Patent Application
20170085130
The described technology generally relates to wireless power transmission. More specifically, the disclosure is directed to devices, systems, and methods related to a wireless power transmitter and transmitter coupler.
In wireless power applications, wireless power transfer systems may provide the ability to charge and/or power electronic devices without physical, electrical connections, thus reducing the number of components required for operation of those electronic devices and simplifying the use of those electronic devices. Such wireless power transfer systems may comprise a transmitter coupler and other transmitting circuitry configured to generate a magnetic field that may induce a current in a receiver coupler that may be connected to the electronic device to be charged or powered wirelessly. The transmitter coupler is preferably able to provide a suitable magnetic field. In some configurations, the transmitter coupler can be inefficient, thus wasting energy, and might provide an uneven magnetic field, thus complicating a process of placing a wireless power receiver relative to the transmitter coupler. Consequently, there is an ongoing need to improve the efficiency of performing wireless power transfer.
The implementations disclosed herein each have several innovative aspects, no single one of which is solely responsible for the desirable attributes of the invention. Without limiting the scope of the invention, as expressed by the claims that follow, the more prominent features will be briefly disclosed here. After considering this description, one will understand how the features of the various implementations provide several advantages over current wireless transfer systems.
A wireless power transmitter coupler for a transmitter pad that provides wireless power via a magnetic field includes electrical inputs for a driving signal and a plurality of coupler loops that divide the current generated by the driving signal. The transmitter coupler can be tuned to provide a distributed magnetic field that is more evenly distributed over the transmitter pad. The currents through different coupler loops can be controlled by the relative loop impedances of the coupler loops. The coupler loops can take on various shapes, such as substantially concentric circular paths and they may overlap. Impedances can be designed using one or more capacitances. Capacitance between coupler loops can be provided. Feed capacitors might be provided at the electrical inputs.
Apportionment of current from the driving signal to the first current and to the second current can be determined by a proportion of a first loop impedance of the first coupler loop and a second loop impedance of the second coupler loop, wherein the first loop impedance and the second loop impedance divide the current from the driving signal to create a distributed magnetic field that is more evenly distributed over the transmitter pad than if the first current and the second current are constrained to be equal. This apportionment can be extended beyond two coupler loops.
The loop impedances of the coupler loops might be inversely proportional to their size, so that more current is carried by larger coupler loops, with loop impedance being determined at a driving signal frequency that could be between 1 MHz and 10 MHz and might be around 6.78 MHz.
Some coupler loop paths might be circular, while others have paths approximating a rectangle for a majority of their paths. Some coupler paths might include added inductors.
One aspect of the disclosure provides a wireless power transmitter for generating a magnetic field. The wireless power transmitter includes a first coupler loop that is coupled between a first electrical connection and a second electrical connection. The first electrical connection and the second electrical connection capable of receiving a driving signal and configured to allow the driving signal applied across the first electrical connection and the second electrical connection to cause a first current to flow in the first coupler loop and generate a first magnetic field component. The wireless power transmitter further includes a second coupler loop that is coupled between the first electrical connection and the second electrical connection. The first electrical connection and the second electrical connection further configured to allow the driving signal applied across the first electrical connection and the second electrical connection to cause a second current to flow in the second coupler loop and generate a second magnetic field component. The first current is different from the second current.
A wireless power transmitter may include circuitry configured to generate a driving signal, a pair of electrical connections including a first electrical connection and a second electrical connection, a transmitter pad coupled to the pair of electrical connections to receive the driving signal, a first coupler loop, a second coupler loop, and tuning elements that tune a resonance of the first coupler loop and the second coupler loop independently of each other. The first coupler loop is along a first path enclosed within the transmitter pad, coupled between the first electrical connection and the second electrical connection. The second coupler loop is along a second path enclosed within the transmitter pad, coupled between the first electrical connection and the second electrical connection, the second coupler loop being electrically in parallel with the first coupler loop and separated from the first coupler loop along a loop longitude sufficient to generate distinguishable magnetic field components among the first coupler loop and the second coupler loop.
A method of providing power wirelessly to devices having wireless power receivers and positioned to wirelessly receive power via a magnetic field might include receiving a driving signal across a pair of electrical connections comprising a first electrical connection and a second electrical connection, apportioning current of the driving signal to a first coupler loop and a second coupler loop, the first coupler loop being along a first path connecting the first electrical connection and the second electrical connection and the second coupler loop being along a second path connecting the first electrical connection and the second electrical connection, generating a first magnetic field component when a first current flows in the first coupler loop, and generating a second magnetic field component when a second current flows in the second coupler loop, wherein the second path is sufficiently distinct from the first path that the first magnetic field component and the second magnetic field component are distinguishable to a wireless power receiver, wherein the first current is different than the second current.
A wireless power transmitter may include means for generating a driving signal, means for conveying a driving signal current, first means for emitting a first magnetic field, second means for emitting a second magnetic field, means for supporting the first means for emitting along a first path and the second means for emitting along a second path separated from the first path sufficient to generate distinguishable magnetic field components as between the first means for emitting and the second means for emitting, means for partitioning the driving signal current between the first means for emitting and the second means for emitting, and means for tuning a resonance of the first means for emitting and the second means for emitting independently of each other.
The following detailed description together with the accompanying drawings will provide a better understanding of the nature and advantages of the present invention.
The above-mentioned aspects, as well as other features, aspects, and advantages of the present technology will now be described in connection with various implementations, with reference to the accompanying drawings. The illustrated implementations, however, are merely examples and are not intended to be limiting. Throughout the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Note that the relative dimensions of the following figures may not be drawn to scale.
In the following detailed description, reference is made to the accompanying drawings, which form a part of the present disclosure. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and form part of this disclosure.
In a specific example, a wireless power transfer system involves transmitters and receivers, wherein a transmitter has a power source, circuitry and/or logic for generating a driving signal that drives a wireless power transmitter coupler. In response to the driving signal, the transmitter coupler generates a magnetic field having certain characteristics. A wireless power receiver includes a receiver coupler that extracts energy from that magnetic field, converts it to usable electrical energy and provides it to the receiver of, for example, an electronic device, circuitry and/or logic for use in various applications. The transmitter coupler may be designed in a way that allows power to be conveyed to the receiver without requiring that the receiver be placed or positioned in an exact position or orientation.
More generally, wireless power transfer 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 (e.g., power may be transferred through free space). The power output into a wireless field (e.g., a magnetic field or an electromagnetic field) may be received, captured by, or coupled by a receiver coupler, such as an antenna or other element, to achieve power transfer from the transmitter to the receiver.
In an exemplary wireless power transfer system, a power source provides input power to a transmitter that generates a driving signal that drives a transmitter coupler to generate a wireless (e.g., magnetic or electromagnetic) field. A receiver has a receiver coupler that absorbs some of the energy of the wireless field when the receiver coupler is present in the wireless field. The receiver uses that energy to power circuitry electrically connected to the receiver and/or to store that energy for later use, such as in a battery. The absorbed energy might be used by a device having an integrated receiver or the device might be connected, via a charging connector on the device for example, to a separate receiver unit. Being wireless power transfer, the transmitter and the receiver are separated by a distance, which might be small or large relative to the transmitter and receiver.
The transmitter includes a transmitter coupler that generates the wireless field. The coupler might be shaped to allow for various placements of one or more receiver couplers relative to the transmitter coupler. The transmitter coupler might be embedded in a transmitter pad constructed of nonconductive material suitable for supporting the receiver and/or the device being charged. The transmitter coupler can be an antenna or coil, and can be designed for resonant or non-resonant use, where resonant use refers to the case where the transmitter coupler forms a portion of a resonant circuit (e.g., an LC circuit) and is driven with a driving signal that has a primary alternating current (AC) time-varying component with a frequency at or near the resonant frequency of the resonant circuit. The transmitter might include circuitry and or logic that alters the driving signal based on feedback about the nature, quantity, etc., of wireless power receivers that are absorbing energy from the wireless field generated by the transmitter coupler.
In some implementations, the wireless field may correspond to the “near-field” of the transmitter coupler. The near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the transmitter coupler that minimally radiate power away from the transmitter coupler. The near-field may correspond to a region that is within about one wavelength (or a fraction thereof) of electromagnetic signals at the designed frequency. The near-field is an area around a coupler that in which electromagnetic fields exist but do not propagate or radiate away from the antenna. They are typically confined to a volume that is near the physical volume of the antenna. In the exemplary embodiments of the invention, magnetic-type antennas, such as single-turn and multi-turn loop antennas might be used in a transmitter coupler and a receiver coupler, since magnetic near-field amplitudes tend to be higher for magnetic-type antennas in comparison to the electric near-fields of an electric-type antenna (e.g., a small dipole).
Regardless of whether near-field or other fields are used, the transmitter coupler is often designed and configured with certain design parameters in mind. For example, a transmitter coupler might be designed and implemented in a way that allows it to transmit power to a receiver device within the charging region of a few feet at a power level sufficient to charge or power the receiver device but is not designed or implemented to transmit significant power across hundreds of feet. Notwithstanding, it should be understood that in generating a wireless field, there are typically not strict boundaries for the wireless field and the wireless field might continue on indefinitely with slowly decreasing intensity. Therefore, while a wireless power transmission system might be described as having a charging field or region, the boundaries need not be precisely defined.
The transmitter coupler and the receiver coupler may further be configured according to a mutual resonant relationship. When the resonant frequency of the receiver coupler and the resonant frequency of the transmitter coupler substantially the same or very close, transmission losses between the transmitter coupler and the receiver coupler are reduced. Resonant inductive coupling techniques may allow for improved efficiency and power transfer over various distances and with a variety of inductive coil configurations. In this manner, the transmitter coupler might output a time-varying magnetic field with a frequency corresponding to the resonant frequency of the transmitter coupler and the receiver coupler, when it is within the wireless field, experiences an induced current from that time-varying magnetic field. The alternating current induced in the receiver coupler may be rectified as described above to produce direct current (DC) energy that may be provided to charge a battery or to power a load. In addition to conveying power wirelessly, the transmitter and receiver might also communicate data using the wireless field and/or communicate on a separate communication channel (e.g., Bluetooth, ZigBee, cellular, etc.).
As mentioned above, the transmitter might comprise a power source and a transmitter coupler. The transmitter might also include various circuitry and logic elements, such as an oscillator, a driver circuit, and various filters, matching circuits and other components. The oscillator may be configured to generate a signal at the desired frequency and that desired frequency might be adjustable in response to a frequency control signal. The driver circuit would have the oscillator signal as its input, then drive input terminals of the transmitter coupler. The electrical connection terminals can be detachable terminals or integrated terminals. The driver circuit would drive the transmitter coupler at, for example, a resonant frequency of the transmitter coupler by applying an input voltage signal to the connection terminals. The driver circuit may be a switching amplifier configured to receive a square wave from the oscillator and output a sine wave or square wave. Filters might be used to filters out harmonics or other unwanted frequencies and matching circuits might be used to match the impedance of the transmitter to the transmitter coupler. As a result of driving the transmitter coupler, the transmitter coupler may generate the wireless field at a level sufficient for conveying energy to the receiver coupler.
As used herein, a “coupler” refers to a component that wirelessly outputs energy or wirelessly receives energy, with a “transmitter coupler” referring to a coupler that wirelessly outputs energy and a “receiver coupler” referring to a coupler that wirelessly absorbs or receives energy. However, even with those uses of those terms, it should be understood that a transmitter coupler might absorb some energy while outputting energy or otherwise and a receiver coupler might emit some energy while absorbing some energy or otherwise. A coupler might be in the form of an antenna, such as a loop of wire or metal, having a particular position. The coupler might be an induction coil.
Where the coupler has a particular shape, that shape might be in the form of an elongated wire, metal strip or conductor having another cross section, and might be described in terms of a path. For example, a flat induction coil might have a spiral path wherein much of the flat induction coil follows a substantially circular path except for perhaps the ends of the flat induction coil, which might be substantially linear with one end of the coil connected to an inner portion of the spiral path passing over other portions of the coil to reach outside the spiral path without significant electrical conductivity with the portions of the coil that are being crossed. The coupler might rely on an air core, a physical core such as a ferrite core, or no core.
The coupler may include, in addition to a conductor having its internal impedance, additional impedance components such as capacitors and inductors. The coupler may form a portion of a resonant circuit configured to resonate at a resonant frequency based on its inductance and its capacitance. For larger diameter antennas, the size of capacitance needed to sustain resonance may decrease as the diameter or inductance of the loop increases. Other resonant circuits formed using other components are also possible.
In examples herein, the transmitter coupler is referred to as being enclosed in, or associated with a transmitter pad, which might be a flat pad that rests on a unit of furniture suitable for placement of receivers, receiver couplers, and/or devices with receiver couplers thereon. The transmitter pad might be integrated into a table, a mat, a lamp, or other stationary configuration.
Specific examples will now be described with reference to the figures.
The receiver 108 may wirelessly receive power when the receiver 108 is located in the wireless field 105 generated by the transmitter 104. The transmitter 104 includes a transmitter coupler 114 for transmitting energy to the receiver 108 via the wireless field 105. The receiver 108 includes a receiver coupler 118 for receiving or capturing energy transmitted from the transmitter 104 via the wireless field 105. The wireless field 105 corresponds to a region where energy output by the transmitter 104 may be captured by the receiver 108 and need not be explicitly defined or contained.
In one exemplary implementation, the wireless field 105 may be a magnetic field and the transmitter 104 and the receiver 108 are configured to inductively transfer power. The transmitter 104 and the receiver 108 may further be configured according to a mutual resonant relationship. When the resonant frequency of the receiver 108 and the resonant frequency of the transmitter 104 are substantially the same or very close, transmission losses between the transmitter 104 and the receiver 108 are reduced. Resonant inductive coupling techniques may allow for improved efficiency and power transfer over various distances and with a variety of inductive coil configurations. When configured according to a mutual resonant relationship, in an implementation, the transmitter 104 outputs a time varying magnetic field with a frequency corresponding to the resonant frequency of transmitter coupler 114.
The wireless field 105 might be nonuniform such that placement and configuration of receiver 108 within the wireless field 105 can determine how efficiently energy is transferred. In some implementations, the frequency is 6.78 MHz, but other frequencies might be used instead, such as 1 MHz to 10 MHz, based on considerations of circuits available to generate the frequencies used, frequencies expected, frequencies that are less likely to interfere with the operation of other electronics, or similar reasons. The 6.78 MHz frequency is useful as that frequency in many jurisdictions is available for uses such as wireless power transfer. The driving signal might not be a single frequency, but might be more varied signal with a primary component at a frequency at which the transmitter coupler and receiver couplers are tuned.
The filter and matching circuit 226 filters out harmonics or other unwanted frequencies and matches the impedance of transmitter 204 to the impedance of transmitter coupler 214. As a result of driving transmitter coupler 214, transmitter coupler 214 may generate a wireless field 205 to wirelessly output power across a distance 219 at a level sufficient for charging a battery such as load 236, for example.
Transmitter 204 might include transmit circuitry, such as a controller 240 that may be implemented using a processor 242 that is coupled with a computer-readable memory 244 that includes program instructions 246 executable by processor 242. In other variations, the controller might comprise a micro-controller, an application-specific integrated circuit (ASIC), or the like. One set of operations of the controller might be to receive information from each of the components of the transmit circuitry, perform calculations based on the received information, and output control signals for each of the components that may adjust the operation of that component. Computer-readable memory 244 might comprise random-access memory (RAM), electrically erasable programmable read only memory (EEPROM), flash memory, or non-volatile RAM, for temporarily or permanently storing data for use in read and write operations performed by the controller and for storing data generated as a result of the calculations of the controller. Other functions are possible, but generally, transmitter 204 is able to generate a driving signal.
The controller might allow for adjusting transmit circuitry 206 and/or its operation, based on changes in the data over time. For example, the controller might provide instructions or signals to oscillator 222 to cause it to generate an oscillating signal at the operating frequency of the wireless power transfer. In some implementations, transmit circuitry 206 is configured to operate at the 6.78 MHz ISM frequency band. The controller may be configured to selectively enable oscillator 222 during a transmit phase (or duty cycle) and may be further configured to adjust the frequency or a phase of oscillator 22 which may reduce out-of-band emissions, especially when transitioning from one frequency to another. As described above, transmit circuitry 206 may be configured to provide an amount of charging power to transmitter coupler 214 via the signal, which may generate energy (e.g., magnetic flux) about transmitter coupler 214.
Transmit circuitry 206 may further include a low pass filter (LPF) operably connected to transmitter coupler 214, configured as the filter portion of matching circuit 226. In some exemplary implementations, the low pass filter may be configured to receive and filter an analog signal of current and an analog signal of voltage generated by driver circuit 224. In some implementations, the low pass filter may alter a phase of the analog signals. For example, the low pass filter may cause the same amount of phase change for both the current and the voltage, canceling out the changes. In some implementations, the controller may be configured to compensate for the phase change caused by the low pass filter. The low pass filter may be configured to reduce harmonic emissions to levels that may prevent self-jamming. Other exemplary implementations may include different filter topologies, such as notch filters that attenuate specific frequencies while passing others.
Transmit circuitry 206 may further include a fixed impedance matching circuit operably connected to the low pass filter and transmitter coupler 214. The matching circuit may be configured as the matching portion of filter and matching circuit 226. The matching circuit may be configured to match the impedance of transmit circuitry 206 to transmitter coupler 214. Other exemplary implementations may include an adaptive impedance match that may be varied based on measurable transmit metrics, such as the measured output power to the transmitter antenna or a DC current of driver circuit 224. Transmit circuitry 206 may further comprise discrete devices, discrete circuits, and/or an integrated assembly of components.
Receiver 208 includes receive circuitry 210 that includes a matching circuit 232 and a rectifier circuit 234. The matching circuit 232 may match the impedance of the receive circuitry 210 to the impedance of receive antenna 218. Rectifier circuit 234 may generate a direct current (DC) power output from an alternating current (AC) power input to charge a load 236, which might be a battery. Receiver 208 and transmitter 204 may additionally communicate on a separate communication channel such as Bluetooth, Zigbee, cellular, or similar channel. Receiver 208 and transmitter 204 may alternatively communicate via in-band signaling using characteristics of wireless field 205.
Additionally, in larger coils, the number of turns must often increase to maintain the same uniformity of field. However, as coil 506 becomes larger, two problems emerge. As coil 506 becomes larger and number of turns increases, the capacitance between each coil turn increases, and eventually coil 506 becomes self-resonant due to the additional capacitance. This self-resonance acts as an unwanted shunt tuning capacitance, causing unwanted behavior and hard-to-control currents. Secondly, as coil 506 becomes larger and number of turns increases, the inductance of coil 506 increases. This is undesirable as the voltage required to drive the coil at a given frequency would go up due to the higher impedance. Also, the electric field (E-field) generated near the terminals of coil 506 goes up as the voltage goes up and the E-field is effectively “wasted energy” as it does not contribute to charging the device, and is generally just a source of inefficiency and EMI. Thirdly, as coil 506 becomes longer, the resistance of the coil might increase.
Often, transmitter designers will avoid the above problems by not adding turns as the transmitter pad size increases. This results in less uniform H-fields, and consequent difficulty in supporting small receivers on the pad.
In a number of examples herein, not intending to be limiting, an apportionment of current from the driving signal to the first coupler loop and the second coupler loop is determined by a proportion of the impedance of the first coupler loop and the impedance of the second coupler loop (e.g., relative impedance). The relative impedances of the first coupler loop and the impedance of the second coupler loop divide the current from the driving signal to create a distributed magnetic field that is more evenly distributed over the transmitter pad than if the first current and the second current are constrained to be equal. This can be extended to more than two coupler loops.
Since the currents in each of the coupler loops do not have to be identical, changes to the configuration of the coupler loops (e.g., changing loop capacitance, loop path length and position, etc.) can be used to more evenly distribute out the field produced by the collection of coupler loops. One way described herein is to alter the impedance of one or more loops, but other ways might be used as well. The relative impedance of the coupler loops can be designed or altered by how the coupler loops are laid out and what capacitance is added to each coupler loop. Where the paths of the coupler loops is fixed, as is often the case with transmitter pads having embedded coupler coils, the intrinsic impedance of the coupler coil and the shape of the magnetic field generated would be relatively fixed, so that tuning the loops by adding capacitance or inductance could be done at the time of manufacture or infrequently.
If tuning need only be done once, it might be done by adding capacitance in a fixed manner. A number of examples of arrangement of coupler loops in a multifilament transmitter coupler are described herein with illustrations and example component values.
Throughout this disclosure, capacitances are identified. It should be understood that such capacitances can be implemented using a capacitor and/or an element other than a capacitor that intentionally and/or parasitically provides the needed capacitance.
The paths of the first coupler loop 601 and the second coupler loop 602 are shown to be substantially circular along a majority of their respective paths, but other variations are possible. In some embodiments, the paths follow rounded rectangles. The paths of the coupler loops are separated by a distance 605, which might be selected to provide for an even field. Typically, the paths are determined by design and are fixed. For example, the paths of the coupler loops might be fixed once the conductors of those loops are embedded into the transmitter coupler pad or other device used to hold the conductors. The relative values of the first capacitor of a loop and the second capacitor might correspond to capacitances that tune the first coupler loop 601 and the second coupler loop 602 so that, at or around a driving signal frequency, the first current and the second current provide a more evenly distributed magnetic field between the first magnetic field component and the second magnetic field component than would be generated if the first current and the second current were equal. In other variations where there are more than two coupler loops, the relative proportions of the impedances of the various loops result in the driving current being apportioned to provide a more evenly distributed magnetic field than would be generated if the driving current had to run through all of the loops in series.
The distances in the figures are not necessarily to scale. In some variations, the loops might be equally spaced throughout by the distance 605, but in other variations, the spacing might vary. The lengths and relative lengths of the loops might vary as well. It should be noted that while
The individual loops in parallel can include tuning elements that can be tuned individually or connected together and tuned externally. This largely avoids the problems of self-resonance and allows the possibility of tuning of current in each loop, and also allows designers to use more turns to achieve a more uniform field. The paths of the individual loops might vary depending on the desired shape of the coupling field. With this approach, a wireless power transmitter might have a power source, circuitry for generating a driving signal, a pair of electrical connections for driving a multifilament transmitter coupler that is part of a transmitter pad coupled to the pair of electrical connections to receive the driving signal at a pair of electrical connections. A first coupler loop enclosed within the transmitter pad and a second coupler loop enclosed within the transmitter pad could be separately tuned. The first and second coupler loop can also be spaced apart along defined paths, in parallel or not parallel, with the first coupler loop and separated from the first coupler loop along a loop longitude sufficient to generate distinguishable magnetic field components among the first coupler loop and the second coupler loop.
These tuning elements might be used once during manufacturing or during setup, but might also be usable for varying the tuning from time to time. Tuning elements may tune a resonance of the first coupler loop and the second coupler loop independently of each other. The tuning elements might be elements that have a variable reactance or impedance. In some embodiments, variability of the reactance or impedance can come from switchable elements that are switched into and out of current paths.
Since each loop 802 is connected in parallel rather than series, the total inductance is far lower, allowing for a lower voltage, higher current drive waveform. Since each loop 802 will start with a similar potential, the effective capacitance between each turn is reduced. The overall resistance is also reduced. Since the overall potential required is reduced, stray E-field is reduced. Multifilament transmitter coupler 800 is shown with the path of the some loops being concentric for a majority of their respective paths, with the first path being entirely inside the second path. A plurality of additional coupler loops is also provided, wherein each coupler loop of the plurality of additional coupler loops has a path approximating a rectangle for a majority of its path and encloses each of its interior loops.
A loop's resonant capacitors can be implemented in various ways. For example, they can all be tuned to resonance. In that case, since smaller loops have smaller inductances, they would have different capacitor values for each loop. This will tend to equalize the current in each loop. Another approach is to tune the resonant capacitors to adjust the power in each loop. Depending on geometry, increasing the current in the outer loops may result in a more evenly distributed magnetic field, and this can be beneficial to wireless chargers.
It may be that the outer loops are tuned to resonance or near resonance, and the inner loops are tuned further from resonance. This may reduce current in the inner loops and result in a more evenly distributed magnetic field overall. In some cases, this may result in similar (or identical) values of capacitor for each loop, as the outer loops are progressively detuned.
It should be apparent upon reading this disclosure that values for coil length, capacitance, resonant frequency, currents, etc. might be different for different applications and can be determined in a straightforward manner without undue experimentation after reading this disclosure. For example, a simulation can be performed as explained herein to identify a desired magnetic field patterned for a proposed set of multifilament coupler loops. From there, some suitable component values might be determined. Then, when a prototype or production device is built, those component values might serve as a starting point for optimizing actually produced devices to account for differences from the simulated environment. For example, in the simulation described above, the coupler loops are completely circular loops. In a practical implementation, there may be some deviation from perfect circles, for example, to allow for connections to capacitors and current input wires. As another example, an actual device might not draw exactly the currents shown in the rightmost column of the table in
Note that the lengths of the coils for the simulated circuit are in increments of 100 millimeters. Assuming circular paths, the area inside each coil would go up as the square of the length of the coil, so the current targets for coils of length 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm are 0.1 A, 0.4 A, 0.9 A, 1.6 A, and 2.5 A respectively. The values of the capacitors and inductors can be determined based on the frequency of the applied voltage and the relative impedances needed to reach those target currents in each coil.
Different shapes and components are possible and circular paths are not required.
As illustrated there, multifilament transmitter coupler 1400 has four loops 1402(1) to 1402(4) and corresponding loop capacitances C11, C12, C21, C22, C31, C32, C41, C42, C51 and C52, as shown. The current induced by the driving signal across connections 1404(1) and 1404(2) would divide over those five loops based on their impedance at the driving signal frequency. Additional capacitance is provided by feed capacitor FC1 in series after connection 1404(1) and feed capacitor FC2 in series after connection 1404(2). Some of these capacitances can be variable to allow for tuning, if needed. The loop capacitances, in some embodiments, are similar in ratio to the values given in
In a specific implementation, feed capacitors, FC1 and FC2 might be 2200 pf or other similar values, and the loop capacitances have the values shown in
For some embodiments, the resistance of each loop is a function of the length of the path of the loop and where identical resistances, or near identical resistances are desired, the lengths of the paths in those embodiments are made close to identical. In the above examples, the loops did not overlap in the plane of the loop's paths and vary in length. This is not necessarily a requirement, as the paths can be in certain layouts with identical, or nearly identical, lengths without overlapping in the plane of the loop's paths. A simple approach to nearly identical lengths uses overlapping loop paths, as
In the example illustrated in
In
A loop-to-loop coupling capacitor, Ca, is between an interior node of loop 1602(1) and an interior node of loop 1602(2), while a loop-to-loop coupling capacitor, Cb, is between the other two interior nodes of loops 1602(1) and 1602(2). Similarly, a loop-to-loop coupling capacitor, Cc, is between an interior node of loop 1602(2) and an interior node of loop 1602(3), a loop-to-loop coupling capacitor, Cd, is between the other two interior nodes of loops 1602(2) and 1602(3), a loop-to-loop coupling capacitor, Ce, is between an interior node of loop 1602(3) and an interior node of loop 1602(4), and a loop-to-loop coupling capacitor, Cf, is between the other two interior nodes of loops 1602(3) and 1602(4).
In some variations, separate capacitances Ca and Cb are not needed, as the proper selection of C11 and C12 could replace effects of capacitances Ca and Cb. The values for those capacitances might be determined using values from the table of
As illustrated there, current applied to connections 1702(1) and 1702(2) would flow through loops 1702(1), 1702(2), 1702(3), and 1702(4). Current in loop 1702(1) flows through inductor L11, capacitor C11, capacitor C12, and inductor L12. Current in loop 1702(2) flows through inductor L21, capacitor C21, capacitor C22, and inductor L22. Current in loop 1702(3) flows through inductor L31, capacitor C31, capacitor C32, and inductor L32. Current in loop 1702(4) flows through inductor L41, capacitor C41, capacitor C42, and inductor L42. The values of these components might be as indicated in the table of
The inductor/transformers may have a number of turns proportional to the current in each loop. Such transformers will have various effects. One effect is that their leakage inductance may serve as an unchanging, non-detunable inductance. Thus, any detuning effect caused by a change in inductance in the loop itself will be reduced, since the total inductance in the coil (transformer leakage+loop itself) will change a smaller percentage. Another effect is that the transformer windings will couple to each other and tend to oppose a change in current ratios. If the currents match the transformer ratios, the transformer will have minimal or no effect and simply pass the current to the resonator.
Using one or more of the elements, techniques and/or components described above, a suitable multifilament transmitter coupler can be designed. Further embodiments can be envisioned to one of ordinary skill in the art after reading this disclosure. In other embodiments, combinations or sub-combinations of the above disclosed invention can be advantageously made. The example arrangements of components are shown for purposes of illustration and it should be understood that combinations, additions, re-arrangements, and the like are contemplated in alternative embodiments of the present invention. Thus, while the invention has been described with respect to exemplary embodiments, one skilled in the art will recognize that numerous modifications are possible.
The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the disclosure. It will be understood by those within the art that if a specific number of a claim element is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, 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,” “comprising,” “includes,” and “including,” 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.
For example, the processes described herein may be implemented using hardware components, software components, and/or any combination thereof. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims and that the invention is intended to cover all modifications and equivalents within the scope of the following claims.
Operations of processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Processes described herein (or variations and/or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions and may be implemented as code (e.g., executable instructions, one or more computer programs or one or more applications) executing collectively on one or more processors, by hardware or combinations thereof. The use of any and all examples is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
