops. In embodiments, any combination of measured, monitored, and/or preset signals may be used in a feedback circuit or system to control the operation of the resonator and/or system.

The tuning algorithm may be used to adjust the frequency, Q, and/or impedance of the magnetic resonator. The algorithm may take as input a reference signal relating to the degree of deviation from a desired operating point of the system and may output a correction or control signal relating to the deviation which controls a variable or tunable element of the system to bring the system back to one or more desired operating points. The reference signals for the magnetic resonators may be acquired when the resonators exchange power in the wireless power transfer system, or they may be switched out of the circuit during system operation. Corrections to the system may be applied or performed continuously, periodically, upon threshold exceedance, digitally, using analog methods, and the like.

In embodiments, lossy foreign materials and objects may bring about a possible reduction in efficiency by absorbing magnetic and/or electrical energy from the resonators of the wireless power transfer system. Those effects may be mitigated in various embodiments by positioning the resonator to minimize the effect of the lossy foreign material and by placing structural field shaping elements (e.g., conductive structures, plates and sheets, magnetic material structures, plates and sheets, and combinations thereof) to minimize the effect thereof.

One way to reduce the effect of lossy materials on the resonator is to use highly conductive materials, magnetic materials, or a combination thereof to shape the resonator field so that they avoid the lossy objects. In an exemplary embodiment, the layered structure of highly conductive and magnetic materials may adjust, shape, orient, reorient, etc. the electromagnetic field of the resonator such that they avoid lossy objects in their vicinity by deflecting the field. Fig. 2D shows a top view of a resonator with a thin sheet of conductor 226 under the magnetic material, which can be used to tune the field of the resonator so that they avoid lossy objects that may be under the thin sheet of conductor 226. The layer or sheet of good conductor 226 may comprise any highly conductive material, such as copper, silver, aluminum, as may be best suited for a given application. In some embodiments, the layer or sheet of good conductor is thicker than the skin thickness of the conductor at the resonator operating frequency. The conductor foil may preferably be larger than the dimensions of the resonator, extending outside the physical range of the resonator.

In environments and systems where the amount of power transmitted may present a safety hazard to humans or animals that may invade the active field volume, safety measures may be included in the system. In embodiments where power levels require specialized safety measures, the packaging, structure, materials, etc. of the resonator may be designed to provide a separation or "keep-out" region from the conductive loop in the magnetic resonator. To provide further protection, the high Q resonator and power and control circuitry may be located in a housing that confines high voltages or currents within the housing, protecting the resonator and electrical components from weather, moisture, sand, dust and other external elements, as well as impacts, vibrations, scratches, explosions and other types of mechanical shock. Such enclosures require attention to various factors (e.g., heat dissipation) to maintain an acceptable operating temperature range for the electrical components and resonators. In embodiments, the housing may be constructed of non-destructive materials such as composites, plastics, wood, concrete, etc., and may be used to provide a minimum distance from the lossy object to the resonator component. A minimum separation distance from a lossy object or environment that may include metal objects, salt water, oil, etc., may increase the efficiency of wireless energy transfer. In an embodiment, the "keep away" region may be used to increase the perturbation Q of the resonator or system of resonators. In embodiments, the minimum separation distance may provide a more reliable or more constant operating parameter of the resonator.

In embodiments, the resonators and their respective sensors and control circuits may have various levels of integration with other electronics and control systems and subsystems. In some embodiments, the power and control circuitry and the device resonator are completely separate modules or housings with minimal integration into existing systems, providing power output and control and diagnostic interfaces. In some embodiments, the device is configured to house the resonator and circuit components in a cavity inside the housing, or integrated into the housing or casing of the device.

Exemplary resonator Circuit

Fig. 3 and 4 show high-level block diagrams depicting power generation, monitoring and control components of an exemplary source of a wireless energy transfer system. Fig. 3 is a block diagram of a source including a half-bridge switching power amplifier and some associated measurement, tuning and control circuits. Fig. 4 is a block diagram of a source including a full bridge switching power amplifier and some associated measurement, tuning and control circuits.

The half-bridge system topology depicted in fig. 3 may include a processing unit that executes a control algorithm 328. The processing unit executing the control algorithm 328 may be a microcontroller, a dedicated circuit, a field programmable gate array, a processor, a digital signal processor, or the like. The processing unit may be a single device, or it may be a network of devices. The control algorithm may run on any part of the processing unit. Algorithms may be customized for certain applications and may include combinations of analog and digital circuits and signals. The main algorithm can measure and adjust voltage signals and levels, current signals and levels, signal phases, digital count settings, etc.

The system may include an optional source/device and/or source/other resonator communication controller 332 coupled to the wireless communication circuit 312. The optional source/device and/or source/other resonator communication controller 332 may be part of the same processing unit that executes the main control algorithm, it may be a part or circuitry within the microcontroller 302, it may be external to the wireless power transfer module, it may be substantially similar to a communication controller used in wired-or battery-powered applications but configured to include some new or different functionality to enhance or support wireless power transfer.

The system may include a PWM generator 306 coupled to at least two transistor gate drivers 334 and may be controlled by a control algorithm. The two transistor gate drivers 334 may be coupled to two power transistors 336 directly or via a gate drive transformer, the two power transistors 336 driving the source resonator coil 344 through an impedance matching network component 342. The power transistor 336 may be coupled with the adjustable DC power supply 304 and powered using the adjustable DC power supply 304, and the adjustable DC power supply 304 may be controlled by the variable bus voltage Vbus. The Vbus controller may be controlled by a control algorithm 328 and may be part of microcontroller 302 or other integrated circuit or integrated into the micro-two power transistor 336 controller 302 or other integrated circuit. Vbus controller 326 may control the voltage output of adjustable DC power supply 304, and adjustable DC power supply 304 may be used to control the power output of the amplifier and the power delivered to resonator coil 344.

The system may include sensing and measurement circuitry including signal filtering and buffering circuitry 318, 320, which signal filtering and buffering circuitry 318, 320 may shape, modify, filter, process, buffer, etc. the signal, for example, before the signal is input to a processor and/or converter (e.g., analog-to-digital converter (ADC) 314, 316). The processor and converters (e.g., ADCs 314, 316) may be integrated into microcontroller 302, or may be separate circuits that may be coupled to processing core 330. Based on the measured signals, the control algorithm 328 may generate, limit, initiate, end, control, adjust, or modify the operation of any of the PWM generator 306, the communication controller 332, the Vbus control 326, the source impedance matching controller 338, the filter/buffer elements 318, 320, the converters 314, 316, the resonator coil 344, and may be part of or integrated into the microcontroller 302 or a separate circuit. The impedance matching network 342 and the resonator coil 344 may include electrically controllable, variable or tunable components (e.g., capacitors, switches, inductors, etc., as described herein), and these components may have their component values or operating points adjusted according to signals received from the source impedance matching controller 338. The components may be tuned to adjust the operation and characteristics of the resonator, including the power delivered to and by the resonator, the resonant frequency of the resonator, the impedance of the resonator, the Q of the resonator, and any other coupling system, among others. The resonator may be any type or structure of resonator described herein, including a capacitively loaded loop resonator, a planar resonator including magnetic material, or any combination thereof.

The full-bridge system topology depicted in fig. 4 may include a processing unit that executes a master control algorithm 328. The processing unit executing the control algorithm 328 may be a microcontroller, a dedicated circuit, a field programmable gate array, a processor, a digital signal processor, or the like. The system may include a source/device and/or source/other resonator communication controller 332 coupled to the wireless communication circuit 312. The source/device and/or source/other resonator communication controller 332 may be part of the same processing unit that executes the master control algorithm, it may be a part or circuitry within the microcontroller 302, it may be external to the wireless power transfer module, it may be substantially similar to a communication controller used in wired-powered or battery-powered applications but configured to include some new or different functionality to enhance or support wireless power transfer.

The system may include a PWM generator 410 having at least two outputs coupled to at least four transistor gate drivers 334, the transistor gate drivers 334 being controllable by signals generated in a master control algorithm. The four transistor gate driver 334 may be coupled to four power transistors 336 directly or via a gate drive transformer, and the four power transistors 336 may drive the source resonator coil 344 through an impedance matching network component 342. The power transistor 336 may be coupled with the adjustable DC power supply 304 and powered using the adjustable DC power supply 304, and the adjustable DC power supply 304 may be controlled by a variable bus voltage Vbus, which may be controlled by a main control algorithm. Vbus controller 326 may control the voltage output of adjustable DC power supply 304, and adjustable DC power supply 304 may be used to control the power output of the amplifier and the power delivered to resonator coil 344.

The system may include sensing and measurement circuitry including signal filtering and buffering circuitry 318, 320 and differential/single-ended conversion circuitry 402, 404, which signal filtering and buffering circuitry 318, 320 and differential/single-ended conversion circuitry 402, 404 may shape, modify, filter, process, buffer, etc., the signals, for example, before they are input to a processor and/or converter (e.g., analog-to-digital converter (ADC) 314, 316). The processor and/or converter (e.g., ADCs 314, 316) may be integrated into microcontroller 302, or may be a separate circuit that may be coupled to processing core 330. Based on the measured signals, the main control algorithm may generate, limit, initiate, end, control, adjust, or modify the operation of any of the PWM generator 410, the communication controller 332, the Vbus controller 326, the source impedance matching controller 338, the filter/buffer elements 318, 320, the differential/single-ended conversion circuits 402, 404, the converters 314, 316, the resonator coil 344, and may be part of or integrated into the microcontroller 302 or a separate circuit.

The impedance matching network 342 and the resonator coil 344 may include electrically controllable, variable or tunable components (e.g., capacitors, switches, inductors, etc., as described herein), and these components may have their component values or operating points adjusted according to signals received from the source impedance matching controller 338. The components may be tuned to achieve tuning of the operation and characteristics of the resonator, including the power delivered to and by the resonator, the resonant frequency of the resonator, the impedance of the resonator, the Q of the resonator, and any other coupling system, among others. The resonator may be any type or structure of resonator described herein, including a capacitively loaded loop resonator, a planar resonator including magnetic material, or any combination thereof.

The impedance matching network may include fixed value components such as capacitors, inductors, and networks of components as described herein. As described herein, portions A, B and C of the impedance matching network may include inductors, capacitors, transformers, and series and parallel combinations of such components. In some embodiments, portions A, B and C of the impedance matching network may be empty (shorted). In some embodiments, portion B includes a series combination of an inductor and a capacitor, and portion C is empty.

The full-bridge topology can use the same DC bus voltage as an equivalent half-bridge amplifier to allow operation at higher output power levels. The half-bridge exemplary topology of fig. 3 may provide a single-ended drive signal, while the exemplary full-bridge topology of fig. 4 may provide differential drive to the source resonator 308. As discussed herein, the impedance matching topology and components and resonator structure may be different for the two systems.

The exemplary system depicted in fig. 3 and 4 may also include a fault detection circuit 340 that may be used to trigger shutdown of a microcontroller in the source amplifier or may be used to alter or interrupt operation of the amplifier. This protection circuit may include one or more high speed comparators to monitor the amplifier return current, the amplifier bus voltage (Vbus) from the DC power supply 304, the voltage across the source resonator 308 and/or optional tuning plate, or any other voltage or current signal that may cause damage to components in the system or may produce undesirable operating conditions. The preferred embodiments may depend on potentially undesirable modes of operation associated with different applications. In some embodiments, protection circuits may not be implemented or circuits may not be aggregated (populated). In some embodiments, system and component protection may be implemented as part of the main control algorithm as well as other system monitoring and control circuitry. In an embodiment, the dedicated fault circuit 340 may include an output (not shown) coupled to the main control algorithm 328, and the main control algorithm 328 may trigger a system shutdown, a reduction in output power (e.g., a reduction in Vbus), a change to a PWM generator, a change in operating frequency, a change to a tuning element, or any other reasonable action that may be implemented by the control algorithm 328 to adjust operating point modes, improve system performance, and/or provide protection.

As described herein, a source in a wireless power transfer system may use a measurement of the input impedance of the impedance matching network 242 that drives the source resonator coil 344 as an error or control signal for a system control loop that may be part of a master control algorithm. In an exemplary embodiment, changes in any combination of the three parameters may be used to tune the wireless power supply to compensate for changes in environmental conditions, changes in coupling, changes in device power requirements, changes in module, circuit, component, or subsystem performance, increases or decreases in the number of sources, devices, or repeaters in the system, user-initiated changes, and the like. In an exemplary embodiment, changes to the amplifier duty cycle, component values to variable electrical components (e.g., variable capacitors and inductors), and DC bus voltage can be used to change the operating point or operating range of the wireless source and increase some system operating value. The details of the control algorithms used for different applications may vary depending on the desired system performance and behavior.

Impedance measurement circuits such as those described herein and shown in fig. 3 and 4 may be implemented using two-channel simultaneous sampling ADCs, and these ADCs may be integrated into a microcontroller chip or may be part of separate circuits. Simultaneous sampling of the voltage and current signals at the impedance matching network of the source resonator and/or the input of the source resonator may yield phase and amplitude information of the current and voltage signals, and may be processed using known signal processing techniques to yield complex impedance parameters. In some embodiments, it may be sufficient to monitor only the voltage signal or only the current signal.

The impedance measurements described herein may use a direct sampling method, which may be relatively simpler than some other known sampling method. In an embodiment, the measured voltage and current signals may be conditioned, filtered, and scaled by a filtering/buffering circuit before being input to the ADC. In embodiments, the filter/buffer circuit may be adjustable to operate at various signal levels and frequencies, and circuit parameters (e.g., filter shape and width) may be adjusted manually, electronically, automatically in response to control signals, by a master control algorithm, or the like. Exemplary embodiments of the filter/buffer circuit are shown in fig. 3, 4 and 5.

Fig. 5 shows a more detailed view of exemplary circuit components that may be used in the filtering/buffering circuit. In embodiments and depending on the type of ADC used in the system design, the single-ended amplifier topology may reduce the complexity of the analog signal measurement path used to characterize the performance of the system, subsystem, module, and/or component by eliminating the need for hardware to convert from a differential signal format to a single-ended signal format. In other embodiments, a differential signal format may be preferred. The embodiment shown in fig. 5 is exemplary and should not be construed as the only possible way to implement the functionality described herein. Rather, it should be understood that the analog signal path may use components having different input requirements, and thus may have different signal path architectures.

In single-ended and differential amplifier topologies, the input current to the impedance matching network 342 driving the resonator coil 344 may be obtained by measuring the voltage across the capacitor 324 or via some type of current sensor. For the exemplary single-ended amplifier topology in fig. 3, current may be sensed on the ground return path from the impedance matching network 342. For the exemplary differential power amplifier depicted in fig. 4, the input current of the impedance matching network 342 driving the resonator coil 344 may be measured using a differential amplifier across the terminals of the capacitor 324 or via some type of current sensor. In the differential topology of fig. 4, the capacitor 324 may be replicated at the negative output terminal of the source power amplifier.

In both topologies, after a single-ended signal representing the input voltage and current of the source resonator and the impedance matching network is obtained, the signal may be filtered (502) to obtain the desired portion of the signal waveform. In an embodiment, the signal may be filtered to obtain a fundamental component of the signal. In embodiments, the type of filtering performed (e.g., low pass, band pass, notch, etc.) and the filter topology used (e.g., (ellipse, Chebyshev, Butterworth, etc.) may depend on the particular requirements of the system. In some embodiments, no filtering will be required.

The voltage and current signals may be amplified by an optional amplifier 504. The gain of the optional amplifier 504 may be fixed or variable. The gain of the amplifier may be controlled manually, electronically, automatically in response to a control signal or the like. The gain of the amplifier may be adjusted in a feedback loop in response to a control algorithm, by a main control algorithm, or the like. In an embodiment, the required performance specifications of the amplifier may depend on the signal strength and the desired measurement accuracy, and may be different for different applications and control algorithms.

The measured analog signals may have a DC offset 506 added to them, which may be needed to bring the signals into the input voltage range of the ADC, which may be 0 to 3.3V for some systems. In some systems, this stage may not be required, depending on the specifications of the particular ADC used.

As described above, the efficiency of power transfer between a power generator and a power load may be affected by how closely the output impedance of the generator matches the input impedance of the load. In the exemplary system shown in fig. 6A, power may be delivered to the load with the greatest possible efficiency when the input impedance of the load 604 is equal to the complex conjugate of the internal impedance of the power generator or power amplifier 602. Designing the generator or load impedance to achieve high and/or maximum power transfer efficiency may be referred to as "impedance matching". Impedance matching may be performed by inserting an appropriate network or collection of elements (e.g., capacitors, resistors, inductors, transformers, switches, etc.) to form an impedance matching network 606 between the power generator 602 and the power load 604 as shown in fig. 6B. In other embodiments, mechanical adjustments and changes in component positioning may be used to achieve impedance matching. As described above for varying loads, the impedance matching network 606 may include variable components that are dynamically adjusted to ensure that the impedance at the generator terminals looking into the load and the characteristic impedance of the generator remain substantially complex conjugates of each other, even in dynamic environments and operating conditions. In embodiments, impedance matching may be achieved by tuning the duty cycle and/or phase and/or frequency of the drive signal of the power generator, or by tuning physical components within the power generator (e.g., a capacitor as shown in fig. 6C). Such an adjustment mechanism may be advantageous because it may allow impedance matching between the power generator 608 and the load without using a tunable impedance matching network or using a simplified tunable impedance matching network 606 (e.g., an impedance matching network with fewer tunable components). In embodiments, tuning the duty cycle and/or frequency and/or phase of the drive signal of the power generator may result in a dynamic impedance matching system with extended tuning range or accuracy, with higher power, voltage and/or current capability, with faster electronic control, with fewer external components, and the like. The impedance matching methods, architectures, algorithms, protocols, circuits, measurements, controls, etc. described below may be useful in systems where a power generator drives a high Q magnetic resonator and in high Q wireless power transfer systems as described herein. In a wireless power transfer system, the power generator may be a power amplifier driving a resonator, sometimes referred to as a source resonator, which may be a load of the power amplifier. In wireless power applications, it may be preferable to control the impedance match between the power amplifier and the resonator load to control the efficiency of power transfer from the power amplifier to the resonator. Impedance matching is achieved or partially achieved by tuning or adjusting the duty cycle and/or phase and/or frequency of the drive signal of the power amplifier driving the resonator.

Efficiency of switching amplifier

A switching amplifier (e.g., a class D, E, F amplifier, or the like, or any combination thereof) delivers power to a load with maximum efficiency when no power is dissipated across the switching elements of the amplifier. This operating condition can be achieved by designing the system such that the most critical switching operations (i.e. those switching operations most likely to cause switching losses) are completed when both the voltage across the switching element and the current through the switching element are zero. These conditions may be referred to as Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) conditions, respectively. When the amplifier operates at ZVS and ZCS, the voltage across or current through the switching element is zero and thus no power can be dissipated in the switch. Because switching amplifiers can convert DC (or very low frequency AC) power to AC power at a particular frequency or range of frequencies, filters can be introduced before the load to prevent unwanted harmonics that may be generated by the switching process from reaching the load and being dissipated there. In an embodiment, the switching amplifier may be designed to have a non-trivial quality factor (such as Q) when connected to>5) And a specific impedanceThe resonant load of (a) operates at maximum efficiency of power conversion, which results in simultaneous ZVS and ZCS. We will turn Z_o=R_o-jX_oIs defined as the characteristic impedance of the amplifier such that maximum power is achievedThe transfer efficiency is equivalent to impedance matching the resonant load to the characteristic impedance of the amplifier.

In a switching amplifier, the switching frequency f of the switching element_switch(wherein f_switch= ω/2 pi) and the duty cycle dc of the on-switching state duration of the switching element may be the same for all switching elements of the amplifier. In this embodiment we will use the term "class D" to denote class D and class DE amplifiers, i.e. having dc<Switch amplifier of = 50%.

The value of the characteristic impedance of the amplifier may depend on the operating frequency of the switching elements, the amplifier topology and the switching order. In some embodiments, the switching amplifier may be a half-bridge topology, and in some embodiments a full-bridge topology. In some embodiments, the switching amplifier may be class D, and in some embodiments, class E. In any of the above embodiments, assuming that the elements of the bridge are symmetrical, the characteristic impedance of the switching amplifier has the form:

R_o=F_R(dc)/ωC_a，X_o=F_X(dc)/ωC_a， (1)

where dc is the duty cycle of the on-switching state of the switching element, function F_R(dc) and F_X(dc) is plotted in fig. 7 (both for class D and E), ω is the frequency at which the switching element is switched, and C_a=n_aC_switchIn which C is_switchIs the capacitance across each switch, including the transistor output capacitance and also a possible external capacitor placed in parallel with the switch, whereas for a full bridge, n is_aAnd for half bridge = 1. n is_aAnd (2). For class D, analytical expressions can also be written:

F_R(dc)=sin²u/π，F_X(dc) = (u-sinu × cosu)/pi, (2) where u = pi (1-2 × dc), indicating that the characteristic impedance level of the class D amplifier decreases when the duty cycle dc drops to 50%. For class D amplifier operation with dc =50%, only if the switching element has practically no output capacitance (C)_a= 0) and the load is exactly at resonance (X)_o= 0), it is only possible to implement ZVS and ZCS, where R_oAnd may be arbitrary.

Impedance matching network

In application, the drive load may have an impedance that is very different from the characteristic impedance of the external drive circuit to which it is connected. Furthermore, the driving load may not be a resonant network. An Impedance Matching Network (IMN) is a circuit network that can be connected before a load as in fig. 6B in order to adjust the impedance seen at the input of the network consisting of the IMN circuit and the load. The IMN circuit may generally achieve this adjustment by generating a resonance near the drive frequency. Because such an IMN circuit achieves all the conditions (resonance and impedance matching-ZVS and ZCS for a switching amplifier) needed to maximize the power transfer efficiency from the generator to the load, in embodiments, an IMN circuit may be used between the driver circuit and the load.

For the arrangement shown in fig. 6B, let the input impedance of the network consisting of the Impedance Matching Network (IMN) circuit and the load (from now on collectively denoted IMN + load) be Z_l=R_l(ω)+jX_l(ω). The network has a characteristic impedance Z_o=R_o-jX_oThen the impedance matching condition of the external circuit is R_l(ω)=R_o、X_l(ω)=X_o。

Method for tunable impedance matching of variable loads

In embodiments where the load may be variable, impedance matching between the load and an external drive circuit (e.g., a linear or switching power amplifier) may be achieved by using adjustable/tunable components in the IMN circuit that may be adjusted to bring the varying load to a fixed characteristic impedance Z of the external circuit (fig. 6B)_oAnd (6) matching. In order to match the real and imaginary parts of the impedance, two tunable/variable elements in the IMN circuit may be required.

In an embodiment, the load may be inductive (e.g. a resonator coil) with an impedance R + j ω L, so the two tunable elements in the IMN circuit may be two tunable capacitive networks, or one tunable capacitive network and one tunable inductive network, or one tunable capacitive network and one tunable mutual inductive network.

In embodiments where the load may be variable, impedance matching between the load and the driver circuit (e.g., a linear or switching power amplifier) may be achieved by using adjustable/tunable components or parameters in the amplifier circuit that may be adjusted to cause the characteristic impedance Z of the amplifier to be adjusted_oMatching the varying (due to load variations) input impedance of the network consisting of IMN circuitry, which may also be tunable, and the load (IMN + load) (fig. 6C). In order to match the real and imaginary parts of the impedance, a total of two tunable/variable elements or parameters in the amplifier and IMN circuitry may be required. The disclosed impedance matching methods may reduce the required number of tunable/variable elements in the IMN circuitry or even eliminate the requirement for tunable/variable elements in the IMN circuitry altogether. In some examples, one tunable element in the power amplifier and one tunable element in the IMN circuitry may be used. In some examples, two tunable elements in the power amplifier may be used and no tunable elements in the IMN circuitry are used.

In an embodiment, the tunable element or parameter in the power amplifier may be a frequency, amplitude, phase, waveform, duty cycle, etc. of a drive signal applied to a transistor, switch, diode, etc.

In an embodiment, the power amplifier with tunable characteristic impedance may be a class D, E, F tunable switching amplifier or any combination thereof. Combining equations (1) and (2), the impedance matching condition of this network is:

R_l(ω)=F_R(dc)/ωC_a，X_l(ω)=F_X(dc)/ωC_a（3）

at a tunable switching amplifierIn some examples of amplifiers, one tunable element may be a capacitor C_aWhich can be tuned by tuning an external capacitor placed in parallel with the switching element.

In some examples of a tunable switching amplifier, one tunable element may be the duty cycle dc of the on-switching state of the switching elements of the amplifier. Regulating the duty cycle dc via Pulse Width Modulation (PWM) has been used in switching amplifiers to achieve output power control. In this specification we disclose that PWM can also be used to achieve impedance matching, i.e. to satisfy equation (3) and thus maximize amplifier efficiency.

In some examples of tunable switching amplifiers, one tunable element may be a switching frequency, which is also the driving frequency of the IMN + load network and may also be designed to be substantially close to the resonant frequency of the IMN + load network. Tuning the switching frequency may change the characteristic impedance of the amplifier and the impedance of the IMN + load network. The switching frequency of the amplifier may be appropriately tuned along with another tunable parameter such that equation (3) is satisfied.

A benefit of tuning the duty cycle and/or the drive frequency of the amplifier for dynamic impedance matching is that these parameters can be adjusted electronically, quickly and over a wide range. In contrast, tunable capacitors that can tolerate large voltages and have a sufficiently large tunable range and quality factor, for example, may be expensive, slow, or unavailable under the necessary component rules.

Examples of methods for tunable impedance matching of variable loads

A simplified circuit diagram of the circuit-level structure of the class D power amplifier 802, the impedance matching network 804 and the inductive load 806 is shown in fig. 8. The figure shows the basic components of a system with a switching amplifier 804 comprising a power supply 810, a switching element 808 and a capacitor. The impedance matching network 804 includes an inductor and a capacitor, and the load 806 is modeled as an inductor and a resistor.

As shown in fig. 8, an exemplary embodiment of this inventive tuning scheme includes a half bridge class D amplifier operating at a switching frequency f and driving an inductive element R + j ω L via IMN.

In some embodiments, L' may be tunable. L' can be tuned by a variable tap on the inductor or by connecting a tunable capacitor to the inductor in series or in parallel. In some embodiments, C_aMay be tunable. For half-bridge topologies, one or two capacitors C can be changed_switchTo tune C_aSince only the parallel sum of these capacitors is important for the amplifier operation. For a full-bridge topology, one, two, three or all of the capacitors C can be changed_switchTo tune C_aSince only their combination (the series sum of the two parallel sums associated with the two halves of the bridge) is important for the amplifier operation.

In some embodiments of tunable impedance matching, two of the components of the IMN may be tunable. In some embodiments, L' and C₂Can be tuned. Then, fig. 9 shows the values of the two tunable components required to achieve impedance matching as a function of R and L for the variation of the inductive element and for f =250kHz, dc =40%, C_a=640pF and C₁Associated variation of the output power (at a given DC bus voltage) of an amplifier of =10 nF. Because the IMN is always adjusted to a fixed characteristic impedance of the amplifier, the output power is always constant when the inductive element is varied.

In some embodiments of tunable impedance matching, the components in the switching amplifier may also be tunable. In some embodiments, the capacitance C_aTogether with IMN capacitor C₂Together can be tuned. Then, fig. 10 shows the values of the two tunable components required to achieve impedance matching as a function of R and L for the variation of the inductive element, and for f =250kHz, dc =40%, C₁Relative variation in output power (at a given DC bus voltage) of amplifiers of =10nF and ω L' =1000 Ω. As can be inferred from FIG. 10, it is desirable to respond primarily to changes in LTuning C₂And the output power decreases when R increases.

In some embodiments of tunable impedance matching, the duty cycle dc and the IMN capacitor C₂Together can be tuned. Then, fig. 11 shows the values of the two tunable components required to achieve impedance matching as a function of R and L for the variation of the inductive element and C for f =250kHz_a=640pF、C₁Relative variation in output power (at a given DC bus voltage) of amplifiers of =10nF and ω L' =1000 Ω. As can be inferred from FIG. 11, it is desirable to tune C primarily in response to changes in L₂And the output power decreases when R increases.

In some embodiments of tunable impedance matching, the capacitance C_aTogether with the IMN inductor L' can be tuned. Then, fig. 11A shows the values of the two tunable parameters required to achieve impedance matching as a function of R for the variation of the inductive element and for f =250kHz, dc =40%, C₁=10nF and C₂Associated variation of the output power (at a given DC bus voltage) of an amplifier of =7.5 nF. From fig. 11A, it can be inferred that the output power decreases as R increases.

In some embodiments of some tunable impedance matching, the duty cycle dc and the IMN inductor L' together may be tuned. Then, fig. 11B shows the values of the two tunable parameters required to achieve impedance matching as a function of the varying R of the inductive element and C for f =250kHz as a function of the varying R of the inductive element_a=640pF、C₁=10nF and C₂Associated variation of the output power (at a given DC bus voltage) of an amplifier of =7.5 nF. From fig. 11B, it can be inferred that the output power decreases as R increases.

In some embodiments of some tunable impedance matching, only the components in the switching amplifier may be tunable, while there are no tunable components in the IMN. In some embodiments, the duty cycle dc and the capacitance C_aTogether can be tuned. FIG. 11C then shows the two tunable parameters needed to achieve impedance matching as a function of the varying R of the inductive elementSum of values of numbers C for f =250kHz₁=10nF、C₂Relative change in the output power of the amplifier (at a given DC bus voltage) of =7.5nF and ω L' =1000 Ω. As can be inferred from fig. 11C, the output power is a non-monotonic function of R. These embodiments may be capable of achieving dynamic impedance matching when the variation in L (and thus the variation in resonant frequency) is modest.

In some embodiments, also when L varies greatly as explained earlier, dynamic impedance matching with a fixed element inside the IMN may be achieved by changing the drive frequency of the external frequency f (e.g., the switching frequency of the switching amplifier) so that it follows the varying resonant frequency of the resonator. Using the switching frequency f and the switching duty cycle dc as two variable parameters, full impedance matching can be achieved without any variable components when R and L are varied. Then, fig. 12 shows the values of two tunable parameters required to achieve impedance matching as a function of R and L for the variation of the inductive element and for C_a=640pF、C₁=10nF、C₂Relevant variation of the output power (at a given DC bus voltage) of amplifiers of =7.5nF and L' =637 μ H. From fig. 12 it can be concluded that the frequency f needs to be tuned primarily in response to changes in L, as explained earlier.

Tunable impedance matching for systems for wireless power transfer

In wireless power transfer applications, the low loss inductive element may be a coil of a source resonator coupled to one or more device resonators or other resonators (e.g., repeater resonators). The impedance of the inductive element R + j ω L may comprise the reflected impedance of the other resonator on the coil of the source resonator. Variations in R and L of the inductive element may occur due to external disturbances or thermal drift of components in the vicinity of the source resonator and/or other resonators. Variations in R and L of the inductive elements may also occur during normal use of the wireless power transfer system due to relative motion of the device and other resonators with respect to the source. Relative movement of these devices and other resonators relative to the source or relative movement or position of other sources can result in varying coupling (and thus varying reflected impedance) of the device to the source. Furthermore, variations in R and L of the inductive element may also occur during normal use of the wireless power transfer system due to variations within other coupled resonators (e.g., variations in the power consumer of its load). All the methods and embodiments disclosed so far are also applicable in this case in order to achieve a dynamic impedance matching of this inductive element with the external circuit driving it.

To demonstrate the presently disclosed dynamic impedance matching method of a wireless power transfer system, consider a source resonator comprising a low-loss source coil inductively coupled to a device coil of a device resonator driving a resistive load.

In some embodiments, dynamic impedance matching may be implemented at the source circuit. In some embodiments, dynamic impedance matching may also be implemented at the device circuitry. When full impedance matching is achieved (at the source and device), the effective resistance of the source inductive element (i.e., the source coil R)_sResistance plus reflected impedance from the device) is(similarly, the effective resistance of the inductive element of the device isWherein R is_dIs the resistance of the device coil. ) The dynamic change of mutual inductance between the coils due to motion results inIs dynamically changed. Thus, when both the source and the device are dynamically tuned, the change in mutual inductance is seen from the source circuit side as a change in the source inductance element resistance R. Note that in this type of variation, the resonant frequency of the resonator may not change substantially, as L may not change. Thus, all of the methods and examples presented for dynamic impedance matching may be used for the source circuit of a wireless power transfer system.

Note that because the resistance R represents the source coil and device coil-to-source coil reflected impedance, in fig. 9-12, as R increases due to increasing U, the associated wireless power transfer efficiency increases. In some embodiments, approximately constant power may be required at a load driven by the device circuitry. To achieve a constant level of power delivered to the device, the required output power of the source circuit may need to be reduced as U increases. If dynamic impedance matching is achieved by tuning some of the amplifier parameters, the output power of the amplifier may change accordingly. In some embodiments, the automatic change in output power preferably decreases monotonically with R such that it matches a constant device power requirement. In embodiments where the output power level is achieved by adjusting the DC drive voltage of the power generator, using a tunable set of parameters that results in an impedance match of the monotonically decreasing output power vs.r would mean that a constant power may be maintained at the power load in the device, with only a modest adjustment of the DC drive voltage. In embodiments where the "knob" used to adjust the output power level is the duty cycle dc or phase of a component inside the switching amplifier or impedance matching network, using a tunable set of parameters that results in an impedance match of monotonically decreasing output power vs.

In the examples of FIGS. 9-12, if R is_s=0.19 Ω, the range R =0.2-2 Ω approximately corresponds to U_sdAnd (5) = 0.3-10.5. For these values, in fig. 14, we show the output power (normalized to the DC voltage squared) needed to maintain a constant power level at the load with a dashed line when both source and device are dynamically impedance matched. A similar trend between the solid and dashed lines explains why a set of tunable parameters with such a variation in output power may be preferred.

In some embodiments, dynamic impedance matching may be implemented at the source circuit, but impedance matching may not be implemented or may only be partially implemented at the device circuit. The varying reflected impedance from device to source may cause a variation in the effective resistance R and the effective inductance L of the source inductive element when the mutual inductance between the source coil and the device coil varies. The methods proposed so far for dynamic impedance matching are applicable and applicable to tunable source circuits of wireless power transfer systems.

As an example, consider the circuit of fig. 14, where f =250kHz, C_a=640pF、R_s=0.19Ω、L_s=100μH、C_1s=10nF、ωL_s′=1000Ω、R_d=0.3Ω、L_d=40μH、C_1d=87.5nF、C_2d=13nF、ωL_d' =400 omega and Z_l=50 Ω, where s and d denote the source and device resonators, respectively, and the system is in U_sdMatch at = 3. Tuning the duty cycle dc of a switching amplifier and a capacitor C_2sMay be used to dynamically impedance match the source when the non-tunable device is moving relative to the source to change the mutual inductance M between the source and the device. In fig. 14, we show the required values of the tunable parameters together with the output power per DC voltage of the amplifier. The dashed line again indicates the output power of the amplifier to be needed, so that the power at the load is a constant value.

In some embodiments, tuning the drive frequency f of the source drive circuit may still be used to achieve dynamic impedance matching at the source for a system of wireless power transfer between the source and one or more devices. As explained earlier, this method achieves full dynamic impedance matching of the source, even in the presence of the source inductance L_sSo too does there be a change in the source resonant frequency. For efficient power transfer from source to device, the device resonant frequency must be tuned to follow the changes in the matched drive and source resonant frequencies. Tuning device capacitance (e.g., C in the embodiment of FIG. 13) when there is a change in the resonant frequency of the source or device resonator_1dOr C_2d) May be necessary. In fact, in a wireless power transfer system with multiple sources and devices, tuning the drive frequency alleviates the need to tune only one source-object resonant frequency, however, all remaining objects may require a mechanism (e.g., such asA tunable capacitor) to tune its resonant frequency to match the drive frequency.

Resonator thermal management

In wireless energy transfer systems, a portion of the energy lost during the wireless transfer process is dissipated as heat. Energy may be dissipated in the resonator component itself. For example, even high Q conductors and components have some loss or resistance, and these conductors and components may heat up as current and/or electromagnetic fields flow through them. Energy may be dissipated in materials and objects surrounding the resonator. For example, eddy currents dissipated in defective conductors or dielectrics around or near the resonator may heat those objects. In addition to affecting the material properties of those objects, this heat may also be transferred to the resonator component by conduction, radiation or convection processes. Any of these heating effects may affect the resonator Q, impedance, frequency, etc. and thus the performance of the wireless energy transfer system.

In a resonator comprising a block or core of magnetic material, heat may be generated in the magnetic material due to hysteresis losses and resistive losses resulting from induced eddy currents. Both of these effects depend on the magnetic flux density in the material, and both can generate significant amounts of heat, particularly in areas where flux density or eddy currents can be concentrated or localized. In addition to flux density, the frequency of the oscillating magnetic field, the magnetic material composition and losses, and the environment or operating temperature of the magnetic material can all affect how hysteresis and resistive losses heat the material.

In embodiments, the properties of the magnetic material (e.g., type of material, size of mass, etc.) and magnetic field parameters may be selected for particular operating power levels and environments to minimize heating of the magnetic material. In some embodiments, the variations, cracks, or defects in the block of magnetic material may increase the loss and heating of the magnetic material in wireless power transfer applications.

For magnetic blocks that have defects or are composed of smaller sized tiles or sheets of magnetic material arranged in larger cells, the losses in the block may be non-uniform and may be concentrated in areas where there is non-uniformity or relatively narrow gaps between adjacent tiles or sheets of magnetic material. For example, if an irregular gap exists in a block of magnetic material, the effective reluctance of the various magnetic flux paths through the material may be substantially irregular, and the magnetic field may be more concentrated in the portion of the block where the reluctance is lowest. In some cases, the effective magnetoresistance may be lowest where the gap between tiles or sheets is narrowest, or where the density of defects is lowest. Because the magnetic material directs the magnetic field, the magnetic flux density may not be substantially uniform throughout the block, but may be concentrated in areas that provide relatively low reluctance. Irregular concentrations of the magnetic field within the block of magnetic material may not be desirable because they may lead to uneven losses and heat dissipation in the material.

For example, consider a magnetic resonator that includes a conductor 1506 wrapped around a block of magnetic material consisting of two separate tiles 1502, 1504 of magnetic material, the two separate tiles 1502, 1504 combining such that they form a slot 1508 perpendicular to the axis of the loop of the conductor 1506, as depicted in fig. 15. An irregular gap in the seam 1508 between the tiles 1502, 1504 of magnetic material may force the magnetic field 1512 (schematically represented by dashed magnetic field lines) in the resonator to be concentrated in the sub-regions 1510 of the cross-section of the magnetic material. Because the magnetic field will follow a path of least reluctance, a path that includes an air gap between two sheets of magnetic material may produce a path of substantially higher reluctance at the point where the sheets of magnetic material contact or have a smaller air gap than a path that traverses the width of the magnetic material. The magnetic flux density may thus preferentially flow through a relatively small cross-sectional area of the magnetic material, resulting in a high concentration of magnetic flux in this small area 1510.

In many magnetic materials of interest, a less uniform flux density distribution results in higher overall losses. Also, a less uniform flux density distribution may result in material saturation and cause local heating of the area where the magnetic flux is concentrated. Local heating can change the properties of the magnetic material, in some cases exacerbating losses. For example, in the relevant operating states of some materials, hysteresis and resistive losses increase with temperature. If heating the material increases material loss, resulting in more heating, the temperature of the material may continue to increase and even runaway (if no corrective action is taken). In some examples, temperatures may reach 100C or more and may degrade the properties of the magnetic material and the performance of wireless power transfer. In some instances, the magnetic material may be damaged, or surrounding electronic components, packaging, and/or housings may be damaged by additional heat.

In an embodiment, variations or irregularities between tiles or sheets of the block of magnetic material may be minimized by machining, grinding the edges of the tiles or sheets to ensure a tight fit between the tiles or sheets of magnetic material, or the like, providing a substantially more uniform magnetic reluctance across the entire cross-section of the block of magnetic material. In embodiments, the block of magnetic material may require means for providing a compressive force between the tiles to ensure that the tiles are pressed together tightly without gaps. In an embodiment, an adhesive may be used between the tiles to ensure that they remain in intimate contact.

In an embodiment, the irregular spacing of adjacent tiles of magnetic material may be reduced by adding an intentional gap between the adjacent tiles of magnetic material. In embodiments, the intentional gap may be used as a spacer to ensure uniform or regular separation between the tiles or sheets of magnetic material. Intentional gaps of flexible material may also reduce irregularities in spacing due to tile motion or vibration. In an embodiment, an electrical insulator may be utilized to bind, impregnate, coat, etc. the edges of adjacent tiles of magnetic material to prevent eddy currents from flowing through the reduced cross-sectional area of the block, thus reducing eddy current losses in the material. In an embodiment, the splitter may be integrated into the resonator package. The spacers may provide a spacing of 1mm or less.

In an embodiment, the mechanical properties of the spacers between the tiles may be selected so as to improve the tolerance of the overall structure to mechanical effects, such as changes in the size and/or shape of the tiles due to intrinsic effects (e.g., magnetostriction, thermal expansion, etc.) and external shocks and vibrations. For example, the spacers may have a desired amount of mechanical resilience to accommodate expansion and/or contraction of the individual tiles, and may help reduce stress on the tiles when they are subjected to mechanical vibrations, thereby helping to reduce the occurrence of cracks and other defects in the magnetic material.

In an embodiment it may be preferred to arrange the individual tiles comprising blocks of magnetic material to minimize the number of slots or gaps between the tiles perpendicular to the dipole moment of the resonator. In an embodiment, it may be preferred that the tiles of magnetic material are arranged and oriented to minimize the gap between the tiles perpendicular to the axis formed by the turns of the conductor comprising the resonator.

For example, consider the resonator structure depicted in fig. 16. The resonator includes a conductor 1604 wrapped around a block of magnetic material that includes six separate individual tiles 1602 arranged in a 3 by 2 array. The arrangement of tiles results in two tile apertures 1606, 1608 when traversing the block of magnetic material in one direction, and only one tile aperture 1610 when traversing the block of magnetic material in a vertical direction. In an embodiment, it may be preferable to wrap the conductor wire 1604 around the block of magnetic material such that the dipole moment of the resonator is perpendicular to the minimum number of tile slots. The inventors have observed that there is relatively little heating induced around the slots and gaps 1606, 1608 parallel to the dipole moment of the resonator. The slots and gaps that extend perpendicular to the dipole moment of the resonator may also be referred to as critical slots or critical slot regions. It may still be desirable to electrically insulate the gaps (e.g., 1606 and 1608) that extend parallel to the dipole moment of the resonator in order to reduce eddy current losses. Uneven contact between tiles separated by such parallel gaps can cause eddy currents to flow through narrow contact points, resulting in large losses at such points.

In an embodiment, when the magnetic material is heated, sufficient cooling of the critical seam region may be used to tolerate irregularities in the spacing to prevent local degradation of the material properties. Maintaining the temperature of the magnetic material below the critical temperature prevents runaway effects caused by sufficiently high temperatures. Wireless energy transfer performance may be satisfactory with proper cooling of critical seam areas despite additional losses and heating effects due to irregular spacing, cracks or gaps between tiles.

Effective heat dissipation from resonator structures to prevent excessive localized heating of magnetic materials presents several challenges. Metallic materials, which are commonly used for heat dissipation and heat conduction, can interact with the magnetic field used for wireless energy transfer through the resonator and affect the performance of the system. Their location, size, orientation and use should be designed so as not to unduly reduce the perturbation Q of the resonator in the presence of these heat sink materials. Furthermore, due to the relatively poor thermal conductivity of magnetic materials (e.g., ferrite), a relatively large contact area between the heat sink and the magnetic material may need to provide sufficient cooling, which may require a significant amount of lossy material to be placed in close proximity to the magnetic resonator.

In an embodiment, sufficient cooling of the resonator may be achieved using strategic placement of thermally conductive materials with minimal impact on wireless energy transfer performance. In an embodiment, a strip of thermally conductive material may be placed between the loops of conductive wire and in thermal contact with the block of magnetic material.

One exemplary embodiment of a resonator having a strip of thermally conductive material is depicted in fig. 17. Fig. 17A shows a resonator structure with conductive strips, and the resonator structure includes smaller tiles of magnetic material forming gaps or slots. A strip of thermally conductive material 1708 may be placed between the loops of conductor 1702 and in thermal contact with the block 1704 of magnetic material as depicted in fig. 17B and 17C. In order to minimize the influence of the strips on the parameters of the resonator, it may be preferred in some embodiments to arrange the strips parallel to the loops of the conductor or perpendicular to the dipole moment of the resonator. The conductor strip may be placed to cover as many slots or gaps between the tiles as possible, in particular slots between the tiles perpendicular to the dipole moment of the resonator.

In an embodiment, the thermally conductive material may include copper, aluminum, brass, thermal epoxy, paste (paste), pads, etc., and may be any material having a thermal conductivity that is at least the thermal conductivity of the magnetic material in the resonator (-5W/(K-m) for some ferrite materials). In embodiments where the thermally conductive material is also electrically conductive, the material may require a layer or coating of an electrical insulator to prevent shorting and direct electrical contact with the magnetic material or the return path of the resonator's conductor.

In embodiments, strips of thermally conductive material may be used to conduct heat from the resonator structure to a structure or medium that can safely dissipate thermal energy. In embodiments, the heat conducting strip may be connected to a heat sink, e.g. a large plate located above the conductor strip, which may dissipate thermal energy to the environment using passive or forced convection, radiation or conduction. In embodiments, the system may include any number of active cooling systems, which may be external or internal to the resonator structure, which may dissipate thermal energy from the thermal conductive strip and may include liquid cooling systems, forced air systems, and the like. For example, the heat conductive strip may be hollow or include channels for a coolant that may be pumped or forced through to cool the magnetic material. In an embodiment, a field deflector made of good electrical conductors (e.g., copper, silver, aluminum, etc.) may dually serve as a heat sink. Adding thermally and electrically conductive strips to the space between the magnetic material and the field deflector can have a minor effect on the perturbation Q, since the electromagnetic field in this space is generally suppressed by the presence of the field deflector. Such conductive strips may be thermally connected to the magnetic material and the field deflector to make the temperature distribution among the different strips more uniform.

In an embodiment, the heat conductive strips are spaced apart to allow at least one loop of conductor to be wrapped around the magnetic material. In an embodiment, the strip of thermally conductive material may be positioned only at the gaps or slits of the magnetic material. In other embodiments, the strip may be positioned to contact the magnetic material substantially throughout its length. In other embodiments, the strips may be distributed to match the flux density within the magnetic material. The region of magnetic material that may have a higher magnetic flux density under normal operation of the resonator may have a higher density of contacts with the heat conductive strip. In embodiments such as depicted in fig. 17A, the highest magnetic flux density in the magnetic material may be observed toward the center of the block of magnetic material, and a lower density may be toward the ends of the block in the direction of the dipole moment of the resonator.

To show how the use of heat conductive strips helps to reduce the overall temperature in the magnetic material and the temperature at potential hot spots, the inventors performed finite element simulations of a resonator structure similar to that depicted in fig. 17C. A structure was simulated operating at a frequency of 235kHz and comprising a block of 30cm x30cm x5mm measured EPCOS N95 magnetic material excited by 10 turns of litz lines (placed symmetrically 25mm, 40mm, 55mm, 90mm and 105mm from the plane of symmetry of the structure) each carrying a peak current of 40A and thermally connected to a field deflector of 50cm x50cm x4mm by three 3x3/4x 1' hollow square tubes (1/8 "wall thickness) of aluminum (alloy 6063) with their central axes placed-75 mm, 0mm and +75mm from the plane of symmetry of the structure. The perturbation Q due to the field deflector and the hollow tube was found to be 1400 (compare with 1710 for the same structure without the hollow tube). The power dissipated in the barrier and tube was calculated to be 35.6W, while the power dissipated in the magnetic material was 58.3W. Assuming that the structure is cooled by air convection and radiation and an ambient temperature of 24 ℃, the maximum temperature in the structure is 85 ℃ (at a point in the magnetic material approximately midway between the hollow tubes), while the temperature in the portion of the magnetic material in contact with the hollow tubes is approximately 68 ℃. In comparison, the same resonator without the thermally conductive hollow tube dissipates 62.0W in the magnetic material for the same excitation current of 40W peak, and the maximum temperature in the magnetic material was found to be 111 ℃.

The advantages of the conductive strip are even more pronounced if we introduce defects in a part of the magnetic material that is in good thermal contact with the tube. A 10cm long air gap 10 placed 0.5mm at the center of the magnetic material and oriented perpendicular to the dipole moment increases the power dissipated in the magnetic material to 69.9W (an additional 11.6W, relative to the defect-free example discussed above, is highly concentrated near the gap), but the conductive pipe ensures a relatively modest increase in maximum temperature in the magnetic material of only 11c to 96 c. In contrast, the same defect without the conductive tube results in a maximum temperature of 161 ℃ in the vicinity of the defect. Cooling solutions other than convection and radiation (e.g. thermally connecting the conductive pipe body with a large thermal block or actively cooling them may result in even lower operating temperatures for this resonator at the same current level.

In embodiments, the strip of thermally conductive material may be positioned in a region that may have the highest probability of developing cracks that may cause irregular gaps in the magnetic material. Such regions may be areas of high stress or strain on the material or areas with poor support or backup from the packaging of the resonator. Strategically positioned heat conductive strips may ensure that when cracks or irregular gaps occur in the magnetic material, the temperature of the magnetic material will be maintained below its critical temperature. The critical temperature may be defined as the curie temperature of the magnetic material or any temperature at which the properties of the resonator have degraded outside of desired performance parameters.

In an embodiment, the heat dissipation structure may provide mechanical support to the magnetic material. In embodiments, the heat dissipation structure may be designed to have a desired amount of mechanical elasticity (e.g., by thermally connecting the different elements of the structure using epoxy, thermal pads, etc. with appropriate mechanical properties) in order to provide the resonator with a greater amount of tolerance to variations in the intrinsic dimensions of its elements (due to thermal expansion, magnetostriction, etc.) as well as external shocks and vibrations, and to prevent the formation of cracks and other defects.

In embodiments where the resonator comprises orthogonal windings wound around the magnetic material, the strips of conductive material may be adapted to make thermal contact with the magnetic material within the area bounded by the two orthogonal sets of adjacent loops. In an embodiment, the bar may comprise a suitable recess to fit around the conductor of at least one orthogonal winding while making thermal contact with the magnetic material at least one point. In an embodiment, the magnetic material may be in thermal contact with a plurality of thermally conductive blocks placed between adjacent loops. The heat conducting blocks may in turn be thermally connected to each other by good heat conductors and/or heat sinks.

Throughout this description, although the term "strip of thermally conductive material" is used as an exemplary sample of the shape of the material, it will be understood by those skilled in the art that any shape and profile may be substituted without departing from the spirit of the invention. Square, oval, bar, dot, elongated shape, etc. would be within the spirit of the present invention.

Medical and surgical applications

Wireless power transfer may be used in hospital and operating room environments. A large number of electrical and electronic devices are used in hospitals and operating rooms to monitor patients, administer medications, perform medical procedures, maintain administrative and medical records, and the like. Electrical and electronic devices are often moved, repositioned, moved with the patient, or attached to the patient. Frequent movement can cause problems with power delivery to the device. The equipment and electronic equipment that is often moved and repositioned can create power cable hazards and management problems due to the cables becoming tangled, tightened, unplugged (which becomes a tripping hazard, etc.). Devices with battery backup that can operate without a direct electrical connection for a period of time require frequent recharging or plugging in and unplugging from an electrical outlet whenever the device is used or repositioned. Wireless power transfer can be used to eliminate the problems and hazards of traditional wired connections in hospital and operating room environments.

Wireless power transmission may be used to power surgical robots, devices, sensors, and the like. Many medical procedures and surgical procedures utilize robots or robotic devices to perform or assist in a medical procedure or procedure. Wireless power transfer may be used to transfer power to robotic devices, portions of devices, or instruments or tools manipulated by devices, which may reduce potentially dangerous and cumbersome wiring of the system.

One exemplary configuration of a surgical robot utilizing wireless power transmission is shown in fig. 18. The figure depicts a surgical robot 1806 and an operating bed 1804. The surgical robot may be powered wirelessly from a wireless source embedded in a bed, floor, or other structure. The wireless energy transmission may allow the robot to be repositioned without changing the position of the power cable. In some embodiments, the surgical robot may wirelessly receive power for surgery or charge its battery or energy storage system. The received power may be distributed to the system or components such as motors, controllers, etc. via conventional wired methods. The surgical robot may have a device resonator in its base 1816, neck 1802, main structure 1808, etc. for capturing the oscillating magnetic energy generated by the source. In some embodiments, the robot may be powered wirelessly from a source 1814 integrated, attached, or proximate to the surgical bed.

In some embodiments, the source resonator or the device resonator may be mounted on an articulating arm or a movable or configurable extension portion as depicted in fig. 19. The arm or mobile extension 1902 may be configured to reposition a source or device to ensure that a sufficient level of power is delivered to the robot in response to a change in the position of the robot, power requirements, or efficiency of the wireless power transfer. In some embodiments, the movable source or device may be moved manually by an operator, or may be automated or computerized and configured to align or maintain a particular separation range or orientation between the source and the device.

In embodiments, the movable arm or extension may be used in situations or configurations where there may be a positional offset, mismatch, late offset, or height offset between the source and the device. In embodiments, the movable arm that houses or is used to position the source or device resonator may be computer controlled and may automatically position itself for optimal power transfer efficiency. The arm may, for example, move in all directions, scan for the most efficient configuration or position, and may use learning or other algorithms to fine-tune its position and alignment. In embodiments, the controller may use any number of measurements from the sensors, including but not limited to impedance, power, efficiency, voltage, current, quality factor, coupling ratio, coupling coefficient measurements, etc., to attempt to align or find the best or most efficient location.

In other embodiments, the surgical robot may use wireless power transmission to power motors, sensors, tools, circuits, devices, or systems of the robot that are manipulated by the robot or integrated into the robot. For example, many surgical robots may have complex appendages with multiple degrees of freedom of motion. Providing power along or through various joints or moving parts of the appendage may be difficult due to the bulkiness, inflexibility, or unreliability of the electrical wires.

Also, the powering of various tools or instruments necessary for the flow may present reliability and safety issues for the power connections and connectors in the presence of bodily fluids. The surgical robot may utilize one or more source resonators 1802 and one or more device resonators 1810, 1812 located in the attachment or tool to power motors, electronics, or devices to allow movement of the attachment or powering of tools, cameras, etc. that the robot may operate, possibly internal or external to the patient. Power may be transmitted wirelessly without any wires regardless of the engagement or rotation of the appendage and may increase the limit or engagement capability of the appendage. In some embodiments, the source may be integrated into the robot and powered by the robot which may receive its own power wirelessly or from a wired connection. In some embodiments, the source for powering the accessories and tools may be mounted on the operating bed, under the bed, or near the patient.

As will be appreciated by those skilled in the art, the system described and illustrated in the figures is a specific exemplary embodiment, and the system may utilize any of a number of different robotic devices, tools, etc. having a variety of shapes and capabilities. Also, the source may be mounted on any number of objects having various sizes depending on the application and use of the robot. The source may be mounted on an operating room bed or table as shown in fig. 18. In other embodiments, the source may be mounted in a floor, wall, ceiling, other device, or the like.

Wireless power transfer may be used to power or recharge a removable device, such as an IV or drug delivery rack or computer stand. Such stands or gantries are often temporarily repositioned or moved with the patient from one location to another. Electronic devices attached to these racks often have battery backup, allowing them to operate for a period of time without direct electrical connections so that they can be moved or repositioned and maintain their functionality. However, whenever a conventional rack is moved or repositioned, it needs to be unplugged and plugged back into the power outlet for recharging or powering, and the cable must be coiled or uncoiled from the other cable.

Problems with traditional mobile wired drug delivery, patient monitoring, or computer racks can be overcome by integrating a wireless power transfer system into the device. For example, an exemplary embodiment of a drug delivery rack and a computer rack is depicted in fig. 20A and 20B. The device resonators 2008, 2006 and power and control circuitry may be integrated or attached to the chassis or body of a rack or support structure, allowing wireless power transfer from a source resonator mounted in a floor, wall, charging station, or other object. To be charged or powered, the rack 2002 or support 2014 may be located near the source, within a meter of the source, or within a one foot spacing of the source. Racks and electrical devices that enable wireless power transfer do not require plugging or unplugging or cable management. Racks and electrical equipment that enable wireless power transfer may be powered by locating the rack or the electrical equipment within a particular area of a room or in proximity to a source, which may be integrated into floors, carpets, walls, dado panels, other equipment, and the like. In this configuration, for example, a device or rack that can only be used for a short period of time to measure or diagnose a patient may be moved from a charging location and brought anywhere near the patient to make a measurement, and moved back to the charging location, without requiring precise positioning of the device or plugging in or unplugging the device.

In some embodiments, the device that captures wireless energy may require additional electrical and electronic components in addition to the resonator. As described herein, additional AC to DC converters, AC to AC converters, matching networks, active components may be necessary to condition, control, and convert the voltage and current from the resonator to a voltage and current that can be used by the device to be powered. In some devices and embodiments, the voltage and current of the resonator may be used directly without additional conditioning or conversion steps. Surgical tools (e.g., cauterizers, powered scalpels, etc.) use an oscillating high voltage to effectively cut, stimulate, or cauterize tissue. The oscillating voltage on the device resonators can be used directly to power such devices, reducing their size, cost and complexity.

For example, in some embodiments, a surgical tool (e.g., a cautery) may be mounted with a device resonator capable of capturing magnetic energy from one or more source resonators. Depending on the inductance, quality factor, resistance, relative distance to the source resonator, power output of the source resonator, frequency, etc., the parameters of the voltage and current across the device resonator may be sufficient to directly cauterize or cut tissue. A voltage of 30 or more volts having a frequency of 1KHz to over 5MHz can be generated across the device resonator and can be used directly as the output of the surgical tool. In some embodiments, monitoring circuitry (e.g., voltage or current sensing circuitry) may be integrated into the device resonator along with wireless communication capabilities to forward the measured values to the source. The source may monitor the received current and voltage values and adjust its operating parameters to maintain a particular voltage, frequency, or current at the device or adjust the current or voltage in response to operator input.

Wireless power transfer for implantable devices

In an embodiment, wireless power transfer may be used to deliver power to electronic, mechanical, and similar devices that may be implanted in a human or animal. Implantable devices, such as Mechanical Circulatory Support (MCS) devices, Ventricular Assist Devices (VADs), Implantable Cardioverter Defibrillators (ICDs), and the like, may require an external energy source to operate for extended periods of time. In some patients and situations, implantable devices require constant or near constant operation and have considerable power requirements requiring connection to an external power source, requiring percutaneous cables or cables that pass through the patient's skin to an external power source, increasing the likelihood of infection and reducing patient comfort.

Some implantable devices may require 1 watt or more or 10 watts or more for periodic or continuous surgery, making a self-contained system that operates solely on the battery power implanted in the patient impractical because the battery will require frequent replacement or replacement after the implantable device is activated.

In embodiments, the wireless power transfer described herein may be used to deliver power to an implantable device without the need for percutaneous wiring. In embodiments, wireless power transfer may be used to periodically or continuously power or recharge an implanted rechargeable battery, supercapacitor, or other energy storage component.

For example, as depicted in fig. 22A, an implantable device 2208 requiring electrical energy may be wired 2206 to a high Q device resonator 2204 implanted in a patient 2202 or animal. The device resonator may be configured to wirelessly receive energy from one or more external high-Q resonators 2212 via an oscillating magnetic field. In embodiments, additional batteries or energy storage components may be implanted within the patient and coupled to the device resonator and the implantable device. The internal battery may be recharged using the captured energy from the device resonator, allowing the implantable device to operate for a period of time even if wireless power is not transferred to or temporarily interrupted for the patient. A block component including an embodiment of a wireless power system is depicted in fig. 22B. A device resonator 2204 implanted inside the patient and coupled to power and control circuitry (not shown) that controls and tunes the operation of the resonator may be coupled to a rechargeable battery or other energy storage element 2210 also implanted inside the patient. The energy captured by the device resonator may be used to directly use the captured energy generated by the external resonator 2212 to charge a battery or power the implantable device 2208.

Wireless energy transfer systems based on the high Q resonator sources and devices described herein can tolerate greater separation distances and greater lateral offsets than conventional induction-based systems. A device resonator implanted in a patient may be energized through multiple sides and angles of the patient. For example, a device resonator implanted within the abdomen of a patient may be powered using a source from the back of the patient. The same device resonator can also be powered from a source located in the front abdominal side of the patient, providing more flexible positioning and orientation configuration options for the source.

In embodiments, the resonator and battery may be integrated into one substantially continuous unit with the implantable device. In other embodiments, the device resonator and battery may be separate from the implantable device and may be electrically wired to the device. The resonator may be implanted in a portion of the body other than the device, the external source resonator may be more accessible, in a portion of the body less visible to the patient, and so forth. In an embodiment, the device resonator may be implanted in or near the patient's buttocks or lower back, etc. In embodiments, the size and placement of the resonator may depend on the amount of power required by the implantable device, the distance of the wireless power transfer, the frequency of power delivery or recharging, and the like. In some embodiments, for example, it may be preferable to use a device resonator that is less than 7cm by 7cm so that it is more easily implanted within the human body while being able to deliver 5 watts or more of power at intervals of at least 2 cm.

In embodiments, an implantable device resonator may comprise a circular or rectangular planar capacitively loaded conductor loop comprising five loops of Litz conductor coupled to a capacitor network as described herein. In embodiments, it may be preferable to enclose the implantable device resonator in a housing that primarily comprises a non-metallic material to minimize losses, or in a housing having at least one side that comprises a non-metallic material.

In embodiments, the implantable medical device may include an inductive element composed of any number of turns of Litz wire, magnetic wire, standard wire, conductive tape (e.g., traces on a printed circuit board, etc.). In embodiments, the implantable medical device may include magnetic materials, ferrite, etc., and may be optimized for a particular frequency or frequency range (e.g., 13.56MHz or 100 or greater kHz).

In embodiments, a patient may have more than one implantable device that is wirelessly powered or recharged. In embodiments, multiple devices may be powered or charged by a single source or multiple sources. In embodiments, multiple devices may operate at the same resonant frequency or at different resonant frequencies. The source, repeater or device resonator may tune its frequency to receive or share power.

In embodiments, the magnetic resonator may include means for communicating with other magnetic resonators. Such communication may be used to coordinate the operation of the wirelessly powered medical device with other wireless systems. In an exemplary environment, an implantable device resonator may adjust its operating parameters in the vicinity of a high power source of another wireless power system. In an embodiment, the medical device source may communicate with another wireless power source in the area and with the patient to avoid or take care in such area.

Embodiments including a high Q device resonator and optionally a high Q source resonator allow for more efficient wireless power transfer and may tolerate greater separation and lateral offset of the source and device resonators than conventional induction-based systems. The high efficiency of the wireless power transfer system described herein reduces heating and heat build-up in the resonator, which may be important for resonators implanted in patients. The described resonator can transmit 5 watts or more of power without significant heating of the element so that the temperature of the component does not exceed 50C.

The separation distance between the external source resonator and the implantable device resonator and the tolerance for lateral offset allow greater freedom of placement of the source resonator. The use of a wireless power transfer system as described herein may also provide greater safety to the patient, as the movement or displacement of the source resonator will not interfere with the power transfer to the implantable device.

In embodiments, power may be transferred from a source resonator, which a patient wears in a backpack, a belt pack, an article of clothing, or the like, to an implantable device resonator. For example, as depicted in fig. 23A, the source resonator 2304 may be embedded in clothing and worn by a person 2302, and the source resonator 2304 may be wired to power and control circuitry and a battery (not shown) to deliver power to an implantable device resonator (not shown). In other embodiments, the source resonator and power source may be included in a backpack or bag as depicted in fig. 23B, 23C, and 23D. A backpack 2306 or other pack 2312 may be integrated with the source resonators 2308, 2314 in a location such that when worn by a patient, the source resonators will be substantially aligned with the implantable device resonators in the patient. For example, for a device resonator implanted in the hip half or lower back, a backpack with a source resonator integrated into the lower back portion provides substantial alignment of the source and device resonators when the backpack is worn by a patient as shown in fig. 23D. In an embodiment, the backpack or bag may also include an additional device resonator 2310 for wirelessly charging an internal energy storage or battery inside the bag. The backpack may be placed near an external source resonator or charging station and wirelessly charged. In some embodiments, the backpack or bag's source and device resonators may be the same physical resonator that alternates function between source and device depending on the use.

In embodiments, the external source resonator may be integrated into furniture such as a chair, bed, couch, car seat, and the like. Due to the tolerance to mismatch of the high Q power transfer systems described herein, the device resonator may be integrated into furniture in a region relatively close to the implantable device resonator (i.e., within 25 cm) and transfer power to the implantable device resonator and implantable device when the patient is working at a table and sitting in a chair, sitting in a couch, driving, sleeping, etc.

In an embodiment, a wireless power transfer system for an implantable device may include a repeater resonator. The repeater resonator may be used to improve energy transfer between the source and device resonators and may be used to increase overall coupling and power transfer efficiency. As described herein, a repeater resonator located near a device resonator may increase the efficiency of wireless power transfer from a distant source resonator to the device resonator.

In an embodiment, the repeater resonator is positioned to improve energy transfer between the source and the device. The location of the repeater resonator that provides the highest improvement in efficiency or coupling may depend on the application, the size of the resonator, the distance, the orientation of the resonator, the location of the lossy object, etc. In some embodiments, improvements in wireless energy transfer efficiency may be obtained by positioning a repeater resonator between the source resonator and the device resonator. In other embodiments, it may be beneficial to position the repeater resonator at an angle or further from the source than the device. The exact placement of the repeater resonator may be determined experimentally, by trial and error, by simulation or calculation, for a particular configuration, power requirements, implantable device, etc.

In embodiments of the system, the repeater resonators may be located or located inside the patient, or they may be located outside the patient, or the system may have both internal and external resonators. The repeater resonator may be internal or implanted in the patient. The repeater resonator may be implanted under the skin of the patient to improve coupling to the device resonator. Because the repeater resonator does not need to be connected to a device, it may be easier to locate or implant a larger repeater resonator than a device resonator connected to an implantable medical device. Due to distance limitations or size limitations between the resonator and the medical device, the device resonator may have to be implanted deeper inside the patient. The repeater resonator may include a coil of conductor, such as Litz wire, connected to a network of capacitors. The repeater resonator may be encased in a flexible material or package (e.g., silicon or other implantable plastic). The entire structure may be implanted inside the body under the skin to provide fine tuning of the wireless energy transfer between the external source and the implantable device.

In embodiments, the repeater resonators may be located outside the patient, in clothing, bags, furniture, etc. outside the patient. For example, a larger repeater resonator having a diameter of 20cm or more may be integrated into an article of clothing (e.g., vest, gown, etc.) or attachable pad and worn by the patient such that the repeater resonator overlaps or is proximate to the implantable device resonator. The repeater resonator may be completely passive or it may have additional circuitry for power and control. Positioning the repeater resonator proximate to the implantable device resonator effectively increases the size of the implantable resonator to substantially the size of the repeater resonator or proximate to the size of the repeater resonator and may allow for more efficient wireless power transfer to the implantable device resonator and device over greater distances. Repeater resonators can be much larger than is feasible for implantation into the human body.

In embodiments, a plurality of repeater resonators, either internal or external to the patient, may be arranged in an array or pattern around the body to allow wireless energy transfer from the source to the implantable device over a wide range of offsets. Each repeater resonator may be specifically tuned or configured to provide sufficient coupling to the implantable device resonator based on its relative position from the device resonator.

In an embodiment, a room, bathroom, vehicle, etc. may be installed with a large active resonator to transfer sufficient power to the patient via the repeater resonator, allowing continuous power transfer and restrictions on mobility while showering, sleeping, cooking, working, etc.

In an embodiment, the repeater resonator may include a wireless power converter function for converting wireless energy having incompatible parameters into an oscillating magnetic field having parameters compatible with the implantable device resonator. A wireless power converter resonator integrated into a vest, bag, or the like, can be worn by the patient and captures wireless power from a variety of sources and transfers the captured wireless power to an implantable device resonator having parameters compatible with the implantable device resonator. In embodiments, the wireless power converter may be configured to capture wireless power from solar energy, RF sources, movement, motion, and the like. In an embodiment, the repeater resonator may act as a power converter limiting the power delivered to the implantable device resonator, preventing too much power from being delivered to the patient.

In embodiments, the repeater resonator or wireless power converter may have an audible, visual, or vibratory alert when it no longer receives power. The repeater resonator may detect when it is not coupled to the implantable device, or may detect that it has not received sufficient power from an external source, and may be configured to alert the patient.

In an embodiment, a fully integrated external source resonator may be encased in a waterproof housing (including a rechargeable battery, an RF amplifier, and a source resonator). The integrated source and circuit may have a form factor to which a belt or strap may be attached, allowing the patient to swim or shower with the integrated source intact. The integrated source and circuit may also have an internal battery charging circuit and rectifier so it can be charged wirelessly by switching the resonator and electronics to capture mode.

In embodiments of the system, the device and the source and repeater resonators may include tuning capabilities to control heat dissipation in the implanted resonator. During wireless energy transfer, the current and voltage induced in the device resonator by the magnetic field of the source resonator during wireless energy transfer may cause heating of the resonator element due to ohmic losses, internal losses, etc. An implanted resonator may have limitations on the amount of heat it can safely dissipate before raising the temperature of the surrounding tissue to undesirable levels. The amount of power that can be safely dissipated may depend on the size of the resonator, the location of the resonator, etc. In some systems, one or more watts of power may be safely dissipated within the patient.

The source or repeater resonators that are external to the patient may be designed to tolerate a higher level of heat dissipation. External source or repeater resonators may have higher limits on safe power dissipation or heating. The source or repeater resonator external to the patient may be designed to safely dissipate 5 watts or more of heat, and may include active cooling means (e.g., fans or water cooling), and may be capable of safely dissipating 15 watts or more of power. In an embodiment, a wireless energy transfer system may control the amount of heat dissipated in a device resonator. Because the source or repeater resonator can tolerate more heat dissipation than the device resonator, the wireless energy transfer system may be tuned to reduce heat dissipation at the device resonator. Systems tuned to reduce heat dissipation at the device may have higher total heat dissipation, with increased heat dissipation occurring at the source or repeater resonators.

Heat dissipation in the device resonator may be controlled by reducing the current oscillating in the implantable device resonator. The current in the device resonator can be controlled by tuning the resonant frequency of the resonator. The current in the device resonator can be controlled by tuning the impedance of the resonator.

In an embodiment, a device resonator may include one or more temperature sensors as well as monitoring circuitry and control logic. When a temperature threshold is detected, the monitoring and control circuitry may detune the resonant frequency away from the resonant frequency of the source or repeater resonator. The monitoring and control circuitry may detune the resonant frequency above the resonant frequency of the source or repeater resonator. The monitoring and control circuitry may detune the resonant frequency below the resonant frequency of the source or repeater resonator. The device may be detuned incrementally until the temperature of the device resonator stabilizes. In embodiments, the frequency may be detuned by 1% or more or in increments of 1kHz or more.

As will be appreciated by those skilled in the art, the resonant frequency may vary with variable components in the device resonator (e.g., variable capacitors, inductors, capacitor banks, etc.).

In embodiments, detuning of the resonant frequency of a device resonator may reduce the efficiency of energy transfer between the source or repeater and the device. To maintain the same level of power delivered to the device, the source may need to increase the power output to compensate for the decrease in efficiency. In an embodiment, the device resonator may signal to the source resonator a temperature condition that may require adjustment of its resonant frequency and the power output of the source resonator.

Similar to controlling the resonant frequency, the effective impedance of the device resonator, which may affect the current and voltage in the resonator, may be controlled by adjusting the components of the resonator (e.g., inductance and capacitance). In an embodiment, the impedance may be tuned by changing the power requirements of the device or by controlling the switching frequency, phase, etc. of the rectifier or the switching dc-to-dc converter of the device.

The device resonator may continuously monitor the temperature of the component and monitor the trend of the temperature and adjust the frequency and value of the component to stabilize the temperature.

In an embodiment, the wireless energy transfer system may be tuned to reduce heat dissipation in the device resonator and distribute the heat dissipation to the repeater resonators. The implantable repeater resonator may be larger than the device resonator and may be capable of dissipating more heat than a smaller device resonator. Also, the repeater resonator may be implanted closer to the patient's skin, thus allowing the repeater resonator to be cooled through the skin using an external cooling pack or pad worn by the patient.

While the invention has been described in connection with certain preferred embodiments, other embodiments will be understood by those of ordinary skill in the art and are intended to be within the scope of the present disclosure, which is to be construed in the broadest possible sense allowable by law.

All documents mentioned herein are hereby incorporated by reference in their entirety as if fully set forth herein.

Claims (16)

1. A wireless energy transfer system for powering a device implanted in a patient, comprising:

a high Q source resonator having a first resonant frequency, the source resonator external to the patient, coupled to a power source, and configured to generate an oscillating magnetic field at substantially the first resonant frequency,

a high Q device resonator having a second resonant frequency, the device resonator coupled to an implantable device requiring a supply of power, the device resonator internal to the patient and configured to capture the oscillating magnetic field generated by the source resonator,

a temperature sensor positioned to measure a temperature of the device resonator,

a tunable component coupled to the device resonator to adjust an effective impedance of the device resonator, an

A repeater resonator;

wherein the repeater resonator is configured to be positioned to improve energy transfer between the source resonator and the device resonator,

wherein the wireless energy transfer system is configured to tune an effective impedance of the device resonator using the tunable component in response to the temperature measured by the temperature sensor and also to increase an output power of the source resonator, thereby reducing heat dissipation at the device resonator, distributing heat dissipation to the repeater resonator, and maintaining a power level delivered to the device resonator by reducing a current of oscillation in the device resonator.

2. The wireless energy transfer system of claim 1, wherein the repeater resonator is external to the patient.

3. The wireless energy transfer system of claim 2, wherein the repeater resonator is integrated into clothing that is wearable by the patient.

4. The wireless energy transfer system of claim 1, wherein the repeater resonator is internal to the patient.

5. The wireless energy transfer system of claim 1, further comprising at least one additional repeater resonator configured to be positioned to improve wireless energy transfer between the source resonator and the device resonator.

6. The wireless energy transfer system of claim 5, wherein the repeater resonator is positioned to provide substantially consistent energy transfer between the source resonator and the device resonator over a range of positions of the source resonator.

7. The wireless energy transfer system of claim 1, wherein the repeater resonator comprises at least one loop of Litz wire.

8. The wireless energy transfer system of claim 1, wherein the source resonator and the device resonator have a Q > 100.

9. The wireless energy transfer system of claim 1, wherein the wireless energy transfer system is configured to adjust the tunable component to change the second resonant frequency to a lower frequency away from the first resonant frequency.

10. The wireless energy transfer system of claim 1, wherein the wireless energy transfer system is configured to adjust the tunable component to change the second resonant frequency to a higher frequency away from the first resonant frequency.

11. The wireless energy transfer system of claim 1, wherein the wireless energy transfer system is configured to adjust the tunable component to maintain a temperature of the device resonator below 50 degrees celsius.

12. The wireless energy transfer system of claim 1, wherein the tunable component is a capacitor.

13. The wireless energy transfer system of claim 1, wherein the tunable component is an inductor.

14. The wireless energy transfer system of claim 1, wherein the wireless energy transfer system is configured to adjust the strength of the oscillating magnetic field generated by the source resonator to maintain a substantially uniform level of power captured by the device resonator.

15. The wireless energy transfer system of claim 14, wherein the wireless energy transfer system is configured to adjust the strength of the oscillating magnetic field generated by the source resonator by changing a drive voltage of the source resonator.

16. The wireless energy transfer system of claim 14, wherein the wireless energy transfer system is configured to adjust the strength of the oscillating magnetic field generated by the source resonator by changing a drive current of the source resonator.