Patent Grant
9972434
The technical field relates generally to wireless power transfer, and more specifically to devices, systems, and methods related to wireless power transfer to remote systems such as vehicles including batteries. In particular the present disclosure relates to improvements in the efficiency of inductive power transfer circuits.
Remote systems, such as vehicles, have been introduced that include locomotion power derived from electricity received from an energy storage device such as a battery. For example, hybrid electric vehicles include on-board chargers that use power from vehicle braking and traditional motors to charge the vehicles. Vehicles that are solely electric generally receive the electricity for charging the batteries from other sources. Battery electric vehicles (electric vehicles) are often proposed to be charged through some type of wired alternating current (AC) such as household or commercial AC supply sources. The wired charging connections require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may sometimes be inconvenient or cumbersome and have other drawbacks. Wireless charging systems that are capable of transferring power in free space (for example, via a wireless field) to be used to charge electric vehicles may overcome some of the deficiencies of wired charging solutions. As such, wireless charging systems and methods that efficiently and safely transfer power for charging electric vehicles are desirable.
Wireless power transfer systems may utilize inductive power transfer (IPT) to transfer power between a wireless charging system base and a mobile device pickup. IPT systems have a base unit which includes a tuned induction coil and drive circuitry and a mobile device which includes a similarly tuned induction coil and receive circuitry. Power may be transferred between the charging system base and the mobile device pickup due to coupling between the tuned induction coils. In single direction power transfer, energy is transferred from the base unit induction coil by way of a generated electromagnetic field within which the mobile device induction coil needs to be positioned. For efficient energy transfer the mobile device induction coil will typically be positioned close above and substantially co-axial to the base unit induction coil so as to achieve a strong degree of coupling between the electromagnetic field and the mobile device induction coil.
Many IPT systems also include a physical core made of a material having a high electromagnetic permeability. A commonly used material is ferrite. The physical core is highly permeable to electromagnetic fields and therefore greatly increases the magnitude of the generated electromagnetic field.
Some IPT systems include induction coils positioned above a ferrite core in the manner of a backing. A further advantage of using a ferrite core as a backing is that the electromagnetic field that surrounds the induction coil is constrained to the ferrite backing material on that side of the induction coil. The reason for this is that it is much easier for the electromagnetic field to travel through the ferrite material than air or other less permeable components.
Due to the ferrite's effect on the electromagnetic field produced by the induction coil, the presence of the ferrite also has a large influence on the inductance of the induction coil and therefore the coupling frequency. If the ferrite material exhibits a large variation in permeability then the induction coil will exhibit a similarly large variation in inductance and tuning making it difficult to achieve consistent tuning.
WO 2010/090539 discloses an IPT system for powering electric vehicles in which a base (usually the primary) coil consists of two separate co-planar coils positioned above a core formed from parallel bars of a material of high electromagnetic permeability, such as ferrite. In this arrangement, there is no straight path through the core that passes through the coils. As such, the coils act as pole areas and lines of electromagnetic flux arc between them in the form of a “flux pipe” above the coils, a zone of high flux concentration. Advantageously, the arrangement results in little leakage of flux below the coils on the side of the core.
Single homogeneous slabs or bars of highly electromagnetically permeable materials of the size typically required for use in wireless power transfer systems are fragile, difficult to obtain, expensive and may not provide suitable consistent permeability.
It is an object of the disclosed embodiments to address the foregoing problems or at least to provide the public with a useful choice. Further aspects and advantages of the present disclosure will become apparent from the ensuing description which is given by way of example only.
Various implementations of systems, methods and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
One aspect of the disclosure provides a method of forming a physical core of a wireless power transfer device. The method can include, for example, positioning two or more electromagnetically permeable members adjacent to one another in a line of electromagnetically permeable members. The step of positioning can involve positioning two or more electromagnetically permeable members adjacent one another within a wireless power transfer device casing. In some embodiments, the method further includes, for example, applying longitudinal pressure to an end of a line of electromagnetically permeable members. The application of longitudinal pressure may be applied by positioning a resilient spring member between an end of each line of electromagnetically permeable members and a first portion of the casing. In some embodiments, the method further includes, for example, positioning a further resilient spring member between the opposite end of each line of electromagnetically permeable members to the resilient spring member and a second portion of the casing. In some embodiments, the method further includes, for example, a partially encapsulating the electromagnetically permeable members in retaining compound. In some embodiments, the method further includes, for example, allowing the retaining compound to at least partially set, and releasing the longitudinal pressure applied to the end of each line of electromagnetically permeable members.
Another aspect of the disclosure provides a method of forming a wireless power transfer device. The method can include, for example, positioning two or more electromagnetically permeable members and an induction coil within a casing. In some embodiments, the method further includes, for example, arranging the electromagnetically permeable members to form a line of electromagnetically permeable members. The positioning of the electromagnetically permeable members can include, for example, positioning the two or more electromagnetically permeable members adjacent one another within a wireless power transfer device casing. In some embodiments, the method further includes, for example, positioning the electromagnetically permeable members in electromagnetic association with the induction coil. In some embodiments, the method further includes, for example, applying longitudinal pressure to an end of each line of electromagnetically permeable members. The application of longitudinal pressure can include, for example, positioning a resilient spring member between an end of each line of electromagnetically permeable members and a first portion of the casing. In some embodiments, the method further includes, for example, at least partially encapsulating the electromagnetically permeable members in a retaining compound. In some embodiments, the method further includes, for example, allowing the retaining compound to at least partially set, and releasing the longitudinal pressure applied to the end of each line of electromagnetically permeable members. In some embodiments, the method further includes, for example, positioning a further resilient spring member between the opposite end of each line of electromagnetically permeable members to the resilient spring member and a second portion of the casing.
In another aspect, a wireless power transfer device is provided. In some embodiments, the device includes a casing. In some embodiments, the casing houses an induction coil, a plurality of electromagnetically permeable members arranged a line or lines, and a retaining compound at least partially encapsulating the electromagnetically permeable members. In some embodiments, each line may include, for example, two or more electromagnetically permeable members abutting one another. The electromagnetically permeable members can be arranged in a plurality of substantially parallel lines. The spacing between adjacent parallel lines can be configured to allow a substantial portion of the electromagnetic field produced by the induction coil to pass through the parallel lines of electromagnetically permeable members. The electromagnetically permeable members can include, for example, ferrite bars. The electromagnetically permeable members and induction coil can be housed within a casing.
These and/or other aspects will become apparent and more readily appreciated from the following drawings, which taken in conjunction with the Detailed Description of Certain Inventive Embodiments section and other sections of the present application, serve to explain the principles of the present disclosure.
The various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may not depict all of the components of a given system, method or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures.
In the following detailed description, only certain exemplary embodiments have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the another element or be indirectly connected to the another element with one or more intervening elements interposed therebetween. Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments and is not intended to represent the only embodiments in which the invention may be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments. It will be apparent that the exemplary embodiments may be practiced without these specific details. In some instances, some devices are shown in block diagram form.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
Wirelessly transferring power may refer to transferring any form of energy associated with electric fields, magnetic fields, electromagnetic fields, or otherwise from a transmitter to a receiver without the use of physical electrical conductors (for example, power may be transferred through free space). The power output into a wireless field (for example, a magnetic field or an electromagnetic field) may be received, captured by, or coupled by a “receiving coil” to achieve power transfer. Accordingly, the terms “wireless” and “wirelessly” are used to indicate that power transfer between charging station and remote system is achieved without use of a cord-type electric conductor therebetween.
An electric vehicle is used herein to describe a remote system, an example of which is a vehicle that includes, as part of its locomotion capabilities, electrical power derived from a chargeable energy storage device (for example, a rechargeable electrochemical cell or other type of battery). As non-limiting examples, some electric vehicles may be hybrid electric vehicles that include besides electric motors, a traditional combustion engine for direct locomotion or to charge the vehicle's battery. Other electric vehicles may draw all locomotion ability from electrical power. An electric vehicle is not limited to an automobile and may include motorcycles, carts, scooters, and the like. By way of example and not limitation, a remote system is described herein in the form of an electric vehicle (EV). Furthermore, other remote systems that may be at least partially powered using a chargeable energy storage device are also contemplated (for example, electronic devices such as personal computing devices, mobile phones, and the like).
The base wireless charging system 102a of various embodiments includes a base system induction coil 104a for wirelessly transferring or receiving power. When an electric vehicle 112 is within range of the base system charging system 102a, power may be transferred between the base wireless induction coil 104a and an electric vehicle induction coil 116 within the electric vehicle 112. In some embodiments, power may be transmitted from the base wireless induction coil 104a to the electric vehicle induction coil 116. Power received by the electric vehicle induction coil 116 can then be transported to one or more components within the electric vehicle 112 to provide power to the electric vehicle 112. Such components within the electric vehicle 112 include, for example, a battery unit 118 and an electric vehicle wireless charging system 114.
In some exemplary embodiments, the electric vehicle induction coil 116 is said to be within range of, and may receive power from, the base system induction coil 104a when the electric vehicle induction coil 116 is located within a target region of the electromagnetic field generated by the base system induction coil 104a. The target region corresponds to at least part of a region where energy output by the base system induction coil 104a may be captured by an electric vehicle induction coil 116. In some cases, the target region may correspond to the “near field” of the base system induction coil 104a. The near-field is at least part of the electromagnetic field produced by the base system induction coil 104a. The near-field may correspond to a region in which there are strong reactive fields that result from the currents and charges in the base system induction coil 104a and that do not radiate power away from the base system induction coil 104a. In some cases the near-field may correspond to a region within about ½π of the wavelength of the base system induction coil 104a. Additionally, in various embodiments, described in more detail below, power may be transmitted from the electric vehicle induction coil 116 to the base system induction coil 104a. In such embodiments, the near-field may correspond to a region that is within approximately ½π of the wavelength of the electric vehicle induction coil 116.
Local distribution 130 may be configured to communicate with external sources (for example, a power grid) via a communication backhaul 134, and with the base wireless charging system 102a via a communication link 108.
In various embodiments, aligning the electric vehicle induction coil 116 such that it is disposed within the near-field region of the base system induction coil 104a may advantageously improve or maximize power transfer efficiency. In some embodiments the electric vehicle induction coil 116 may be aligned with the base system induction coil 104a and, therefore, disposed within a near-field region simply by the driver properly aligning the electric vehicle 112 relative to the base system induction coil 104a. In other embodiments, the driver may be given visual feedback, auditory feedback, or combinations thereof to determine when the electric vehicle 112 is properly placed for wireless power transfer. In yet other embodiments, the electric vehicle 112 may be positioned by an autopilot system, which may move the electric vehicle 112 back and forth (for example, in zig-zag movements) until an alignment error has reached a tolerable value. This may be performed automatically and autonomously by the electric vehicle 112 without or with only minimal driver intervention provided the electric vehicle 112 is equipped with a servo steering wheel, ultrasonic sensors, and intelligence to adjust the vehicle. In still other embodiments, the electric vehicle induction coil 116, the base system induction coil 104a, or a combination thereof may have functionality for displacing and moving the induction coils 116 and 104a relative to each other to more accurately orient them and develop more efficient coupling therebetween.
The base wireless charging system 102a may be located in a variety of locations. As non-limiting examples, some suitable locations include a parking area at a home of the electric vehicle 112 owner, parking areas reserved for electric vehicle wireless charging modeled after petroleum-based filling stations, and parking lots at other locations such as shopping centers and places of employment.
Charging electric vehicles wirelessly may provide numerous benefits. For example, charging may be performed automatically, virtually without driver intervention and manipulations thereby improving convenience to a user. There may also be no exposed electrical contacts and no mechanical wear out, thereby improving reliability of the wireless power transfer system 100. Manipulations with cables and connectors can be avoided, and there may be no cables, plugs, or sockets that may be exposed to moisture and water in an outdoor environment, thereby improving safety. There may also be no sockets, cables, and plugs visible or accessible, thereby reducing potential vandalism of power charging devices. Further, since an electric vehicle 112 may be used as distributed storage devices to stabilize a power grid, a docking-to-grid solution may be used to increase availability of vehicles for Vehicle-to-Grid (V2G) operation.
A wireless power transfer system 100 as described with reference to
As a further explanation of the vehicle-to-grid capability, the wireless power transmit and receive capabilities may be configured to be reciprocal such that the base wireless charging system 102a transfers power to the electric vehicle 112 and the electric vehicle 112 transfers power to the base wireless charging system 102a for example, in times of energy shortfall. This capability may be useful to stabilize the power distribution grid by allowing electric vehicles to contribute power to the overall distribution system in times of energy shortfall caused by over demand or shortfall in renewable energy production (for example, wind or solar).
2. Embodiments described herein may use capacitively loaded wire loops (for example, multi-turn coils) to form a resonant structure capable of efficiently coupling energy from a primary structure (transmitter) to a secondary structure (receiver) via a magnetic or electromagnetic near field if both primary and secondary are tuned to a common resonant frequency. In some such embodiments, the electric vehicle induction coil 216 and the base system induction coil 204 may each comprise multi-turn coils. Using resonant structures for coupling energy may be referred to as “magnetic coupled resonance,” “electromagnetic coupled resonance,” and/or “resonant induction.” The operation of the wireless power transfer system 200 will be described based on power transfer from a base wireless power charging system 202 to an electric vehicle 112, but is not limited thereto. For example, as discussed above, the electric vehicle 112 may transfer power to the base wireless charging system 102a.
With reference to
The base system transmit circuit 206 including the base system induction coil 204 and electric vehicle receive circuit 222 including the electric vehicle induction coil 216 may be tuned to substantially the same frequencies and may be positioned within the near-field of an electromagnetic field transmitted by one of the base system induction coil 204 and the electric vehicle induction coil 216. In this case, the base system induction coil 204 and electric vehicle induction coil 216 may become coupled to one another through the electromagnetic field therebetween such that power may be transferred to the electric vehicle receive circuit 222 including a tuning network 221 and electric vehicle induction coil 216. The tuning network 221 may be provided to form a resonant circuit with the electric vehicle induction coil 216 configured to resonate at a desired frequency. The mutual coupling coefficient resulting at coil separation is represented by k(d). Equivalent resistances Req,1 and Req,2 represent the losses that may be inherent to the induction coils 204 and 216 and any anti-reactance capacitors that may, in some embodiments, be provided in the base charging system tuning circuit 205 and electric vehicle charging system tuning circuit 221 respectively. The electric vehicle receive circuit 222 including the electric vehicle induction coil 316 and tuning network 221 receives power P2 from the base wireless power charging system 202 via the electromagnetic field between induction coils 204 and 216. The electric vehicle receive circuit 222 then provides the power P2 to an electric vehicle power converter 238 of an electric vehicle charging system 214 to enable usage of the power by the electric vehicle 112.
The electric vehicle power converter 238 may include, among other things, a LF/DC converter configured to convert power at an operating frequency back to DC power at a voltage level matched to the voltage level of an electric vehicle battery unit 218. The electric vehicle power converter 238 may provide the converted power PLDC to charge the electric vehicle battery unit 218. The power supply 208, base charging system power converter 236, and base system induction coil 204 may be stationary and located at a variety of locations as discussed above. The battery unit 218, electric vehicle power converter 238, and electric vehicle induction coil 216 may be included in an electric vehicle charging system 214 included or formed as part of electric vehicle 112 or part of a battery pack (not shown). The electric vehicle charging system 214 may also be configured to provide power wirelessly through the electric vehicle induction coil 216 to the base wireless power charging system 202 to feed power back to the grid. Each of the electric vehicle induction coil 216 and the base system induction coil 204 may act as transmit or receive induction coils based on the mode of operation.
While not shown, the wireless power transfer system 200 may include a load disconnect unit (LDU) to safely disconnect the electric vehicle battery unit 218 or the power supply 208 from the wireless power transfer system 200. For example, in case of an emergency or system failure, the LDU may be triggered to disconnect the load from the wireless power transfer system 200. The LDU may be provided in addition to a battery management system for managing charging to a battery, or it may be part of the battery management system.
Further, the electric vehicle charging system 214 may include switching circuitry (not shown) for selectively connecting and disconnecting the electric vehicle induction coil 216 to the electric vehicle power converter 238. Disconnecting the electric vehicle induction coil 216 may suspend charging and also may adjust the “load” as “seen” by the base wireless charging system 202 (acting as a transmitter), which may be used to decouple the electric vehicle charging system 214 (acting as the receiver) from the base wireless charging system 202. The load changes may be detected if the transmitter includes the load sensing circuit. Accordingly, the transmitter, such as a base wireless charging system 202, may have a mechanism for determining when receivers, such as an electric vehicle charging system 214, are present in the near-field of the base system induction coil 204.
As described above, in operation, assuming energy transfer towards the vehicle or battery, input power is provided from the power supply 208 such that the base system induction coil 204 generates a field for providing the energy transfer. The electric vehicle induction coil 216 couples to the radiated field and generates output power for storage or consumption by the electric vehicle 112. As described above, in some embodiments, the base system induction coil 204 and electric vehicle induction coil 216 are configured according to a mutual resonant relationship such that the resonant frequency of the electric vehicle induction coil 216 and the resonant frequency of the base system induction coil 204 are very close or substantially the same. Transmission losses between the base wireless power charging system 202 and electric vehicle charging system 214 are minimal when the electric vehicle induction coil 216 is located in the near-field of the base system induction coil 204.
As stated, an efficient energy transfer occurs by coupling a large portion of the energy in the near field of a transmitting induction coil to a receiving induction coil rather than propagating most of the energy in an electromagnetic wave beyond the near-field. When in the near field, a coupling mode may be established between the transmit induction coil and the receive induction coil. The area around the induction coils where this near field coupling may occur is referred to herein as a near field coupling mode region.
While not shown, the base charging system power converter 236 and the electric vehicle power converter 238 may both include an oscillator, a driver circuit such as a power amplifier, a filter, and a matching circuit for efficient coupling with the wireless power induction coil. The oscillator may be configured to generate a desired frequency, which may be adjusted in response to an adjustment signal. The oscillator signal may be amplified by a power amplifier with an amplification amount responsive to control signals. The filter and matching circuit may be included to filter out harmonics or other unwanted frequencies and match the impedance of the power conversion module to the wireless power induction coil. The power converters 236 and 238 may also include a rectifier and switching circuitry to generate a suitable power output to charge a battery or power a load.
The electric vehicle induction coil 216 and base system induction coil 204 as described throughout the disclosed embodiments may be referred to or configured as “loop” antennas, and more specifically, multi-turn loop antennas. The induction coils 204 and 216 may also be referred to herein or be configured as “magnetic” antennas. The term “coils” is intended to refer to a component that may wirelessly output or receive energy for coupling to another “coil.” The coil may also be referred to as an “antenna” of a type configured to wirelessly output or receive power. As used herein, coils 204 and 216 are examples of “power transfer components” of a type that are configured to wirelessly output, wirelessly receive, and/or wirelessly relay power. Loop (for example, multi-turn loop) antennas may be configured to include an air core or a physical core such as a ferrite core. An air core loop antenna may allow the placement of other components within the core area. Physical core antennas including ferromagnetic or ferrimagnetic materials may allow development of a stronger electromagnetic field and improved coupling. Unlike a transformer core, the physical core of an IPT coil does not necessarily pass through the center of a coil, the core may simply be positioned in close proximity to an associated coil.
As discussed above, efficient transfer of energy between a transmitter and receiver occurs during matched or nearly matched resonance between a transmitter and a receiver. However, even when resonance between a transmitter and receiver are not matched, energy may be transferred at a lower efficiency. Transfer of energy occurs by coupling energy from the near field of the transmitting induction coil to the receiving induction coil residing within a region (for example, within a predetermined frequency range of the resonant frequency, or within a predetermined distance of the near-field region) where this near field is established rather than propagating the energy from the transmitting induction coil into free space.
A resonant frequency may be based on the inductance and capacitance of a transmit circuit including an induction coil (for example, the base system induction coil 204) as described above. As shown in
As described above, according to some embodiments, coupling power between two induction coils in the near field of one another is disclosed. As described above, the near field may correspond to a region around the induction coil in which electromagnetic fields exist but may not propagate or radiate away from the induction coil. Near-field coupling-mode regions may correspond to a volume in proximity to the physical volume of the induction coil, typically within a small fraction of the wavelength. According to some embodiments, electromagnetic induction coils, such as single and multi-turn loop antennas, are used for both transmitting and receiving since magnetic near field amplitudes in practical embodiments tend to be higher for magnetic type coils in comparison to the electric near fields of an electric type antenna (for example, a small dipole). This allows for potentially higher coupling between the pair. Furthermore, “electric” antennas (for example, dipoles and monopoles) or a combination of magnetic and electric antennas may be used.
The base wireless charging system 302 includes a base charging system controller 342 and the electric vehicle charging system 314 includes an electric vehicle controller 344. The base charging system controller 342 may include a base charging system communication interface 162 to other systems (not shown) such as, for example, a computer, and a power distribution center, or a smart power grid. The electric vehicle controller 344 may include an electric vehicle communication interface to other systems (not shown) such as, for example, an on-board computer on the vehicle, other battery charging controller, other electronic systems within the vehicles, and remote electronic systems.
The base charging system controller 342 and electric vehicle controller 344 may include subsystems or modules for specific application with separate communication channels. These communications channels may be separate physical channels or separate logical channels. As non-limiting examples, a base charging alignment system 352 may communicate with an electric vehicle alignment system 354 through a communication link 376 to provide a feedback mechanism for more closely aligning the base system induction coil 304 and electric vehicle induction coil 316, either autonomously or with operator assistance. Similarly, a base charging guidance system 362 may communicate with an electric vehicle guidance system 364 through a guidance link to provide a feedback mechanism to guide an operator in aligning the base system induction coil 304 and electric vehicle induction coil 316. In addition, there may be separate general-purpose communication links (for example, channels) supported by base charging communication system 372 and electric vehicle communication system 374 for communicating other information between the base wireless power charging system 302 and the electric vehicle charging system 314. This information may include information about electric vehicle characteristics, battery characteristics, charging status, and power capabilities of both the base wireless power charging system 302 and the electric vehicle charging system 314, as well as maintenance and diagnostic data for the electric vehicle 112. These communication channels may be separate physical communication channels such as, for example, Bluetooth, zigbee, cellular, etc.
Electric vehicle controller 344 may also include a battery management system (BMS) (not shown) configured to manage charge and discharge of the electric vehicle principal battery, a parking assistance system based on microwave or ultrasonic radar principles, a brake system configured to perform a semi-automatic parking operation, and a steering wheel servo system configured to assist with a largely automated parking ‘park by wire’ that may thus provide higher parking accuracy, thus reducing the need for mechanical horizontal induction coil alignment in any of the base wireless charging system 102a and the electric vehicle charging system 114. Further, electric vehicle controller 344 may be configured to communicate with electronics of the electric vehicle 112. For example, electric vehicle controller 344 may be configured to communicate with visual output devices (for example, a dashboard display), acoustic/audio output devices (for example, buzzer, speakers), mechanical input devices (for example, keyboard, touch screen, and pointing devices such as joystick, trackball, etc.), and audio input devices (for example, microphone with electronic voice recognition).
Furthermore, the wireless power transfer system 300 may include detection and sensor systems. For example, the wireless power transfer system 300 may include sensors for use with systems to properly guide the driver or the vehicle to the charging spot, sensors to mutually align the induction coils with the required separation/coupling, sensors configured to detect objects that may obstruct the electric vehicle induction coil 316 from moving to a particular height and/or position to achieve coupling, and safety sensors for use with systems to perform a reliable, damage free, and safe operation of the system. For example, a safety sensor may include a sensor for detection of presence of animals or children approaching the wireless power induction coils 104a, 116 beyond a safety radius, detection of metal objects near the base system induction coil 304 that may be heated up (induction heating), detection of hazardous events such as incandescent objects on the base system induction coil 304, and temperature monitoring of the base wireless power charging system 302 and electric vehicle charging system 314 components.
The wireless power transfer system 300 may also support plug-in charging via a wired connection. A wired charge port may integrate the outputs of the two different chargers prior to transferring power to or from the electric vehicle 112. Switching circuits may provide the functionality to support both wireless charging and charging via a wired charge port.
To communicate between a base wireless charging system 302 and an electric vehicle charging system 314, the wireless power transfer system 300 may employ both in-band signaling or an RF data modem (for example, Ethernet over radio in an unlicensed band) or both. The out-of-band communication may provide sufficient bandwidth for the allocation of value-add services to the vehicle user/owner. A low depth amplitude or phase modulation of the wireless power carrier may serve as an in-band signaling system with minimal interference.
In some embodiments, communication may be performed via the wireless power link without using specific communications antennas. For example, the wireless power induction coils 304 and 316 may also be configured to act as wireless communication transmitters and/or receivers. Thus, some embodiments of the base wireless power charging system 302 may include a controller (not shown) for enabling keying type protocol on the wireless power path. By way of illustration, keying the transmit power level (amplitude shift keying) at predefined intervals with a predefined protocol may provide a mechanism by which the receiver may detect a serial communication from the transmitter. The base charging system power converter 336 may include a load sensing circuit (not shown) for detecting the presence or absence of active electric vehicle receivers in the vicinity of the near field generated by the base system induction coil 304. By way of example, a load sensing circuit monitors the current flowing to the driver or power amplifier, which is affected by the presence or absence of active receivers in the vicinity of the near field generated by base system induction coil 104a. Detection of changes to the loading on the power amplifier may be monitored by the base charging system controller 342 for use in determining whether to enable the oscillator for transmitting energy, to communicate with an active receiver, or a combination thereof.
To enable wireless high power transfer, some embodiments may be configured to transfer power at a frequency in the range from 10-60 kHz. This low frequency coupling may allow highly efficient power conversion that may be achieved using solid state devices. In addition, there may be less coexistence issues with radio systems compared to other bands.
The wireless power transfer system 100 described may be used with a variety of electric vehicles 102 including rechargeable or replaceable batteries.
It may be useful for the electric vehicle induction coil to be integrated flush with a bottom side of electric vehicle battery unit or the vehicle body so that there are no protrusive parts and/or so that the specified ground-to-vehicle body clearance may be maintained. This configuration may require some room in the electric vehicle battery unit dedicated to the electric vehicle wireless power subsystem. The electric vehicle battery unit 422 may also include a battery-to-EV cordless interface 422, and a charger-to-battery cordless interface 426 configured to provide contactless power and communication between the electric vehicle 412 and a base wireless charging system 102a as shown in
In some embodiments, and with reference to
The design of this deployable electric vehicle induction coil module 542b is similar to that of
As discussed above, the deployed electric vehicle induction coil module 542d may contain only the coil 536d (for example, Litz wire) and ferrite material 538d. Ferrite backing may be provided to enhance coupling and to prevent from excessive eddy current losses in a vehicle's underbody or in the conductive shield 532d. Moreover, the electric vehicle induction coil module 542d may include a flexible wire connection to power conversion electronics and sensor electronics. This wire bundle may be integrated into the mechanical gear for deploying the electric vehicle induction coil module 542d.
In certain embodiments, the physical core is made of ferrite. Ferrite is commonly used for inductor coils because of its high electromagnetic permeability and low electrical conductivity. However, other materials may be used in other embodiments of the disclosure. In the following description, properties of ferrite cores and embodiments of the disclosure including, for example, ferrite cores will be discussed by way of example. It will be understood that these properties may also be characteristics of other materials suitable for use in a physical core of a wireless power transfer device and embodiments may also include such other materials. For example amorphous metal alloys or tempered silicon steel.
The physical core 602 is typically wider and longer than the area covered by induction coils 601. This ensures any electromagnetic fields on the ferrite side of the induction coils 601 are constrained to the ferrite cores.
In practice, bars of ferrite 604a-f as shown in
As shown in
In one embodiment, the physical core includes a single ferrite bar which itself includes a plurality of smaller bars abutting end to end. Depending on the dimensions of the physical core required, ferrite bars of varying sizes (including available standard sizes) may be placed side by side in some embodiments, instead of end to end.
Because ferrite is much more magnetically permeable than air, electromagnetic fields will concentrate so as to pass through the low reluctance path of the ferrite rather than through air or any other nearby material having a higher reluctance. This characteristic means a single ferrite slab may be replaced by a series of parallel spaced bars of ferrite material, as shown in
One particular issue that may arise with ferrite structures constructed from a plurality of separate standard sized ferrites, such as ferrite bars 604a-f shown in
In order to reduce air gaps between adjacent ferrite bars 603 when they are positioned end to end to form a bar 604, or positioned together to form a grid, a longitudinal pressure may be applied along the lines of short ferrite bars in some embodiments. This pressure ensures tight coupling between the ferrite bars and therefore results in a permeability which is substantially the same as if the ferrite was formed from a single piece of ferrite.
When longitudinal pressure is applied to a series of ferrite bars as has been described, the bars can jump out of place, particularly if they are not placed on a flat surface. This is analogous to laying a number of blocks in a line end for end and pressing inwards on the outermost ends of the line of blocks. As the pressure is increased any irregularities in the blocks will result in the line of blocks bowing and jumping out of position. Furthermore, the type of Ferrite which can be used in non-permanent magnetic structures may be referred to as a ‘soft ferrite.’ A ‘soft ferrite’ refers to the coercivity of the material rather than its physical attributes. Soft ferrites are, like most other ceramics, hard and brittle. Therefore, the ferrites are prone to shearing if an uneven or excessive force is applied.
To address this problem, some embodiments of the disclosure include, for example, a method in which, once the bars are in position and squeezing pressure is applied by spring members 903, the casing is at least partially filled with a retaining compound such as resin 901 and allowed to set. Once the retaining compound has set spring members 903 may be removed. Tight coupling is maintained between the ferrite bars 900 due to the retaining compound. The casing 902 may also house other components of an IPT system, including the induction coil (not shown). The retaining compound 901 therefore retains the relative spacing of and pressure between adjacent ferrite bars as well as the spacing and orientation of an associated induction coil.
In some embodiments upon applying pressure with a resilient spring members 903 to the ferrite bars 900 the ferrite bars 900 may be bonded together with glue or other adhesive to maintain the applied pressure once the resilient spring members 903 are removed.
In some embodiments a resilient spring member 903 may be positioned at one end of a line of ferrites, the other end of the line of ferrite bars 900 may press against an opposite side of the casing 902 to which the resilient spring member 903 pushes. Alternatively, although the walls of casing 902 provide a convenient fixed surface by which resilient spring members are able to impart an inward force on ferrite bars 900, in other embodiments the resilient spring members or one end of the line of ferrite bars 900 may press against any other fixed structure in the casing 902.
In the embodiment of
In some embodiments of the disclosure, the resilient spring members are left in place in the wireless power transfer device. This may be considered an alternative or an addition to using resin to hold the ferrite bars in position. In such embodiments, the resilient spring members may be formed of a magnetically and electrically insulating material to avoid interfering with power transfer with another wireless power transfer device.
In certain embodiments the ferrites are held together by resin, epoxy or the like. In such embodiments the spring members 903 may be removed once the resin has set sufficiently to hold the ferrites in position relative to one another.
In such embodiments the force applied to the line of ferrite bars 900 by the spring member 903 may be configured to establish a degree of magnetic coupling between adjacent ferrites and/or to prevent the ingress of resin or the like between adjacent ferrites.
The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations.
Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, electromagnetic fields or particles, optical fields or particles, or any combination thereof.
The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the embodiments of the disclosure.
The various illustrative blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor or a plurality of microprocessors, in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm and functions described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted over as an instruction, instructions or code on a tangible, non-transitory computer-readable medium. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD ROM, or any other form of storage medium known in the art. A storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the embodiments described herein.
The various illustrative blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm and functions described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a tangible, non transitory computer-readable medium. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD ROM, or any other form of storage medium known in the art. A storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
For purposes of summarizing the disclosure, certain aspects, advantages and novel features have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
While this invention has been described in connection with what is are presently considered to be practical embodiments, it will be appreciated by those skilled in the art that various modifications and changes may be made without departing from the scope of the present disclosure. It will also be appreciated by those of skill in the art that parts mixed with one embodiment are interchangeable with other embodiments; one or more parts from a depicted embodiment can be included with other depicted embodiments in any combination. For example, any of the various components described herein and/or depicted in the Figures may be combined, interchanged or excluded from other embodiments. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. Thus, while the present disclosure has described certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, and equivalents thereof.
This is a divisional application of U.S. patent application Ser. No. 13/671,325, filed on Nov. 7, 2012, which claims priority to and the benefit of U.S. Provisional Application No. 61/613,351, filed on Mar. 20, 2012, the entire content of the foregoing applications being hereby incorporated by reference herein in their entireties.
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| Child | 14876511 | US |
