Method and inspection device for inspecting output stage for broadband high-frequency power line communication

Abstract

The invention relates to a method and a checking device (100) for checking impedance matching of an output stage (545) for power line communication of devices, in particular electric vehicles and charging infrastructures. It is proposed to sample a broadband high-frequency signal transmitted from an output stage (545) to be examined over a charging cable (310, 320) and to determine and evaluate an associated spectral power density spectrum (PSD spectrum) from the acquired temporal transients. The spectral power density spectra are preferably acquired for different cables (300, 310, 320) having different lengths, respectively. If there is a correct match in the impedance of the output stage to be checked, the difference in the average values of the spectral power densities acquired for cables of different lengths, among other things, is zero in the range of tolerances. The inspection device (100) is designed to carry out such a method.

Description

Technical Field

[0001] The invention relates to a testing device and a method for testing an output stage, in particular of an electric vehicle or a charging station, for broadband, high-frequency power line communication via different cables, in particular pluggable cables. Background Art

[0002] Electric vehicles typically have at least one electrical storage device in the form of a battery, which stores electrical energy for driving the vehicle's drive motor. To charge this storage device, the electric vehicle is connected to a charging station using a charging cable. The charging cable typically has a charging cable plug, at least on one side of the electric vehicle, which plugs into a charging cable connector, also called a charging cable socket.

[0003] Because electric vehicles (EVs) and charging stations (EVSEs) are designed differently, for example with regard to the charging currents that the charging stations can provide and use to charge the electric vehicles, communication between the electric vehicles and the charging station occurs over the conductor pairs of a charging cable.

[0004] In charging cables with a so-called TYP2 plug, for example, lines known as a control pilot (CP) and a protective conductor (PE) are used for this purpose.

[0005] It is known, for example, to use a square-wave voltage signal for pulse width modulation in order to signal the maximum charging current intensity that can be used to charge an electrical storage device of an electric vehicle.

[0006] In order to also exchange other data, especially more data, such as for automatic calculation of charging currents, power line communication is also carried out on the same wire pair using broadband high-frequency signals. For example, the high-frequency signals are modulated using orthogonal frequency division multiplexing (OFDM).

[0007] Here, information is transmitted via multiple frequency channels of a broadband high-frequency signal.

[0008] In order to enable power line communication to proceed undisturbed in the frequency range of, for example, 1.8 MHz to 30 MHz, the output stage and the cable used for transmission, ie the charging cable, need to be tuned to one another in terms of their impedance in the frequency range used.

[0009] Generally speaking, the terminal impedance of the output stage to be checked is , the following complex relationships apply:

[0010]

[0011] in, represents the line impedance, represents the load impedance, represents the wave propagation constant of the line, Indicates the line length.

[0012] When the line impedance and the terminal impedance of the output stage are tuned for the useful frequency range, the .

[0013] If there is no correct impedance matching in the output stage, reflections will occur there for individual frequencies or frequency ranges. These reflections can lead to resonances and cancellations in individual or multiple frequency channels. This disrupts the information transmission in these frequency channels. These disturbances can, for example, prevent the charging process from starting or cause it to be prematurely interrupted.

[0014] Therefore, broadband power line communication is typically performed on the charging cable wire pairs using OFDM modulation with a peak-to-peak (Vpp) frequency of 1.2 volts in the 1.8 MHz to 30 MHz range, using 1,150 channels spaced 24.124 kHz (kilohertz). A pulse-width modulated (PWM) square wave signal with a voltage range of +12 V to -12 V and a frequency of 1 kHz is superimposed on this high-frequency signal.

[0015] Methods known from the prior art for checking correct impedance matching in the relevant frequency range fail due to the simultaneous use of two different transmission methods.

[0016] US 2022 / 0163603 A1 provides for using an impedance network, for example integrated in the plug of a charging cable, which attenuates specific frequencies. This document provides for checking the correct connection to the charging cable by determining whether this specific frequency is correctly attenuated.

[0017] To reduce transmission losses, US 2016 / 0112135 A1 proposes a transmission device comprising a transmitter that generates a first electromagnetic wave for data transmission. A coupler couples the first electromagnetic wave to a single-wire transmission medium having an outer surface to form a second electromagnetic wave, which is guided so that it propagates along the outer surface of the single-wire transmission medium through at least one guided wave mode, including an asymmetric or non-fundamental mode with a lower frequency limit. The carrier frequency of the second electromagnetic wave is selected to be within a limited range of the lower frequency limit, thereby concentrating the majority of the electric field within a certain distance from the outer surface that is less than half the maximum cross-sectional dimension of the single-wire transmission medium and / or to reduce propagation losses.

[0018] US 2017 / 0018830 A1 describes a system that performs method steps for identifying signal degradation of guided electromagnetic waves bound to a transmission medium without using an electrical return path, wherein the guided electromagnetic waves have a non-optical frequency range, and the method steps include adjusting the orientation of at least a portion of the field of the guided electromagnetic waves so as to reduce the signal degradation. Summary of the Invention

[0019] The technical problem to be solved by the present invention is to provide an improved method, device and system with which output stages, in particular remote output stages connected or to be connected via a cable, can be checked with respect to correct impedance matching for signal transmission.

[0020] According to the invention, this object is achieved by a method having the features of claim 1, an inspection device having the features of claim 8, and a system having the features of claim 13. Advantageous embodiments of the invention are disclosed in the dependent claims.

[0021] The present invention is based on the idea of evaluating a broadband, high-frequency signal, such as that used in power line communication. This broadband, high-frequency signal is typically generated at the start of the power line communication and transmitted via the cable starting from the output stage to be tested. The transmitted signal is sampled to detect at least one temporal transient. Based on this at least one temporal transient, a spectral power density spectrum, also referred to in the prior art as power spectral density (PSD), is determined. This spectral power density spectrum is the spectral power density of the transmitted signal plotted against frequency, with the transmitted signal being transmitted over a frequency bandwidth. By definition, the frequency bandwidth can be selected to be infinitesimally small. However, in practice, a power density spectrum is typically obtained with values that are dependent on a preselected, finite bandwidth, the resolution bandwidth (RBW). Mathematically, the spectral power density can also be understood as the Fourier transform of the autocorrelation function of the signal transmitted in a time-dependent manner. Therefore, the spectral power density spectrum is also referred to as the autopower spectrum. By evaluating the individual frequency ranges of the spectral power density spectrum, ie the PSD spectrum, it is possible to determine whether interference occurs in these sections due to reflections that interfere with the communication.

[0022] Therefore, a method is provided in particular for checking an output stage, in particular of an electric vehicle or a charging station, for broadband high-frequency power line communication via a cable, comprising the following steps:

[0023] a) Connect the output stage to be checked and the test device to one of the cables in the cable,

[0024] b) determine the terminal impedance of the cable on or in the test device,

[0025] c) sampling, at an end of the one of the cables associated with the inspection device, a broadband high-frequency signal transmitted from the output stage to be inspected on the one of the cables according to the Nyquist-Shannon sampling theorem and acquiring at least one time transient, the broadband high-frequency signal being generated with a constant spectral power density within each frequency range of the broadband high-frequency signal used for high-frequency communication, both sampling and acquiring being performed during transmission of the broadband high-frequency signal,

[0026] d) determining a spectral power density spectrum associated with the one of the cables and the determined terminal impedance based on at least one time transient acquired for the determined terminal impedance when the one of the cables is in use,

[0027] e) evaluating the spectral power density spectrum of one or more frequency ranges used for communications,

[0028] f) wherein, in step b), the terminal impedance is determined to a value that matches the impedance of the cable, and in step e) during the evaluation, it is checked whether deviations occur in one or more ranges of the spectral power density spectrum relative to a spectral power density spectrum that is expected or acquired when communicating with an output stage that is correctly matched in terms of impedance, and

[0029] g) Outputting a result of the evaluation, the result of the evaluation comprising at least one indication as to whether the impedance matching of the output stage to be checked is correct or incorrect.

[0030] If, within the frequency range used for information transmission in power line communication, the spectral power density is found to be excessively high and / or low compared to the expected spectral power density (which may be related to the bandwidth resolution), a mismatch can be concluded. If the spectral power density decreases too sharply by more than 40% of the total transmission spectrum, it can be assumed that communication is no longer possible without interference. In the excessively high range, electromagnetic compatibility regulations may be violated.

[0031] Correspondingly, a testing device is provided for testing output stages, in particular of electric vehicles or charging stations, which are used for broadband high-frequency power line communication via a cable, comprising:

[0032] A cable connector, used for connecting one end of one of the cables, the other end of the cable being connected to the output stage to be inspected;

[0033] a cable termination device connected to the cable connector, for determining a terminal impedance of a line connected to the cable connector on or in the device for performing an inspection;

[0034] a sampling device connected to the cable connector, for sampling the broadband high-frequency signal transmitted on the one of the cables according to the Nyquist-Shannon sampling theorem and acquiring at least one time transient, both sampling and acquiring being performed during transmission of the broadband high-frequency signal;

[0035] a calculation unit for determining a spectral power density spectrum associated with the one of the cables based on at least one time transient acquired while using the one of the cables;

[0036] evaluation means for evaluating one or more frequency ranges of the spectral power density spectrum;

[0037] wherein during the evaluation a check is performed to determine whether deviations occur in one or more frequency ranges of the spectral power density spectrum relative to a spectral power density spectrum that is expected or acquired during communication with an output stage that is correctly matched in terms of impedance; and

[0038] An output device is provided for outputting a result of the evaluation, the evaluation outputting at least one indication as to whether the impedance matching of the output stage to be checked is correct or incorrect.

[0039] The system includes an embodiment of the described inspection device and a set of cables of different lengths.

[0040] The result of the check is accordingly a statement as to whether the output stage to be checked provides a guarantee that, when used with a cable that generally corresponds to the prior art, the output stage to be checked enables undisturbed communication due to correct impedance matching, or whether disturbances can be expected during operation due to incorrect impedance matching.

[0041] The evaluation can be performed without specific knowledge of the spectral power density spectrum of power line communication with an impedance-correctly matched output stage. No fluctuations above a threshold value occur with a correctly tuned output stage. Therefore, in one embodiment, the checking in method step e) for deviations from the spectral power density spectrum expected or acquired during communication with the impedance-correctly matched output stage in one or more ranges of the spectral power density spectrum includes checking whether fluctuations of the spectral power density above a threshold value occur in the determined spectral power density spectrum.

[0042] Since the occurrence of reflections and resonances depends on the length of the cable used, in a preferred embodiment, it is provided that the transmission of the high-frequency signal, its sampling and the determination of the spectral power density spectrum associated with the cable are also carried out for another cable of the cables, which has a different length than the previously selected one of the cables. If the output stage is correctly matched in terms of impedance, there are no differences in the spectral power density spectrum that are related to the correspondingly associated cable lengths. This means that the spectral power density spectra for the different cable lengths used are identical within the range of statistical variation. Therefore, it is possible to evaluate the following check, namely to check whether the spectral power density spectra determined for cables of different lengths show deviations at least in individual frequency ranges. Ideally, the difference over the entire frequency range for broadband power line communication is zero within the tolerance limits, taking into account the variations in attenuation caused by the known attenuation of the cables.

[0043] Therefore, in one embodiment, correct impedance matching can be inferred from the fact that the difference in the determined spectral power density spectra for cables of different lengths is zero, or that the spectral power density spectra do not differ at least within a tolerance limit.

[0044] The evaluation can be simplified by evaluating the average value of the spectral power density spectrum.

[0045] Therefore, one embodiment provides that steps a) to d) are performed additionally using at least one further cable of the cables, wherein the at least one further cable of the cables has a different length than the at least one cable of the cables and the terminating impedance is determined in step b) in the same way as for the at least one cable of the cables when performing steps a) to d), and the evaluation of step e) comprises: for the determined spectral power density spectrum, the average spectral power density is calculated accordingly in the frequency range used for power line communication, and the average values are compared in pairs for the spectral power density spectra acquired for different cable lengths but the same terminating impedance, and if a deviation above a mean value threshold occurs here, the output stage to be checked is classified as incorrectly tuned.

[0046] One embodiment provides that steps a) to d) are performed additionally using at least one further cable of the cables, wherein the at least one further cable of the cables has a different length than the at least one cable of the cables and the terminating impedance is determined in step b) in the same way as for the at least one cable of the cables when performing steps a) to d), and the evaluation of step e) comprises: for the determined spectral power density spectrum, an average spectral power density is calculated accordingly in the frequency range used for power line communication, and for spectral power density spectra acquired for different cable lengths but the same terminating impedance, the average values are compared in pairs, and if a deviation above a mean value threshold occurs in this case, the output stage to be checked is classified as incorrectly tuned.

[0047] By extending the method, it is even possible to estimate the impedance of an incorrectly tuned output stage to be tested. Advantageously, sampling and evaluation are performed not only for different cable lengths, provided the lines terminate identically on or in the testing device, but also for different line terminations. This means that not only the cable length but also the terminating impedance of the line is varied. For at least two different impedance terminations of the line on or in the testing device, the transmissions from the output stage to be tested over lines of different lengths are sampled and evaluated. The sampling and evaluation is performed accordingly for transmissions in which only a broadband high-frequency signal, whose spectral power is uniformly distributed within the frequency range used for power line communication, is transmitted from the output stage to be tested. This means that the difference in mean values attributable to variations in cable length is essentially independent of the selected line termination on or in the testing device. This difference, determined from the mean values for different cable lengths but identical line terminations, is a measure of the incorrectly tuned impedance of the output stage to be tested, at least when it is equal to the difference in impedance determined for another line termination.

[0048] If a difference above a predetermined tolerance threshold occurs from two mean values of the spectral power density for different cable lengths but identical line termination, this indicates that the impedance Z of the output stage for the corresponding frequency is given in good approximation by E :

[0049] Z E = Difference x Z A

[0050] The difference can be converted from the physical unit dBm / Hz to a factor, and Z A is the impedance of the cable used.

[0051] Therefore, according to a preferred embodiment of the method, method steps a) to d) are performed for a plurality of cables having different lengths, wherein steps a) to d) are performed at least twice for each of the plurality of cables, wherein different terminal impedances are determined in method step b) and, in the evaluation in method step e), the differences in the average spectral power densities of the spectral power density spectra determined for different cable lengths but identical terminal impedances are compared for at least two of the differently determined terminal impedances, and when these differences in the average values are equal within a tolerance range but different from zero, the terminal impedance of the output stage to be checked is estimated based on this difference by converting the difference into a factor and multiplying it by the impedance of the cable.

[0052] In a preferred embodiment, the terminating impedance is determined to a value that matches the impedance of the cable by connecting a line connected to a corresponding one of the cables via an ohmic terminating resistor whose value corresponds to the impedance of the line of the cable in or on the testing device, or by connecting the corresponding one of the cables via a line to a further output stage circuit of the high-frequency transmitting and receiving unit, which is correctly tuned in terms of impedance over the entire frequency range used for power line communication and attenuates its own transmission during reception of the high-power signal of the output stage to be tested.

[0053] The cable used preferably comprises a two-wire line for power line communication. A preferred embodiment of the system provides a cable having a two-wire line for power line communication, wherein the cable has an impedance of 100 ohms. Accordingly, a 100 ohm resistor is preferably used as a terminating resistor to match the impedance of the cable.

[0054] One embodiment of the testing device provides that the cable terminal device comprises an ohmic terminating resistor corresponding to the impedance of the cable.

[0055] If a different terminating impedance is required, it is preferred to use a terminating impedance that matches the impedance of the cable. The different impedance used for this is preferably selected to have a large impedance difference from the impedance of the cable. Preferably, an infinite impedance or a nearly infinite impedance is selected. This impedance can be set and determined by interrupting, i.e., disconnecting, the line connected to the corresponding cable in the test device in or on the test device. For example, the connection can be established using an open line.

[0056] Therefore, a preferred embodiment provides that the different impedances determined in method step b) include an infinite impedance, which is determined by disconnecting a line connected to a corresponding one of the cables in or on the testing device.

[0057] In one embodiment of the inspection device, the cable termination device may include a switching device for terminating the line in or on the device for performing the inspection by a terminal resistor corresponding to the impedance of the cable, or switching the line to an open circuit state to simulate infinite impedance, or connecting the line to the output stage of a high-frequency transmitting and receiving unit of a power line communication device that is correctly matched in terms of impedance to establish optimal matching of the cable terminal.

[0058] Implementations may include only two of the three possibilities envisioned here.

[0059] For example, it is possible to switch between an ohmic terminating resistor and an open line.

[0060] The reliability of the determined result can be further increased in that, in one embodiment, it is provided that the iterative method steps are carried out for more than two cables, all of which have different lengths.

[0061] A further improvement in reliability can also be achieved if the iterative method steps are carried out for at least three terminating impedances. Preferably, an ohmic terminating resistor matched to the impedance of the cable, an open line for infinite resistance, and a connection to a correctly tuned output stage of the power line communication device are used as the three different terminating impedances.

[0062] An optimal test can be to sample and evaluate the termination of a cable that is formed by an impedance-correctly matched output stage of the power line communication device by connecting it to a line that is connected to the cable in the test device and to which the sampling device is coupled.

[0063] The evaluation device is adapted accordingly in order to carry out these improved evaluation methods.

[0064] It should be emphasized that a broadband high-frequency signal of the output stage to be tested, which is required for the test, is usually generated within the scope of the power line communication protocol. This broadband high-frequency signal is generated and emitted with a constant spectral power density. Many charging stations emit this broadband high-frequency signal, which is usually time-limited, at regular intervals to facilitate the activation of the power line communication.

[0065] In another embodiment, it can be configured that a signal is transmitted to the output stage to be checked for broadband high-frequency power line communication (the signal can also be referred to as a start signal) to trigger the emission of a broadband high-frequency signal, which is generated with a constant spectral power density within each frequency range of the broadband high-frequency signal used for high-frequency communication.

[0066] In a preferred embodiment of the device, the testing device is a component of the power line communication device. The start signal can then be generated simply by the power line communication device. To prevent interference with the measurement of the response of the output stage to be tested, the output stage that generates the start signal is then attenuated, i.e., this output stage is prevented from generating a high-frequency signal that is fed to the line and, via it, to a corresponding cable in the cables, via which a connection to the output stage to be tested is established.

[0067] The power line communication device and the inspection device can be independent units or an integrated one-piece unit. When the inspection device is a component of the power line communication device, the inspection device can also be implemented in an electric vehicle or a charging station.

[0068] The signal required for sampling and having a uniform spectral power density can be generated by transmitting suitable information which distributes the spectral power density as uniformly as possible over the entire broadband high-frequency range.

[0069] Particularly preferably, orthogonal frequency division multiplexing is used as the modulation method. In orthogonal frequency division multiplexing, information is transmitted on equally spaced frequency channels that are arranged uniformly and at equal intervals within the frequency range used for communication.

[0070] In another embodiment, a radio-frequency signal having a uniformly distributed spectral power density is generated according to method step d) within the resolution bandwidth used to calculate the spectral power density spectrum. This means that in frequency segments corresponding to the width of the resolution bandwidth used to generate the spectral power density spectrum, the same transmission power is emitted in the transmission signal.

[0071] This is achieved, for example, in an orthogonal frequency division multiplexing modulated signal if the same information corresponding to the maximum radiated emission power in the corresponding frequency channel is transmitted in each of the equidistant frequency channels used here.

[0072] The output device can be, for example, a display or an acoustic device that outputs an acoustic signal that signals a correct or incorrect match. If a deviation in the impedance matching is determined based on the difference in the determined spectral power density, the output device preferably includes a digital or analog display. In other embodiments, the output device can alternatively and / or additionally be configured as an interface, via which a digital and / or optical signal is output, in which the evaluation result is encoded. In particular, this can be a network interface, for example, for wireless communication via WLAN or Bluetooth.

[0073] The device for testing forms a system together with a cable, preferably a plurality of cables of different lengths. This results in a system for testing the impedance matching of output stages, in particular of electric vehicles or charging stations, which are used for broadband high-frequency power line communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will be described in more detail below with reference to the accompanying drawings.

[0075] Figure 1 A schematic diagram showing an inspection device for inspecting an output stage for impedance matching of the output stage is shown;

[0076] Figure 2 A flow chart of a method for checking an output stage in terms of impedance matching for power line communication is shown;

[0077] Figure 3 A schematic diagram showing the power density spectrum of a correctly matched output stage;

[0078] Figure 4 shows the spectral power density spectrum of a correctly tuned output stage using a pass length according to Figure 3 In an embodiment, the transmission is performed by twice the cables;

[0079] Figure 5 Shown with Figure 3 a spectral power density spectrum corresponding to the spectral power density spectrum of , which was recorded on or in the test device with a correctly tuned output stage but with an “open-circuited” terminating resistor;

[0080] Figure 6 Shown with Figure 4 a spectral power density spectrum corresponding to the spectral power density spectrum of , which was recorded on or in the test device with a correctly tuned output stage but with an “open-circuited” terminating resistor;

[0081] Figure 7 Shown with Figure 3 A similar spectral power density spectrum of where the output stage to be inspected is not correctly matched in terms of impedance, but the cable is correctly terminated on the inspection device;

[0082] Figure 8 Shown with Figure 4 A similar spectral power density spectrum is shown for a case where the output stage to be checked is not correctly matched in terms of impedance, but the cable is correctly terminated on the test device and the length of the cable is Figure 3 、 Figure 5 and Figure 7 twice as much;

[0083] Figure 9 Shown with Figure 5 a spectral power density spectrum similar to that of where the output stage to be inspected is not correctly matched in impedance and a cable is open circuit on or in the inspection device; and

[0084] Figure 10 Shown with Figure 6 A similar spectral power density spectrum is shown in which the output stage to be checked is not correctly matched in terms of impedance and the cable is open-circuited on or in the device under test, where the length of the cable is Figure 3 、 Figure 5 、 Figure 7 and Figure 9 Twice as much. DETAILED DESCRIPTION

[0085] exist Figure 1 Schematically depicts a testing device 100 for testing the impedance matching of an output stage 545 for power line communication. This testing device can be, for example, a separate testing device or a component of the electric vehicle 10 or another device. In the example shown, device 100 is a component of the electric vehicle 10. The output stage 545 to be tested of the power line communication device 530 is a component of a high-frequency transmitting and receiving unit 540. This high-frequency transmitting and receiving unit 540 is configured for power line communication using broadband high-frequency signals. For example, power line communication is performed in the frequency range of 1.8 MHz (megahertz) to 30 MHz using the orthogonal frequency division multiplexing (OFDM) modulation method. Frequency bands within this range can be left unused.

[0086] The power line communication device 530 is in turn a component of the communication device 520 , via which, in addition to the power line communication, low-frequency communication using pulse width modulation is also performed.

[0087] Output stage 545 to be checked can also be a component of another communication device of the electric vehicle or of another device belonging to the charging infrastructure of the electric vehicle, for example.

[0088] The inspection device 100 and the output stage 545 are interconnected via a charging cable 310 from among a plurality of charging cables 300 having different lengths. The cables 300 preferably include a two-wire line 305 for power line communication and low-frequency communication. The cable may include additional lines for charging. For example, all charging cables 300 are designed for the same impedance, for example, 100Ω, and have an attenuation of approximately -0.33 dB / m.

[0089] The inspection device 100 includes a cable connector 110 to which the charging cable 310 is connected.

[0090] To check whether output stage 545 is correctly tuned with respect to impedance, testing device 100 includes a sampling device 150. For this purpose, sampling device 150 is coupled to line 120, which is connected to cable connector 110. Sampling device 150 can sample the broadband high-frequency signal transmitted via charging cable 310, while the broadband high-frequency signal of high-frequency transmitting and receiving unit 40 is being transmitted via charging cable 310. Sampling is performed using a sampling rate that is at least twice the highest frequency occurring in the broadband high-frequency signal used for information transmission. During sampling, temporal transients are captured.

[0091] Whether reflections occur on cable 310, for example, two-wire line 305 of cable 310, depends on the tuning of the output stage 545 to be tested and the termination of cable 310 or the line 120 connected thereto in the testing device 100. For this purpose, the testing device includes a cable termination device 130 for determining a terminating impedance in or on the testing device. In the illustrated embodiment, cable termination device 130 includes an ohmic terminating resistor 145. This ohmic terminating resistor 145 is matched to the line impedance of cable 300. If cable 300 includes a two-wire line 305 with a line impedance of 100 ohms for communication, the 100 ohmic terminating resistor 145 is matched to the line impedance.

[0092] If the cable 310 is terminated during the measurement in the testing device 100 with an impedance matched to its line impedance by an ohmic terminating resistor 145 , no reflections are formed on the cable 310 if the impedance is correctly matched to the output stage 545 to be tested.

[0093] The temporal transient data obtained through sampling is used in calculation unit 170 to calculate the spectral power density spectrum. This calculation is typically performed over a predetermined frequency bandwidth, known as the resolution bandwidth (RWB). If power line communication uses frequencies in the range of 1.8 MHz to 30 MHz, a resolution bandwidth of 10 kHz is selected for evaluation, for example.

[0094] The power line communication of the electric vehicle charging infrastructure uses an Orthogonal Frequency Division Multiplexing (OFDM) modulation method, employing 1,150 carriers spaced 24.124 kHz apart. These carriers are distributed within the frequency range of 1.8 MHz to 30 MHz. The voltage capacitively coupled to the charging cable 310 is nominally 1.2 volts peak-to-peak (Vpp). Additionally, low-frequency communication is carried out via the charging cable using a pulse-width modulated signal with a 1 kHz square wave voltage of + / - 12 V. For simplicity, the components involved and required are not shown here.

[0095] When there is no interference due to incorrect impedance matching of the output stage 545, the spectral power density spectrum 3100-1 has an almost uniform constant value within the frequency range 3040 for high-frequency communication. Figure 3 Such a power density spectrum is schematically illustrated in . Spectral power density 3010 is plotted in dBm / Hz against frequency 3020. Within the frequency range 3050 used for power line communication, the spectral power density (PSD) is constant. Identifiable gaps 3060 exist within this frequency range, as these are reserved for other communications not taking place on the cable. For the aforementioned type of power line communication (in which 250 nW of high-frequency power is used for each carrier), determining the power density spectrum, for example, with a resolution bandwidth (RBW) of 10 kilohertz (kHz), yields a value of approximately -35 dBm RBW 10 kHz.

[0096] The test device 100 includes an evaluation device 200, in which the spectral power density spectrum thus determined is evaluated. If the spectral power density spectrum corresponds to the expected spectral power density spectrum, the output stage 545 to be tested is considered to be correctly matched with respect to impedance. To this end, it can be compared, for example, with a spectral power density spectrum stored in the memory 210 of the evaluation device 200. Alternatively or additionally, excesses and / or reductions / sags in the spectral power density spectrum can be determined.

[0097] If excessive peaks or dips occur in the spectrum of the spectral power density, this is a sign that the output stage 545 being tested is not correctly tuned with respect to impedance. The result of the evaluation is output via the output device 280 .

[0098] Output device 280 can be a digital or analog display. Alternatively, an acoustic output is also possible. In addition to graphical or visual output, an acoustic output can also be provided. The output device can also be an interface for transmitting the evaluation results to other devices. All known interfaces are contemplated, including wired and wireless interfaces.

[0099] To eliminate the need for evaluations that are dependent on the specific cable length of charging cable 310, in a preferred embodiment, cable 310 having one length is replaced by another cable 310 having a different length than the first. RF transmitting and receiving unit 540 again transmits the RF signal to output stage 545 to be tested, during which sampling is performed by sampling device 150 and further time transients are detected. A further spectral power density spectrum is determined using computing unit 170.

[0100] Figure 4 Shown is a spectral power density spectrum 3100 - 2 , which is likewise transmitted by a correctly tuned output stage 545 via a cable 320 , which is twice as long as the cable 300 and which is likewise terminated in the testing device by an ohmic terminating resistor.

[0101] The spectral power density spectrum 3100 - 2 also does not show any obvious excessive increase or sudden drop in the spectral power density 3010 .

[0102] In contrast, Figure 5 The spectral power density spectrum 3100-3 and Figure 6 The spectral power density spectrum 3100 - 4 shows significant fluctuations 3070 of the spectral power density 3010 within the frequency range 3050 used for communication. Figure 5 The spectral power density spectrum 3100-3 with Figure 3 The spectral power density spectrum corresponds to 3100-1. Figure 6 The spectral power density spectrum 3100-4 with Figure 4 All of these spectral power density spectra 3100-1 to 3100-4 are generated using a correctly tuned output stage 545.

[0103] Spectral power density spectra 3100-1 and 3100-2 are respectively collected using the following cables 310, which are terminated with terminal resistors that correctly match the impedance of the corresponding cables 310, but their lengths are different. Unlike spectral power density spectra 3100-1 and 3100-2, spectral power density spectra 3100-3 and 3100-4 are recorded with the ends of the cables 310 "open circuit".

[0104] To this end, the cable termination device 130 includes a switching device 140. The switching device 140 can selectively connect the line to an ohmic termination resistor 145 or an open-circuited cable end 146. Alternatively, the switching device 140 can be switched to an open state to disconnect the line 120.

[0105] exist Figure 5 and Figure 6 In the figure, we can see the overshoot 3080 in the spectral power density due to reflections and the overall strong fluctuations.

[0106] However, the spectral power density spectra 3100-1, 3100-2 and 3100-3, 3100-4 collected using the same cable joint each have the same average spectral power density in pairs. For example, the spectral power density spectra 3100-1 and 3100-2 have an average value of -52 dBm, while the spectral power density spectra 3100-3 and 3100-4 have an average value of -43 dBm.

[0107] Figures 7 to 10 Comparable spectral power density spectra 3100 - 5 to 3100 - 8 are shown, which are produced at the output stage 545 to be checked which is not correctly matched in terms of impedance.

[0108] It can be seen that significant fluctuations 3070 in spectral power density 3010 occur in spectral power density spectra 3100-5 and 3100-6 acquired in inspection device 100 using ohmic terminating resistor 145. Excessive peaks 3080 due to reflections can also be seen. For example, the average value of spectral power density spectrum 3100-5, which is -43 dBm, differs by 3 dBm from the average value of spectral power density spectrum 3100-6, which is -46 dBm, acquired with twice the cable length.

[0109] Two similar spectral power density spectra 3100 - 7 and 3100 - 8 , each acquired in the inspection device 100 with an open cable 310 , ie, a disconnected line 120 , also show strong fluctuations 3070 as expected, but also the same 3 dBm difference between the mean values of −37 dBm and −40 dBm.

[0110] From this difference, it is possible to infer a deviation in the impedance of the output stage 545 to be tested. The difference, which is given in dBm / Hz as a factor, is multiplied by the impedance of the charging cable used to obtain the impedance of the output stage 545. The conversion of the decibel value to the factor F is carried out in the manner customary, for example, in the conversion of energy or power variables: , where D is the difference in dBm / Hz, and 0 dBm / Hz is associated with a factor of 1.

[0111] A deviation of 3 dBm corresponds approximately to a factor of 2. Therefore, it can be estimated that: Z E = 2·Z A , where Z A = 100 Ohm. Therefore, the incorrectly tuned output stage to be checked has an estimated impedance of approximately 200 Ohm, or Z E = 2·100Ohm = 200 Ohm.

[0112] Additionally, line 120 can also be connected to another output stage 45 of another power line communication device 40, which is correctly tuned in terms of impedance, via switching device 140 of cable termination device 130. This termination of cable 310 thus represents a third termination option. A spectral power density spectrum can also be acquired correspondingly with this termination. However, this requires operating this other output stage 45 so that it does not emit any high-frequency signals during the sampling of the high-frequency signals of output stage 545 to be tested, and the signals are correspondingly attenuated.

[0113] The other power line communication device 30 is, for example, a component of the other communication device 20 arranged in the electric vehicle 10 .

[0114] Terminating the line 120 and the cable 310 by another correctly tuned output stage 45 can facilitate the start of the emission of the high-frequency signal of the output stage 454 to be tested. Emission is usually performed at the start of transmission according to the transmission protocol. A broadband high-frequency signal is often emitted in an iterative manner, the spectral power density of which is constant over the entire frequency range used, i.e., often over a plurality of spaced-apart frequency ranges.

[0115] exist Figure 2, a method 1000 for checking an output stage for impedance matching is again schematically shown. First, a cable, preferably a charging cable, is selected 1010. A cable of a certain length is selected. The output stage to be checked is then connected 1020 to a device for checking the output stage. The terminating impedance of the cable is determined 1030 in or on the testing device. It is preferably initially set to a value corresponding to the line resistance of the cable. During transmission via the charging cable, a broadband high-frequency signal is sampled 1040. This broadband high-frequency signal is generated by a high-frequency transmitting and receiving unit of a power line communication device and coupled to the charging cable by the output stage to be checked. This is done according to the Nyquist-Shannon sampling theorem. Temporal transients are acquired 1050.

[0116] A spectral power density spectrum (PSD spectrum) is determined 1060 from the time transients acquired for the one cable having the one length.

[0117] In the simplest embodiment, an evaluation is performed 1100. Here, the spectral power density spectrum determined based on the time transient is checked 1120 for deviations from the expected spectral power density spectrum in at least one frequency range, preferably in multiple frequency ranges. If, for example, an overshoot or a dip is detected in a specific frequency range, the output stage being checked is classified as incorrectly tuned. Conversely, if the spectral power density spectrum corresponds to the expected value in one or more of the checked frequency ranges, the output stage is classified as correctly tuned with respect to the impedance. The result is output 1200.

[0118] In a refined embodiment, after acquiring a temporal transient and determining a spectral power density spectrum for the one charging cable of the one length, a check is performed 1070 to determine whether another charging cable of a different length exists. If so, the determined spectral power density spectrum is stored 1080 for later evaluation. Subsequently, when reselecting 1010 one of the cables, another charging cable of the different length is selected. The following method steps are then repeated for the other charging cable of the different length: connecting 1020 the output stage to be tested to a testing device using the other charging cable, determining 1030 the cable end, sampling 1040 the high-frequency signal, and acquiring 1050 a temporal transient. The cable end is determined in the same manner as for the first cable. The associated spectral power density spectrum is then converted 1060 for the second, now acquired temporal transient. During the evaluation, this spectral power density spectrum is also checked for peaks or dips. Additionally or alternatively, an average value is determined 1130 for each of the two determined spectral power density spectra. They are compared 1140. If they are identical, it can be assumed that the output stage to be checked is correctly tuned.

[0119] The evaluation can be further improved by carrying out method steps 1010 to 1080 in the test device for a plurality of cable lengths, in particular two cable lengths, and also for a plurality of different line terminations. In one embodiment, this is checked in method step 1065. Here, it is checked whether, for the cable measured so far, at least two different, preferably three different, cable terminations have been used in terms of impedance for determining the spectral power density spectrum. If this is not the case, the following method steps are iterated, namely storing 1080 the last determined power density spectrum, determining 1030 the termination impedance, sampling 1040 the high-frequency signal of the output stage to be tested, acquiring 1050 the time transients, and determining 1060 the spectral power density spectrum. The evaluation steps 11xx can also be carried out after acquiring one or more spectral power density spectra or at the end of the method.

[0120] In one variant of the method described, if multiple cable lengths and cable ends are used, for each line the spectrum is first acquired and determined for the different cable ends and then the cable is changed. However, this can also be done in a different order.

[0121] If a difference is detected in the mean value evaluation for different cable lengths but the same cable end, the impedance of the output stage to be tested can be estimated 1150. This evaluation is preferably subjected to a plausibility check, wherein a check is performed to determine whether the mean value differences of the respective cable pairs for the different cable ends are equal within a predefined tolerance range for two different cable ends when different cables are used. If this is the case, the estimate of the impedance of the output stage to be tested can be classified as reliable.

[0122] In some embodiments, the estimated impedance is determined or output only when the mean value difference of the terminal impedances of at least one cable pair with cables of different lengths for two different cable terminations, i.e., in or at the testing device, is equal to one another within a predetermined tolerance. The terminal impedance established by the open-circuited line 146 is preferably selected to be infinite. Another impedance is preferably selected to match the cable impedance and is implemented by terminating with an ohmic terminating resistor. Alternatively, a tuned output stage of the power line communication device can be used.

[0123] The calculation unit and the evaluation device are preferably implemented by means of a program-controlled computing unit. Alternatively, electronic circuits can also be used which, in particular, calculate the spectral power density spectrum.

[0124] Those skilled in the art will appreciate that only exemplary embodiments are described herein, and that features of different embodiments may be used in any combination with one another to form further embodiments.

[0125] Reference Signs List

[0126] 10 Electric vehicles

[0127] 20 communication devices

[0128] 30 Power line communication device

[0129] 40 high frequency transmitting and receiving units

[0130] 45 output stage

[0131] 100 Inspection device for inspecting the output stage

[0132] 110 cable terminal

[0133] Line 120

[0134] 130 cable terminal device

[0135] 140 switching device

[0136] 145 ohm terminal resistor

[0137] 146 open circuit

[0138] 150 sampling device

[0139] 170 computing units

[0140] 200 evaluation devices

[0141] 210 memory

[0142] 220 comparison device

[0143] 280 output device

[0144] 300 cable

[0145] 305 two-wire cable

[0146] 310 one length of a cable

[0147] 320 Another cable of another length

[0148] 500 charging piles

[0149] 520 communication device

[0150] 530 Power Line Communication Device

[0151] 540 high frequency transmitting and receiving unit

[0152] 545 output stage

[0153] 1000 Method for checking the output stage

[0154] 1010 Select one of the cables or another of the cables with a different length

[0155] 1020 Connect the output stage to the device for checking

[0156] 1030 Determine the terminal impedance

[0157] 1040 samples the transmitted high-frequency signal

[0158] 1050 acquisition time transient

[0159] 1060 Determine spectral power density spectrum

[0160] 1065 Is the currently connected cable used with different impedance terminations?

[0161] 1070 Check if there is a cable with a different length

[0162] 1080 stores the determined spectral power density spectrum

[0163] 1100 evaluates one or more spectral power density spectra

[0164] 1120 Check for deviations from expected / correct spectral power density spectrum

[0165] 1130 Determine the average value of the spectral power density spectrum

[0166] 1140 Compare averages / differences

[0167] 1150 Convert the estimated impedance of the output stage to be checked

[0168] 1200 Output results / evaluation results

[0169] 3010 spectral power density

[0170] 3020 frequency

[0171] 3040 frequency range

[0172] Frequency range used by 3050

[0173] 3060 gap

[0174] 3070 fluctuations

[0175] 3100, 3100-x spectral power density spectrum, -x count index

Claims

1. A method for checking an output stage (545), in particular of an electric vehicle or a charging station, for broadband high-frequency power line communication via a cable (300, 310, 320), comprising the following steps: a) connecting the output stage (545) to be checked and the checking device to one of the cables (310), b) determine the terminal impedance of the cable on or in the test device, c) sampling a broadband high-frequency signal transmitted from an output stage to be inspected on said one of the cables (310) at an end of said one of the cables (310) associated with the inspection device (100) and acquiring at least one time transient according to the Nyquist-Shannon sampling theorem, said broadband high-frequency signal being generated with a constant spectral power density within each frequency range (3050) of said broadband high-frequency signal used for high-frequency communication, said sampling and acquiring both being performed during the transmission of said broadband high-frequency signal, d) determining a spectral power density spectrum (3100) associated with the one of the cables (310) and the determined terminal impedance based on at least one time transient acquired for the determined terminal impedance when using the one of the cables (310), e) evaluating the spectral power density spectrum of one or more frequency ranges used for communication (3050), f) Among them, In step b), the terminal impedance is determined to a value that matches the impedance of the cable (300), and in step e), during the evaluation, it is checked whether deviations occur within one or more ranges of the spectral power density spectrum relative to a spectral power density spectrum that is expected or acquired when communicating with an output stage that is correctly matched in terms of impedance, and g) outputting a result of the evaluation, said result of the evaluation comprising at least one indication as to whether the impedance matching of the output stage (545) to be checked is correct or incorrect.

2. The method according to claim 1, characterized in that In method step e), checking whether deviations occur within one or more ranges (3050) of the spectral power density spectrum (3100-x) relative to a spectral power density spectrum that is expected or acquired when communicating with an output stage that is correctly matched in terms of impedance includes: checking whether fluctuations in the spectral power density above a threshold value occur in the spectral power density spectrum determined for a terminal impedance that is matched to the impedance of the cable.

3. The method according to claim 1 or 2, characterized in that Steps a) to d) are additionally performed using at least one further cable (320) of the cables, wherein the at least one further cable (320) of the cables has a different length than the at least one cable (310) of the cables, and the terminal impedance is determined in step b) in the same manner as for the at least one cable of the cables when performing steps a) to d), and the evaluation of step e) comprises: for the determined spectral power density spectrum, correspondingly calculating the average spectral power density within the frequency range (3050) used for power line communication, and comparing the average values in pairs for spectral power density spectra (3100-x) acquired for different cable lengths but the same terminal impedance, and classifying the output stage to be checked as incorrectly tuned if a deviation above a mean value threshold occurs in this case.

4. The method according to claim 3, characterized in that Method steps a) to d) are performed for a plurality of cables having different lengths, wherein steps a) to d) are performed at least twice for each of the plurality of cables (300), wherein different terminal impedances are determined in method step b) and, in the evaluation in method step e), for at least two of the differently determined terminal impedances, the differences in the average spectral power densities of the spectral power density spectra determined for different cable lengths but identical terminal impedances are compared and, when these differences in the average values are equal within a tolerance range but different from zero, the terminal impedance of the output stage to be checked is estimated based on the differences by converting the differences into a factor and multiplying them by the impedance of the cable.

5. The method according to any one of the preceding claims, characterized in that The terminating impedance is determined to a value that matches the impedance of the cable by connecting a line connected to the corresponding one of the cables via an ohmic terminating resistor whose impedance corresponds to the line impedance of the cable in or on the testing device, or by connecting the corresponding one of the cables to an output stage circuit of a high-frequency transmitting and receiving unit (40) in or on the testing device, which is correctly tuned in terms of impedance over the entire frequency range for power line communication and attenuates its own transmission during reception of the high-power signal of the output stage (545) to be tested.

6. The method according to any one of the preceding claims, characterized in that The different impedances determined in method step b) include an infinite impedance determined by disconnecting a line (120) connected to a corresponding one of the cables (300) in or on the testing device. The method according to any of the preceding claims, characterized in that a cable (300) with a two-wire line (305) is provided for power line communication, and the impedance of the cable (300) is respectively 100 Ohm.

7. The method according to any one of the preceding claims, characterized in that For broadband high-frequency power line communication, a signal is transmitted to the output stage (545) to be checked to trigger the emission of a broadband high-frequency signal, which is generated with a constant spectral power density within each frequency range of the broadband high-frequency signal used for high-frequency communication.

8. A testing device (100) for testing an output stage (545), in particular of an electric vehicle or a charging station (500), the output stage being used for broadband high-frequency power line communication via a cable (300, 310, 320), the testing device comprising: a cable connector (110) for connecting one end of one of the cables (310), the other end of the one cable (310) being connected to an output stage (545) to be inspected; a cable terminal device (120) connected to the cable connector (110), for determining a terminal resistance of a line (120) connected to the cable connector (110) on or in the inspection device; a sampling device (150) connected to the cable connector (110), for sampling a broadband high-frequency signal transmitted on the one of the cables (310) according to the Nyquist-Shannon sampling theorem and acquiring at least one time transient, both sampling and acquiring being performed during the transmission of the broadband high-frequency signal; a calculation unit (170) for determining a spectral power density spectrum associated with said one of the cables (310) based on at least one time transient acquired while using said one of the cables (310); An evaluation device (200) for evaluating one or more frequency ranges (3050) of the spectral power density spectrum (3100-x); wherein during the evaluation, it is checked whether deviations occur in one or more frequency ranges (3050) of the spectral power density spectrum (3100-x) relative to a spectral power density spectrum that is expected or acquired when communicating with an output stage that is correctly matched in terms of impedance; and An output device (280) is used to output a result of the evaluation, wherein the evaluation outputs at least one indication of whether the impedance matching of the output stage (545) to be checked is correct or incorrect.

9. The inspection device (100) according to claim 8, characterized in that The cable terminal device (130) includes an ohmic terminal resistor (145) corresponding to the impedance of the cable.

10. The inspection device (100) according to claim 9, characterized in that The cable termination device comprises a switching device for terminating the line in or on the device for performing an inspection by an ohmic terminal resistor corresponding to the impedance of the cable (300), or switching the line to an open circuit state to simulate infinite impedance, or connecting the line to the output stage of a high-frequency transmitting and receiving unit (40) of a power line communication device (30) that is correctly matched in terms of impedance, so as to establish an optimal match of the cable terminal.

11. The inspection device (100) according to any one of claims 8 to 10, characterized in that The inspection device is a component of the power line communication device (30).

12. The inspection device (100) according to any one of claims 8 to 11, characterized in that The testing device is designed to carry out the method according to claims 1 to 7 .

13. A system (500) for checking an output stage (545), in particular of an electric vehicle or a charging station, with respect to its impedance matching, the output stage being used for broadband high-frequency power line communication, the system comprising: An inspection device (100) according to any one of claims 8 to 12 and at least one cable (300), preferably a plurality of cables (300, 310, 320) of different lengths, for power line communication, for connection to one of the output stages (545) to be inspected, said cable being impedance-matched to a high-frequency transmitting and receiving unit (40) of the device (100).

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