Contactless charger for dynamically charging a vehicule

Abstract

The invention relates to a contactless charger (311) for dynamically charging a vehicle (322), comprising at least one transmitter coil (312), having a length, configured to generate a charging magnetic field. A plurality of auxiliary coils (314) having a coil size shorter than the transmitter coil (312) is arranged along the length of the transmitter coil (312) and is configured to generate a cancelling magnetic field which is out of phase with a portion of charging magnetic field in proximity to the corresponding auxiliary coil (314). A vehicle positioning sensor circuit (310) is provided for detecting a receiver coil (316) arranged in the vehicle that moves over the transmitter coil (312) and the one or more auxiliary coil (314), and deenergizes the at least one auxiliary coil (314), which is in proximity to the receiver coil (316).

Description

CONTACTLESS CHARGER FOR DYNAMICALLY CHARGING A VEHICLEFIELD OF THE INVENTION

[0001] The present invention relates to a contactless or wireless charger for vehicles. In particular, the present invention relates to a contactless charger for dynamically charging electric vehicles or electric hybrid vehicles.BACKGROUND OF THE INVENTION

[0002] The subject matter discussed in the background section should not be assumed to be prior art merely because of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may correspond to implementations of the claimed technology.

[0003] Of late, vehicles driven partially or fully by electrical energy has acquired centre stage in the automobile industry. Also, due to favourable Government policies, increasingly, electric vehicles and electric hybrid vehicles are gaining acceptability among masses. These vehicles are powered by multiple batteries, which are placed collectively in a vehicle in the form of a battery pack. The electric motor draws energy from the battery pack and imparts motion to the vehicle. Once batteries got consumed, they are required to be recharged by connecting to an external source of electricity or in case of hybrid electric vehicles, the charging of on-board battery takes place by phenomenon known as regenerative braking.

[0004] In traditional way of charging, the vehicle is parked at a designated place and connected to an external power source by a fixed cable, popularly known as plug-in charging. However, this method of charging suffers from variousdrawbacks, and the most prominent being the requirement for a vehicle to be parked idle at a designated place connected by a charging cord to the external power supply for a substantial period of time.

[0005] In order to overcome this drawback, the contactless or wireless charging of battery pack of the vehicle was introduced. In this method of charging transfer of energy takes place by inductive coupling of the magnetic flux generated by a transmitter coil installed on a charging pad placed in a parking area and a receiver coil installed on underside of chassis of a vehicle. In this method, requirement of a charging cable is eliminated and also, it eliminates manual connecting of the charging cord to the vehicle. However, still the vehicle is required to be parked at a designated charging place for whole period of charging.

[0006] In a more recent development, contactless or wireless dynamic charging of electric vehicles has been introduced, which has a potential to revolutionise the field of automated charging of electric vehicles on the go. This method allows to extend the range of an electric vehicle without need of increasing size of battery or erecting new charging infrastructure. There are two well-known methods for contactless or wireless dynamic charging of electric vehicles namely i) Short Ground Coil Method (SGCM), and ii) Long Ground Coil Method (LGCM).

[0007] In SGCM, multiple short ground coils are installed along the path of travel of a vehicle, whereas, in LGCM, a single ground coil of very large length compared to the length of a vehicle is installed along the path of travel of a vehicle. The Long Ground Coil Method (LGCM) of contactless dynamic charging has a marked advantage over Short Ground Coil Method (SGCM), since it involves less copper and ferrite usage, and requires fewer inverters with simpler control logic; thus, reducing the overall cost of installation. However, LGCM suffers from a serious drawback of leakage of magnetic flux during the process of dynamic charging.

[0008] In LGCM, the power transfer is done by excitation of the entire length of the ground coil leading to leakage of magnetic flux in the region where vehicleis not present at a given time. In order to create high power charging system (say > 10 kW), high current flow is required to be maintained in the coil so that a stronger magnetic field can be generated for maximum power transfer. However, this also leads to increase in leakage flux values, which could cross the permissible limit as prescribed under the Society of Automobile Engineers (SAE) & International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines.

[0009] In state of art, the leakage flux is mitigated by providing protective shields of heavier alloy -metals such as ferrite, aluminium etc. Although this method of shielding might be effective in case of SGCM; however, providing shielding in case of LGCM is not feasible, since shielding is possible only at the vehicle location at a given time. Further, implementing live object detection at multiple locations might lead to loss of continuous power transfer from ground coil to receiver coil of a vehicle.

[0010] In view of the above-mentioned shortcomings, there arises a need to provide a system which can provide the convenience of contactless dynamic charging of vehicle by Long Ground Coil Method (LGCM) along with minimisation of leakage flux to a large extent.OBJECTS OF THE INVENTION

[0011] An objective of the present invention is to provide a contactless charger for dynamically charging a vehicle with optimal magnetic field coupling and minimal magnetic flux leakage.

[0012] Another object of the present invention is to minimise the usage of Ferrite and Aluminium for shielding magnetic flux leakage.

[0013] Yet another object of the present invention is to minimise the overall cost of installation of charging infrastructure.

[0014] Still another object of the present invention is to enhance the safety of driver / passenger from uncoupled electromagnetic radiation.SUMMARY OF THE INVENTION

[0015] The summary is provided to introduce aspects related to contactless charger for a vehicle, and the aspects are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0016] The present invention provides a contactless dynamic charging device which comprises at least one transmitter coil, having a length and configured to generate a charging magnetic field. The charging device further comprises a plurality of auxiliary coils having a coil size shorter than the transmitter coil arranged along the length of the transmitter coil. Each of the auxiliary coils is normally, in energized condition and configured to generate a cancelling magnetic field which is out of phase with a portion of the charging magnetic field generated by the transmitter coil lying in proximity to the corresponding auxiliary coils. Further, the charging device includes a detection means for detecting a receiver coil arranged in the vehicle that moves over the transmitter coil and the auxiliary coils. As the receiver coil passes over a given length of the transmitter coil, the corresponding auxiliary coil is deenergized so that the charging magnetic field of the transmitter coil can couple with the receiver coil to induce electric current. The magnetic flux leakage due to part of the transmitter coil lying beyond the receiver coil is neutralized / minimized by the cancelling magnetic field of the corresponding auxiliary coils.

[0017] According to an embodiment of the invention, a low voltage current injector is coupled to the detection means. The low voltage current injector circuit is switched-on when the receiver coil is not detected and switched-off when the receiver coil is detected. Further, the voltage provided to the auxiliary coil is lower than the voltage provided to the transmitter coil.

[0018] According to one embodiment of the invention, at least one phase shifter is connected to each of the plurality of auxiliary coils to generate out of phase current and provide to the auxiliary coil.

[0019] According to one embodiment of the invention, the current injected to the auxiliary coil is out of phase with the current injected to the transmitter coil, and the current injected to the auxiliary coil and the transmitter coil has same magnitude.

[0020] According to one embodiment of the invention, the auxiliary coils are placed within the loop of the transmitter coil in the same plane to that of the transmitter coil and have one or more loops, however, the number of loops of each the auxiliary coil is less than that of the transmitter coil.

[0021] According to one embodiment of the invention, the auxiliary coils are placed within the loop of the transmitter coil, in a plane above the transmitter coil.

[0022] According to one embodiment of the invention, the auxiliary coils are placed adjacent to the loop of the transmitter coil.

[0023] The invention also relates to a system comprising of the contactless charger for dynamically charging the vehicle and at the same time minimizing the leakage magnetic flux to make it human operation safe.

[0024] Other objects, features and advantages of the present invention will be readily appreciated, as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0025] The accompanying drawings constitute a part of the description and are used to provide a further understanding of the present invention. Such accompanying drawings illustrate the embodiments of the present invention used to describe the principles of the present invention. The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment in this invention are not necessarily to the same embodiment, and they mean at least one. In the drawings:

[0026] Fig. 1A illustrates a schematic view of Long Ground Coil Method (LGCM) for contactless dynamic charging, in accordance with the prior art;

[0027] Fig. IB illustrates energized charging track in accordance with the prior art;

[0028] Fig. 2 illustrates a schematic view of a conventional set up for contactless charging of a vehicle, in accordance with the state of the art;

[0029] Fig. 3 illustrates a schematic view of a contactless charger for a vehicle, in accordance with an embodiment of the present invention;

[0030] Fig. 4 illustrates a schematic view of the contactless charger having the transmitter coil and the one or more auxiliary coils, in accordance with the embodiment of the present invention;

[0031] Fig. 5 illustrates a block diagram of a controlling circuit of the contactless charger, in accordance with an embodiment of the present invention; and

[0032] Fig. 6 illustrates preferred auxiliary coil arrangements, in accordance with various embodiments of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0033] The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the present invention and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose ofproviding a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0034] The terms “or” and “and / or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and / or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

[0035] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words “comprising,” “having,” “containing,” and “including,” and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items.

[0036] Reference herein to “cancelling magnetic field” means that the vector addition of two magnetic fields, which are of equal magnitude and opposite in direction, results in zero. For example, if a charge is hypothetically considered to move through this field, one magnetic field will exert a force in one direction and the other will exert an equal force in opposite direction so that the net force on the charge is mathematically zero.

[0037] Reference numerals appearing in this specification are by way of illustration only and shall have no limiting effect on the scope of the claims. While not explicitly described, the present examples and variants may be employed in any combination or sub-combination.

[0038] In contactless / wireless charging, a transmitter coil is configured to generate a charging magnetic field which is inductively coupled to a receiving coil of a vehicle to charge the battery of the vehicle. However, in absence of any receiving coil of the vehicle, the transmitter coil may continue to generate magneticfield resulting in leakage of magnetic flux which possess a health hazard to the driver and / or passenger of the vehicle.

[0039] Fig. 1A illustrates a schematic view of Long Ground Coil Method (LGCM) 100 for contactless dynamic charging, in accordance with the prior art. Here, the transmitter coil is embedded in a charging track along the ground on which the vehicle may move thereon. Fig. IB illustrates energized charging track wherein the transmitter coil embedded in the charging track along the ground generates magnetic flux. The entire length of the transmitter coil produces charging magnetic field when energised in response to the presence of vehicle over the charging track.

[0040] Fig. 2 illustrates a schematic view of conventional set up 200 for contactless charging of a vehicle, in accordance with state of the art. When a vehicle passes over the charging track, a high voltage and high frequency power flows to the transmitter coil to energise the transmitter coil. The entire length of the transmitter coil produces the charging magnetic field. The charging magnetic field so produced, inductively couples with the receiver coil installed in the chassis of the vehicle. However, only the charging magnetic field in the vicinity of the receiver coil inductively couples to transfer the inductive power. The inductive power so induced is ultimately used for charging the on-board battery of the vehicle. The uncoupled magnetic field generated by the transmitter coil constitutes the leakage magnetic flux. The leakage magnetic flux not only diminishes the efficiency of power transfer, substantially but also poses a serious health hazard to the driver, passenger and / or the person nearby the transmitter coil by making them vulnerable to exposure to the leakage magnetic flux.

[0041] The use of Long Ground Coil Method (LGCM) for contactless dynamic charging is advantageous over Short Ground Coil Method (SGCM), since it involves less usage of copper and ferrite, and requires fewer inverters with simpler control logic; thus, reducing overall cost of installation. However, LGCM suffersfrom a serious drawback of continuous leakage of magnetic flux during the process of dynamic charging.

[0042] In LGCM, the power transfer is done by energisation of the entire length of the ground coil leading to leakage of magnetic flux in the region where vehicle is not present at a given time. In order to create high power charging system (say > 10 kW), high current flow is required to be maintained in the transmitter coil so that a stronger charging magnetic field can be generated for maximum power transfer. However, this also leads to increase in leakage magnetic flux, which may surpass the permissible safe limit, as prescribed under the Society of Automobile Engineers (SAE) & International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines.

[0043] In state of the art, the leakage magnetic flux is mitigated by providing protective magnetic shields made of heavy metal-alloys such as ferrite, aluminium etc. This method of magnetic shielding is effective in case of SGCM, since the transmitter coils lying in proximity to the moving vehicle are only energised at a given time. In LGCM, the entire length of transmitter coil is generating charging magnetic field and heavy metal-alloy shielding is possible only at the vehicle location at a given time. Further, implementing live object detection at multiple locations may lead to loss of continuous power transfer from the ground transmitter coil to the receiver coil of a vehicle. Therefore, in case of LGCM, providing heavy metal-alloy shielding is not feasible.

[0044] The Society of Automobile Engineers (SAE) & International Commission on Non-Ionizing Radiation Protection (ICNIRP) have prescribed the maximum limit as 38.2 pT for healthy individual and 21.2 pT for person having pacemaker installed within body for safe operation. These magnetic field is required to be measured at 200 mm distance from the edge of the vehicle as per standard ISO 19363 :2020(E). Therefore, in order to make the contactless charger for a vehicle safe for regular human operations, the leakage magnetic flux at the measurement plane should be less than limitation prescribed in SAE and ICNIRP guidelines.

[0045] In view of the above-mentioned shortcomings, there arises a need to provide a contactless charger, which can provide the convenience of contactless dynamic charging of the vehicle by the Long Ground Coil Method (LGCM) along with minimisation of leakage flux to a large extent.

[0046] Therefore, the present invention provides an efficient wireless / contactless charger which eliminates the leakage magnetic flux. Various embodiments of the wireless / contactless charger in accordance with the present invention is explained below in reference to Figs. 3 to 6.

[0047] Fig. 3 illustrates a schematic view of a contactless charger for a vehicle 322, in accordance with an embodiment of the present invention. The contactless charger 311 comprises a transmitter coil 312 and one or more auxiliary coils 314 arranged in proximity to the transmitter coil 312, and the contactless charger 311 is configured to generate a magnetic flux for charging the vehicle 322.

[0048] The vehicle 322 comprises a receiver coil 316, a battery 320, a rectifier 317 and a DC-DC converter 318. The receiver coil 316 of the vehicle 322 is inductively coupled to the contactless charger 311 for charging the battery 320 of the vehicle 322. In an embodiment, the contactless charger 311 includes a controlling circuit 308 electrically coupled to the auxiliary coils 314. The controlling circuit 308 comprises a current injector circuit 309 and a vehicle positioning sensor circuit 310. The current injector circuit 309 and the vehicle positioning sensor circuit 310 controls the current injected to the auxiliary coils 314 and detects position of the moving vehicle 322 with respect to the transmitter coil 312, respectively.

[0049] In an embodiment, the current injector circuit 309 is coupled to a voltage regulating circuit 306. The voltage regulating circuit 306 comprises a grid 301, a rectifier 302, a DC-DC converter 303, a High Frequency (HF) inverter 304. In an exemplary embodiment, the power supply from the grid 301 is provided to the rectifier 302 for rectifying the AC power to DC power. The rectifier 302 is electrically connected to the DC-DC converter 303 where the DC power from therectifier 302 is converted to low voltage DC. At this stage, a part of DC power of appropriate voltage may be drawn to feed a wireless communication means / Wi-Fi means 305. The DC-DC converter 303 is electrically connected to the High Frequency (HF) inverter 304. The DC power entering the HF inverter 304 is converted to high frequency AC power. In a preferred embodiment, a full H-bridge inverter is used as HF inverter 304 to convert the DC power to a desired AC power of high frequency. The sinusoidal high frequency AC power enters the transmitter coil 312 generating a charging magnetic field of appropriate strength.

[0050] The contactless charger 311 is configured to inductively couple with the receiver coil 316 and ultimately charge the battery 320 of the moving vehicle 322. Various embodiments of the contactless charger 311 will be discussed in detail with reference to Fig. 4. The contactless charger 311 is embedded in the ground and provides a charging track over which the receiver coil 316 of the vehicle 322 is inductively coupled for contactless charging.

[0051] Fig. 4 illustrates a schematic view of a contactless charger 311 having the transmitter coil 312 and the one or more auxiliary coils 314, in accordance with the embodiment of the present invention. As illustrated, the transmitter coil 312 is of substantial length and placed in the ground along the charging track. This ensures that while the vehicle is in dynamic motion over the charging track, the length of the transmitter coil 312 provides sufficient duration for energy transfer from the transmitter coil 312 to the receiver coil 316 of the vehicle 322. Further, in order to ensure maximum energy by inductive coupling, it is desirable to maintain least possible distance between the transmitter coil 312 and receiver coil 316.

[0052] As illustrated, the auxiliary coils 314 are placed in proximity to the transmitter coil 312. In one arrangement, the plurality of auxiliary coils is placed at the center of the transmitter coil 314 within the proximity, along the length of the transmitter coil 312. In one embodiment, the size of each of the auxiliary coils 314 placed along the transmitter coil 312 is substantially shorter than that of the transmitter coil 312. In another example, the size of the auxiliary coils 314 may besmaller or comparable to that of the receiver coil 316. Consequently, the number of turns in each of the auxiliary coils 314 may be lesser when compared to that of the transmitter coil 312. The comparative size of the auxiliary coils 314 to the receiver coil 316 ensures effective cancellation of charging magnetic field generated by the corresponding portion of the transmitter coil 312.

[0053] The transmitter coil 312 is configured to generate a charging magnetic field which inductively couples with the receiver coil 316 of the vehicle 322 to charge the on-board battery 320. Further, the plurality of the auxiliary coils 314 placed in proximity to the transmitter coil 312 is configured to generate cancelling magnetic field to neutralize the magnetic field of the portion of the transmitter coil 312. In a further embodiment, the magnitude of current flowing through the transmitter coil 312 and the plurality of auxiliary coils 314 is same. Further, the voltage of current provided to the transmitter coil 312 is greater than the one provided to plurality of the auxiliary coils 314.

[0054] The arrangement of the transmitter coil 312 and the plurality of the auxiliary coils 314 according to the present invention provides for charging of vehicle’ s battery 320 when the vehicle 322 moves over the charging track and, when the vehicle 322 is not present over the charging track, the plurality of auxiliary coil 314 cancel out the magnetic field of the transmitter coil 312, thereby preventing the magnetic flux leakage.

[0055] In normal course of operation, when the vehicle 322 is not present for charging, the transmitter coil 312 and the auxiliary coil 314 are in energized state and the auxiliary coils 314 are referred to be in ‘ON’ state. However, the alternating current flowing in the auxiliary coil 314 is out of phase to that of the transmitter coil 312 by a phase difference of 180°. The high frequency AC current flowing in the transmitter coil 312 induces charging magnetic field. Since, the current flowing in the auxiliary coil 314 is out of phase to that of the transmitter coil 312, the magnetic field generated is cancelling magnetic field. The cancelling magnetic field generated by the respective auxiliary coils 314 is able to neutralize or at leastminimize the charging magnetic field generated by the transmitter coil 312 located in proximity.

[0056] In one implementation, when the vehicle positioning sensor circuit 310 detects presence of the vehicle 322 over a part of the transmitter coil 312, the corresponding auxiliary coils 314 proximate to the vehicle 322 are instantly deenergized by switching OFF the current flowing to the auxiliary coils 314. The transmitter coil 312 in proximity to the de-energized auxiliary coil 314 continues to produce the charging magnetic field. The charging magnetic field inductively couples with the overhead receiver coil 316 of the vehicle 322 leading to development of an emf in the receiver coil 316. The difference of emf at ends of the receiver coil 316 produces high frequency power which is ultimately used to charge the on-board battery 320 of the vehicle 322. At the given instant, the charging magnetic field produced by remaining part of the transmitter coil 312 is neutralized or minimized to a safe range by the auxiliary coils 314 placed in proximity which are in ‘ON’ state. This neutralization of uncoupled charging magnetic field produced by the transmitter coil 312, prevents magnetic flux leakage in the remaining part of the transmitter coil 312.

[0057] In one implementation, when the vehicle 322 is in dynamic motion on the charging track, the auxiliary coils 314 placed in a portion of the transmitter coil 312 which is able to couple with the receiver coil 316 of the vehicle 322, is successively switched ‘OFF’ followed by ‘ON’ with change in position of the vehicle 322. The successive switching of the auxiliary coils 314 is regulated by a switching means (not shown). The switching means works on the logic such that the latency of auxiliary coils 314 for transforming from switched ‘ON’ condition to ‘OFF’ and again to switched ‘ON’ condition adjusts with the travelling speed of the vehicle. The said transformation is almost instantaneous such that the efficient transmission of energy from the transmitter coil 312 to the receiver coil 316 is maintained.

[0058] Fig. 5 illustrates a block diagram of a controlling circuit 308 of the contactless charger 311, in accordance with an embodiment of the present invention. The power supplied to the contactless charger 311 from the grid 301 is of low frequency (-50-60 Hz) and high voltage (-11 / 33 / 66 kV). Whereas, in order to achieve maximum power transfer from the transmitter coil 312, to the receiver coil 316 of the vehicle 322, a high frequency power is required. Accordingly, the low frequency power from the grid 301 is transformed to high frequency power at the transmitter coil 312 by the Voltage Regulating Circuit (VRC) 502. The Voltage Regulating Circuit (VRC) 502 is electrically coupled to the controlling circuit 308. The Voltage Regulating Circuit (VRC) 502 regulates power supply to the transmitter coil 312 and the controlling circuit 308 regulates power supply to each of the auxiliary coils 314.

[0059] The VRC 502 further comprises of the rectifier 504, the DC-DC converter 506 and the high frequency (HF) inverter 508. The AC power from the grid 301 passes to the rectifier 504 where it is rectified from AC to DC. The rectifier 504 is in communication with the DC-DC converter 506. The high voltage DC power from the rectifier 504 is step-down to the DC power of appropriate voltage at DC-DC converter 506. This low voltage DC power is supplied to various components of the contactless charging system such as the vehicle positioning sensor circuit 310 etc. The DC-DC converter 506 is in communication with the HF inverter 508. Typically, full bridge HF inverters 508 are used so that the high frequency power is available for supplying to the transmitter coil 312. The high frequency power at the transmitter coil 312 ensures that the power transmission to the receiver coil 316 of the vehicle 322 takes place at resonance frequency to implement efficient power transmission.

[0060] A part of the HF power flows from the VRC 502 to the controlling circuit 308. The controlling circuit 308 comprises of the current injector circuit 510 and the phase shifter (not shown). The flow of power to the auxiliary coils 314 is regulated by the signals received from the vehicle positioning sensor circuit 310 which comprises a plurality of detection means 512. The vehicle positioning sensorcircuit 310 detects presence of the vehicle 322 by sensing the inductive coupling of a portion of the transmitter coil 312 and the receiver coil 316. The detection means 512 corresponding to the auxiliary coils 314 lying in proximity to the inductively coupled transmitter coil 312 sends signal to the current injector circuit 510. The current injector circuit 510 instantly restricts the power flow to the auxiliary coils 314, thus turning the auxiliary coils 314 to switch ‘OFF’ condition.

[0061] As the vehicle 322 moves forward over the charging track, the corresponding portion of transmitter coil 312 uncouples from the receiver coil 316. This leads to interruption of signal from the detection means 512 to the current injector circuit 510. The current injector circuit 510 is in electrical communication with the phase shifter. The current injector circuit 510 draws power from the voltage regulating circuit 502 and sends low voltage current to the auxiliary coils 314 after passing through the phase shifter. The phase shifter leads to inversion of sinusoidal AC wave flowing to the auxiliary coils 314 by a phase difference of 180°. This ensures generation of cancelling magnetic field by the auxiliary coils 314 which minimizes / neutralizes the charging magnetic field generated by the transmitter coil 312 when the receiver coil 316 is not present for coupling.

[0062] As the vehicle 322 moves along the transmitting pad, the transformation of auxiliary coil 314 from ‘ON’ to ‘OFF’ and back to ‘ON’ state continues to ensure minimization of the leakage magnetic flux. The flow of current to the auxiliary coils 314 is regulated such that the latency period between the ‘ON’ ‘OFF’ transition of the auxiliary coils 314 pursuant to the speed of travel of the vehicle 322 is minimum to ensure maximum efficiency of inductive coupling.

[0063] Advantageously, a compensatory circuit (not shown) consisting of resonant network is provided between the HF inverter 508 and transmitter coil 312 to compensate the transformation current losses. The compensatory circuit is configured to transfer the AC current at resonance frequency to maximize the inductive power transfer from the transmitter coil 312 to the receiver coil 316. The receiver coil 316 is configured to receive current at resonant frequency to maximizethe inductive coupling. An emf is generated at the receiver coil 316 of the vehicle 322 leading to the generation of high frequency AC power. The AC power at the receiver coil 316 is passed through the rectifier 317 and DC-DC converter 318 leading to the production of DC power of appropriate voltage to charge the onboard battery 320 of the vehicle 322.

[0064] Fig. 6 illustrates preferred auxiliary coil arrangements 600 according to various embodiments of the present invention. In one embodiment, the plurality of auxiliary coils 314 is placed in the plane of the transmitter coil 312 within the loop of the transmitter coil 312. As previously mentioned, the loop size of each of the auxiliary coil 314 is smaller compared to that of the transmitter coil 312. The loops of each of the auxiliary coils 314 are insulated from the transmitter coil 312 and placed in pads few inches below the ground level on the charging track. The number of loops of the transmitter coil 312 is more than that of the auxiliary coils 314. The number of loops of each of the auxiliary coils 314 may vary from a single loop to multiple loops. The number of loops of the auxiliary coils 314 may vary depending upon the magnitude of cancelling magnetic flux required to neutralize the charging magnetic field generated by the transmitter coil 312 lying in proximity.

[0065] In one embodiment, the plurality of auxiliary coils 314 is placed within the loop of the transmitter coil 312 in a plane parallel to the plane of the transmitter coil 312.

[0066] In another arrangement, the plurality of auxiliary coils 314 is placed within the loop of transmitter coil 312 in a plane parallel to the plane of the transmitter coil 312 on either side of the transmitter coil 312.

[0067] In another arrangement, the plurality of auxiliary coils 314 is placed in proximity of the transmitter coil 312 on adjacent sides.

[0068] The above-mentioned arrangements are non-limiting in depicting the arrangement of the plurality of auxiliary coils 314 with respect to the transmitter coil 312. The above-mentioned embodiments may be used in combination to achieve the desired or acceptable level of magnetic flux leakage.

[0069] The present invention is suited to enhance the distance travelled by a vehicle, including an electric vehicle without significantly increasing the battery storage capacity. Due to controlled excitation logic of the auxiliary coil 314, the magnetic flux leakage in the Long Ground Coil Method (LCGM) of contactless dynamic charging, is substantially minimized and brought to the permissible level, as prescribed by the SAE and the ICNIRP. Different shapes of the receiver coil 316 and the transmitter coil 312 and limitations to modify the shape of the coils may pose a challenge to increase the efficiency of inductive coupling to transfer the power; however still it is comparable to that of the distributed ground coil or the long ground coil without having auxiliary coil 314 with cancelling magnetic field. Since, the proposed charging device and arrangement of the transmitter coil 312 and the auxiliary coil 314 significantly reduce the leakage magnetic flux; therefore, requirement of ferrite or aluminum for shielding of leakage magnetic field is minimal or nil. This reduces the overall cost of installation of the proposed charging device. Due to the presence of additional auxiliary coil loops, there is overall increase in copper usage in comparison to the transmitter coil 312 arrangement without the auxiliary coils 314, however, the safety provided to the passenger / driver is much greater when compared to the distributed ground coil or arrangement without the plurality of auxiliary coils 314.

[0070] In the above detailed description, reference is made to the accompanying drawings that form a part thereof, and illustrate the best mode presently contemplated for carrying out the invention. However, such description should not be considered as any limitation of scope of the present invention. The structure thus conceived in the present description is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice, the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit. The embodiments shown herein are only exemplary and further embodiments are possible within the scope of the invention.

Claims

We claim:

1. A contactless charger (311) for dynamically charging a vehicle (322), comprising: at least one transmitter coil (312), having a length, configured to generate a charging magnetic field; a plurality of auxiliary coils (314) having a coil size shorter than the transmitter coil (312) arranged along the length of the transmitter coil (312), each of the auxiliary coil (314) configured to generate a cancelling magnetic field which is out of phase with a portion of charging magnetic field in proximity to the corresponding auxiliary coil (314); and a vehicle positioning sensor circuit (310, 512) for detecting a receiver coil (316) arranged in the vehicle (322) that moves over the transmitter coil (312) and the one or more auxiliary coil (314), and deenergizing the at least one auxiliary coil (314), which is in proximity to the receiver coil (316), wherein when the auxiliary coil (314) is deenergized, the portion of the transmitter coil (312) in proximity to the deenergized auxiliary coil (314) magnetically couples to the receiver coil (316) to induce electric field at the receiver coil (316), wherein the magnetic field of remaining portions of the transmitter coil (312) is cancelled by the cancelling magnetic field of the energized auxiliary coil (314) to prevent magnetic flux leakage in the remaining portions of the transmitter coil (312).

2. The contactless charger (311) as claimed in claim 1, comprising a low voltage current injector circuit (309, 510) coupled to the vehicle positioning sensor circuit (310, 512), wherein the low voltage current injector circuit (309, 510) is switched-on when the receiver coil (316) is not detected and switched-off when the receiver coil (316) is detected.

3. The contactless charger (311) as claimed in claim 1, comprising at least one phase shifter connected to each of the plurality of auxiliary coils (314) to generate out of phase current and provide to the auxiliary coil (314).

4. The contactless charger (311) as claimed in claim 3, wherein the current injected to the auxiliary coil (314) is out of phase with the current injected to the transmitter coil (312), and the current injected to the auxiliary coil (314) and the transmitter coil (312) has same magnitude.

5. The contactless charger (311) as claimed in claim 4, wherein the voltage provided to the auxiliary coil (314) is lower than the voltage provided to the transmitter coil (312).

6. The contactless charger (311) as claimed in claim 1, wherein the auxiliary coils (314) are placed within the loop of the transmitter coil (312) in the same plane to that of the transmitter coil (312).

7. The contactless charger (311) as claimed in claim 1, wherein the auxiliary coils (314) include one or more loops.

8. The contactless charger (311) as claimed in claim 1, wherein the auxiliary coils (314) are placed within the loop of the transmitter coil (312), in a plane above the transmitter coil (312).

9. The contactless charger (311) as claimed in claim 1, wherein the auxiliary coils (314) are placed adjacent to the loop of the transmitter coil (312).

10. A contactless charging system comprising of the contactless charger (311) for dynamically charging the vehicle (322), as claimed in claims 1 to 9.

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