TRANSMITTING UNIT AND METHOD FOR INTEGRING AN ELECTRICAL TRANSMITTING SIGNAL INTO A DC VOLTAGE LINE

Abstract

A transmitter unit (10) for coupling an electrical transmission signal into a DC line (26.1, 26.2) with two output terminals (20) between which the transmission signal is present and which are provided for connection to a coupling means (21) in the DC line (26.1, 26.2), wherein the transmitter unit (10) has an amplifier circuit (12) with a clocked amplifier and the amplitude of the transmission signal is proportional to a supply voltage (Vcc) of the clocked amplifier, wherein the transmitter unit (10) includes a compensation circuit (14) which is configured to detect the amplitude of the transmission signal via a differential voltage measurement at the output terminals (20) and to adjust the supply voltage (Vcc) of the clocked amplifier as a function of the amplitude of the transmission signal.

Description

TECHNICAL AREA

[0001] The application relates to a transmitter unit for coupling an electrical transmission signal into a DC power line, as well as a photovoltaic inverter with such a transmitter unit. The application further relates to a method for coupling an electrical transmission signal into a DC power line. STATE OF THE ART

[0002] In the DC lines of an electrical installation, such as a power generation plant, electrical transmission signals can be induced, transmitted, and extracted, particularly for powerline communication between various devices connected to the DC lines. In the case of a photovoltaic system, for example, the SunSpec specification of the SunSpec Alliance defines requirements for powerline communication (PLC) between photovoltaic inverters and electronic units on or near the photovoltaic generators. Photovoltaic systems, in particular, therefore typically include a transmitter unit in the inverter that generates a defined electrical transmission signal and couples it onto the DC lines.

[0003] DE 101 19 039 B4 discloses a device for more effective data transmission over a power supply network, comprising an input for a data signal, an amplifier, a power supply and a coupling circuit, wherein a switched amplifier is used which only generates power loss during the short switching times of its switching elements and enables adaptation to fluctuating network impedances.

[0004] From DE 10 2006 060 870 A1, an integrable circuit arrangement is known which provides a high-frequency output signal by means of a control voltage and comprises a clocked DC voltage converter which supplies the control voltage depending on a control signal, wherein the control signal depends on the high-frequency output signal.

[0005] DE 10 2005 010 904 A1 discloses a voltage control circuit for a supply voltage for high-frequency transmission architectures in mobile communication devices, which in particular enables fast amplitude modulation with high efficiency by splitting the amplitude modulation signal into two paths of different bandwidth and combining them at the output of the voltage control circuit.

[0006] From DE 10 2014 015 308 B4 a method for transmitting communication data between electrical devices of a motor vehicle is known, in which the data is transmitted as an alternating voltage signal via a common supply line, wherein the supply current of each device is guided via a current control circuit which has a minimum impedance above a certain frequency. TASK

[0007] The application is based on the task of improving such a transmitting unit and such a method for coupling a transmit signal into a DC line. SOLUTION

[0008] The problem is solved by a transmitting unit with the features of claim 1 and a method with the features of claim 17. Embodiments are specified in the dependent claims. DESCRIPTION OF THE INVENTION

[0009] A transmitter unit couples an electrical signal into a DC power line. Two output terminals are provided for coupling, between which the signal is applied. These output terminals are designed for connection to a coupling device in the DC power line. The transmitter unit includes an amplifier circuit with a switched-mode amplifier. The amplitude of the signal is proportional to the supply voltage of the switched-mode amplifier. The transmitter unit incorporates a compensation circuit that detects the signal amplitude by measuring the differential voltage across the output terminals and adjusts the supply voltage of the switched-mode amplifier accordingly.

[0010] The electrical transmission signal is generated by the transmitter, output via the output terminals, and coupled into the DC line via the coupling device. The coupling can be inductive or capacitive, with the coupling device potentially including a coil for inductive coupling. The switched-mode amplifier of the amplifier circuit can, for example, consist of a bridge circuit with switches that are controlled in a clocked manner.

[0011] The compensation circuit can, in particular, include an analog circuit section for differential voltage measurement. Differential voltage measurement has the advantage that the amplitude of the transmitted signal can be determined even if the output terminals between which the transmitted signal is applied do not have a defined ground reference. Optionally, the compensation circuit can rectify and smooth the measurement signal.

[0012] A properly registered transmitter unit allows the transmission signal to be automatically adjusted to a desired amplitude value and compensates for any deviations caused, for example, by component tolerances, changes in environmental conditions, or modifications to the DC units connected to the DC lines. This improves the quality of the electrical transmission signal and thus the data transmission, without requiring manual intervention in the transmitter unit, for example, after installation of the transmitter unit or inverter, or after modifications to the photovoltaic system.

[0013] In a further development of the transmitter unit, the compensation circuit is configured to output a compensation signal dependent on the amplitude of the transmitted signal in order to adjust the supply voltage of the switched-mode amplifier. This compensation signal, dependent on the amplitude of the transmitted signal, allows the actual amplitude of the transmitted signal at the output terminals to be taken into account when adjusting the supply voltage of the switched-mode amplifier, even if the supply voltage is generated separately, i.e., not by the compensation circuit itself but by a separate power supply. The transmitter unit, in turn, is configured such that the amplitude of the transmitted signal is proportional to the supply voltage of the switched-mode amplifier, so that the amplitude can be adjusted to the desired value by means of the described design of the compensation circuit.

[0014] In one embodiment of the transmitter unit, a nominal DC supply voltage is provided, wherein the supply voltage of the switched-mode amplifier is adjustable, depending on the nominal DC supply voltage and the compensation signal, within a range between half and twice the nominal DC supply voltage. The nominal DC supply voltage can, in particular, be a nominal output voltage of a power supply for the switched-mode amplifier, which can be manipulated by means of the compensation signal. Depending on the compensation signal, the supply voltage of the switched-mode amplifier, and thus the amplitude of the transmitted signal, can then be varied within the range between half and twice a nominal value.This allows for feedback of the actual amplitude of the transmitted signal to ensure a signal with a sufficient amplitude. The supply voltage of the switched-mode amplifier can be adjusted, in particular, within a range of approximately 4 volts to approximately 10 volts.

[0015] In one embodiment, the transmitter unit includes a DC / DC converter configured to generate the supply voltage of the switched-mode amplifier from a higher-level vehicle electrical system voltage, depending on the amplitude of the transmitted signal or the compensation signal. The DC / DC converter can receive either the amplitude of the transmitted signal or a value dependent on it from the compensation circuit to generate the supply voltage. Alternatively, the DC / DC converter can receive the compensation signal from the compensation circuit to generate or scale the supply voltage. The compensation signal can be either analog or digital.

[0016] In one embodiment, the transmitting unit includes a processor configured to generate the compensation signal digitally as a clock sequence with a duty cycle and transmit it to the compensation circuit, the duty cycle being set by the processor depending on the amplitude of the transmitted signal. This embodiment has the advantage that the digital signal processing in the processor can be performed separately from the compensation circuit, which can be designed as an analog circuit.

[0017] In one embodiment of the transmitter, the compensation circuit outputs the clock sequence as a digital compensation signal, used as a control signal for the semiconductor switches of the DC / DC converter. In this embodiment, the compensation circuit can then directly control the semiconductor switches of the DC / DC converter, allowing for a fast response from the DC / DC converter and thus rapid control of the supply voltage generation. The control of the semiconductor switches of the DC / DC converter can be performed either as an alternative or in addition to control of the semiconductor switches by a control unit of the DC / DC converter.

[0018] In one embodiment of the transmitter unit, the compensation circuit includes a filter that generates the compensation signal as an analog voltage level from the clock sequence and outputs it to a control input of the DC / DC converter. In this embodiment, the analog compensation signal acts as a control signal for the generation of the supply voltage, in particular by scaling a nominal output voltage of the DC / DC converter using the analog compensation signal.

[0019] In one embodiment of the transmitter unit, two transmission channels can be coupled via the transmission signal. The transmitter unit is switchable between the two transmission channels. The supply voltage of the clocked amplifier or the compensation signal can be alternately switched between a first and a second supply voltage or between a first and a second compensation signal, depending on the transmission channel. This embodiment thus enables dual-channel operation of the transmitter unit, in which the amplitude of the transmission signal for each channel can be precisely controlled independently of the other channel.

[0020] In one embodiment of the transmitter unit, the compensation circuit includes a temperature sensor for temperature detection. The supply voltage of the clocked amplifier, or the compensation signal, depends on the detected temperature. This allows for compensation of temperature dependencies, which further improves the quality of the transmitted signal.

[0021] In one embodiment of the transmitter unit, the amplifier circuit is configured to generate a modulation of the transmitted signal based on a binary input signal. The amplifier unit can thus convert a binary input signal into a modulated transmitted signal, which can then be coupled into the DC power line. The binary input signal can be generated, for example, from a desired continuous waveform using pulse-width modulation or delta-sigma modulation. The transmitted signal can, for example, be frequency-modulated with a fixed, predetermined amplitude and may have several, in particular two, alternatively usable frequencies.

[0022] In one embodiment, the clocked amplifier can comprise a half-bridge circuit with semiconductor switches that are driven by a clock signal. The gain of the amplifier circuit depends directly on the supply voltage, and the transmitted signal is generated by appropriately clocking the semiconductor switches of the half-bridge.

[0023] In one embodiment of the transmitter unit, the amplifier circuit incorporates a Class D amplifier. A Class D amplifier is a switching amplifier that can be used as a power amplifier. The Class D amplifier operates in switching mode to amplify a binary signal. Semiconductor power switches, such as transistors, in the bridge circuit of the Class D amplifier operate in two discrete states: either conducting or isolating. This results in low power dissipation for the Class D amplifier.

[0024] A photovoltaic inverter has the transmission unit required for registration. The transmission unit is designed to couple the transmission signal into the DC lines of the DC bus. The DC bus connects the inverter to at least one photovoltaic generator for electrical power exchange. The described transmission unit enables the inverter to communicate with connected receivers via the DC bus. Optionally, components already installed in the inverter can be used to control the amplitude of the transmission signal via the transmission unit. This minimizes the additional effort required to influence the amplitude of the transmission signal. For example, the inverter's on-board voltage can be used to generate the supply voltage for the amplifier circuit. Furthermore, for example...A DC / DC converter integrated into the inverter can be used to generate the supply voltage for the amplifier circuit from the vehicle's electrical system. This reduces the cost and complexity of the transmitter unit and / or the inverter.

[0025] A photovoltaic system can include the inverter described. The photovoltaic system can also include at least one photovoltaic generator and a DC bus. The DC bus connects the inverter to the photovoltaic generator for electrical power transfer. The transmitter unit then enables data communication between the inverter and the receivers assigned to the photovoltaic generator.

[0026] In a method for coupling a transmitted signal into a DC power line, the transmitted signal is present between two output terminals connected to a coupling device in the DC power line. An amplifier circuit with a switched-mode amplifier generates the transmitted signal with an amplitude proportional to the amplifier's supply voltage. A compensation circuit detects the amplitude of the transmitted signal by measuring the differential voltage across the output terminals and adjusts the supply voltage of the switched-mode amplifier accordingly. BRIEF DESCRIPTION OF THE FIGURES

[0027] The registration process is further explained and described below using the examples shown in the figures. Fig. Figure 1 schematically shows a first embodiment of a transmitter unit. Fig. Figure 2 schematically shows a second embodiment of a transmitting unit. Fig. Figure 3 schematically shows an example of a photovoltaic system. Fig. Figure 4 schematically shows a method for coupling in a transmit signal. Fig. Figure 5 schematically illustrates a two-channel operation. Fig. Figure 6 schematically shows a procedure for voltage adjustment for two-channel operation.

[0028] The same reference symbols are used in the figures for identical or similar elements. The representations in the figures cannot be to scale. FIGURE DESCRIPTION

[0029] Fig. Figure 1 shows a first embodiment of a transmitter unit 10. The transmitter unit 10 is connected to a DC bus 26 via output terminals 20. The DC bus 26 has two DC lines 26.1 and 26.2. The output terminals 20 of the transmitter unit 10 are connected to one of the DC lines 26.1 of the DC bus 26. An electrical transmission signal present between the output terminals 20 can be coupled to the DC line 26.1 via a coupling device 21, e.g., an inductor. The transmitter unit 10 is used to transmit information encoded in the transmission signal via the DC bus 26 using powerline communication. The transmitter unit 10 can, for example, be a powerline transmitter that is generally compatible with the SunSpec standard and / or similar relevant standards for communication, particularly in a photovoltaic system.

[0030] An amplifier circuit 12 of the transmitter unit 10 comprises a clocked amplifier, which may in particular be a half-bridge with semiconductor switches. The amplifier's gain is achieved by appropriately clocked switching of a supply voltage Vcc via the semiconductor switches. The amplifier thus amplifies a binary input signal TX0 and generates the electrical transmit signal, which is then present between the output terminals 20. The amplifier circuit is designed such that the amplitude of the transmit signal is proportional to the supply voltage Vcc of the clocked amplifier and may, for example, include a Class D amplifier.

[0031] A signal generator 18 is supplied by a signal generator supply voltage VS. The signal generator 18 outputs a binary preset signal TX0, which can be generated from a continuously defined signal waveform by means of encoding. The defined signal waveform can, in particular, qualitatively correspond to the waveform of the desired transmitted signal. Suitable encodings of the desired transmitted signal or the continuous signal waveform include, for example, delta sigma modulation or pulse width modulation. An input signal 22 can be stored in the signal generator 18, for example, via a programming interface in a flash memory. The input signal 22 can be identical to the binary preset signal TX0, which, for example, is used for the in Fig. 1. The single-channel transmitter unit 10 shown continuously outputs a transmission signal.

[0032] The input signal TX0 is preferably derived from a continuous signal, which, for example, exhibits a desired signal waveform with various fixed frequencies, each with a fixed amplitude. The amplifier 10 translates the input signal TX0 from its coded binary form back into an analog electrical transmit signal by means of suitable clocking and filtering. This transmit signal is applied to the coupling device 21. The amplitude of the transmit signal at the coupling device 21 is proportional to the supply voltage Vcc of the clocked amplifier and can also vary due to component tolerances in the amplifier circuit, as well as depending on environmental conditions or the DC units connected to the DC bus 26. Therefore, precise acquisition, control, and adjustment of the transmit signal amplitude is advantageous for the quality of data transmission over the DC bus.

[0033] In this way, any scattering or unwanted variation in the amplitude of the transmitted signal can be compensated for as per the application. The scattering can occur, for example, due to component tolerances, and a variation in the amplitude of the transmitted signal can occur, for example, due to the aging of ceramic capacitors and / or temperature-related dependencies and / or as a dependency on the electrical parameters of a connected PV generator 36.

[0034] The transmitter unit 10 has a compensation circuit 14, which is supplied with electrical power from the vehicle's electrical system voltage VB and supplies the switched-mode amplifier with the supply voltage Vcc. Optionally, the supply voltage Vcc of the switched-mode amplifier can be generated by the compensation circuit 14 itself from the vehicle's electrical system voltage VB.

[0035] The compensation circuit 14 also detects the electrical transmit signal at the output terminals 20 via a differential voltage measurement. The compensation circuit is designed to adjust the supply voltage Vcc of the switched-mode amplifier as a function of the amplitude of the transmitted signal. This has the advantage that the actual amplitude of the transmitted signal can be detected at the output terminals 20 and the supply voltage Vcc of the switched-mode amplifier can be adjusted accordingly to match the amplitude to the desired value.

[0036] The detection of the amplitude of the transmitted signal and the adjustment of the supply voltage Vcc of the clocked amplifier can be carried out by means of an analog circuit arrangement of the compensation circuit 14.

[0037] Optionally, information dependent on the detected amplitude of the transmitted signal can be passed from the compensation circuit 14 to a processor 16. Based on this information, the processor 16 can generate a digital compensation signal, which can be transmitted from the processor 16 to the compensation circuit 14, for example, as a clock sequence with a defined duty cycle. The duty cycle of the digital compensation signal can be set by the processor 16 as a function of the transmitted signal's amplitude, for example, using a proportional controller and / or a proportional controller, each optionally with a characteristic curve.The supply voltage Vcc of the clocked amplifier can then be adjusted by the compensation circuit 14 depending on the digital compensation signal received from the processor 16, in particular by clocked switching of the on-board voltage VB according to the clock sequence of the digital compensation signal received by the processor 16. In a basic embodiment, the compensation circuit 14 can include, in addition to differential voltage detection, the analog signal conditioning of the measured signals to the processor 16 and the clocked compensation signal from the processor 16 by means of filters or similar devices.

[0038] In Fig. Figure 2 shows a second embodiment of the transmitter unit 10. In contrast to Fig. In this embodiment, the transmitter unit 10 includes a DC / DC converter 24. The DC / DC converter 24 is, for example, clocked and has controllable semiconductor switches. The DC / DC converter 24 generates the supply voltage Vcc for the amplifier circuit 12 from the vehicle electrical system voltage VB, depending on a compensation signal SFB received by the compensation circuit 14. The compensation circuit 14 itself can also be powered by the vehicle electrical system voltage VB in this embodiment.

[0039] The compensation circuit 14 generates the compensation signal SFB as a function of the amplitude of the transmitted signal. The amplitude of the transmitted signal can be adjusted analogously to that of the transmitting unit 10. Fig. 1. The measured amplitude or information proportional to it can be forwarded to a processor 16, which, depending on this information, can generate a digital compensation signal by means of a controller and / or a characteristic curve and return it to the compensation circuit 14.

[0040] In this embodiment, the compensation circuit 14 can output a compensation signal SFB, which in digital form is suitable as a control signal for semiconductor switches of the DC / DC converter 24. The compensation circuit 14 can then, for example, directly control the semiconductor switches of the DC / DC converter 24, particularly if the digital compensation signal generated by the processor 16 is used directly or after suitable filtering as the compensation signal SFB.

[0041] The compensation circuit 14 can also include a filter that generates an analog voltage level from the digital compensation signal received by the processor 16 and outputs this voltage level as the compensation signal SFB to a control input of the DC / DC converter. The compensation signal SFB can then directly specify the supply voltage Vcc to be output by the DC / DC converter 24 or modify a nominal DC supply voltage of the DC / DC converter 24, thus scaling the supply voltage Vcc. Alternatively, it would be possible to use the compensation signal SFB directly as the supply voltage of the DC / DC converter 24, i.e., instead of the vehicle electrical system voltage VB (not shown here).

[0042] The transmitter unit 10 is designed for dual-channel transmission, allowing it to be switched between at least two transmission channels. The respective transmission signal can be coupled into different DC buses via these two channels. The currently used channel can be selected using a channel selection signal SEL. The signal generator 18 can alternately output two binary preset signals TX0 and TX1. The first preset signal TX0, with a supply voltage Vcc, is output to the output terminals 20 via the amplifier circuit 12 with a first value. The second preset signal TX1, with a supply voltage Vcc, is output to the output terminals of a second amplifier circuit (not shown) with a second value that differs from the first and is coupled into a second DC bus (not shown).The input signal 22 can be identical to the respective binary preset signals TX0 and TX1, which can be output continuously and alternately. The compensation signal SFB can be switched alternately between a first and a second compensation signal SFB, depending on the transmission channel. The first compensation signal SFB is generated at the coupling device 21, depending on the amplitude of the transmission signal, and the second compensation signal SFB is generated at a further coupling device (not shown) in a DC line of the second DC bus (not shown), depending on the amplitude of the transmission signal. This allows at least the components compensation circuit 14, processor, signal generator 18, and DC / DC converter 24 to be used multiple times to generate PLC signals on different DC buses, potentially with differing DC unit configurations.

[0043] In Fig. Figure 3 schematically depicts a photovoltaic system 40 with an inverter 30, a DC bus with DC lines 26.1 and 26.2, a PV generator 36, and a disconnect switch 32. If multiple PV generators 36 are connected, either in series to the single DC bus or in parallel to the inverter 30 via multiple DC buses, a disconnect switch 32 can be provided for each DC bus or for each PV generator 36.

[0044] The inverter 30 has an inverter bridge 28 and at least one coupling device 21 for each connected DC bus. The coupling device 21 is designed to couple the transmit signal, which is present between the output terminals 20 of the transmitter unit 10, into a DC voltage line 26.1 of the DC bus 26.

[0045] The disconnect circuit 32 represents, as an example, a receiver for the transmission signal and includes a receiving unit 34, which is configured to receive the transmission signal emitted by the transmitting unit 10. Depending on the received transmission signal, the disconnect circuit 21 can, for example, disconnect the PV generator 36 from the inverter 30 by opening an electronic DC switch or connect it to the inverter 30 by closing the electronic DC switch.

[0046] A fail-safe switching device for PV generators can be implemented, for example, using such a disconnect circuit 32 with the receiver unit 34 for communication via the DC bus. One advantage of communication via the DC bus 26 is that no additional cabling needs to be installed or radio interfaces provided. The transmission signal for communication via the DC bus is generated and coupled in, as described, for example, by the transmitter unit 10 in the inverter, whereby the compensation circuit, as specified in the patent application, ensures sufficient signal quality of the transmission signal.

[0047] To ensure single-fault safety of the PV system 40, a specific signal can be sent by the transmitter unit 10, for example, every second, during normal operation of the PV system 40. The disconnect switch 32 evaluates the signal received by the receiver unit 34 and, upon detection of the correct bit stream, switches the DC voltage of the PV generator 36 to the DC bus. Should the DC bus 26 be interrupted, the inverter 30 be defective, or the PV system 40 be switched off for any other reason, preventing the signal from reaching the PV generator 36, the disconnect switch 32 can automatically switch off the PV generator 36. Thus, the entire PV system 40 can be reliably de-energized when necessary.

[0048] Fig. Figure 4 schematically shows a method for coupling the transmit signal into the DC line 26.1. The transmit signal is present between the two output terminals 20, which are connected to the coupling device 21 in the DC line 26.1.

[0049] In 301, the compensation circuit 14 detects the amplitude of the transmitted signal via a differential voltage measurement at the output terminals 20, which are connected to the coupling device 21. In 302, the compensation circuit 14 rectifies the detected voltage of the transmitted signal, e.g., by means of a diode. In 303, the compensation circuit 14 smooths the detected rectified voltage. The smoothing can be achieved, for example, by a type of peak value calculation through integration of the rectified voltage. In 304, the compensation circuit 14 sets the supply voltage Vcc of the switched-mode amplifier. The setting in 304 can be achieved, for example, by directly adjusting the supply voltage Vcc via the compensation circuit 14 (see Figure 304). Fig. 1) or by outputting the compensation signal SFB to a DC / DC converter 24 (compare Fig. 2) take place.

[0050] Fig. Figure 5 schematically illustrates a two-channel operation. Fig. 5 e) denotes those time periods 400 for a first channel in which the supply voltage Vcc for the clocked amplifier connected to a first DC bus is optimized by feedback of the amplitude of the transmitted signal on this first DC bus, and denotes those time periods 401 for a second channel in which the supply voltage Vcc for the clocked amplifier connected to a second DC bus is optimized by feedback of the amplitude of the transmitted signal on this first DC bus. Fig. 5a) 402 denotes the period during which the transmit signal of the first channel is active, while, largely simultaneously, during period 404, the regulation of the supply voltage Vcc is active as a function of the measured amplitude of the transmit signal on the first channel. After the supply voltage Vcc switches to the second channel, the activity of the second channel begins at 403, and correspondingly, during 405, the regulation of the supply voltage Vcc as a function of the measured amplitude of the transmit signal on the second channel takes place. Fig. As can be seen in section 5, the channels transmit during the transmission pause of the other channel. The regulation of the supply voltage Vcc is initiated proactively even before the transmission signal of the respective channel is active.

[0051] Dual-channel operation is made possible by alternating operation. Two independent control processes are defined in the software for this purpose. Predictive voltage switching enables a seamless transition between the channels.

[0052] Fig. Figure 6 schematically shows a procedure for voltage adjustment for two-channel operation. The procedure according to Fig.Process 6 can, for example, run in processor 16. In 501, the active channel is received. In 502, the digitized values ​​of the smoothed amplitude of the active channel's transmit signal are received. In 503, the average value is calculated from the values ​​received in 502 for noise suppression. In 504, the control algorithm for amplitude adjustment is executed. In 505, the compensation signal SFB, e.g., in the form of a duty cycle or an analog voltage level, is generated and used to adjust the supply voltage Vcc. In 506, the process waits until the currently active channel is switched off, and in 507, the control of the supply voltage Vcc is switched to dependence on the amplitude of the transmit signal of the other channel. In 508, the temperature of the transmitter unit 10 is optionally measured to enable optional additional temperature compensation.

[0053] By using active control, the amplitude of the transmitted signal can be maintained within very tight tolerances of the required amplitude. Deviations caused, for example, by component tolerances, can be reliably compensated for. By using the averaged measured value in the control system, the entire output signal can be used as the controlled variable, rather than a single oscillation of the amplitude. This makes the control system robust against disturbances such as harmonics from inverter 30. REFERENCE MARK LIST 10 transmitting units 12 Amplifier circuit 14 Compensation circuit 16 processor 18 Signal generator 20 output ports 21 coupling means 22 Input signal 24 DC / DC converters 26 DC bus 26.1, 26.2 DC lines 28 Inverter bridge 30 inverters 32 Disconnect circuit 34 receiving units 36 Photovoltaic (PV) generator 40 Photovoltaic (PV) systems VB On-board electrical system voltage Vcc supply voltage VS Signal Generator Supply Voltage SEL Channel Selection SFB compensation signal TX0 binary preset signal first transmit channel TX1 binary preset signal second transmission channel 400, 401 Voltage setting Transmit channels 402, 404 Activity Transmitting Channels 403, 405 Activity Regulation Transmitting Channels 301-304, 501-508 Procedural steps

Claims

[1] Transmitter unit (10) for coupling an electrical transmission signal into a DC line (26.1, 26.2) with two output terminals (20) between which the transmission signal is present and which are provided for connection to a coupling means (21) in the DC line (26.1, 26.2), wherein the transmitter unit (10) has an amplifier circuit (12) with a clocked amplifier and the amplitude of the transmission signal is proportional to a supply voltage (Vcc) of the clocked amplifier, wherein the transmitter unit (10) includes a compensation circuit (14) which is configured to detect the amplitude of the transmission signal via a differential voltage measurement at the output terminals (20) and to adjust the supply voltage (Vcc) of the clocked amplifier as a function of the amplitude of the transmission signal. [2] Transmitter unit (10) according to claim 1, wherein the compensation circuit (14) is configured to output a compensation signal (SFB) depending on the amplitude of the transmit signal in order to adjust the supply voltage (Vcc) of the clocked amplifier. [3] Transmitter unit (10) according to claim 2, wherein a nominal DC supply voltage is provided, wherein the supply voltage (Vcc) of the clocked amplifier is adjustable depending on the nominal DC supply voltage and the compensation signal (SFB) in a range between half the nominal DC supply voltage and twice the nominal DC supply voltage. [4] Transmitter unit (10) according to claim 3, wherein the supply voltage (Vcc) is adjustable in a range from approximately 4 volts to approximately 10 volts. [5] Transmitter unit (10) according to one of the preceding claims, comprising a DC / DC converter (24) which is configured to generate the supply voltage (Vcc) from a higher-level vehicle electrical system voltage (VB) depending on the amplitude of the transmit signal or depending on the compensation signal (SFB). [6] Transmitting unit (10) according to one of the preceding claims, wherein the compensation signal (SFB) output by the compensation circuit (14) is analog or digital. [7] Transmitter unit (10) according to one of claims 2 to 6, wherein the transmitter unit (10) has a processor (16) which is configured to generate the compensation signal (SFB) in digital form as a clock sequence with a duty cycle and to transmit it to the compensation circuit (14), wherein the duty cycle is set by the processor (16) depending on the amplitude of the transmitted signal. [8] Transmitter unit (10) according to claim 7, wherein the compensation circuit (14) outputs the clock sequence as a compensation signal (SFB) in digital form as a control signal for semiconductor switches of the DC / DC converter (24). [9] Transmitter unit (10) according to claim 7, wherein the compensation circuit (14) has a filter which generates the compensation signal (SFB) from the clock sequence as a voltage level in analog form and outputs it to a control input of the DC / DC converter (24). [10] Transmitting unit (10) according to one of the preceding claims, wherein two transmitting channels can be coupled via the transmitting signal, wherein the transmitting unit (10) is switchable between the two transmitting channels, and wherein the supply voltage (Vcc) of the clocked amplifier or the compensation signal is alternately switchable between a first and a second supply voltage or between a first and a second compensation signal (SFB) depending on the transmitting channel. [11] Transmitter unit (10) according to one of the preceding claims, wherein the compensation circuit (14) has a temperature sensor for temperature detection (508) and wherein the supply voltage (Vcc) of the clocked amplifier or the compensation signal (SFB) depends on the detected temperature. [12] Transmitting unit (10) according to one of the preceding claims, wherein the amplifier circuit (12) is configured to generate a modulation of the transmit signal depending on a binary preset signal (TX0, TX1). [13] Transmitter unit (10) according to one of the preceding claims, wherein the clocked amplifier comprises a half-bridge circuit with semiconductor power switches. [14] Transmitter unit (10) according to one of the preceding claims, wherein the amplifier circuit (12) comprises a class D amplifier circuit. [15] Photovoltaic inverter (30) with a transmitter unit (10) according to one of the preceding claims, wherein the transmitter unit (10) is provided for coupling the transmission signal into the DC line (26.1, 26.2), wherein a DC bus (26) comprises the DC line (26.1, 26.2), and the DC bus (26) connects the inverter (30) to at least one photovoltaic generator (36) for electrical power exchange. [16] Photovoltaic system (40) comprising an inverter (30) according to claim 15, at least one photovoltaic generator (36) and the DC bus (26) for electrical power transfer. [17] Method for coupling a transmit signal into a DC line (26.1, 26.2), wherein the transmit signal is present between two output terminals (20) which are connected to a coupling means (21) in the DC line (26.1, 26.2), wherein an amplifier circuit (12) with a clocked amplifier generates the transmit signal with an amplitude proportional to a supply voltage (Vcc) of the clocked amplifier, wherein a compensation circuit (14) detects the amplitude of the transmit signal via a differential voltage measurement at the output terminals (20) and adjusts the supply voltage (Vcc) of the clocked amplifier.

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