Wireless power transfer arrangement

Abstract

A wireless power transfer arrangement (20) for wireless power transfer across an air gap (9) by inductive coupling, for example for charging a battery (31) of an electric vehicle, comprises a primary side (21) with a primary pad (22) for generating a magnetic field (28) into the air gap (9), and a secondary side (24) arranged on the other side of the air gap (9), which picks up the magnetic field (28) and provides the energy received by the magnetic field (28) to the battery (31). The primary side (21) is for example mounted at a charging station, and the secondary side (24) is comprised by the electric vehicle. For controlling the charging process during power transfer, a wireless communication channel (38) is provided between the primary (21) and the secondary (24) by means of two wireless transceivers (35, 36). According to the invention, the wireless transceivers (35, 36) are adapted such that their communication range is less than twice the maximum spatial extent of the primary pad. In this way, the communication between the charging station and the vehicle can not be received by other charging stations or vehicles located in the same charging area. And if other vehicles and other charging stations of the same charging area are also adapted according to the invention, their communication does not interfere or otherwise disturb each other, so that a complex and laborious pairing process can be avoided.

Description

TECHNICAL FIELD

[0001] The present invention relates to a wireless power transfer arrangement for wireless power transfer across an air gap by inductive coupling for charging an energy storage device of an electric vehicle, wherein the wireless power transfer arrangement comprises a primary unit comprising a wireless transceiver and a primary pad for inducing a magnetic field into the air gap, a secondary unit comprised by the electric vehicle comprising a wireless transceiver and a secondary pad for receiving power transferred by the magnetic field, the wireless transceivers comprising an antenna for transmitting and receiving communication signals and being adapted for providing a wireless communication link between the primary unit and the secondary unit, and a controller for controlling the power transfer. BACKGROUND

[0002] Electric vehicles (EVs) have become increasingly popular. The term electric vehicle can for example include motorized vehicles such as cars, trucks, motorcycles, trains, boats, ships, submarines, airplanes, helicopters, etc., but also industrial vehicles such as forklifts, AGVs (automated guided vehicles), cleaning machines, elevators, etc. Electric vehicles typically comprise electric motors for driving the vehicle, and they typically comprise energy storage devices for supplying energy to the electric motors. The electric power stored in the energy storage devices can also for example be used for operating electric drive equipment of such EVs for lifting, displacing or transporting any kind of goods.

[0003] In most cases, the energy storage devices are rechargeable batteries. Recharging is typically performed at dedicated charging areas. Typically, such charging areas comprise a plurality of charging stations where two or more vehicles can simultaneously charge their batteries. In most cases, each charging station is permanently installed at the charging area, for example on a wall or floor of the site. In order to charge the batteries of the EVs, the vehicles are moved to the charging area and then parked in the vicinity of one of the charging stations where electric power can be transferred from the charging station to the vehicle.

[0004] Although lead-acid batteries have been and still are used, lithium-ion batteries are increasingly being used as traction batteries of EVs. Lithium-ion batteries have the advantage that they can be charged at a high c-rate of up to 1 c, which reduces the charging time. Thus, a lithium-ion battery with a capacity of 600 ampere hours (Ah) can be charged with a current of up to 600 amperes (A), which reduces the charging time down to about one hour, whereas a lead-acid battery with the same capacity can only be charged at a c-rate of about 0.1 c to 0.2 c, resulting in a charging time of five to ten hours. Furthermore, lithium-ion batteries can be charged occasionally without causing damage to the battery, whereas lead-acid batteries will cause damage to the battery when multiple short charging periods of only a few minutes are applied.

[0005] However, utilizing high charging currents for lithium-ion batteries can cause problems with wire-based chargers, in which the charging current is fed from a charging station to the vehicle via a cable connection, wherein the cable is connected to the source and / or the battery by connectors. High charging currents will require charging cables with large copper diameters and heavy connectors. Thus, the charging cables are difficult to handle and the connectors will wear out quickly. In case of occasional charging, such connectors will wear out within a few weeks.

[0006] To overcome the problems of charging cables, charging of such batteries is usually done by wireless power transfer. Such wireless power transfer systems are also designated as wireless charging systems (WCS) or as inductive power transfer (IPT) systems, in case the power is transferred wirelessly by inductive coupling. Such systems do work with loosely coupled inductors.

[0007] The primary side of such a wireless power transfer arrangement is usually connected to a power grid, such as a mains power supply or any other power supply network capable of providing the required amount of power. The power received from the grid is then converted into AC power, which is fed to a primary pad. The primary pad comprises a resonator, which generates a magnetic field more or less directed in a certain direction. The secondary side of such a wireless power transfer arrangement is usually comprised by the EV and comprises a secondary pad with a resonator, which picks up the magnetic field and provides AC power at its output. Thus, the vehicle has to be positioned correctly, so that the magnetic field generated by the primary side is mainly directed to the secondary pad of the vehicle. The AC power received by the secondary pad can then be used, for example, to charge the battery of the vehicle or to directly drive any electrical load of the vehicle. Of course, the AC power provided by the secondary pad can first be converted into a suitable form to charge the battery or to drive the load.

[0008] To control the power transfer, the system can comprise a controller in the primary and a separate controller in the secondary, which do not communicate with each other, such as described, for example, in US 9,287,040 B2 (Thoratec Corp.).

[0009] Another option to control the power transfer is to provide a communication link between the primary and the secondary, so that the power transfer control can be based on information of the primary as well as the secondary. Such a communication link is also needed for a closed-loop control of the power transfer during charging of the battery. Such a communication link can be a wired or a wireless communication link. However, a wireless communication link is preferred for a wireless charging process. Establishing a communication link between the charging station and the EV first by connecting a suitable cable between the charging station and the EV before the charging process can start would be an additional effort and even more important, such a connection would have to be established manually in most cases.

[0010] The document EP 3 591 824 A1, Delta Electronics (Thailand) Public Co., Ltd. discloses such a wireless charging system which comprises a wireless communication link between the primary and the secondary for control purposes. This document mentions multiple communication technologies such as LTE, UMTS, GSM, WLAN and Bluetooth.

[0011] Although the use of a wireless communication between the primary and the secondary is generally a good idea, such a technology does indeed have major drawbacks, especially in case multiple charging stations are provided at the charging area. Since the communication range of these technologies is from tens of meters up to several hundreds of meters, each charging station can receive the communication of each vehicle positioned in or near the charging area. And each vehicle can receive the communication of each charging station of the charging area. Therefore, the pairing process, i.e. the process of pairing a vehicle with the correct charging station to set up the charging process, is difficult, especially in case two vehicles arrive at the charging area at the same time. A lot of effort has to be made to distinguish who is communicating with whom.

[0012] For example, all charging stations and vehicles can be assigned a unique address, so that a vehicle can address a specific charging station. However, in this case, the vehicle also has to know the address and the physical location of this specific primary vehicle to drive to this primary vehicle and to give the vehicle secondary the notification about the primary address.

[0013] Another way in which the vehicle does not need to know the address-location- correlation of the charging station is that the secondary and the primary undergo an arbitration routine at the beginning of each charging. This can be done, for example, by the secondary, after entering the charging area, sending a request to take over the charging combined with its own temporary address. This request is received by all primaries within reach. All free primaries start and try to charge the secondary. Now only the charging station in front of which the vehicle stands is able to give the charge, so it will know the requesting vehicle secondary is in front of it and continues the charging. All other charging stations will enter the standby state again. To complete the pairing, the charging station gives the vehicle the notification about its temporary address. For the rest of the charging process, both have identified each other and can ignore any other broadcast. Or in other words, once the pairing process has been completed, the charging station and the vehicle know each other's address so that they can communicate with each other to exchange data for controlling the charging process.

[0014] However, such a pairing process is quite complex. It requires a lot of time, a dedicated protocol and can even require additional hardware.

[0015] The known communication link does indeed have further disadvantages. Since usually all charging stations of a charging area and all vehicles intending to charge at this charging area communicate using the same frequency band, interference can occur. Furthermore, the more stations and vehicles use the same frequency band, the higher the probability of collisions and blocked channels becomes. Additionally, in industrial environments certain frequency bands, such as for example the 2,4 GHz band, are also used for data traffic by many different other applications and are therefore extremely busy. Overall, this not only makes communication more difficult, but can also consume correspondingly more time than necessary and lead to communication interruptions. SUMMARY

[0016] It is therefore an object of the present invention to create a wireless power transfer arrangement belonging to the initially mentioned technical field which allows for a simplified pairing process and simple and undisturbed communication during charging. It is a further object of the present invention to provide a primary or secondary pad for such a wireless power transfer arrangement and a corresponding method for wireless power transfer.

[0017] The invention relates to the following solution for a wireless power transfer arrangement. A wireless power transfer arrangement for wireless power transfer across an air gap by inductive coupling for charging an energy storage device of an electric vehicle, the wireless power transfer arrangement comprising a primary unit, a secondary unit comprised by the electric vehicle and a controller for controlling the power transfer, wherein the primary unit comprises a wireless transceiver and a primary pad for inducing a magnetic field into the air gap, the secondary unit comprises a wireless transceiver and a secondary pad for receiving power transferred by the magnetic field, and the wireless transceiver comprises an antenna for transmitting and receiving communication signals and is adapted for providing a wireless communication link between the primary unit and the secondary unit.

[0018] According to the invention, the wireless communication link has a communication range which is less than twice the maximum spatial extent of the primary pad, and wherein the controller is adapted to control the power transfer based on data transmitted by the wireless communication link during the power transfer.

[0019] While the secondary unit with the secondary pad is comprised by the vehicle, the primary unit and the primary pad usually form part of a charging station and are therefore permanently installed at a site such as a charging area. However, the primary unit or only the primary pad can also be mobile such that the primary unit or pad can be positioned correctly in the vicinity of the vehicle for enabling the power transfer.

[0020] The maximum spatial extent of a primary pad depends on the size of the primary pad, wherein the size of the pad depends on the requirements of the specific application. For example, a smaller pad can be used in case a smaller amount of power is to be transferred, whereas a larger pad can be used in case a larger amount of power is to be transferred. For example, in case the available space is limited, or in case the secondary side is integrated into a smaller vehicle, a smaller pad can also be used. Then again, if the vehicle is large or the available space is large, a larger pad can be used, independent of whether a large or small amount of power is to be transferred. The size of the pad can also depend on other circumstances of the specific application, such as, for example, environmental conditions or requirements regarding the mutual positioning accuracy of the pads.

[0021] The maximum spatial extent of a primary pad typically corresponds to its largest diameter perpendicular to the direction of power transfer. For example, if the primary pad is a circular pad, its maximum spatial extent is typically the diameter of the circular pad. If the primary pad is a rectangular pad, its maximum spatial extent is typically the diagonal of the pad. In the following, the maximum spatial extent of a pad is designated as the diagonal of the pad.

[0022] The diagonal of a typical primary pad ranges from about 10 or 15 centimeters (cm) up to two meters or even more meters (m). Such pads are typically circular or rectangular. However, other shapes and sizes are also possible.

[0023] By using a communication link having a rather short communication range of less than twice the diagonal of the corresponding primary pad, the above disadvantage can be avoided. Due to the short communication range, a communication signal transmitted by a certain charging station can only be received by a vehicle positioned in the immediate vicinity of the charging station. Thus, only a vehicle to be charged by a certain charging station can receive the communication signal transmitted by this charging station. And of course, this is also true the other way round.

[0024] In order to charge the battery of an EV, the EV must therefore only be positioned in a charging position in the vicinity of a free charging station, and then the charging station and the vehicle can start communicating without interfering or otherwise disturbing or being disturbed by the communication of other charging stations and vehicles in the charging area. The other charging stations and vehicles do not notice the communication between the charging station and the vehicle to be charged at this charging station at all. And of course, the communication between one pair of charging station and vehicle is not disturbed or otherwise interfered with by the communication of other pairs. This is of course also true for third party devices, i.e. devices different from the involved charging station and vehicle that are transmitting signals in the same area.

[0025] The need for a specific method to detect a charging pair (charging station and vehicle) for power transfer can thus be avoided.

[0026] Thus, the pairing process is very simple and only comprises a communication request by the charging station or the vehicle and a corresponding answer by the other communication partner. No address has to be assigned to identify the other communication partner. In the preferred embodiment of the present application, the pairing process is initiated by the vehicle, as soon as it is positioned in front of a certain charging station, it sends a communication request. If the vehicle is correctly positioned in front of the charging station, the charging station can receive the communication request and answer accordingly. Thus, the vehicle transceiver is the master transceiver and the transceiver of the charging station acts as a slave transceiver. As soon as the pairing is completed, the vehicle and the charging station can communicate with each other by exchanging data as required by the specific application. For example, they can exchange information during the power transfer from the charging station to the vehicle, which is required by the controller to control the process of charging the vehicle battery so that the power provided to the vehicle battery matches the amount of power required by the battery at certain points in time during the charging process.

[0027] Furthermore, due to the limited communication range, collisions and blocked channels during communication can be avoided or at least reduced to a great extent, which also leads to faster and more reliable communication.

[0028] In the context of this description, the term "communication range" refers to the spatial area or distance from a transmitter, within which an area or distance from a transmitter, within which a receiver can receive a signal transmitted by the transmitter with reasonable quality, wherein the term "transmitter" in this respect refers to the antenna of the transmitter, which is the source of the transmitted signal. Or in other words, the term "communication range" refers to the area or distance from a transmitter, within which a receiver can retrieve the transmitted data from the communication signal with sufficient quality. Depending on the coding scheme, protocol, error correction, algorithm, etc. used for the communication, the communication signal can be received correctly at different distances from the transmitter.

[0029] In addition, it is to be considered that the communication range can not be the same in each direction from the transmitter. The antenna can emit a directional signal so that the communication range in a certain direction is higher than in another direction. In the application of power transfer from a charging station to a vehicle, the communication direction can also be directed from the station in the direction in which the vehicle should be positioned for the power transfer and also from the vehicle in the direction of the station.

[0030] The term "unit" as used herein does not necessarily refer to a physical unit comprising all components of the unit. Unless otherwise mentioned, the term "unit" more accurately refers to a logical unit, which can encompass one or more physical units. For example, the term "primary unit" refers to a combination of several components, such as for example an input stage for converting the power received from the power grid into AC power and a primary resonator for receiving the AC power and for inducing a magnetic field. These two components can or can not be provided in a single physical unit.

[0031] In a preferred embodiment of the application, the energy storage device comprises a battery, in particular a traction battery of a vehicle. Such a battery can be used in an EV, which has a reasonable capacity of several hundred or even several thousand Ah.

[0032] Depending on the requirements of the particular application, the energy storage device can alternatively or additionally also comprise a capacitive storage element, such as for example a supercapacitor or other capacitor. A supercapacitor can be a good choice, for example, if high charging and discharging rates are required.

[0033] Since the primary and secondary pads are usually positioned next to each other in order to transfer power from the primary to the secondary, the communication range is preferably even less than the diagonal of the primary pad.

[0034] During power transfer, the distance between the primary and secondary pads is usually in the range from a few centimeters up to 20 cm or 30 cm. However, in some cases, the pads can be arranged at a larger distance of up to about 50 cm. In an even more preferred embodiment of the application, the communication range is preferably less than the diagonal of the primary pad but more than 5 cm.

[0035] However, it will also be possible to design the antennas and electronics of the transceiver such that the communication range is below 5 cm or twice the diagonal of the primary pad and above.

[0036] In general, a wide range of frequencies can be used for the wireless communication. The transceiver can for example be adapted for communication using radio frequencies of approximately between 3 kHz and 1 GHz, depending on what frequency range is available for the particular use at a given location, for example.

[0037] In a preferred embodiment of the application, frequencies in the medium frequency (MF) range to the very high frequency (VHF) range are used, i.e. approximately between 300 kHz and 300 MHz.

[0038] In an even more preferred embodiment, the transceiver is adapted for communication using frequencies between 3 MHz and 50 MHz. This part of the electromagnetic spectrum or rather the lower range of the ISM band is more or less reserved internationally for industrial, scientific and medical (ISM) purposes and can be used for unlicensed use. This part of the ISM band and the higher parts are also used by other wireless communication technologies, such as for example cordless phones, Bluetooth devices, near field communication (NFC) devices, garage door openers, baby monitors and wireless computer networks (WiFi).

[0039] Most preferably, the transceiver is adapted for communication at frequencies between 10 MHz and 15 MHz. This is the frequency range also used by NFC (Near Field Communication) technology, which is a technology that enables two electronic devices to establish communication over a relatively short distance, typically less than one meter. However, NFC is not a single well-defined standard, but rather a set of different standards with different prerequisites, communication protocols, etc. And NFC is not suitable for the wireless communication required in the present invention for several reasons. First, NFC does not work, for example, in highly interfered environments as present in the present invention, in which the transceiver is located close to the primary and secondary pads for power transfer. Second, the protocol of the communication, data rate and timing do not comply with the needs of the present invention, for example with respect to closed loop control of the power transfer. In addition, NFC does indeed allow high error rates, and furthermore, typically has a high demand for collision avoidance. Both of these properties contradict the application of the present invention. Furthermore, the primary pads not only emit an energy field for power transfer, but also unintentionally emit noise. Both the intentional energy field as well as the unintentional noise massively influence the wireless communication between the pads. A standard NFC antenna placed somewhere close to such a wireless charging system will induce high voltages at the energy transfer frequency, which can damage the NFC transceiver. And the noise will corrupt the data transfer. And some NFC standards, for example those defined for larger communication distances of up to one meter, are designed for simplex communication, and thus typically do not allow duplex or half duplex communication as required in the present invention.

[0040] Therefore, the transceiver has to be designed to be robust against the power field frequency and the noise created by the primary.

[0041] One aspect of the transceiver design is the placement of the antenna. In general, it will be possible to position the antenna somewhere outside the pads but within their communication range to allow data exchange. However, in such an arrangement, it can happen that although the charging station and the vehicle can communicate with each other, power transfer is not possible because the primary and secondary pads are displaced or otherwise too far apart to transfer power.

[0042] To ensure that power transfer from the primary to the secondary is possible as soon as communication is established, the antenna of the transceiver is preferably arranged such that the wireless communication takes place through the air gap. This is best achieved by including the antenna in the respective primary or secondary pad.

[0043] In a further preferred embodiment of the application, the transceivers are adapted in such a way that their communication range is limited to the spatial area directly in front of the pads. Or in other words, communication is not possible if one of the transceivers is arranged outside the lateral limits of the other pad. In such an embodiment, the communication range is limited to a cylindrical area created by the mental displacement of the boundary of the transmitting pad perpendicular to this pad in the direction of the receiving pad.

[0044] The best results in this respect are achieved if the antennas of the transceivers, preferably both transceivers, are not arranged in the area close to the edge of the pads, but in the central area of the respective pad, i.e. the pad of the primary or secondary unit to which the receiver belongs.

[0045] Placing the antennas in the center of the power transfer coils of the pads has the advantage that wireless power transfer as well as wireless communication is independent of the orientation of the pads. This does not matter as long as the antennas face each other, for example, if the pads are not oriented in the same direction, but are arranged twisted relative to each other.

[0046] If the antennas are placed near the edge of the pads, it is important that the pads have the correct orientation relative to each other so that power transfer and communication can take place at the same time. For example, if one of the pads is slightly twisted relative to the other pad, then either communication or power transfer or even both can not work.

[0047] Independent of the relative orientation of the pads, power transfer as well as wireless communication can of course only work if the primary pad and the secondary pad are positioned in such a way that the antennas in the center of the pads are correctly arranged relative to each other. The term "correctly arranged" thereby means that the pads are arranged within the allowed tolerances. These tolerances can for example include allowed values for deviations in the pad distance as well as amounts of offset in the two directions parallel to the pads. Or in other words, the entire positional tolerance of the wireless power transfer system can be solved with only one antenna in the primary and only one antenna in the secondary.

[0048] The antennas of the transceivers are for example and preferably arranged on top of the power coil(s) of the respective pad, wherein the top side of those coil(s) designates the side that is directed to the other pad during power transfer.

[0049] The transceivers are therefore preferably adapted in such a way that their communication range is not only limited to the spatial area directly in front of the pads, but in addition is more or less symmetrical with respect to an axis running through the center of the pads.

[0050] And of course, simultaneous power transfer and communication can only work if the communication range of the antenna is at least slightly larger than the range of the power transfer field. Or in other words, to ensure that communication between primary and secondary can take place, the transceiver is preferably designed such that the spatial extension of the communication range is larger than the distance between the primary and secondary pads during charging.

[0051] In this connection, the term "distance" refers to the distance between the pads in a direction perpendicular to the respective pad during charging. However, the communication range does not have to be much larger than the distance between the pads, it is sufficient if it extends only slightly beyond the range of the power transfer field.

[0052] In such a placement of the antenna in the center of the pad, the majority of the physical space in which communication takes place is the same physical space in which power transfer is accomplished. So the fields of communication and power transfer do overlap.

[0053] Due to this overlap, communication has to be robust against the power field frequency and the noise created by the primary side, i.e. by the pad and / or by other electronic components of the primary side.

[0054] To avoid that the antenna is damaged by the power field, the antenna of the transceiver, preferably of both transceivers, comprises at least one coil which is shaped and arranged such that the voltage induced in said at least one coil by the magnetic field during power transfer is minimized. Or in simple words, the antenna is designed and arranged such that the voltage induced in the antenna coil(s) by the magnetic field used for power transfer is zero or close to zero.

[0055] Due to such a design of the antenna, the power transfer field and the communication antenna do not interfere or damage each other.

[0056] There are generally two different ways to realize such an antenna. The antenna is designed such that as little magnetic flux as possible flows through the coil(s) of the antenna. Or the antenna comprises two or more coils which are arranged such that the magnetic flux flowing through these coils compensates each other as much as possible. When designing the antenna, the shape and arrangement of the respective pad must also be taken into account.

[0057] In a first embodiment, the primary pad comprises for example two power coils arranged next to each other in a common plane, wherein during power transfer, a current is flowing in one direction in a first coil of the power coils and a current is flowing in opposite direction in a second coil of the power coils. Such a coil arrangement is commonly referred to as DD coil arrangement. Thus, the magnetic field generated by such a coil arrangement is flowing in opposite directions through both coils, but in the center of the pad, the magnetic field is essentially parallel to the common plane of the coils. The coils can be formed by a single common wire, or they can be formed by different wires, and each coil can comprise one turn or multiple turns. In such a case, the antenna preferably comprises a loop coil arranged parallel to the common plane comprising the power coils. Or in other words, because the loop coil of the antenna is arranged in the center of the pad, it is arranged parallel to the magnetic field lines, thus no or very little magnetic field flux is flowing through the loop antenna coil.

[0058] Depending on the specific application, the loop coil can have a single turn, or it can comprise two turns or more turns.

[0059] In another embodiment, the primary pad comprises a loop power coil, which induces a more or less homogeneous magnetic field in the center of the primary pad. Again, the power coil can comprise one turn or multiple turns. In this case, the transceiver antenna comprises an octal coil, i.e. a kind of coil comprising two series loops formed by a single wire, wherein the two loops have opposite circulation directions. When such an antenna coil is arranged in a power field, the first loop of the octal coil picks up the magnetic field, thus a first voltage is induced in this first loop, and the second loop of the octal coil also picks up the magnetic field, thus a second voltage is induced in this second loop with opposite sign. Or in other words, the voltage in the first loop caused by the magnetic field results in a current in the second loop compared to the current generated by the voltage induced in the second loop in opposite direction, so that the currents completely or at least to a large extent compensate each other.

[0060] In another preferred embodiment of the present invention, the controller is adapted to establish a closed control loop for the closed loop control of the power transfer, wherein the closed control loop comprises the wireless communication link.

[0061] The controller controlling the power transfer can be arranged in the primary unit or in the secondary unit. In order to control the power transfer correctly and efficiently, the controller has to be able to control the generation of the magnetic field in the primary, whereby information from the secondary is taken into account, such as for example battery state of charge (battery SOC), battery voltage, charging current setpoint, charging voltage setpoint, charging power setpoint. The controller can also need further process data, like actual current, temperature and status information from both sides, log data or power consumption data, etc.

[0062] Thus, if the controller is arranged in the primary, at least some of the above-mentioned information generated in the secondary has to be transferred to the controller in the primary. This is done by sending corresponding information in data form from the secondary transceiver to the primary transceiver over the wireless communication link. Likewise, for controlling the power transfer, the controller can take into account further information generated directly in the primary. The terms generated thereby can include measurements, readings, calculations or otherwise determining the required information. However, the information generated in the primary can be provided directly to the controller, e.g. by a corresponding wired, optical or other connection suitable for transferring data. Based on all or a part of the above-mentioned information, the controller can control the power transfer, e.g. by controlling the power conversion from the power grid to the AC power fed to the primary pad, such as the frequency, phase and / or amplitude of the AC voltage or current. The controller can also control the magnetic field generated by the primary pad, and thus the power transfer, by e.g. controlling the resonance frequency of the resonance circuit of the primary pad.

[0063] However, if the controller is arranged in the secondary, the information generated directly in the secondary can be provided directly to the controller. However, at least some of the above-mentioned information generated in the primary has to be transferred to the controller in the secondary via the wireless communication link. And the control signals determined by the controller for controlling the power transfer have to be transferred to the primary in order to control the power conversion from the power grid to the AC power and / or to control the primary pad accordingly.

[0064] Thus, by using the wireless communication link for transferring the required information from the primary to the secondary and / or from the secondary to the primary during the power transfer, the controller closes the control loop and can thus efficiently perform closed-loop control of the power transfer from the primary to the secondary.

[0065] However, the controller is preferably arranged in the primary unit, i.e. in the charging station. In this way, it is sufficient to provide one single controller for controlling the power transfer from this charging station to any number of vehicles. If the controller were to be arranged in the secondary, i.e. in the vehicle, each vehicle would have to comprise such a controller.

[0066] In a further preferred embodiment of the present application, at least one of the transceivers is adapted for half-duplex communication, such as e.g. time-division duplex communication. This is e.g. achieved in that the transceiver is adapted to switch between a transmit mode and a receive mode, which can e.g. be achieved by a switch connecting the antenna to either the transmitter part of the transceiver or the receiver part of the transceiver.

[0067] Of course, preferably both transceivers are adapted accordingly.

[0068] Instead of providing a transceiver that can be switched between a transmit mode and a receive mode, separate transmitter and receiver units can be provided, each having its own antenna. Such an arrangement will generally also allow full duplex communication between the primary and the secondary, however this can also require additional measures to avoid interference or other disturbances resulting from simultaneous data transmission in both directions.

[0069] Generally, the transceiver comprises an antenna matching circuit in order to match the antenna input impedance to the impedance of the radio module connected to the antenna. The better the match, the higher the power delivered by the antenna or the lower the power of the transmission can be in order to achieve the same communication range and the sensitivity of the receiving circuit becomes higher. Such a matching circuit generally comprises inductance or capacitance elements connected in parallel and / or in series.

[0070] Although the matching circuit is generally only used for impedance matching, in a preferred embodiment of the application the antenna matching circuit is not only used for matching purposes but comprises a first high-pass filter for attenuating the frequency of the magnetic field used for power delivery.

[0071] In a preferred embodiment of the application the first high-pass filter comprises one or more capacitance elements connected in series. However, the matching circuit can also comprise further elements connected in series and / or in parallel in order to provide the required matching and to create the desired cut-off frequency of the first high-pass filter. For example, the cut-off frequency of the first high-pass filter has to be higher than the frequency of the magnetic field generated by the primary pad, which can depend on the specific application. In some applications the frequency of the magnetic field is for example in the range of a few kHz to a few hundred kHz.

[0072] In a power delivery system, where the power delivery field has for example a frequency of 50 kHz and where the communication frequency is for example between 10 MHz and 15 MHz, the high-pass filter is designed to have a cut-off frequency between 100 kHz and 5 MHz.

[0073] In order to extract the data from the communication signals transmitted over the communication link, the transceiver generally also comprises a modulation / demodulation circuit (modem). The modem also provides the extracted data for further processing, which is generally a digital signal.

[0074] Although the modem is generally only used for extracting the transmitted data, in a preferred embodiment of the application the modem is not only used for data extraction and provides a digital signal representing the extracted data, but the modem comprises a second high-pass filter for further attenuating or even blocking the frequency of the magnetic field used for power delivery.

[0075] The second high-pass filter preferably comprises an RC circuit provided at the input of the modem. For example, the RC circuit comprises a terminal resistor in parallel and a capacitor in series.

[0076] Again, the second high-pass filter is designed such that its cut-off frequency is higher than the magnetic field frequency.

[0077] Furthermore, the elements of the antenna matching circuit and the cable matching circuit together can also be used as a high-pass filter. Such a high-pass filter can for example be provided by the series capacitor of the antenna matching circuit and the parallel resistor of the cable matching circuit.

[0078] In a further preferred embodiment of the application, the modem additionally comprises an amplifier for amplifying the output of the second high-pass filter, an envelope detector for generating an envelope signal of the amplifier output, a low-pass filter for removing noise from the output of the envelope detector, and a comparator for converting the output of the low-pass filter into a digital signal. The comparator for example compares the received and filtered signal with a reference voltage to extract data from the received signal.

[0079] However, the communication between the primary and the secondary is not only influenced by the magnetic field and the noise, but also depends on the distance and lateral offset of the primary and secondary pads. In particular, the amplitude of the received signal varies depending on the distance between the antennas and depending on other conditions such as for example environmental conditions like the presence of other electromagnetic fields. Therefore, in another preferred embodiment of the application, the reference signal is adjusted for each new power transfer during the power transfer, or even for each communication, such as for example before each transmission of a communication message. To adjust the reference signal, the transmitting transceiver transmits a defined signal sequence, such as for example a signal that is high for a predetermined amount of time and then low for a predetermined amount of time. From the received signal, the receiving transceiver determines the level of the low signal and the level of the high signal and thereby determines the reference level, for example exactly between the received low level and the high level. This signal sequence can of course also comprise other high and low signal sequences suitable to thereby determine the high level and the low level of the received signal and the reference level.

[0080] However, other modem architectures can also be used.

[0081] The solution of the present application with respect to the primary or secondary pads is as follows. The primary or secondary pad according to the present application, i.e. a primary or secondary pad for a wireless power transfer arrangement as described above comprises an antenna of a corresponding wireless transceiver.

[0082] As further outlined above, it is advantageous to include the antenna of the transceiver into the respective pad, such that the wireless communication during the power transfer takes place through the air gap between the primary and secondary pad.

[0083] The solution according to the invention for a method for wireless power transfer is as follows. Such a method comprises the steps of inducing a magnetic field into an air gap with a primary pad of a primary unit, receiving power transferred through the magnetic field with a secondary pad of a secondary unit comprised by a vehicle, and providing a wireless communication link between the primary unit and the secondary unit. According to the invention, the method further comprises the steps of providing the wireless communication link with a communication range that is less than twice the maximum spatial extent of the primary pad, and controlling the wireless power transfer by transmitting data through the wireless communication link during the power transfer.

[0084] Further advantageous embodiments and combinations of features are derived from the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0085] The accompanying drawings illustrate for the purpose of explanation of embodiments:

[0086] Figure 1 is a schematic representation of a charging application with a wireless charging system according to the invention;

[0087] Figure 2 is a block diagram of a wireless charging system according to the invention;

[0088] Figure 3 is a schematic representation of a communication range and a power transfer range with a larger distance between a primary and a secondary pad;

[0089] Figure 4 is a schematic representation of a communication range and a power transfer range with a shorter distance between a primary and a secondary pad;

[0090] Figure 5 is a schematic representation of a primary pad with an antenna for communication between a primary side and a secondary side from above;

[0091] Figure 6 is a schematic representation of a primary pad with a communication antenna as shown in Figure 7 from a side looking upwards;

[0092] Figure 7 is a schematic representation of another primary pad with a communication antenna from above;

[0093] Figure 8 is a schematic representation of a primary pad with a communication antenna as shown in Figure 9 from a side looking upwards;

[0094] Figure 9 is a block diagram of a transceiver for use in the invention;

[0095] Figure 10 is a block diagram of a transceiver for use in the invention;

[0096] Figure 11 is a block diagram of a demodulator for use in the present application;

[0097] Figure 12 is a schematic representation of a demodulator circuit for use in the present application;

[0098] Figure 13 is a schematic representation of an antenna and corresponding cable for use in the present application; and

[0099] Figure 14 is a schematic representation of a transmission signal and a corresponding demodulated signal.

[0100] In the figures, identical components are given the same reference numerals. DETAILED DESCRIPTION

[0101] Figure 1 The use of the wireless power transfer arrangement according to the present application for charging a traction battery 11 of a vehicle is shown. In this example, the vehicle is a forklift 10 that is electrically driven by an electric motor 13.

[0102] The primary side of the wireless power transfer arrangement comprises a wall box 1 and a primary pad 2. The wall box 1 is mounted on a wall 7 of a house 5, such as for example a garage, a car port, a charging station, a parking area, etc. The wall box 1 is connected to a power supply network 6 of the house 5, from which the wall box 1 receives energy to be transferred to a vehicle. The primary pad 2 is mounted on or near another wall 8 of the house 5 and is connected to the wall box 1 by means of a fixed cable 3. The primary pad 2 can be partly or completely integrated into the wall 8, so that it will require less or no additional space near the wall 8. The primary pad 2 can also be mounted on the same wall 7 as the wall box 1. Or the primary pad 2 and the wall box 1 can be integrated into the same housing. The primary pad 2 can also be arranged horizontally on the floor of the garage, car port, parking area, etc.

[0103] The forklift 10 comprises a secondary side 4 of the power transfer arrangement, which secondary side 4 comprises a secondary pad and some further electronics and power electronics to convert and provide the energy received from the primary pad 2 for further use within the forklift 10.

[0104] The wall box 1 receives energy from the power supply network 6, converts it into AC power and provides it to the primary pad 2 via the cable 3. The primary pad 2 generates a magnetic field that is directed into an air gap 9 between the primary pad 2 and the secondary side 4 of the forklift 10, which is positioned near the primary pad 2 to receive the energy transferred by the magnetic field wirelessly. The power transfer from the primary side to the secondary side 4 is controlled by a controller (not shown in Figure 1 However, the controller can also be comprised in the primary pad 2 or in the secondary side 4.

[0105] The forklift 10 further comprises a battery 11 with a BMS 12 (Battery Management System) and two electric motors 13, 14 which are fed with energy from the battery 11. However, the electric motors 13, 14 can also be fed directly with energy from the primary side. The electric motor 13 is used to drive the forklift 10 and the electric motor 14 is used to drive the lift 15 of the forklift 10. The BMS 12 manages the energy flowing into the battery 11 and usually also out of the battery 11.

[0106] In order to provide a charging current to the battery 11 of the forklift 10, the secondary side 4 is connected to the battery 11 via a charging line 16 and the secondary side 4 is also connected to the BMS 12 by a signal line 17. In order to charge the battery 11, the BMS 12 defines the charging current allowed or required at a certain point in time and provides this set value to the secondary side 4 via the signal line 17, for example to a charging controller (not shown) included in the secondary side 4. The secondary side 4, for example, measures the actual current provided to the battery 11, compares this actual current with the set current and calculates therefrom an error signal which is transmitted to the wall box 1 via the wireless communication link 18 established by the wireless transceiver 19. Or more generally stated, the information required for the controller to control the charging of the battery 11 is exchanged between the wall box 1 and the secondary side 4 via the wireless communication link 18. Based on these information, the controller then controls the primary side such that the required amount of power is transferred to the secondary side.

[0107] One of the transceivers 19 is included in the secondary side 4 and one of the transceivers 19 is included in the primary pad 2. The antenna of each transceiver 19 can of course also be separated from the transceiver electronics and connected thereto by means of a suitable cable.

[0108] Since the distance between the primary pad 2 and the secondary side 4 is in the range of a few centimeters to a maximum of a few decimeters, the transceivers 19 are adapted for a rather short communication range. The transceivers are designed such that their maximum communication range is slightly higher than the distance between the primary pad 2 and the secondary side 4 during power transfer. In this way, it is ensured that no other vehicle or other transceivers of another primary side can receive the signals transmitted between the transceivers 19.

[0109] Figure 2 A block diagram of a wireless charging system 20 according to the present application is shown.

[0110] The wireless charging system 20 comprises a primary side 21 and a secondary side 24. The primary side 21 further comprises a controller 27 for controlling the power transfer from the primary side 21 to the secondary side 24. And the primary side 21 comprises electronic components 23 for converting input power 29 from a power grid into AC power, and a primary pad 22 receiving the AC power from the electronic components 23 and generating a magnetic field 28 therefrom for wirelessly transferring power across the air gap 9. The secondary side 24 comprises a secondary pad 25 picking up the magnetic field 28 and converting the power received by the magnetic field 28 into AC output power. The secondary side 24 further comprises electronic components 26 connected to the secondary pad 25 and converting the AC output power into output power which is then provided as output power 34 at the output of the wireless power transfer arrangement 20.

[0111] The secondary side 24 is constituted by the vehicle 10, and the output power 34 is provided to a battery 31 of the vehicle 10 for charging the battery 31. In this case, the output power 34 is a DC output power. The power flowing into and out of the battery 31 is controlled by a BMS 32 which communicates with the secondary side 24 via a communication link 33. The electronic components 26 comprise for example a charge controller which communicates with the BMS 32 in order to control the power flowing from the secondary side 24 to the battery 31. Since the vehicle 10 comprises the BMS 32 as well as the secondary side 24, the communication link 33 is a wired communication link such as for example a CAN bus. Thus, the BMS 32 controls the power flowing into and out of the battery 31 and provides accordingly to the secondary side 24 the information required therefrom such as set points for power, current and / or voltage etc.

[0112] For establishing a communication between the primary side 21 and the secondary side 24, both sides comprise transceivers 35, 36 providing a wireless communication channel 38. The transceiver 35 in the primary side 21 is comprised in the primary pad 22. Depending on the requirements of the specific application, the antenna and electronics of the transceiver 35 can also be separated and connected to each other via a suitable cable. The transceiver 36 in the secondary side 21 is comprised in the electronic components 26, and its antenna 36’ is arranged in the secondary pad 25 and connected to the transceiver 36 by a suitable cable. Depending on the requirements of the specific application, the antenna and electronics of the transceiver 36 can also be implemented as a single unit integrated into the secondary pad 25. Thus, the wireless communication channel 38 between the primary side 21 and the secondary side 24 runs through the air gap 9 and accordingly through the magnetic field 28 used for the power transfer.

[0113] The controller 27 controls the transfer of electric power through the air gap 8 from the primary side 21 to the secondary side 24 in order to meet the requirements of the application, in this case the requirements of the vehicle, and in particular the requirements of the BMS 32, and possibly further requirements from other sources. The controller 27 controls the primary side 21, for example in order to meet a certain output power 34 requested by the BMS 32.

[0114] In order to receive the required information and to transmit corresponding control signals to the relevant components, the controller 27 is connected within the primary side 21 via a communication line 37 to the electronic components 23 and to the transceiver 35, and further via a wireless communication channel 38 also to the secondary side 24. The communication within the primary side, i.e. between the controller 27, the electronic components 23 and the transceiver 35 and possibly further components, can be realized by a wired communication technology such as for example a CAN bus.

[0115] The information received from the controller 27 can for example include the battery SOC and voltage, the charging current, voltage and / or power set points, and typically also further data such as actual current, voltage and / or power, temperature and status information from both sides, log data or power consumption data, etc.

[0116] In such a configuration, the control signals include for example signals controlling the power conversion within the electronic components 23, the primary pad 22 generating the magnetic field 28, and can also include signals controlling the secondary side 24 generating the output power 34. In order to convert the input power 29, the electronic components 23 typically include a converter arrangement, for example including an AC / DC stage, a DC link and a DC / AC inverter providing AC power to the primary pad 22. The control signals then include for example also signals controlling the inverter switch switching. However, the controller 27 can also control other components and components of the wireless charging system 20.

[0117] Figure 3 and 4 A schematic representation of the communication range and the power transfer range between the primary pad 42 and the secondary pad 45 is shown. The transceivers or their antennas are not shown respectively.

[0118] Figure 3 The pads 42, 45 are shown arranged at a larger distance 44, and in Figure 4In Fig. 2 it is shown that they are arranged at a short distance 44'. The two figures also show the communication range 43 of the primary pad 42 and the power transfer range 46 of the primary pad. It can be seen that in the direction perpendicular to the pads 42, 45 the power transfer range 46 does not start on the surface of the primary pad 42 but at a distance 48 above the primary pad 42. The distance 48 is for example about 100 mm. And the power transfer range 46 extends to a certain distance 49 above the primary pad 42. The distance 49 is for example about 150 mm. The extension of the communication range 43 perpendicular to the pads 42, 45 is larger than the maximum extension of the power transfer range 46 in this direction. It can further be seen that the extension of the communication range 43 parallel to the pads 42, 45 is smaller than the length of the pads 24, 45.

[0119] In Figure 3 It can be seen in Fig. 2 that the distance 44 between the primary pad 42 and the secondary pad 45 is smaller than the communication range 43 but larger than the reachable distance of the power transfer range 46. Thus, the pads can communicate with each other but it is not possible to perform a power transfer. In addition, Figure 3 It is shown that the communication range 43 is smaller than the diagonal of the pads 42, 45. Since the diagonal of the pads 42, 45 is in Figure 3 In Fig. 2 it is shown that the length 40 of the pads 42, 45 is clearly smaller than the communication range 43. And since the length 40 is equal to or smaller than the diameter of the pads 42, 45, the communication range 43 is smaller than the diagonal of the pads 42, 45 independent of the shape of the pads 42, 45. The comparison of the length 40 with the communication range 43, which is shown as a spatial area, is simply done by comparing the distance of every point within the communication range 43 from the transmitter. As Figure 3 As is shown schematically in Fig. 2, the position 41 of the transmitter is at the top and in the center of the pad 42.

[0120] In Figure 4 In Fig. 2 it is shown that the distance 44 between the primary pad 42 and the secondary pad 45 is smaller than the communication range 43 but larger than the reachable distance of the power transfer range 46. Thus, the pads can communicate with each other but it is not possible to perform a power transfer. In addition,

[0121] Figure 3 In Fig. 2 it is shown that the distance 44 between the primary pad 42 and the secondary pad 45 is smaller than the communication range 43 but larger than the reachable distance of the power transfer range 46. Thus, the pads can communicate with each other but it is not possible to perform a power transfer. In addition, Figure 4 Further shown is the position of a reference 47 at the secondary pad 42. The reference 47 is positioned in the center of the secondary pad 45 and on the surface of the pad 62 directed towards the primary pad 42. Thus, as long as the reference 47 is within the power transfer range 46, a power transfer from the primary pad 42 to the secondary pad 45 is possible and efficient. As can be seen, the pads 42, 45 can also be horizontally displaced relative to each other, i.e. parallel to the pads 42, 45, for a certain distance before the reference 47 is outside the power transfer range 46.

[0122] Figure 5 and 6 A schematic representation of a primary pad 52 is shown, which has a circular coil 53 and an antenna 57 for communication between the primary side and the secondary side. Figure 5 is a view from above and the view Figure 6 is a view from the side and upwards.

[0123] The primary pad 52 comprises a substantially circular ferrite core plate 53 and a circular coil 54 arranged on the ferrite core plate 53, which has a diameter 59 corresponding to the diameter of the circular ferrite core plate 53. The current flowing within the coil 54 is shown by arrows 55, flowing in a counter-clockwise direction. During power transfer, the current flowing in the coil 54 generates a magnetic field 56, as shown by the field lines running through the central region of the coil 54. Figure 6

[0124] In the center of the primary pad 52, an antenna 57 of a corresponding transceiver (not shown) is arranged. The antenna 57 comprises a coil having two antenna coil loops 57.1, 57.2, which are connected to each other such that they form an 8-shaped coil. The arrows 58 show the direction resulting from the current flowing within the 8-shaped coil for the two antenna coil loops 57.1, 57.2, respectively, as induced by the voltage in the antenna loops 57.1, 57.2 from the magnetic field 56.

[0125] As can be seen, as long as the antenna 57 is arranged in the center of the coil 54, i.e. in the center of the pad 52, the magnetic flux flowing through both coil loops 57.1, 57.2 is equal. Since the two coil loops 57.1, 57.2 have different directions of circulation, the induced voltages in both coil loops 57.1, 57.2 are equal, but they have different signs, such that they compensate each other. Thus, the resulting voltage within the antenna 57 induced by the magnetic field 56 is zero or at least very close to zero, independent of the strength of the magnetic field.

[0126] Figure 7 and Figure 8 A schematic representation of another primary pad 62 is shown. Figure 7 is a view from above and the view Figure 8 is a view from the side and upwards.

[0127] The primary pad 62 comprises a substantially rectangular ferrite core plate 63 and a power coil, wherein two coils 64.1, 64.2 are arranged next to each other on the ferrite core plate 63. In a central region of the pad 62, one or more turns of the coils 64.1, 64.2 run in parallel. The primary pad 62 has a diameter 69 corresponding to the diagonal of the rectangular ferrite core plate 63. ​

[0128] The primary pad 62 is designed such that the current flowing in one coil 64.1 runs in opposite direction to the current flowing in the other coil 64.2. While the current in coil 64.1 runs in clockwise direction, the current in coil 64.2 runs in counter-clockwise direction, as indicated by arrows 65. Thus, during power transfer, the currents flowing in coils 64.1, 64.2 generate a magnetic field 66, as indicated by some of the field lines. The magnetic field 66 runs from below the pad 62 upwards through coil 64.2, over coil 64.1, through coil 64.1 back below the pad 62, and over coil 64.2 below the pad 62. Thus, the resulting magnetic field 66 in the center of the pad 62 directly above the pad is generally parallel to the pad 62. Figure 8

[0129] A corresponding transceiver (not shown) antenna 67 is precisely arranged in the center of the primary pad 62 and directly on top of it. The antenna 67 comprises a single circular coil. Thus, the antenna 67 is arranged essentially parallel to the field lines of the magnetic field 66 generated by the power coils 64.1, 64.2. However, even though some magnetic flux lines of the magnetic field 66 flow through the coil of the antenna 67, these magnetic flux lines run back through the coil of the antenna 67, since the magnetic field 66 generated by the power coils 64.1, 64.2 above the ferrite core plate 63 is generally symmetric with respect to a plane perpendicular to the coils 64.1, 64.2 and arranged between the coils 64.1, 64.2. Thus, hardly any of the resulting magnetic flux flows through the coil of the antenna 67, such that essentially no voltage induced by the power transfer field source is present in the coil of the antenna 67.

[0130] Figure 9 A block diagram of a communication system for use in the present application is shown. The communication system comprises a first microprocessor 70 which provides data to be transmitted to transmitter electronics 71. The transmitter electronics 71 are connected via a cable 73 to a transmitting antenna 75, wherein a cable matching circuit 72 is provided between the transmitter electronics 71 and the cable 73 and an antenna matching circuit 74 is provided between the cable 73 and the transmitting antenna 75. The data is then wirelessly transmitted via a wireless transmission 76 to a receiving antenna 75', provided via a cable 73' to receiver electronics 71', wherein an antenna matching circuit 74' is provided between the receiving antenna 75' and the cable 73' and a cable matching circuit 72' is provided between the cable 73' and the receiver electronics 71'. The receiver electronics 71' provide the transmitted data to a microprocessor 70' for further processing.

[0131] While Figure 9 ​Only a single communication direction is shown, namely from microprocessor 70 to microprocessor 70', the communication system can also transmit data in the other direction from microprocessor 70' to microprocessor 70 in the same way. The components of the communication system are adapted for such two-way communication.

[0132] Figure 10 A block diagram of a transceiver 80 for use in the application is shown. In the transmission path, the transceiver 80 comprises a transmitter 82, a cable matching circuit 84 and an RF (Radio Frequency) switch 85. The transmitter 82 receives data 81 from a microprocessor or the like (not shown) and prepares the data 81 for transmission, such as for example by modulating it by means of a suitable modulation technique. The resulting transmission signal 83 is provided via the cable matching circuit 84 to the RF switch and further to the RF switch 85. An antenna cable (not shown) connects the RF switch of the transceiver 80 to an antenna (not shown) for transmitting the transmission signal 83. For transmitting the transmission signal, the RF switch 85 is controlled by means of a control signal 88 into a transmission mode, i.e. connecting the transmission path to the antenna cable connecting the transceiver to the antenna. The control signal 88 is for example also received from the microprocessor.

[0133] In the reception path, the transceiver comprises a cable matching circuit 86 and a demodulation circuit 87. For receiving a transmission signal 83 transmitted by another transceiver, the RF switch 85 is controlled via the control signal 88 into a reception mode, i.e. connecting the antenna cable to the cable matching circuit 86. The received transmission signal 83 is then demodulated by the demodulation circuit 87 and the extracted data 81 is provided for further use. The data 81 is for example provided to a microprocessor for further processing.

[0134] Figure 11 A block diagram of a demodulator 90 for use in the application is shown. A received RF signal 97 received via an antenna of a transceiver comprising the demodulator 90 has for example been provided to the demodulator 90 via an antenna matching circuit, an antenna cable and a cable matching circuit.

[0135] For extracting the data transmitted via the transmission signal 97, the demodulator 90 comprises at its input a high pass filter 91, followed by an amplifier 92, i.e. an RF amplifier, which amplifies the received and high pass filtered RF signal 97. The amplifier 92 is followed by an envelope detector 93, comprising a rectifier, a low pass filter 94 and a comparator 95, for generating a digital signal 96 representing the data transmitted with the received transmission signal 97. The digital signal 96 is then provided for further processing, for example to a microprocessor.

[0136] Figure 12 A schematic representation of an exemplary circuit 100 of a demodulator for use in the application is shown.

[0137] The circuit 100 comprises a high-pass filter 102 at the input 101, followed by an amplifier 103. The output of the amplifier 103 is provided to an envelope detector 104, which is followed by a low-pass filter 105. Finally, the output of the low-pass filter 105 is provided to an input of a comparator 106, which generates a digital output signal 115 representative of the data received at the input 101.

[0138] The high-pass filter 102 at the input 101 comprises an RC circuit with a series capacitor 109 and a resistor 107 at the input of the amplifier 103. In the embodiment shown in Figure 12 In the embodiment shown in Fig. 1, the parallel resistor 108, here realized in the form of two parallel resistors, is a line termination resistor of an RF cable connecting the demodulator to the antenna. The amplifier 103 amplifies the received signal by means of an op-amp 110, the output of which is connected to the envelope detector 104, which detects the envelope of the received and amplified signal by means of a diode 111. The output of the envelope detector 104 is then provided to the low-pass filter 105, which removes the high frequencies from the rectified envelope signal. The low-pass filter comprises an RC circuit, for example, with a series resistor and a parallel capacitor. In order to extract the data from the received signal, the low-pass filtered signal is compared to a reference signal 112. This is done by means of the comparator 106, which comprises an op-amp 113, wherein the reference signal 112 is connected to the positive input of the op-amp 113, and wherein the low-pass filtered envelope signal is connected to the negative input of the op-amp 113. The output of the op-amp 113 provides the resulting digital signal 115, which is supplied at the output of the circuit 100.

[0139] The level of the reference signal can be fixed, determined for each new charging process, or, preferably, determined for each message to be transmitted by sending an initial signal sequence, measuring the high and low levels of the received signal and determining the level of the reference signal from this in order to best distinguish between the high and low levels of the received signal.

[0140] Figure 13 Another example of an antenna and corresponding cable for use in the present application is shown. Figure 13 An antenna 120 connected to an antenna matching circuit 121 is shown, which comprises a series capacitor 122 and a parallel capacitor 123. The antenna 120 in this example is a circular antenna with three turns, wherein the outermost turn and the innermost turn are connected to the antenna matching circuit 121. The antenna matching circuit 121 is connected via a cable 124 to a filter 125 for the power transfer field. The filter 125 comprises a series circuit of a capacitor 126 and an inductance 127 connected across the cable 127. As already outlined above, the transceiver is adapted to switch between a transmit mode and a receive mode. To this end,Figure 13 The diagram shows an RF switch 129 connected to filter 125. Therefore, switch 129 is controlled, for example, by a microprocessor, or connects transmission path 130 to cable 124, or receive path 131 to cable 124. It should be noted that receive path 131 in this example also includes terminating resistor 128.

[0141] In this example, the antenna matching circuit 121 and the terminating resistor are not only used for matching purposes, but the capacitor 122 of the antenna matching circuit 121 and the terminating resistor 128 together do form a high-pass filter that suppresses the frequency of the power transmission field in the communication signal received through the power transmission field.

[0142] Figure 14 A schematic diagram of the transmitted signal and the corresponding demodulated signal is shown. On the horizontal axis, time is represented in 20 μs (microseconds) segments.

[0143] The transmission signal 140 is a modulated signal with a carrier frequency of 13.56 MHz, the same frequency used in the NFC protocol. The transmission signal 140 in... Figure 14 The upper part is shown on the vertical axis in 1V (volts) segments. Positive bits are represented by signal segments with an amplitude of approximately 4V, and negative bits are represented by signal segments with an amplitude of 0V. The amplitude of positive bits can also have different amplitudes, wherein the amplitude can be fixed, or wherein the amplitude is dynamically adapted for each new power transmission or even during a power transmission. And as is known in the art, negative bits can also be represented by signal segments with a non-zero amplitude, which is different from the amplitude of positive bits. Furthermore, the representation of positive and negative bits can also be inverted, such that positive bits are represented by a small amplitude or zero amplitude, and negative bits are represented by a high amplitude.

[0144] Figure 14 The middle section further illustrates the received signal 141, i.e., the signal received at the input of the demodulation circuit. The received signal 141 is shown on the vertical axis at 0.5V per section and has an amplitude of approximately 1V. It can be seen that although the signal has been transmitted through the power transmission field and has also been affected by noise, the power transmission field and noise are largely attenuated, resulting in a clearly decoded digital signal 142 from the demodulation, such as... Figure 14 The lower part is shown, where each partition on the vertical axis is 0.5V, and where the signal level is 5V. The digital signal 142 is then forwarded to, for example, a microprocessor for further processing. As can be seen, the decoded digital signal 142 has only a certain delay compared to the transmitted signal 140.

[0145] In summary, it should be noted that the present application not only enables a simplified pairing procedure before power is transferred from the primary side to the secondary side, but also enables a simple and rather secure communication between the primary side and the secondary side during power transfer, although the presence of a high magnetic field causes a harsh environment during power transfer.

Claims

1. A wireless power transmission arrangement for wireless power transmission across an air gap via inductive coupling for charging an energy storage device of an electric vehicle, wherein... a) The wireless power transmission arrangement includes a primary unit, secondary units included in the electric vehicle, and a controller for controlling the power transmission. b) The primary unit includes a wireless transceiver and primary pads for inducing magnetic fields into the air gap. c) The secondary unit includes a wireless transceiver and secondary pads for receiving power transmitted via a magnetic field. d) The wireless transceiver includes an antenna for transmitting and receiving communication signals and is adapted to provide a wireless communication link between the primary and secondary units. e) The wireless communication link has a communication range less than twice the maximum spatial extent of the primary pad, and the controller is adapted to control power transmission based on data transmitted via the wireless communication link during power transmission, the controller is adapted to establish a closed control loop for closed-loop control of power transmission, the controller is adapted to control the magnetic field sensed by the primary unit based on parameters of the energy storage device, and the closed control loop includes the wireless communication link.

2. The wireless power transmission arrangement according to claim 1, wherein the energy storage device comprises a battery.

3. The wireless power transmission arrangement according to claim 2, wherein the battery is a traction battery of a vehicle.

4. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein the wireless transceiver is adapted for a maximum space extent smaller than the primary pad.

5. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein the wireless transceiver is adapted for a communication range smaller than the maximum spatial extent of the primary pad but greater than 5 cm.

6. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein the wireless transceiver is adapted for communication at frequencies between 3 kHz and 1 GHz.

7. The wireless power transmission arrangement according to claim 6, wherein the frequency is between 300 kHz and 300 MHz.

8. The wireless power transmission arrangement according to claim 6, wherein the frequency is between 3 MHz and 50 MHz.

9. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein the antenna of the wireless transceiver is arranged such that wireless communication occurs through an air gap.

10. The wireless power transmission arrangement according to claim 9, wherein at least one of the antennas is arranged in the central region of the respective pad.

11. The wireless power transmission arrangement of claim 9, wherein two of the antennas are arranged in the central region of their respective pads.

12. The wireless power transmission arrangement according to any one of claims 10 to 11, wherein during charging, the spatial extension of the communication range is greater than the distance between the primary and secondary pads.

13. The wireless power transmission arrangement according to any one of claims 10 to 11, wherein at least one of the antennas comprises at least one coil, wherein the at least one coil is shaped and arranged such that the voltage induced in the at least one coil by a magnetic field during power transmission is minimized.

14. The wireless power transmission arrangement according to any one of claims 10 to 11, wherein two of the antennas comprise at least one coil, wherein the at least one coil is shaped and arranged such that the voltage induced in the at least one coil by a magnetic field during power transmission is minimized.

15. The wireless power transmission arrangement of claim 13, wherein the primary pad comprises two power coils arranged adjacent to each other in a common plane, wherein during power transmission, current flows in one direction in a first coil of the power coils and current flows in the opposite direction in a second coil of the power coils, wherein the at least one antenna comprises a loop coil arranged parallel to the common plane.

16. The wireless power transmission arrangement of claim 13, wherein the primary pad includes a loop transmission coil for inducing a magnetic field, and wherein at least one of the antennas includes an octagonal coil arranged to pick up the magnetic field induced by the loop transmission coil.

17. The wireless power transmission arrangement of claim 13, wherein the primary pad includes a loop transmission coil for inducing a magnetic field, and wherein two of the antennas include octagonal coils arranged to pick up the magnetic field induced by the loop transmission coil.

18. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein at least one of the wireless transceivers is adapted for half-duplex communication, wherein the at least one wireless transceiver is adapted to switch between a transmit mode and a receive mode.

19. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein two of the wireless transceivers are adapted for half-duplex communication, and wherein the two wireless transceivers are adapted to switch between a transmit mode and a receive mode.

20. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein at least one of the wireless transceivers includes an antenna matching circuit having a first high-pass filter for damping the magnetic field frequency for power transmission, wherein the first high-pass filter includes one or more capacitor elements connected in series.

21. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein two of the wireless transceivers include an antenna matching circuit having a first high-pass filter for damping the magnetic field frequency for power transmission, wherein the first high-pass filter includes one or more capacitor elements connected in series.

22. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein at least one of the transceivers includes a modulation / demodulation circuit for extracting data from a communication signal and providing a digital signal representing the extracted data, wherein the modulation / demodulation circuit includes a second high-pass filter for damping the magnetic field frequency for power transmission.

23. The wireless power transmission arrangement of claim 22, wherein the second high-pass filter comprises an RC circuit.

24. The wireless power transmission arrangement of claim 22, wherein the modulation / demodulation circuit further comprises an amplifier for amplifying the output of the second high-pass filter, an envelope detector for generating an envelope signal of the output of the amplifier, a low-pass filter for removing noise from the output of the envelope detector, and a comparator for converting the output of the low-pass filter into a digital signal.

25. The wireless power transmission arrangement according to any one of claims 1 to 3, wherein the primary or secondary pad includes an antenna corresponding to the wireless transceiver.

26. A method for wireless power transmission across an air gap via inductive coupling for charging an energy storage device of an electric vehicle, the method comprising the following steps: a) The magnetic field is induced into the air gap using the primary pads of the primary cell. b) Utilize the secondary pads of the secondary units included in the vehicle to receive power transmitted via a magnetic field. c) Provide a wireless communication link between the primary unit and the secondary unit. d) Provide a communication range for the wireless communication link that is less than twice the maximum spatial extent of the primary pad, and control wireless power transmission by transmitting data through the wireless communication link during power transmission, and establish a closed control loop for closed-loop control of power transmission, the closed-loop control including a magnetic field sensed by the primary unit based on parameters of the energy storage device, wherein the closed control loop includes the wireless communication link.

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