Active electromagnetic shielding for high power dynamic wireless charging and related systems, methods, and devices

Active electromagnetic shielding for dynamic high power wireless charging and related electrified roadway systems, method, and wireless power transmitters is disclosed. A wireless power transmitter includes a first canceling coil offset from a power transmission coil, a second canceling coil offset from the power transmission coil, and circuitry electrically connected to the first canceling coil and the second canceling coil. The circuitry is configured to deliver canceling currents to the first canceling coil and the second canceling coil to destructively interfere with portions of electromagnetic fields generated by the power transmission coil.

TECHNICAL FIELD

The present disclosure relates generally to electromagnetic shielding for wireless power systems, and more specifically to active electromagnetic field canceling in wireless power systems such as dynamic inductive power transfer (dIPT) systems.

BACKGROUND

Dynamic wireless power transfer, or equivalently dynamic inductive power transfer (dIPT), is a newly developed convenient, flexible, and state-of-the-art wireless charging technology with the potential capability of enabling fully automated in-motion charging for wirelessly chargeable vehicles traveling in electrified roadways.

BRIEF SUMMARY

In some embodiments, a wireless power transmitter includes a first canceling coil offset from a power transmission coil, a second canceling coil offset from the power transmission coil, and circuitry electrically connected to the first canceling coil and the second canceling coil. The circuitry is configured to deliver canceling currents to the first canceling coil and the second canceling coil to destructively interfere with portions of electromagnetic fields generated by the power transmission coil.

In some embodiments, an electrified roadway system includes a plurality of wireless power transmitters. Each wireless power transmitter of the plurality of wireless power transmitters includes a power transmission coil and a plurality of canceling coils. The power transmission coil is configured to inductively couple to and provide wireless power to receive coils of wirelessly chargeable vehicles. The plurality of canceling coils are configured to generate canceling electromagnetic fields to destructively interfere with portions of electromagnetic fields generated by the power transmission coil.

In some embodiments, a method of assembling a wireless power transmitter includes positioning a power transmission coil, positioning a first canceling coil proximate to the power transmission coil, positioning a second canceling coil proximate to the power transmission coil, and electrically connecting circuitry to the first canceling coil and the second canceling coil. The circuitry is configured to excite the first canceling coil and the second canceling coil out of phase with a transmit current of the power transmission coil.

In some embodiments, a method of operating a wireless power transmitter includes providing a transmit current to a power transmission coil to transmit power to a receive coil of a wireless power receiver. The method also includes providing a first canceling current to a first canceling coil laterally offset from the power transmission coil, the first canceling current out of phase with the transmit current. The method further includes providing a second canceling current to a second canceling coil laterally offset from the power transmission coil. The second canceling current is out of phase with the transmit current.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views of any particular method, system, device, or structure, but are merely idealized representations that are employed to describe the embodiments of the present disclosure. In some instances similar structures or components in the various drawings may retain the same or similar numbering for the convenience of the reader; however, the similarity in numbering does not necessarily mean that the structures or components are identical in size, composition, configuration, or any other property.

It will be readily understood that the components of the embodiments as generally described herein and illustrated in the drawings could be arranged and designed in a wide variety of different configurations. Thus, the following description of various embodiments is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments may be presented in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

Those of ordinary skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. Some drawings may illustrate signals as a single signal for clarity of presentation and description. It will be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present disclosure may be implemented on any number of data signals including a single data signal.

For charging power up to the 100 kilo Watt (100 kW) or 200 kW levels for light duty electric vehicles (LDEVs), electromagnetic (EM) safety in regard to human health surrounding dIPT systems becomes a concern. Passive shielding solutions (e.g., using ferrite shielding) may improve EM safety in stationary 100 kW to 200 kW level wireless charging. Due to the high cost of ferrite for dIPT systems, however, costs for producing wireless power transmitters may be decreased if less ferrite were used (e.g., on the ground-side but also on the vehicle side in some instances) for shielding solutions.

Different from stationary inductive power transfer (IPT), in-motion wireless charging is a feature of dIPT. For LDEVs dIPT offers a wireless charging solution for fully autonomous driving. For example, dIPT offers the potential of electric vehicles (EVs) to travel relatively long distances without stops to recharge and increasing the size of the on-board battery, as compared to stationary IPT solutions. As a result, energy storage capacity for LDEVs may be reduced in dIPT systems as compared to stationary IPT systems.

High power charging (e.g., 100 kW or greater) enables less of the roadway to be electrified as compared to low power charging in order to meet vehicle energy requirements. In other words, the more power received by an EV as it passes each wireless charging station, the fewer wireless charging stations may be used along the roadway. As a general rule, the high the power of charging, the less ground-side infrastructure may be used, which may result in lower equipment and maintenance costs.

Disclosed herein is active shielding of wireless power transmitter coils (e.g., using canceling coils). This active shielding may be used as a supplement to passive shielding such as ferrite shielding. Embodiments disclosed herein may be used in dIPT systems such as for LDEVs.

FIG.1andFIG.2are views of a roadway system100, according to some embodiments.FIG.1is a perspective view of the roadway system100.FIG.2is a plan view of a portion of the roadway system100.

Referring toFIG.1andFIG.2together, the roadway system100includes an electrified roadway102and a non-electrified roadway104. The electrified roadway102may include wireless power transmitters108along the electrified roadway102. Each of the wireless power transmitters108may include a power transmission coil110, a first canceling coil112, and a second canceling coil114. The power transmission coil110is configured to inductively couple to and provide wireless power to receive coils of wirelessly chargeable vehicles116(e.g., the wirelessly chargeable vehicle202) in the electrified roadway102. By way of non-limiting example, the power transmission coil110may provide high frequency resonant charging currents. The first canceling coil112is spaced laterally from the power transmission coil110and the second canceling coil114is spaced laterally from the power transmission coil110opposite from first canceling coil electrified roadway102across the power transmission coil110. By way of non-limiting example, the first canceling coil112and the second canceling coil114may be positioned at the edges of a lane of the electrified roadway102, as illustrated inFIG.1andFIG.2. Centers of the first canceling coil112and the second canceling coil114may be positioned at least 0.4 meters from the power transmission coil110, without limitation. Also, centers of the first canceling coil112and the second canceling coil114should be spaced at a distance from the center of the power transmission coil110that is greater than or equal to a width (in a vehicle's side-to-side direction) of the power transmission coil110.

Although only two canceling coils (i.e., first canceling coil112and second canceling coil114) are illustrated for each of the wireless power transmitters108inFIG.1andFIG.2, a number of canceling coils (e.g., the first canceling coil112, the second canceling coil114) of each of the wireless power transmitters108may be any positive even number (e.g., 2, 4, 6, . . . ).

The electrified roadway102and the non-electrified roadway104are configured to generate canceling electromagnetic fields to destructively interfere with portions of electromagnetic fields generated by the power transmission coil110. By way of non-limiting example, the first canceling coil112and the second canceling coil114may be electrically connected in series with the power transmission coil110, but excited by currents in a reverse direction from that of the power transmission coil110to generate electromagnetic fields of opposite magnitudes. Also by way of non-limiting example, canceling currents provided to the first canceling coil112and the second canceling coil114may be out of phase (e.g., substantially 180 degrees out of phase) with a transmit current provided to the power transmission coil110. The first canceling coil112and the second canceling coil114are smaller coils than the power transmission coil110. The first canceling coil112and the second canceling coil114may generate reverse magnetic fields simultaneously to magnetic fields generated by the power transmission coil110to minimize magnetic field emissions.

Wirelessly chargeable vehicles116such as wirelessly chargeable vehicle202may travel in the electrified roadway102and vehicles118(which may include non-wirelessly chargeable vehicles and wirelessly chargeable vehicles116) may travel in the non-electrified roadway104. In some embodiments, one or more of the wirelessly chargeable vehicles116may include LDEVs. When wirelessly chargeable vehicles116pass by the wireless power transmitters108, the power transmission coil110, the first canceling coil112, and the second canceling coil114are activated simultaneously and alternatively to charge batteries of the in-motion wirelessly chargeable vehicles116.

As previously discussed, during the wireless charging process, generated electromagnetic fields may cause safety issues (e.g., for drivers of the wirelessly chargeable vehicles116). The first canceling coil112and second canceling coil114may generate canceling electromagnetic fields that cancel a portion of electromagnetic fields generated by the power transmission coil110to reduce the severity of these safety issues. For example, the first canceling coil112and the second canceling coil114may generate reverse magnetic fields that are reverse to main fields from the power transmission coil110to reduce stray magnetic field emissions.

FIG.3is a front view of a wireless power system300, according to some embodiments. The wireless power system300includes the wirelessly chargeable vehicle202ofFIG.2and the power transmission coil110ofFIG.1andFIG.2. The wireless power system300also includes a receive coil302of the wirelessly chargeable vehicle202. The power transmission coil110is configured to provide wireless power to the receive coil302.

During transmission of wireless power from the power transmission coil110to the receive coil302, electromagnetic fields may be emitted. Magnitudes of these electromagnetic fields may be regulated to improve safety of wireless power systems such as the wireless power system300ofFIG.3. For example, the Society of Automotive Engineers International (SAE International) regulates electromagnetic fields in an under vehicle region304, an over vehicle region306, and an inside vehicle region308in a specification defined in SAE J2954. SAE J2954 also defines a maximum allowed magnetic field of 27 micro Tesla (μT) at a distance D1of 0.8 meters (m) from the center of the vehicle-side coil (receive coil302) for LDEV stationary inductive power transfer (IPT), as shown inFIG.3. Although the 27 μT at a distance of D1of 0.8 m standard of SAE J2954 is designed for stationary IPT, the 27 μT at a distance D1of 0.8 m standard may still apply to dIPT systems because the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2010 standard provides a health protection standard of 27 μT and the 0.8 m criteria is derived from a typical width of a 1.6 m wide LDEV (0.8 is half of 1.6 m, corresponding to the distance from the center of the power transmission coil110to a side edge of the wirelessly chargeable vehicle202).

The use of canceling coils (e.g., the first canceling coil112and the second canceling coil114) to actively cancel electromagnetic radiation from the power transmission coil110, as discussed in various embodiments herein, may reduce the magnitude of electromagnetic fields at the distance D1from the center of the receive coil302. Such reduction may enable compliance with a 27 μT standard at the distance D1of 0.8 m from the center of the receive coil302in high power (e.g., 100 kW to 200 kW or more) wireless power systems.

FIG.4is a schematic illustration of a wireless power system400, according to some embodiments. The wireless power system400includes a transmitter406and a receiver408. The transmitter406is configured to transmit wireless power414to the receiver408. The transmitter406includes circuitry412including an active front end (AFE) and power factor compensation (PC) circuitry (AFE and PF compensation402), an H-bridge circuit420, and a resonator circuit410. The AFE and PF compensation402is configured to receive a grid voltage potential vgridfrom grid power106and provide a direct current (DC) voltage potential Vdo, to the H-bridge circuit420.

The H-bridge circuit420includes transistors T1, T2, T3, and T4and diodes D1, D2, D3, and D4. Diode D1is electrically connected in parallel across transistor T1, diode D2is electrically connected in parallel across transistor T2, diode D3is electrically connected in parallel across transistor T3, and diode D4is electrically connected in parallel across transistor T4. Switching of the transistors T1, T2, T3, and T4may be electrically controlled responsive to switch signals426(e.g., from a controller404). By way of non-limiting example, the controller404may be configured to operate the H-bridge circuit420as an inverter to provide an alternating current voltage potential (transmit voltage potential vt) to the resonator circuit410. For example, the controller404may be configured to switch the transistors T1, T2, T3, and T4at a select frequency to control a frequency of the transmit voltage potential vt. The H-bridge circuit420includes a first node n1between transistor T1and transistor T2, and a second node n2between transistor T3and transistor T4. The H-bridge circuit420is configured to receive the DC voltage potential Vdo, from the AFE and PF compensation402and provide, across nodes n1and n2, a transmit voltage potential vtto the resonator circuit410at a transmit current it.

The resonator circuit410includes a transmitter capacitor Ct, the power transmission coil110(Lt) connected in series with the transmitter capacitor Ct, the first canceling coil112LC1electrically connected in series with the power transmission coil110, the second canceling coil114LC2electrically connected in series with the power transmission coil110, current controllers416configured to control currents iC1and iC2provided to the first canceling coil112and the second canceling coil114, respectively, and a line inductance424electrically connected in series with the power transmission coil110and in parallel with the first canceling coil112and the second canceling coil114. The resonator circuit410is electrically connected between node n1and node n2of the H-bridge circuit420. Accordingly, the resonator circuit410is configured to receive the transmit voltage potential vtand the transmit current it from the H-bridge circuit420and provide wireless power414from the power transmission coil110to a receive coil302of the receiver408via inductive coupling422.

The receiver408includes the receive coil302(Lr), a receiver capacitor Cr, a rectifier circuit418, and a battery428(e.g., a battery of a vehicle). The receiver capacitor Cr is electrically connected between the receive coil302and the rectifier circuit418. The receive coil302is configured to receive the wireless power414from the power transmission coil110and provide a receive current it to the receiver capacitor Cr. The receiver capacitor Cr is configured to provide the receive current it and a receive voltage potential vrto the rectifier circuit418. The rectifier circuit418includes rectifying diodes D5, D6, D7, and D8and an output capacitor Co. The rectifying diodes D5, D6, D7, and D8are electrically connected in a diode bridge arrangement to rectify the receive voltage potential vrreceived from the receive coil302and the receive capacitor Cr. As a result, the output capacitor Co is configured to smooth a rectified voltage potential provided by the diodes D5, D6, D7, and D8to provide a DC output voltage potential Vo at an output current Io to the battery428. As a result, the battery428may be charged responsive to the wireless power414provided by the transmitter406to the receiver408.

Since the first canceling coil112and the second canceling coil114are electrically connected in series with the power transmission coil110, the first canceling coil112and the second canceling coil114may be excited with currents in an opposite direction to that of a transmit current it of the power transmission coil110to cause the first canceling coil112and the second canceling coil114to generate canceling electromagnetic fields that are 180 degrees out of phase with electromagnetic fields generated by the power transmission coil110. By way of non-limiting example, the first canceling coil112and the second canceling coil114may be fed with the canceling currents iC1and iC2at an opposite end of the coils as compared to an end of a the power transmission coil110that the transmit current it is fed to.

Also, the current controllers416may limit the magnitude of canceling currents iC1and iC2conducted through the first canceling coil112and the second canceling coil114as compared to a transmit current it conducted through the power transmission coil110to reduce the amount of power expended by the first canceling coil112and second canceling coil114to actively cancel electromagnetic fields generated by the power transmission coil110. By way of non-limiting example, the current controllers416may be configured to limit magnitudes of each of the canceling currents iC1and iC2to substantially six percent (6%) or less of the magnitude of the transmit current it. Since some standards governing operation of wireless charging systems require that transmission of wireless power be 88% efficient, canceling currents iC1and iC2each having magnitudes that are 6% of the magnitude of the transmit current it would press the wireless power system400to the limit of an 88% efficiency requirement assuming 100% efficiency otherwise (because two times 6% (6% per canceling coil) is 12%, and 100% minus 12% is the 88% efficiency requirement). Also by way of non-limiting example, the current controllers416may be configured to limit magnitudes of the canceling currents iC1and iC2to substantially 2.5% of the transmit current it. In addition, the inductance values of the first canceling coil112and the second canceling coil114may be adjustable and may be less than an inductance value of the power transmission coil110to cause most (e.g., greater than 95%) of the transmit current it to bypass the first canceling coil112and the second canceling coil114through the power transmission coil110and the conducted wire (represented by the line inductance424). In this way losses due to current passing through the first canceling coil112and the second canceling coil114may be reduced.

Furthermore, the first canceling coil112and the second canceling coil114may include fewer turns than the power transmission coil110. By way of non-limiting example, the first canceling coil112and the second canceling coil114may each include about one fourth the number of turns (e.g., two turns assuming the power transmission coil110includes eight turns) of the power transmission coil110. Also by way of non-limiting example, the first canceling coil112and the second canceling coil114may include three turns or less. In addition, the first canceling coil112and the second canceling coil114may implement smaller Litz wire diameter as compared to that of the power transmission coil110.

In some embodiments, a size of the first canceling coil112and the second canceling coil114may be less than a size of the power transmission coil110. By way of non-limiting example, the size of the first canceling coil112and the second canceling coil114may be about fifty percent (50%) or less than a size of the power transmission coil110.

In some embodiments, shapes of the first canceling coil112and the second canceling coil114may be at least substantially the same as that of the power transmission coil110(e.g., scaled-down versions of the shape of the power transmission coil110). By way of non-limiting example, the power transmission coil110, the first canceling coil112, and the second canceling coil114may all be shaped as double-D coils. In some embodiments, however, one or more of the first canceling coil112and the second canceling coil114may have shapes that are different from that of the power transmission coil110.

When one of the wirelessly chargeable vehicles116passes by one of the wireless power transmitters108(e.g., the transmitter406), the highest transferred wireless power414will be received by the receiver408of the vehicle when the receive coil302and the power transmission coil110are substantially aligned. Considering only the safety of a driver of the vehicle, the fully aligned situation is considered as the worst case because of the highest magnitude receive current it received. It is noted that some misaligned scenarios might lead to higher electromagnetic emissions near the power transmission coil110.

FIG.5is a perspective view of examples of coils500of the wireless power system400ofFIG.4. The coils500include the power transmission coil110, the first canceling coil112, the second canceling coil114, and the receive coil302ofFIG.4.FIG.5also illustrates a transmitter ferrite back shield502behind the power transmission coil110and a receiver ferrite back shield504behind the receive coil302. The transmitter ferrite back shield502and the receiver ferrite back shield504are configured to provide passive shielding to electromagnetic fields generated by the power transmission coil110and the receive coil302. As previously discussed, the first canceling coil112and the second canceling coil114are configured to provide active shielding to the electromagnetic fields generated by the power transmission coil110and the receive coil302.

As may be observed in the example ofFIG.5, the power transmission coil110, the receive coil302, the first canceling coil112, and the second canceling coil114are each implemented as double D shaped coils. Accordingly, the first canceling coil112and the second canceling coil114are of the same shape as the power transmission coil110, but of a smaller size than the power transmission coil110.

As also previously discussed, the canceling flowing in the first canceling coil112and the second canceling coil114are 180 degrees opposite to the transmit current it flowing in the power transmission coil110. To actively control the spray magnetic field and minimize the losses in the power transmission coil110, currents flowing through the first canceling coil112and the second canceling coil114are adjusted (e.g., using the current controllers416ofFIG.4) to be very low. Also, two canceling coils (first canceling coil112and second canceling coil114) are installed on two sides of the power transmission coil110with relatively large horizontal gap distances (e.g., substantially 0.4 meters or more) between the power transmission coil110and each of the first canceling coil112and the second canceling coil114so that the canceling coils and the power transmission coil110are decoupled, which would reduce the impact of the first canceling coil112and the second canceling coil114on a coupling factor between the power transmission coil110and the receive coil302. The transmitter capacitor Ct (FIG.4) may be tuned to compensate for inductances LC1and LC2of the first canceling coil112and the second canceling coil114, respectively.

Although not shown, in some embodiments, a wireless power receiver may include canceling coils, similar to those of the wireless power transmitters disclosed herein. It should be noted, however, that in order to space centers of canceling coils 0.4 meters from a center of a receive coil, a relatively wide vehicle (e.g., a heavy-duty electric vehicle) may be used to provide sufficient space under the vehicle for the receive coil and the canceling coils.

FIG.6is a plot600illustrating an impact of canceling coils according to embodiments of the disclosure on electromagnetic fields in a 100 kW wireless power system (e.g., the wireless power system300ofFIG.3or the wireless power system400ofFIG.4). As a typical example of a high-power IPT system, a 100 kilo Watt (kW) IPT system was simulated to observe the impact of the first canceling coil112and the second canceling coil114on electromagnetic fields generated by the power transmission coil110and the first canceling coil112. Two canceling coils (first canceling coil112and second canceling coil114) were simulated at two sides of a power transmission coil110with centers of the canceling coils at a distance of 0.8 meters from the center of the power transmission coil110. To minimize the impact of the canceling coils on the power transmission coil110in terms of efficiency reduction, the first canceling coil112and the second canceling coil114were simulated as only having two turns each. Also, canceling currents (e.g., iC1and iC2ofFIG.4) with magnitudes of 4.275 amperes (A) were simulated, which is only about 2.5% of the transmit current (e.g., it ofFIG.4) simulated in the power transmission coil110. Table 1 summarizes the parameters of the simulation.

The plot600includes simulated magnetic field magnitudes as a function of distance from a center of the power transmission coil110and the receive coil302(which are simulated as perfectly aligned) both with canceling coils and without canceling coils. Accordingly, the plot600includes without canceling coils magnetic field602and with canceling coils magnetic field604. The plot600also illustrates a 27 μT level606associated with a 27 μT at 0.8 m from the center of the power transmission coil110requirement, as mandated by ICNIRP 2010. The with canceling coils magnetic field604is preliminarily verified by a magnetic field measurement608at a 1.1-m distance with IPT operated at 100 kW.

As illustrated in the plot600, the with canceling coils magnetic field604is about 18.2 μT 0.8 m from the center of the coil, as compared to about 37.2 μT of the without canceling coils magnetic field602at 0.8 m. Accordingly, the canceling coils are shown in the plot600to reduce magnetic field emission from 37.2 μT to 18.2 μT at a 0.8-m distance from the center of the power transmission coil110. Also, all magnetic field emission levels of the with canceling coils magnetic field604over 0.8 m are below the 27 μT requirement mandated by ICNIRP 2010. Since only 2.5% of the transmit current it of the power transmission coil110is flowing in the canceling coils, the downside of applying active canceling coils in terms of increasing coil losses is acceptable.

FIG.7is a plot700illustrating an impact of canceling coils according to embodiments of the disclosure on electromagnetic fields in a 200 kW wireless power system (e.g., the wireless power system300ofFIG.3or the wireless power system400ofFIG.4). A similar simulation to that ofFIG.6was conducted using a 200 kW wireless power system and with different canceling-coil currents. For example, the plot700includes a no canceling coil magnetic field702, a 2.5% canceling current magnetic field704, and a 4% canceling current magnetic field706. The no canceling coil magnetic field702is a magnetic field magnitude plotted against side-to-side distances from the center of the power transmission coil110without the first canceling coil112and the second canceling coil114. The 2.5% magnetic field current704is a magnetic field magnitude plotted against side-to-side distances from the center of the power transmission coil110while a current provided to the first canceling coil112and the second canceling coil114is 2.5% of that of the current provided to the power transmission coil. Likewise, the 4% magnetic field current706is a magnetic field magnitude plotted against side-to-side distances from the center of the power transmission coil110while a current provided to the first canceling coil112and the second canceling coil114is 4% of that of the current provided to the power transmission coil.FIG.7also illustrates the 27 μT level606associated with a 27 μT at 0.8 m from the center of the power transmission coil110requirement, as mandated by ICNIRP 2010.

It is observed that the field emission around 0.8 m from the center of the power transmission coil110can be limited to less than the 27 μT level606in 200 kW operation by adjusting the currents in the first canceling coil112and the second canceling coil114. With canceling-coil currents increasing from no canceling current (no canceling coil magnetic field702) to 2.5% of power transmission coil110cancelling current (2.5% canceling current magnetic field704) to 4% of transmission coil canceling current (4% canceling current magnetic field706), the EM field at 0.8 m drops significantly from 53.2 μT to 25.8 μT to 13.1 μT, respectively, at 0.8 meters from the center of the power transmission coil110.

FIG.8is a flowchart illustrating a method800of assembling a wireless power transmitter, according to some embodiments. At operation802, the method800includes positioning a power transmission coil. At operation804, the method800includes positioning a first canceling coil proximate to the power transmission coil. At operation806, the method800includes positioning a second canceling coil proximate to the power transmission coil. By way of non-limiting example, centers of the first canceling coil and the second canceling coil may be positioned substantially 0.4 m or more from a center of the power transmission coil.

At operation808, method800includes electrically connecting circuitry to the first canceling coil and the second canceling coil. The circuitry is configured to excite the first canceling coil and the second canceling coil out of phase with a transmit current of the power transmission coil. By way of non-limiting example, the circuitry may be configured to excite the first canceling coil and the second canceling coil 180 degrees out of phase with the transmit current of the power transmission coil.

FIG.9is a flowchart illustrating a method900of operating a wireless power transmitter, according to some embodiments. At operation902, the method900includes providing a transmit current to a power transmission coil to transmit power to a receive coil of a wireless power receiver. At operation904, the method900includes providing a first canceling current to a first canceling coil proximate to the power transmission coil. The first canceling current is out of phase with the transmit current. At operation906, the method900includes providing a second canceling current to a second canceling coil proximate to the power transmission coil. The second canceling current is out of phase with the transmit current.

EXAMPLES

A non-exhaustive, non-limiting list of example embodiments follows. Not each of the example embodiments listed below is explicitly and individually indicated as being combinable with all others of the example embodiments listed below and embodiments discussed above. It is intended, however, that these example embodiments are combinable with all other example embodiments and embodiments discussed above unless it would be apparent to one of ordinary skill in the art that the embodiments are not combinable.

Example 1: A wireless power transmitter, comprising: a first canceling coil offset from a power transmission coil; a second canceling coil offset from the power transmission coil; and circuitry electrically connected to the first canceling coil and the second canceling coil, the circuitry configured to deliver canceling currents to the first canceling coil and the second canceling coil to destructively interfere with portions of electromagnetic fields generated by the power transmission coil.

Example 2: The wireless power transmitter of Example 1, wherein magnitudes of the canceling currents for each of the first canceling coil and the second canceling coil are less than or equal to six percent (6%) of a magnitude of a transmit current provided to the power transmission coil.

Example 3: The wireless power transmitter according to any one of Examples 1 and 2, wherein numbers of turns of the first canceling coil and the second canceling coil are less than a number of turns of the power transmission coil.

Example 4: The wireless power transmitter of Example 3, wherein the numbers of turns of the first canceling coil and the second canceling coil are substantially one quarter of the number of turns of the power transmission coil.

Example 5: The wireless power transmitter according to any one of Examples 3 and 4, wherein the numbers of turns of the first canceling coil and the second canceling coil are less than or equal to three turns.

Example 6: The wireless power transmitter according to any one of Examples 1-5, wherein the first canceling coil and the second canceling coil are electrically connected in series with the power transmission coil and in parallel with each other.

Example 7: The wireless power transmitter of Example 6, wherein the circuitry includes current controllers electrically connected between the power transmission coil and the first canceling coil and the second canceling coil, the current controllers configured to reduce the canceling currents delivered to the first canceling coil and the second canceling coil as compared to a transmit current provided to the power transmission coil.

Example 8: The wireless power transmitter according to any one of Examples 1-7, wherein sizes of the first canceling coil and the second canceling coil are less than a size of the power transmission coil.

Example 9: The wireless power transmitter of Example 8, wherein the sizes of the first canceling coil and the second canceling coil are less than or equal to fifty percent (50%) of the size of the power transmission coil.

Example 10: The wireless power transmitter according to any one of Examples 1-9, wherein at least one of the first canceling coil and the second canceling coil has at least substantially a same shape as a shape of the transmit coil.

Example 11: The wireless power transmitter according to any one of Examples 1-10, wherein centers of the first canceling coil and the second canceling coil are positioned at least 0.4 meters from a center of the power transmission coil.

Example 12: The wireless power transmitter of Example 11, wherein the centers of the first canceling coil and the second canceling coil are positioned substantially 0.8 meters from the center of the power transmission coil.

Example 13: The wireless power transmitter according to any one of Examples 1-9, 11, and 12, wherein at least one of the first canceling coil and the second canceling coil has a shape that is different from a shape of the power transmission coil.

Example 14: An electrified roadway system, comprising: a plurality of wireless power transmitters, each wireless power transmitter of the plurality of wireless power transmitters including: a power transmission coil configured to inductively couple to and provide wireless power to receive coils of wirelessly chargeable vehicles; and a plurality of canceling coils configured to generate canceling electromagnetic fields to destructively interfere with portions of electromagnetic fields generated by the power transmission coil.

Example 15: The electrified roadway system of Example 14, wherein the plurality of canceling coils comprises a first canceling coil spaced laterally from the power transmission coil and a second canceling coil spaced laterally from the power transmission coil opposite from first canceling coil across the power transmission coil.

Example 16: The electrified roadway system according to any one of Examples 14 and 15, wherein a number of coils of the plurality of canceling coils is an even number of canceling coils.

Example 17: The electrified roadway system of Example 16, wherein the number of coils of the plurality of canceling coils is four (4).

Example 18: The electrified roadway system according to any one of Examples 14-17, wherein each of the plurality of canceling coils is excited with a canceling current of an opposite direction as compared to a transmitter current of the power transmission coil.

Example 19: A method of assembling a wireless power transmitter, the method comprising: positioning a power transmission coil; positioning a first canceling coil proximate to the power transmission coil; positioning a second canceling coil proximate to the power transmission coil; and electrically connecting circuitry to the first canceling coil and the second canceling coil, the circuitry configured to excite the first canceling coil and the second canceling coil out of phase with a transmit current of the power transmission coil.

Example 20: The method of Example 19, wherein electrically connecting circuitry to the first canceling coil and the second canceling coil comprises electrically connecting the first canceling coil and the second canceling coil in series with the power transmission coil.

Example 21: The method of Example 20, wherein electrically connecting the first canceling coil and the second canceling coil in series with the power transmission coil comprises electrically connecting current controllers between the power transmission coil and the first canceling coil and the second canceling coil, the current controllers configured to reduce magnitudes of canceling currents provided to the first canceling coil and the second canceling coil with respect to a transmit current of the power transmission coil.

Example 22: The method according to any one of Examples 20 and 21, wherein electrically connecting the first canceling coil and the second canceling coil in series with the power transmission coil comprises electrically connecting the first canceling coil and the second canceling coil in parallel with each other.

Example 23: The method according to any one of Examples 19-22, wherein positioning the power transmission coil, the first canceling coil, and the second canceling coil comprises positioning the power transmission coil, the first canceling coil, and the second canceling coil beneath a surface of an electrified roadway.

Example 24: The method according to any one of Examples 19-23, further comprising positioning a ferrite back shield behind the power transmission coil.

Example 25: A method of operating a wireless power transmitter, the method comprising: providing a transmit current to a power transmission coil to transmit power to a receive coil of a wireless power receiver; providing a first canceling current to a first canceling coil laterally offset from the power transmission coil, the first canceling current out of phase with the transmit current; and providing a second canceling current to a second canceling coil laterally offset from the power transmission coil, the second canceling current out of phase with the transmit current.

Example 26: The method of Example 25, wherein providing a first canceling current and a second canceling current out of phase with the transmit current comprises providing the first canceling current and the second canceling current substantially one hundred and eighty degrees out of phase with the transmit current.

CONCLUSION

As used in the present disclosure, the term “combination” with reference to a plurality of elements may include a combination of all the elements or any of various different subcombinations of some of the elements. For example, the phrase “A, B, C, D, or combinations thereof” may refer to any one of A, B, C, or D; the combination of each of A, B, C, and D; and any subcombination of A, B, C, or D such as A, B, and C; A, B, and D; A, C, and D; B, C, and D; A and B; A and C; A and D; B and C; B and D; or C and D.

While the present disclosure has been described herein with respect to certain illustrated embodiments, those of ordinary skill in the art will recognize and appreciate that the present invention is not so limited. Rather, many additions, deletions, and modifications to the illustrated and described embodiments may be made without departing from the scope of the invention as hereinafter claimed along with their legal equivalents. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the invention as contemplated by the inventor.