Inductive charging device, system for inductive energy transfer and method for generating a control current

Abstract

The invention relates to an inductive charging device comprising a first energy coil, a positioning device, and a control device for generating a control current to control the at least one transmitting coil of the positioning device. The control device is configured to generate the control current by receiving or generating an AC signal with a carrier frequency, pulse shaping, and amplitude modulation of the AC signal to generate an amplitude-modulated AC signal by multiplication with a pulse signal and filtering to attenuate harmonics of the amplitude-modulated AC signal.

Description

[0001] The invention relates to an inductive charging device, a system for inductive energy transfer and a method for generating a control current, in particular for a transmitting coil of a positioning device.

[0002] An inductive charging system for charging a vehicle is described in the standard SAE J 2954:2024-08-13. This standard (Chapter 12; Annexes C and D) proposes the so-called differential inductive positioning system (DIPS) as a standardized positioning system. This system features a positioning device (also referred to as a positioning transmitter) located on the transmitting side, which is arranged in a stationary first inductive charging unit (also referred to as a ground assembly or GA), preferably located in or on the ground. According to the standard, this transmitting positioning device has five transmitting coils, each generating a positioning magnetic field as an alternating magnetic field with a different frequency. Each transmitting coil is thus driven by an alternating current, with each alternating current having a specific carrier frequency.

[0003] On the receiving side, a positioning device (also referred to as a positioning receiver device) is provided, which is arranged in a mobile second inductive charging unit (also referred to as a vehicle assembly or VA), preferably located in or on the underbody of a vehicle. According to the standard, this receiving-side positioning device has two receiving coils that detect the positioning magnetic fields generated by the transmitting coils, which are distinguishable due to their different frequencies. From this, the relative positioning of the inductive charging units to each other, and thus ultimately the positioning of the vehicle relative to the underbody inductive charging unit, can be determined.

[0004] Alternative configurations of inductive charging devices can also use a different number of transmitting and / or receiving coils. For example, it is generally sufficient if the transmitting positioning device has at least one transmitting coil and the receiving positioning device has at least one receiving coil.

[0005] Such charging devices or parts thereof are also known from DE 102022203489 A1, DE 102022120691 A1 and DE 102022107568 A1.

[0006] The present invention is based on the objective of optimizing the control of the at least one transmitting coil, particularly with regard to distortion, EMC properties of the generated magnetic fields and system stability.

[0007] According to one aspect of the present invention, an inductive charging device is provided with: - a first energy coil for generating an alternating magnetic field for inductive energy transfer to a second energy coil of a second inductive charging device in an energy transfer operation; - a positioning device with at least one transmitting coil for generating a positioning magnetic field for detecting the relative positioning of the energy coils to each other in a positioning operation; and - a control device for generating a control current for controlling the at least one transmitting coil, wherein the control device is designed to generate the control current by - Receiving or generating an alternating current signal with a carrier frequency, - Pulse shaping of the AC signal to generate an amplitude-modulated AC signal by multiplication with a pulse signal and - Filtering to dampen harmonics of the amplitude-modulated alternating current signal.

[0008] According to a further aspect of the present invention, a system for inductive energy transfer is provided with an inductive charging device according to one of the preceding claims and a further inductive charging device, in particular a mobile inductive charging device for attachment to and / or in a vehicle, wherein the further inductive charging device comprises: - a second energy coil for receiving energy inductively transferred from the first energy coil during energy transmission operation; and - a positioning device with at least one receiving coil for detecting the positioning magnetic field and for recognizing the relative positioning of the energy coils to each other during positioning operation.

[0009] According to a further aspect of the present invention, a method is provided for generating a control current for controlling at least one transmitting coil of a positioning device of an inductive charging device with a first energy coil for generating an alternating magnetic field for inductive energy transfer to a second energy coil of a second inductive charging device in an energy transfer mode and with a positioning device with at least one transmitting coil for generating a positioning magnetic field for detecting the relative positioning of the energy coils to each other in a positioning mode, wherein the control current is generated by - Receiving or generating an alternating current signal with a carrier frequency, - Pulse shaping of the AC signal to generate an amplitude-modulated AC signal by multiplication with a pulse signal and - Filtering to dampen harmonics of the amplitude-modulated alternating current signal.

[0010] Preferred embodiments of the invention are defined in the dependent claims. It is understood that the claimed method and the claimed system have similar and / or identical preferred embodiments to the claimed inductive charging device, in particular as defined in the dependent claims and as disclosed herein.

[0011] The invention is based on the idea of ​​processing a modulated signal onto the carrier signal (the AC signal) by pulse shaping and filtering in such a way that switching on and off does not occur via steep edges. For this purpose, the AC signal is multiplied, among other things, by a pulse signal, e.g., a predefined or (for example, in a microcontroller) generated raised cosine signal, to transform the overall signal (the drive current) carrier signal into a desired pulse shape that exhibits "smoother" transitions instead of steep edges in order to reduce or completely avoid distortion and harmonics. Pulse shaping is thus achieved by multiplying the carrier signal by the pulse signal (which can also be referred to as the modulation signal). This multiplication corresponds to amplitude modulation.By choosing the waveform of the pulse signal, it is ultimately possible to influence the spectrum of the transmitted signal (i.e., the positioning magnetic field) emitted by the transmitting coil. If the pulse signal were rectangular (the simplest case), compliance with certain criteria (OBW, transmission band limits, etc.) would be difficult or impossible. Selecting a suitable pulse signal, such as a raised cosine signal, makes it possible to meet these criteria.

[0012] According to the invention, a control and drive concept for the transmitting coil(s) of the positioning device of the transmitting-side inductive charging unit is proposed, which can be used, for example, for the GA transmitting coils of the DIPS described in the aforementioned SAE standard. In the proposed solution, the transmitting coil(s) is / are supplied with a (e.g., sinusoidal) carrier current (the "AC signal") with low distortion and a high degree of amplitude modulation freedom. Therefore, the magnetic field generated by a transmitting coil driven in this way can meet stringent EMC requirements and improve system stability.

[0013] In the solution according to the invention, the alternating current signal in the transmitting coil represents a carrier, the transmitting coil frequency represents the carrier frequency of the transmitting coil, and the filtering filters the carrier. Amplitude modulation in the form of pulse shaping and filtering thus together generate the drive current for controlling at least one transmitting coil. Preferably, an individual drive current is generated for each transmitting coil.

[0014] In a preferred embodiment, the control device is configured to generate a pulse-width modulation signal as an alternating current signal. This represents a simple and easily processed carrier signal.

[0015] Preferably, the control device is further configured for low-pass or band-pass filtering of the amplitude-modulated AC signal. This allows unwanted harmonics to be eliminated or at least attenuated.

[0016] The control device can further be configured to adjust the RMS value of the current and / or to amplitude modulation by adjusting the duty cycle and phase of the AC signal. Adjusting the phase and duty cycle can also achieve compliance with standards, as this allows, for example, component tolerances to be compensated for.

[0017] The control device can further be configured for pulse shaping of the amplitude-modulated AC signal by means of a pulse shaping filter, in particular a raised-cosine filter, a root-raised-cosine filter, a sinc filter, and a Gaussian filter. The pulse signal used, with which the AC signal is multiplied, results in the desired smoothed transitions instead of steep edges.

[0018] In a further embodiment, the control device is designed to amplify or attenuate the filtered amplitude-modulated AC signal. This allows the amplitude of the AC signal to be adjusted to the desired strength.

[0019] Furthermore, in one embodiment, the control device is configured to amplify the power of the filtered amplitude-modulated AC signal. This power amplification can be used when the current-carrying capacity of the other components of the control device is insufficient for the required current of the drive current for the transmitting coil(s).

[0020] The control device can be implemented, for example, by a processor, controller (e.g., a microcontroller), or another common component. Alternatively, the control device can be implemented by separate components such as a signal generation unit, a filter unit, and an amplifier unit, each implemented by dedicated hardware components, a processor, or a controller.

[0021] Furthermore, one embodiment provides that the control device has an overcurrent protection circuit and / or an overvoltage protection circuit on its output side. This serves to protect the components of the control device if, for example, an overvoltage is induced in a transmitting coil during power transmission operation.

[0022] While a single transmitting coil is generally sufficient for positioning, the positioning device preferably has several transmitting coils, in particular four or five, to generate a positioning magnetic field as an alternating magnetic field with a different carrier frequency. The control device is designed to generate a different control current for each transmitting coil.

[0023] Preferably, the inductive charging device according to the invention is a stationary inductive charging device, e.g. a GA in the sense of the aforementioned standard, for mounting on and / or in a floor surface.

[0024] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0025] Exemplary embodiments of the invention are illustrated in the following drawings and are explained in more detail in the following description, where identical reference numerals refer to identical, similar, or functionally equivalent components. The drawings show: Fig. 1 a highly simplified representation of a vehicle with an inductive charging device according to the invention; Fig. 2 a top view of an inductive charging device according to the invention with a near positioning transmitter and a far positioning transmitter; Fig.3 an inductive charging device with a positioning receiving device for a vehicle charging system according to the invention; Fig. 4 a block diagram of an embodiment of a system according to the invention for inductive energy transfer; Fig. 5 diagrams to illustrate requirements for modulation width; Fig. 6 diagrams to illustrate the spectrum of a carrier signal with and without distortion; Fig. 7 a diagram to explain the phase angle; Fig. 8 a diagram of an FFT simulation example for three different signal shapes; Fig. 9 a block diagram of an embodiment of a control device according to the invention; Fig. 10 a diagram of an exemplary output signal for generating the desired alternating current signal; Fig. 11 a diagram of a pulse signal as the output of a pulse shaping filter; Fig. 12 a diagram of an amplitude-modulated alternating current signal; Fig. 13 a block diagram of an exemplary embodiment of a signal conditioning stage of the control device according to the invention; Fig. 14 a diagram of a binary data stream to be transmitted; Fig. 15 a diagram of an envelope generated by a pulse-shaping filter; and Fig. 16 a diagram of an amplitude-modulated alternating current signal.

[0026] Fig. Figure 1 shows an exemplary mobile inductive charging device 1a, which is arranged on a vehicle 2 with an energy storage device 3 and is positioned above a stationary inductive charging device 1b. During operation, energy can be transferred from the stationary inductive charging device 1b to the mobile inductive charging device 1a, thereby charging the energy storage device of the vehicle 3.

[0027] The mobile inductive charging device 1a and the stationary inductive charging device 1b together form, or are part of, a vehicle charging system 8. In principle, it is also possible to operate the vehicle charging system 8 bidirectionally. In this case, energy can be temporarily transferred from the mobile inductive charging device 1a to the stationary inductive charging device 1b. The in Fig.A stationary inductive charging device 1b, arranged on the surface 35, can alternatively be recessed into the roadway (not shown here). In a recessed arrangement, the inductive charging device 1b can be covered by certain layers of the roadway or be flush with the roadway surface. The mobile inductive charging device 1a is, for example, mounted in or on the underbody of the vehicle 2. Both inductive charging devices 1a and 1b each have an energy transfer winding (energy coil) and preferably several flux guide elements.

[0028] Fig.Figure 2 shows a top view of an embodiment of an inductive charging device 1b. In this example, it has a positioning device (also referred to as a positioning transmitter) with a near-positioning transmitter NAH-POS and a far-positioning transmitter FERN-POS. The near-positioning transmitter NAH-POS is implemented here as four near-positioning windings 13 (transmitting coils) designed as flat coils, but can also be implemented with more or fewer transmitting windings. The far-positioning transmitter FERN-POS is implemented here as a solenoid (positioning signal winding), but can also be omitted. During a positioning process, the far-positioning transmitter FERN-POS emits a far-positioning signal FERN-SIG in the form of an alternating magnetic field (also referred to as a far-positioning magnetic field).The near-positioning transmitter NAH-POS transmits several near-positioning signals NAH-SIG in the form of alternating magnetic fields (also referred to as near-positioning magnetic fields) during a positioning operation. These signals differ, for example, from each other and from the far-positioning signal FERN-SIG by their frequency. Furthermore, an energy transmission winding 4b (energy coil), preferably designed as a flat coil, and flux guide elements 5b, for example in the form of ferrite plates, are provided.

[0029] Fig.Figure 3 shows a mobile inductive charging device 1a, which has a positioning device (also called a positioning receiver) with two sensor windings 9a1 and 9a2 (receiving coils), whereby in principle only one sensor winding or more sensor windings can also be used. In the present embodiment, eight flux guide elements 5a are shown, which are arranged radially around the center 7 of the energy transfer winding 4a in the plane. However, there can also be more or fewer flux guide elements. The energy transfer winding 4a, preferably designed as a flat coil, which is hidden in the top view by the flux guide elements 5a, is indicated by dashed lines. The sensor windings 9a1, 9a2 are designed here as a solenoid (also called a cylindrical coil).

[0030] In this example, the first sensor winding 9a1 is arranged axially symmetrically to the second sensor winding 9a2 with respect to the vehicle's longitudinal direction 6. The first sensor winding 9a1 and the second sensor winding 9a2 intersect at least approximately at the center 7 of the energy transfer coil 4a. The first sensor winding 9a1 has a first radial longitudinal direction 11a1, and the second sensor winding 9a2 has a second radial longitudinal direction 11a2. The angle between the first radial longitudinal direction 11a and the vehicle's longitudinal direction 6 is at least approximately the same as the angle between the second radial longitudinal direction 11b and the vehicle's longitudinal direction 6; however, the angles can also be different. The sensor windings 9a1 and 9a2 thus form a cross-shaped arrangement.

[0031] During the charging process, the vehicle 2 is positioned above the stationary inductive charging device 1b, and energy is transferred to the inductive charging device 1a. The flux guide elements perform the function of flux guidance. In the charging state, the field lines of the magnetic field run approximately radially within them. Since the first radial longitudinal direction 11a1 and the second radial longitudinal direction 11a2 are also radially aligned and thus at least approximately parallel to the magnetic field lines, relatively little to no voltage is induced in the first sensor winding 9a1 and the second sensor winding 9a2. This is advantageous because, with the high power levels of energy transfer and thus high flux densities, the sensor windings could otherwise easily be destroyed. Therefore, no additional effort is required to prevent damage to the arrangement.

[0032] The inductive charging device 1b and the inductive charging device 1a according to the invention can be part of a vehicle charging system 8 according to the invention. In this system, one positioning receiver can receive signals from both the near-positioning transmitter NAH-POS and the far-positioning transmitter FERN-POS. This is advantageous because one positioning receiver can operate two different positioning methods that function optimally at two different distance ranges. Further details of the basic structure and operation of the inductive charging devices 1a and 1b can be found in the aforementioned documents, to which explicit reference is made here.

[0033] Fig.Figure 4 shows a block diagram of an embodiment of a system 100 according to the invention for inductive energy transfer with a first (preferably stationary) inductive charging device 110 and a second (preferably mobile) inductive charging device 120. The first inductive charging device 110 can be designed in principle like the one described in Figure 4. Fig. The second inductive charging device 120 can be designed in the same way as the one shown in 2. Fig. The charging device shown in section 1a should be designed as shown in section 3.

[0034] The first inductive charging device 110 comprises a first energy coil 111 for generating an alternating magnetic field for inductive energy transfer to a second energy coil 121 of the second inductive charging device 120 in an energy transfer mode. It further comprises a positioning device 112 with at least one transmitting coil for generating a positioning magnetic field for detecting the relative positioning of the energy coils 111 and 121 to each other in a positioning mode, and a control device 113 for generating a control current to control the at least one transmitting coil.The second inductive charging device 120 comprises the second energy coil 121 for receiving energy inductively transferred from the first energy coil 111 during energy transfer operation, and a positioning device 122 with at least one receiving coil for detecting the positioning magnetic field and for recognizing the relative positioning of the energy coils 111 and 121 to each other during positioning operation. The positioning devices 112 and 122 can be configured as described in the aforementioned SAE standard or the documents referenced therein, or differently.

[0035] Since the positioning device 112, as used, for example, in DIPS, is classified as a radio system in the 9 kHz–30 MHz frequency range, strict criteria apply. The most important of these criteria can be found in rows 1–3 of Table 1. The criterion in row 4 is a further additional criterion closely related to criterion 3. Table 1: Criteria Nr . criterion 1 Operating frequency ranges (OBW criterion) 2 Modulation bandwidth 3 Limit values ​​for interference emissions 4 Inductive phase angle between transmit current and excitation voltage, interoperability • Criterion 1: This criterion states that 99% of the energy of the modulated transmitted signal must lie within the transmission band limits. • Criterion 2: This criterion defines requirements for the modulation bandwidth, which are illustrated by diagrams in Fig. 5 will be illustrated. Fig. Figure 5A shows a diagram illustrating the definition of the modulation bandwidth for carrier frequencies <135 kHz. Fig. Figure 5B shows a diagram illustrating the definition of the modulation bandwidth for carrier frequencies >135 kHz. This places high demands on the signal shape, as the modulation bandwidth should be within the transmit band or ±7.5% of the carrier frequency. The stricter of the two options should be applied. • Criterion 3: This criterion describes that limit values ​​for interference emissions exist in the 9kHz-30MHz and 30MHz-1GHz ranges, which must be adhered to. • Criterion 4: This criterion describes the problem caused by the change in inductance of the transmitting coils due to the introduction of additional ferrite material into the system. This can be used when a GA is operated with a VA with a different ferrite arrangement. This criterion serves to ensure interoperability.

[0036] In order for the positioning device 112 to simultaneously meet the four criteria mentioned above, a correspondingly designed control circuit 113 is provided according to the invention.

[0037] Table 2 below shows how well the criteria for the positioning device can be met for various possible control methods, in particular possible combinations of control stage and signal processing. It is evident that only by combining a distortion-free carrier signal with a deliberately chosen pulse shaping for amplitude modulation is it possible to reliably meet all criteria. Table 2: Compliance with the criteria processing Criterion 1 Criterion 2 Criterion 3 Criterion 4 Carrier with distortion + without pulse shaping - 0 0 0 Carrier with distortion + with pulse shaping - 0 0 0 Carrier without distortion + without pulse shaping - 0 + + distortion-free carrier with pulse shaping + + + + (Legend: -: Compliance not possible, 0: Compliance possible but complex, + Compliance possible)

[0038] Without pulse shaping, it is therefore not possible to comply with criteria 1 and 2 at suitable transmission frequencies (for example, those specified in the SAE standard for DIPS), since the Fig.The spectrum shown in 6A is relatively broadband and contains a lot of energy in the sidebands. This also has a negative impact on criterion 3. The spectrum shown in Fig. The spectrum shown in Figure 6B depicts the combination of "carrier without distortion + with pulse shaping". Significantly fewer and less energetic sidebands are visible here. Therefore, this combination is well-suited to fulfilling criteria 1 and 2.

[0039] Another requirement for the transmit current is that it should have as inductive a phase angle as possible (criterion 4) in order to minimize the influence of ferrite materials, such as VA, on the amplitude of the transmit current. The reason for this is found in Fig. Diagram 7 illustrates the choice of a large phase angle for the transmitting coil circuit.

[0040] Curve 200 shows the level of the coil current in dB versus frequency. The reactive power compensation of the transmitting coil is designed here, as an example, for a resonant frequency of 100 kHz. Curve 201 shows the possible case in which the inductance of the transmitting coil increases due to the addition of further ferrite material. This results in the resonant frequency dropping to approximately 40 kHz with the same reactive power compensation design. If the system were operated at resonance with the original transmitting coil inductance (operating point 202), the new operating point would be at 203 with the increased inductance. This would cause the transmitting current to drop sharply, which is undesirable. The goal is to ensure that the influence of additional ferrite material (for example, operating the system with a VA from a different manufacturer) remains largely unaffected to guarantee interoperability.This can be achieved by a large inductive phase angle between the transmitting coil current and its excitation voltage. This case is illustrated in operating point 204. Here it can be seen that the effect of the change in the transmitting coil's inductance due to additional ferrite material on the coil current is significantly less pronounced (operating point 205) than is the case in operating points 202 and 203.

[0041] For example, if a Class D amplifier is used, its carrier waveform becomes highly distorted at large inductive phase angles and is no longer a sine wave, but rather resembles a triangle wave. Therefore, it is difficult to meet criteria 3 and 4 if the drive of the transmitting coil(s) is not properly designed.

[0042] Fig.Figure 8 shows a diagram of an FFT simulation example for three different waveforms at an example frequency of 100 kHz and an amplitude of 5 V for a wider frequency range. This diagram illustrates the problem of the potential EMC emissions of three different waveforms that differ in their slope (curve 210: square wave; curve 211: triangle wave; curve 212: sine wave). The simulation examples contain noise, but nevertheless show the relationships. The simulation results of the signals in the time domain show that the square wave 210 can radiate significantly higher amplitudes in higher frequency ranges >1 MHz than the triangle wave 211 (carrier with distortion) or the sine wave 212 (carrier without distortion). The envelope of the triangle signal drops off at 40dB / decade from the lower cutoff frequency, whereas the envelope of the square signal drops off at only 20dB / decade.An ideal sine wave signal would only radiate at its fundamental frequency, in this case 100 kHz. Since the simulation contains errors and noise, and the sine wave signal is therefore not ideal, a frequency spectrum is also visible here, which, however, exhibits the fastest roll-off towards higher frequencies of all three waveforms. This clearly demonstrates the advantage of a near-sinusoidal waveform from an EMC perspective compared to triangular and rectangular waveforms.

[0043] Furthermore, calibrating the transmit currents in the case of a triangular signal is challenging and very complex. The RMS of the fundamental current wave must be set to a specific value, which can lead to significant variation in triangular waves with similar settings. Consequently, the variance between different systems would be too high. This would be a major disadvantage, especially in mass production.

[0044] Since the PWM signal, which can be generated by a microcontroller (µC) for example, is not used directly in the combination of "distortion-free carrier + pulse-shaping," but must be processed accordingly, the coil current always has a sinusoidal waveform, regardless of its phase angle (criterion 4). This signal processing can be implemented, for example, using a low-pass or band-pass filter stage. Therefore, criteria 3 and 4 are not mutually exclusive in this combination; both can be fulfilled simultaneously.

[0045] Fig. Figure 9 shows a block diagram of a first embodiment of a control device 113 according to the invention, which is preferably used in a stationary inductive charging device (1b in Fig. 1 and Fig. 2; Fig. 110 in Fig.4) can be used. The control device 113 is designed to generate a control current for controlling the at least one transmitting coil (13, 41 in Fig. 2) According to the invention, the control device 113 is configured to generate the control current by receiving or generating an alternating current signal with a carrier frequency, pulse shaping of the alternating current signal to generate an amplitude-modulated alternating current signal by multiplication with a pulse signal, and filtering to attenuate harmonics of the amplitude-modulated alternating current signal. In the Fig. The embodiment shown in Figure 9 includes, for example, a control stage 130, a filter / amplifier stage 131, an (optional) output stage 132, and an (optional) protection stage 133. The functions of the various stages / units are as follows.

[0046] The main function of control stage 130 is to generate (or maintain) an AC signal with a specific frequency and to amplitude-modulate the current through the transmitting coil, thus controlling the RMS value of the AC signal's fundamental frequency. The AC signal output by control stage 130 can have any waveform. Control stage 130 is typically implemented by a microcontroller, with the output signal being an AC signal, such as a PWM signal. The frequency of this PWM signal corresponds to the carrier frequency of the current in the transmitting coil and remains constant. The duty cycle and phase of the PWM signal can be adjusted to achieve flexible amplitude modulation of the carrier current in the transmitting coil. These parameters allow control of the transmitting coil's current. Fig.Figure 10 shows a diagram of an exemplary output signal 140 (voltage signal) of the control stage 130, which is responsible for generating the desired current signal.

[0047] The main functions of signal conditioning stage 131 are filtering and amplifying or attenuating the signal. Since the control stage 130 typically lacks current-carrying capacity and the PWM signal still contains many harmonics, this stage is designed to further process the PWM signal. Signal conditioning stage 131 can first remove the harmonics contained in the carrier signal, as shown in Fig.Figure 11 shows a diagram of an output signal 141 of the signal conditioning circuit 131 with a low-distortion carrier and amplitude modulation. Additionally, flexible amplitude modulation is achieved by controlling the duty cycle and phase of the PWM signal, enabling various pulse shaping and further improving the EMC performance of the signal. Fig. Figure 12 shows a diagram of an exemplary raised-cosine modulation achieved with the proposed circuit scheme. Thanks to the flexible amplitude modulation and the low-distortion carrier signal, as well as the chosen modulation (e.g., the raised-cosine modulation, which is selected to closely resemble a sine wave), the modulated signal 142 exhibits good EMC characteristics and meets stringent legal requirements. The signal strength can also be adjusted at this stage.

[0048] The signal conditioning stage 131 can comprise a filter stage and an amplifier stage. Depending on the topology, a low-pass or band-pass filter stage can preferably be provided as the filter stage to filter high frequency components from the AC signal and achieve a nearly sinusoidal waveform without distortion. In some cases, balancing of the AC signal can also be provided, for example, if it is necessary to convert the AC signal from a single-end to a differential signal for further processing.

[0049] An amplifier stage generally serves to adjust the voltage level between individual stages. This can result in either amplification or attenuation of the desired signal. Since, for example, a PWM signal generated by a microcontroller typically has a low amplitude, the function of the amplifier stage in this case is to amplify the amplitude of the AC signal. This allows the defined current in the transmitting coils to be achieved later in the final stage. To accomplish this, the AC signal is amplified, preferably by an operational amplifier, to a larger amplitude, although smaller amplitudes are also possible. In some cases, this function can also be performed by the filter stage.

[0050] The transmitting coil of a DIPS typically requires a specific drive current. If the current driving capability of the signal conditioning stage 131 is insufficient, it can be cascaded with a power amplifier stage 132 to achieve adequate current driving capability. The power amplifier stage 132 corresponds to the final stage of a power amplifier and ensures that the required current is supplied to the transmitting coils. Generally, various topologies can be used here. These can include, for example, push-pull output stages, push-pull circuits, or inverter circuits.

[0051] Due to the current transmission mode, an overvoltage can be induced in a transmitting coil of the positioning device. In this case, it is advantageous to protect the drive circuit by cascading a protection stage 133, for example, by an overvoltage protection circuit (OVP), to protect sensitive electronics.

[0052] Fig. Figure 13 shows a block diagram of an exemplary embodiment of the signal conditioning stage 131, in particular to illustrate the operating principle of pulse shaping. A binary data stream 150 containing information that is to be modulated, for example, onto the positioning magnetic field generated by a transmitting coil, is shown in the Fig. This is illustrated in diagram 14. This information can then be transmitted to the vehicle's inductive charging system, for example, to transmit information concerning the stationary inductive charging system.

[0053] The binary data stream 150 is fed into a pulse-shaping filter 151 and generates the desired envelope 152, which is in the Fig. The diagram shown in section 15 illustrates this. Compared to the one in Fig.In the binary data stream 150 shown in Figure 14, the envelope 152 is much smoother and therefore exhibits better EMC characteristics. It is worth noting that the generation of the in Fig. The signal shown in Figure 152 can be processed, for example, using a pulse-shaping filter implemented in a microcontroller. Alternatively, the waveform can be pre-generated in a computer and stored in the microcontroller.

[0054] The duty cycle and phase of the PWM signal are adjusted according to this signal 152 in the setting unit 153. If the PWM signal is set correctly, the following will occur: Fig. 16 shown amplitude-modulated carrier signal 154 (alternating current signal) obtained, i.e., the signal 152 is amplitude-modulated onto the carrier.

[0055] The duty cycle of the PWM signal corresponds to the amplitude of the carrier signal. Depending on the downstream electrical circuit (filter, amplifier), this relationship can be described as a function: Amplitude = f (Duty Cycle). Preferably, this can be: Amplitude = k * (abs(Duty Cycle - 0.5)). The larger the duty cycle, the larger the carrier amplitude. The phase matching of the PWM signal corresponds to the case in which the envelope is less than zero, as represented by the circle in Fig. 15 is displayed. To make the carrier amplitude negative, the PWM signal is therefore phase-shifted by 180°.

[0056] The type of pulse shaping filter, the parameter settings of the pulse shaping filter and the modulation depth can generally be adjusted flexibly.

[0057] The duty cycle and phase of the PWM signal with amplitude = f (duty cycle) can be generated in the microcontroller. Alternatively, it can be generated in advance, e.g., on the computer, and stored in the microcontroller.

[0058] In preferred embodiments, a filter stage can generate a low-distortion sine wave signal. The drive circuit according to the invention is also characterized by a simple structure, high accuracy, high EMC, and high stability. Thanks to these properties, a positioning device based on this driver circuit can be easily integrated into a general arrangement (GA). Pulse shaping can be achieved by controlling the AC output of the control stage. The aim is to suppress the side lobe of the modulation signal. Effective implementations of pulse shaping include the sinc filter, the raised cosine filter, and the Gaussian filter.

[0059] The control PWM signals provided by a microcontroller typically have a rectangular waveform and a low signal amplitude, for example, 0 to 3.3V. The filter stage serves to filter the high-frequency components from the output signal of the control stage in order to generate a nearly sinusoidal signal at the frequency of the corresponding transmit coil. This can be achieved, for example, with a low-pass or, preferably, a band-pass filter circuit. To achieve the necessary harmonic attenuation, the filter can contain several first- or higher-order stages, especially when a rectangular PWM signal is used as the output signal. The advantage of a band-pass filter stage is that, in this case, even low frequencies can be effectively filtered. These interfering frequencies arise, for example, from harmonics of components with a low switching frequency, such as DC-DC converters.Furthermore, a bandpass filter circuit typically achieves steeper filter curves with the same number of stages. This filter circuit also allows for gain and offset of the output signal, eliminating the need for an additional amplifier stage.

[0060] In general, the PWM output signal has a low amplitude. This makes it impossible to generate high coil currents. Therefore, amplification of the transmitted signal is necessary. For example, the signal can be amplified to an amplitude of 0 to 12V; however, other amplification levels are also conceivable. In general, active filter circuits, preferably with an operational amplifier, are used in this frequency range, as they have the advantage over passive filters of not requiring large and expensive components. If the transmitted signal is in the kHz range, as with DIPS, for example, the disadvantage of a passive filter circuit of the same order as an active filter circuit is that relatively large inductance values ​​(in the example of an LC filter) are required. This negatively impacts cost and installation space. The dynamic behavior of the active filter circuit can be adjusted by selecting the parameter values ​​(RC sizing).In this case, there are high demands on the dynamic behavior so that pulse shaping can be implemented effectively.

[0061] The output stage can be implemented simply and inexpensively. Class B / AB amplifiers use two or more transistors that are biased so that each transistor conducts only during one half-cycle. The BJTs receive an input signal of the same amplitude, but with a phase shift of 180°. MOSFETs or, preferably, bipolar junction transistors (BJTs) can be used. Compared to Class A amplifiers, Class B and Class AB amplifiers have the advantage that heat losses can be reduced, since the individual transistors conduct for the entire period. The circuit can be built with BJTs of the same transmission line type (e.g., two NPN transistors) as well as with BJTs of complementary transmission line types (NPN, PNP).

[0062] The connected transmitting coil can have a center tap. In this case, the center-tapped inductor acts as the transmitting coil. Its function is to recombine the two 180° phase-shifted output signals from the two BJTs, which provide the power to the load. The load current is thus divided between the two BJTs. The emitter terminals of both NPN BJTs shown are connected to ground (GND) via a resistor. The gain of the output current can be adjusted by changing the value of this resistor. The positive half-wave is amplified by one transistor, and the negative half-wave by the other. The base quiescent current can be adjusted via resistors R1 and R2. This also enables class AB operation, which is advantageous because it avoids distortion at the zero crossing of the transistor's input signal.The connected transmitting coil cannot have a center tap. The undocumented circuit section serves to simulate a center tap in the circuit.

[0063] To drive the push-pull output stage from the single-ended output signal of the filter stage, a balun can be used. As mentioned above, the two NPN transistors must be driven with out-of-phase input signals. The circuit should therefore be designed to generate two signals of the same amplitude, phase-shifted by 180°, from the filter output signal. The output signals are applied to the collector and emitter resistors, respectively. An alternative method for generating the drive signals for the output transistors would be to use a center-tapped driver transformer.

[0064] Furthermore, the output stage can also be implemented using integrated circuits (ICs). For example, a high-current operational amplifier (op-amp) in a voltage follower configuration can be used as the output stage. The filter stage and the output stage can be implemented separately using different op-amps. In this case, the gain is also generated by the bandpass filter circuit.

[0065] If a high-current op-amp is used directly as the filter op-amp, the output stage can even be omitted, as it can also generate the necessary inductor current. However, the disadvantage of this solution is that, depending on the number of stages, multi-channel op-amps with high current handling are relatively expensive. Therefore, a solution using inexpensive amplifier op-amps for the filter circuit is preferred. In this case, only one high-current op-amp is required in the output stage. The output stage in this case is the high-current op-amp in a voltage follower configuration.

[0066] In summary, the present invention proposes a control and drive concept for the transmitting coil(s) of a positioning device of an inductive charging system, with which the transmitting coil(s) is / are supplied with a sinusoidal carrier current with low distortion and a high degree of amplitude modulation freedom. The generated transmitting coil magnetic field can thereby meet stringent EMC requirements and improve system stability. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102022203489 A1

[0005] DE 102022120691 A1

[0005] DE 102022107568 A1

[0005]

Claims

Inductive charging device comprising: - a first energy coil for generating an alternating magnetic field for inductive energy transfer to a second energy coil of a second inductive charging device in an energy transfer mode; - a positioning device with at least one transmitting coil for generating a positioning magnetic field for detecting the relative positioning of the energy coils to each other in a positioning mode; and - a control device for generating a control current for controlling the at least one transmitting coil, wherein the control device is configured to generate the control current by: - ​​receiving or generating an alternating current signal with a carrier frequency, - pulse shaping of the alternating current signal to generate an amplitude-modulated alternating current signal by multiplication with a pulse signal, and - filtering to attenuate harmonics of the amplitude-modulated alternating current signal. Inductive charging device according to claim 1, characterized in that the control device is designed to generate a pulse width modulation signal as an alternating current signal. Inductive charging device according to one of the preceding claims, characterized in that the control device is designed for low-pass or band-pass filtering of the amplitude-modulated alternating current signal. Inductive charging device according to one of the preceding claims, characterized in that the control device is designed for adjusting the RMS value of the current and / or for amplitude modulation by adjusting the duty cycle and the phase of the AC signal. Inductive charging device according to one of the preceding claims, characterized in that the control device is designed for pulse shaping of the amplitude-modulated alternating current signal by means of a pulse shaping filter, in particular a raised cosine filter, a root raised cosine filter, a sinc filter and a Gaussian filter. Inductive charging device according to one of the preceding claims, characterized in that the control device is designed to amplify or dampen the filtered amplitude-modulated alternating current signal. Inductive charging device according to one of the preceding claims, characterized in that the control device is designed for power amplification of the filtered amplitude-modulated alternating current signal. Inductive charging device according to one of the preceding claims, characterized in that the control device comprises a signal generation unit, a filter unit and an amplifier unit. Inductive charging device according to one of the preceding claims, characterized in that the control device has an overcurrent protection circuit and / or an overvoltage protection circuit on the output side. Inductive charging device according to one of the preceding claims, characterized in that the positioning device has several transmitting coils, in particular four or five transmitting coils, for generating a positioning magnetic field as an alternating magnetic field with different carrier frequencies, and that the control device is designed to generate a different control current for controlling a transmitting coil. Inductive charging device according to one of the preceding claims, characterized in that the inductive charging device is a stationary inductive charging device for mounting on and / or in a floor surface. System for inductive energy transfer with an inductive charging device according to one of the preceding claims and a further inductive charging device, in particular a mobile inductive charging device for attachment to and / or in a vehicle, wherein the further inductive charging device comprises: - a second energy coil for receiving energy inductively transferred from the first energy coil in energy transfer operation; and - a positioning device with at least one receiving coil for detecting the positioning magnetic field and for recognizing the relative positioning of the energy coils to each other in positioning operation. Method for generating a control current for controlling at least one transmitting coil of a positioning device of an inductive charging device with a first energy coil for generating an alternating magnetic field for inductive energy transfer to a second energy coil of a second inductive charging device in an energy transfer operation and with a positioning device with at least one transmitting coil for generating a positioning magnetic field for detecting the relative positioning of the energy coils to each other in a positioning operation, wherein the control current is generated by: - ​​receiving or generating an alternating current signal with a carrier frequency, - pulse shaping of the alternating current signal to generate an amplitude-modulated alternating current signal by multiplication with a pulse signal and - filtering to attenuate harmonics of the amplitude-modulated alternating current signal.

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