Method and apparatus for transmitting data between circuit modules of an electrical device

Abstract

The invention relates to a method and an apparatus for transmitting data (D) between circuit modules (10) of an electrical device (1), said circuit modules (10) each containing a controller (11) having a memory (12), a microcontroller and a serial peripheral interface (13) having a data input (Di) and a data output (Do) as a digital interface and being connected to power supply lines (14), and a coupling circuit (15) is provided in each circuit module (10) and the data (D) are able to be transmitted via the power supply lines (14). According to the invention, the microcontroller of the controller (10) of each circuit module (10) is designed to transmit the data (D), to process the data (D) and to form a modulation signal (M) from the processed data (D') by way of a non-coherent modulation method using a clock signal (T) and to forward the modulation signal (M) via the data output (Do) of the serial peripheral interface (13) and to couple the modulation signal (M), via the coupling circuit (15), into the power supply lines (14) and, for reception purposes, to couple the modulation signal (M) out of the power supply lines (14) via the coupling circuit (15), to transmit the modulation signal (M) via the data input (Di) of the serial peripheral interface (13) of the controller (11), to demodulate the modulation signal (M) and to extract the data (D) therefrom.

Description

[0001] Method and device for transmitting data between circuit modules of an electrical device

[0002] The invention relates to a method for transmitting data between circuit modules of an electrical device, for example a welding device, which circuit modules each contain a control device with a memory, a microcontroller and an SPI (Serial Peripheral Interface) interface with a data input and a data output as a digital interface and are connected to power supply lines, and the data is transmitted via the power supply lines.

[0003] Furthermore, the invention relates to a device for transmitting data between circuit modules of an electrical device, for example a welding device, which circuit modules each contain a control device with a memory, a microcontroller and an SPI (Serial Peripheral Interface) interface with a data input and a data output as a digital interface and are connected to power supply lines, and a coupling circuit is provided in each circuit module and the data can be transmitted via the power supply lines.

[0004] The invention relates to a wide variety of electrical devices with multiple circuit modules between which data is to be transmitted. For example, electrical welding devices consist of a welding power source with multiple circuit modules or circuit boards, such as a control unit and a power supply, as well as a wire feeder, which in turn can consist of multiple circuit modules or circuit boards.

[0005] However, the invention is not limited to circuit modules of welding devices, but can relate to a wide variety of other electrical devices, such as inverters, in particular photovoltaic inverters, or battery chargers.

[0006] To transmit data between circuit modules within an electrical device, separate data cables with adapted connectors and protocols (e.g. RS-485, CAN, Ethernet, etc.) are usually used. Connectors take up space, are expensive and often prone to errors because mechanical influences such as vibrations or shocks, as well as thermal influences, affect the contact. Due to the increasing miniaturization of printed circuit boards, the space required by connectors is also becoming an increasing problem. Plug-in connections are therefore a source of many different types of errors, which can range from loose contacts to total failure of the electrical device.

[0007] WO 2014 / 009380 A2 describes an improved connector for transmitting data between two connectors, using permanent magnets for mechanically fixing the connectors.

[0008] Data transmission between different electrical devices via power lines, known as powerline communication (PLC), is now a well-established technology. However, the challenges posed by interference and changing impedances often lead to costly solutions. Therefore, PLCs are not typically used for communication between individual circuit modules within electrical devices.

[0009] WO 02 / 073568 A1 describes a device for data transmission between vehicle sensors, mentioning data transmission via power line via digital interfaces.

[0010] US 2015 / 0224591 A1 describes a method and a device for improving the signal quality of control signals between components of a welding device, wherein the data is preferably transmitted via the power supply lines using the LON (Local Operating Network) standard.

[0011] US 2016 / 0175972 A1 describes a welding device with access to a network via the power supply lines. The data to be transmitted can be modulated using various modulation types before being transmitted over the power supply lines.

[0012] The object of the present invention is to provide an above-mentioned method and an above-mentioned device for transmitting data between circuit modules of an electrical device, which avoid or at least reduce the above-mentioned problems of plug connections.

[0013] In terms of the method, the object of the invention is achieved in that the data for transmission is processed in the microcontroller of the control device of the circuit module, a modulation signal is formed from the processed data with a clock signal using a non-coherent modulation method, and the modulation signal is forwarded via the data output of the SPI interface of the control device and coupled into the power supply lines via a coupling circuit provided in the circuit module, and for reception the modulation signal is decoupled from the power supply lines via the coupling circuit and received via the data input of the SPI interface of the control device, and the modulation signal is demodulated via the control device and the data is extracted from it.By transmitting data over existing power lines, plug-in connections are no longer required, thus eliminating the associated problems. In particular, mechanical problems with plug-in connections, such as loose contacts or complete failure of the connector, can be prevented, and the space requirements and costs associated with such plugs and sockets are eliminated. On the other hand, by optimally and creatively utilizing the existing control device with the microcontroller and its SPI interface as a digital interface, the effort required for data transmission via powerline over the power lines can be kept to a minimum.The effort is limited to a software implementation of the data processing and modulation as well as demodulation and data extraction and to a hardware implementation of a simply constructed and inexpensive coupling circuit for coupling the modulation signal into the power supply lines when sending the data and for coupling the modulation signal out of the power supply lines when receiving the data. The modulation or formation of the modulation signal takes place via a non-coherent modulation method in two steps, whereby in the first modulation step a data packet or processed data is formed from the data and in the second modulation step the processed data is supplemented with a clock signal or timing information to form the modulation signal M or the modulation signal M is formed, which is then transmitted via the power supply lines.With a non-coherent modulation method, no reconstruction of the clock signal or carrier signal is necessary, which makes the method easier to implement. When data is received, the data packets or processed data are first obtained from the modulation signal coupled out of the power supply lines in two demodulation steps, and the data is extracted from these. This means that no separate connectors are required for data transmission between the circuit modules, as the data is transmitted via the existing power supply lines. Even though the power supply lines are usually also connected to the circuit modules via connectors, these connectors are usually larger and more robust than data connectors, and the reduced number of contacts also greatly reduces the probability of a contact error.Processed data means, for example, data packets consisting of a given number of data.

[0014] The modulation signal can be inductively coupled into or extracted from the power supply lines via an inductive coupling circuit, particularly a transformer. This inductive coupling is primarily used for AC power supply lines and is very simple and cost-effective to implement.

[0015] Alternatively, the modulation signal can be capacitively coupled into or out of the power supply lines via a capacitive coupling circuit. This coupling method is primarily used for DC power supply lines.

[0016] Mixed forms between inductive and capacitive coupling circuits are also possible and, due to parasitic capacitances in an inductive transmission element, are also a reality.

[0017] The processed data is preferably modulated or demodulated using a differential modulation method. In particular, a DBPSK (Differential Binary Phase Shift Keying) method is used. The characteristic feature of this type of modulation is that there is no need for the demodulator to generate a phase-synchronous carrier signal. The data signal can be reconstructed relatively easily, for example, by multiplying the received modulation signal by a signal delayed by one bit time and low-pass filtering the higher-frequency part of the digital signal.

[0018] The modulation signal is generated from the processed data, preferably using a clock signal with a specific carrier frequency between 100 kHz and 10 MHz. These frequencies represent an ideal and easily achievable range. The upper limit of the carrier frequency is determined by the SPI interface, which serves as the digital interface of the control device of the circuit module of the electrical device.

[0019] The SPI (Serial Peripheral Interface) interface of the circuit module's microcontroller limits the maximum permissible frequency of the carrier signal and thus the clock rate at which the data can be transmitted.

[0020] Advantageously, the data is processed into data packets of a predetermined length. This simplifies the processing and extraction of the data and the necessary software effort. According to one feature of the invention, the data is transmitted over the power supply lines at a maximum data transmission rate of 1 Mbit / s and with a maximum delay of 100 ms. These are limits that are sufficient for most applications in the field of the present invention.

[0021] If the modulation signal is filtered before being coupled into or after being extracted from the power supply lines, high-quality transmitted data and a low error rate can be achieved. Both analog and digital filters can be used as filters. Low-pass filters, preferably second-order low-pass filters, are used on the transmit and receive sides to smooth the signal.

[0022] It is also advantageous if the modulation signal is amplified before being coupled into the power supply lines or after being coupled out of the power supply lines. Simple operational amplifiers are used as amplifiers, preferably with a resistor and capacitor circuit to compensate for the capacitive load. Furthermore, it is advantageous when receiving data if the received signal is shaped, in particular digitized, in a shaper after amplification and filtering.

[0023] The present invention is particularly intended for the transmission of data over power supply lines with a length of less than 10 m. For data transmission between circuit modules of a welding device, lengths of less than 1 m will be sufficient. For transmission over longer hose packages, the data may need to be transmitted over several meters under certain circumstances. For transmission over greater distances, other methods are more suitable.

[0024] As mentioned above, the power supply lines can be either direct current or alternating current. Depending on the type of power supply (direct current or alternating current), the coupling circuit (inductive, capacitive, or mixed) is selected.

[0025] The object is also achieved by an above-mentioned device, wherein the microcontroller of the control device of each circuit module is designed to send the data, to process the data and to form a modulation signal via a non-coherent modulation method from the processed data with a clock signal and to forward the modulation signal via the data output of the SPI interface and to couple the modulation signal via the coupling circuit into the power supply lines and to receive the modulation signal, to decouple it from the power supply lines via the coupling circuit, to transmit the modulation signal via the data input of the SPI interface of the control device, to demodulate the modulation signal and to extract the data therefrom.With the exception of a coupling circuit and any filters and / or amplifiers and possibly formers, the invention can be implemented in software by programming the microcontroller of the existing control device accordingly. This makes data transmission very simple and cost-effective without the need for separate connectors for data transmission via the existing power supply lines. For further advantages that can be achieved in this way, reference is made to the above description of the data transmission method. The present invention creatively uses the existing SPI interface of each microcontroller of each circuit module for data transmission.

[0026] As already mentioned above, the coupling circuit can be formed by an inductive coupling circuit, in particular a transformer, a capacitive coupling circuit, or a mixed form of a capacitive and inductive coupling circuit.

[0027] Ideally, the control device of the circuit modules is designed to modulate or demodulate the processed data using a non-coherent modulation method, in particular a differential modulation method, particularly preferably a DBPSK (Differential Binary Phase Shift Keying) method.

[0028] If a filter, in particular a low-pass filter, particularly preferably a second-order low-pass filter, is provided in each circuit module for filtering the modulation signal before coupling it into the power supply lines or after coupling it out of the power supply lines, the quality of the data during transmission can be increased and the error rate can be reduced.

[0029] To improve data transmission, each circuit module can also contain an amplifier, particularly an operational amplifier, to amplify the modulation signal before coupling it into the power supply lines or after coupling it out of the power supply lines. While this slightly increases the hardware complexity, it improves the quality of the transmitted data. Furthermore, a shaper can be provided to shape or digitize the received signal after amplification and filtering.

[0030] As a rule, the power supply lines are less than 10 m long.

[0031] The power supply lines can be formed by both direct current power supply lines and alternating current power supply lines.

[0032] The invention is explained in more detail with reference to the accompanying drawings, in which:

[0033] Fig. 1 is a block diagram of three circuit modules of an electrical device with data transmission lines according to the prior art;

[0034] Fig. 2 is a block diagram of three circuit modules of an electrical device, wherein the data transmission according to the invention takes place via the power supply lines;

[0035] Fig. 3A to 3C show various variants of a coupling circuit; Fig. 4 shows a more detailed block diagram of two circuit modules designed to carry out the method according to the invention for data transmission via the power supply lines;

[0036] Fig. 5 is a detailed block diagram of a control device of a formwork module; and

[0037] Fig. 6 is a flow chart illustrating the method according to the invention.

[0038] Fig. 1 shows a block diagram of three electronic circuits 10 of an electrical device 1 according to the prior art. The individual circuit modules 10 are connected to power supply lines 14. The power supply lines 14 can be direct current power supply lines 19 or DC power supply lines or also alternating current power supply lines 20 or AC power supply lines. The transmission of data D usually takes place via separate data transmission lines L, which are connected to the circuit modules 10 with separate plug connections (not shown). Apart from the space required and the cost of such plug connectors for the data transmission line L for transmitting the data D between the circuit modules 10 of the electrical device 1, these plug connections represent potential sources of error.It is therefore an aim to avoid the plug connections of the data transmission lines 14 .

[0039] Fig. 2 shows a block diagram of three circuit modules 10 of an electrical device 1, wherein the transmission of the data D takes place according to the invention via the power supply lines 14. This means that the data transmission lines L and the plug connections required for this can be omitted. To transmit the data D via the power supply lines 14, the control devices 11 present in the circuit modules 10 with their digital interfaces 13 and their memories 12 are programmed in a suitable manner and the data D is processed and modulation signals M are formed, which are coupled into the power supply lines 14 or decoupled again via corresponding coupling circuits 15 (for details see Fig. 3A-3C, 4, 5 and 6). The effort for implementing the method and realizing the device is relatively low and inexpensive.

[0040] 3A to 3C show, by way of example, various variants of coupling circuits 15 with which the modulation signals M with the processed data D' can be coupled into the power supply lines 14 or decoupled again. Fig. 3A shows an inductive coupling circuit 16, in particular a transformer 17, via which the modulation signal M is inductively coupled into the power supply lines 14 or decoupled from the power supply lines 14. The capacitor C (on the left in Figs. 3A to 3C) is in each case part of the voltage supply, for example its buffer capacitor or filter capacitor. The voltage supply is responsible for different voltage levels of the switching module 10, but can also supply other components of the electrical device 1.

[0041] Alternatively, Fig. 3B shows a coupling circuit 15, which is implemented in the form of a capacitive coupling circuit 18, with which the modulation signal M is capacitively coupled into the power supply lines 14 or decoupled from the power supply lines 14. The inductance L functions as a decoupling choke to increase the coupling impedance.

[0042] Mixed forms of coupling circuits 15 according to Fig. 3C between the inductive and capacitive coupling circuit are also possible or by parasitic capacitances C P with an inductive transformer 17 this is also reality.

[0043] Fig. 4 shows a more detailed block diagram of two circuit modules 10 of an electrical device 1, which are designed to carry out the method according to the invention for data transmission via the power supply lines 14. The power supply lines 14 can be direct current power supply lines 19 or alternating current power supply lines 20. Each circuit module 10 has a control device 11 with a memory 12, a microcontroller and an SEI (Serial Peripheral Interface) interface as a digital interface 13 (explained in detail in Fig. 5), which is used in a different way according to the invention. The modulation signal M is only sent and received via a single port of the SPI interface 13; other ports of the SPI interface 13 are not used (see Fig. 5).The control device 11 is connected to a peripheral 28 in which the data D to be transmitted is provided or the received data D is stored. A clock signal T with which the data D is transmitted is determined via a clock generator 29. The clock signal T defines the speed of the transmission accordingly. A coupling circuit 15 is provided in each circuit module 10 and forms the connection to the power supply lines 14. The data D is transmitted in the form of modulation signals M via the power supply lines 14. For this purpose, the control devices 11 of each circuit module 10 are designed to transmit the data D, to process the data D and to form a modulation signal M. In a first modulation step, data D' processed in the control device 11 is formed from the data D.In a second modulation step, the modulation signal M is formed from the processed data D' with the clock signal T, which is coupled into the power supply lines 14 via the coupling circuit 15.

[0044] The data is transmitted in a non-coherent manner, so that no carrier recovery is required. In particular, a DBPSK (Differential Binary Phase Shift Keying) method is used. Of course, other modulation methods are also possible. The data transmission (transmission and reception) of the modulation signal M is preferably carried out via PLC (Power Line Communication). The modulation signal M is forwarded via the SPI interface 13 of the control device 11 and coupled into the power supply lines 14 via the coupling circuit 15 and transmitted. The modulation signal M is smoothed in a filter 23, in particular low-pass filter 24, and converted into an analog modulation signal M and amplified in an amplifier, in particular operational amplifier 26, before it reaches the coupling circuit 15. The coupling circuit 15 can be implemented by an inductive coupling circuit 16, in particular a transformer 17 (see Fig.3A), by a capacitive coupling circuit 18 (see Fig. 3B) or a mixed form thereof (see Fig. 30).

[0045] To receive the data D, the modulation signal M is coupled out of the power supply lines 14 via the coupling circuit 15 of the receiving circuit module 10 and optionally fed to an amplifier 25, in particular operational amplifier 26, and a filter 23, in particular low-pass filter 24. The signal is then preferably shaped accordingly in a shaper 27, and the analog modulation signal M is digitized and received via the SPI interface 13 of the control device 11, and the data D is extracted therefrom by software and stored in the periphery

[0046] 28 can be filed.

[0047] Fig. 5 shows a detailed block diagram of a control device 11 of a circuit module 10. The control device 11 includes a central processing unit 30 or CPU (central processing unit), the memory 12, a memory access unit 31, a clock generator 32 and the digital interface 13. The clock generator 32 is connected to the clock

[0048] 29 or an oscillator and sets the clock signal T with which the modulation signal M is transmitted. The clock for the central processing unit 30 is also generated this way. At this point it should also be noted that the clock signal T is configured identically for each circuit module 10 so that data exchange is possible. The data D provided in the periphery 28 are read in and prepared via the central processing unit 30. During the preparation of the data D (addressing, etc.) redundancy is additionally added for transmission reliability so that a data packet or data D ' processed in the first modulation step is formed from the data D and moved or written into the memory 12. The memory access unit 31, in particular a Direct Memory Access (DMA), has access to the memory 12 and makes the processed data D' available to the interface 13 when required.In the interface 13, in the second modulation step with the clock signal T, the processed data D' are supplemented with timing information and the modulation signal M is formed and then sent.

[0049] After the interface 13, the signal is filtered and amplified before the modulation signal M is coupled into the power supply lines 14 via the coupling circuit 15 (see Fig. 4). The digital interface is an SPI interface 13 integrated in the control device 11, which is used according to the invention. Accordingly, the modulation signal M is sent only via a single port (data output Do) of the SPI interface 13. Additional ports of the SPI interface 13 are not required for transmission.

[0050] When the data D or the modulation signal M is received, it is first coupled out of the power supply lines 14 via the coupling circuit 15 and, after appropriate amplification, filtering and forming or digitization (see Fig. 4), received via the SPI interface 13 (this takes place according to the inventive use of the SPI interface 13 for receiving solely via the "data input Di" port). The timing information is then removed from the modulation signal M in the first demodulation step, and the processed data D' is extracted in the second demodulation step. The processed data D' is then transferred to the memory access unit 31. This in turn makes it available to the memory 12 so that the central processing unit 30 can access it to extract / recover the data D. The data D can thus be made available to the peripherals 28 again.The ports (data output Do, data input Di) for the inventive use of the SPI interface 13 are marked accordingly in Fig. 5.

[0051] Finally, Fig. 6 shows a flowchart illustrating the method according to the invention. The method starts with an initialization (block 101). This is followed by a collection block 102 symbolizing the start of an endless loop.

[0052] When data D is required to be sent (query 103), the data D is first preprocessed to form corresponding processed data D', for example data packets (block 104). This takes place according to the first modulation step in the central processing unit 30, where the processed data D' is also written to the memory 12. According to block 105, the reception option is blocked in the memory access unit 31 of the control device 11 in order to enable the data D to be sent. For sending, the processed data D' is read from the memory 12 into the memory access unit 31 and then into the SPI interface 13. In the second modulation step, the timing information is added in the SPI interface 13, the modulation signal M is formed and the modulation signal M is sent (block 106). As a result, all data is sent until the sending process is completed (block 107).After the sending process has been completed, the system returns to block 102.

[0053] If, according to the query (block 103), no data D is ready to be sent, a receive mode is started (block 108). In the receive mode, a received bit stream, consisting of several data blocks with the processed data D ' including interference, is written into the memory 12 by means of DMA and examined by the CPU for contained data D until the data D has been completely extracted or reconstructed (block 109). According to block 110, the processed data D' is extracted / demodulated from the received modulation signal M in the first demodulation step and finally the data D is extracted / demodulated in the second demodulation step. The recovered data D can then be transmitted to the peripheral 28. Once reception is complete, the system returns to block 102.

[0054] The method steps described above can be implemented relatively easily by software in the existing control devices 11 of the circuit modules 10, so that transmission of the data D or modulation signals M, which contain the data D or processed data D', is made possible via the power supply lines 14 and conventional data transmission lines L with their own plug connections can be dispensed with.

Claims

Patent claims:

1. A method for transmitting data (D) between circuit modules (10) of an electrical device (1), for example a welding device, which circuit modules (10) each contain a control device (11) with a memory (12), a microcontroller and an SPI (Serial Peripheral Interface) interface (13) with a data input (Di) and a data output (Do) as a digital interface and are connected to power supply lines (14), and the data (D) are transmitted via the power supply lines (14), characterized in that the data (D) are processed for transmission in the microcontroller of the control device (11) of the circuit module (10), a modulation signal (M) is formed from the processed data (D') with a clock signal (T) via a non-coherent modulation method,and the modulation signal (M) is forwarded via the data output (Do) of the SPI interface (13) of the control device (11) and coupled into the power supply lines (14) via a coupling circuit (15) provided in the circuit module (10), and for receiving, the modulation signal (M) is decoupled from the power supply lines (14) via the coupling circuit (15) and received via the data input (Di) of the SPI interface (13) of the control device (11), and the modulation signal (M) is demodulated via the control device (11) and the data (D) are extracted therefrom., 2. Method according to claim 1, characterized in that the modulation signal (M) is transmitted via an inductive coupling circuit (16), in particular a transformer (17) is inductively coupled into the power supply lines (14) or decoupled from the power supply lines (14).

3. Method according to claim 1 or 2, characterized in that the modulation signal (M) is capacitively coupled into the power supply lines (14) or decoupled from the power supply lines (14) via a capacitive coupling circuit (18).

4. Method according to one of claims 1 to 3, characterized in that the processed data (D' ) are modulated or demodulated via a differential modulation method, in particular by a DBPSK (Differential Binary Phase Shift Keying) method.

5. Method according to one of claims 1 to 4, characterized in that the data (D) are divided into data packets of predetermined length (1 D ) are processed.

6. Method according to one of claims 1 to 5, characterized in that the modulation signal (M) is filtered before being coupled into the power supply lines (14) or after being coupled out of the power supply lines (14).

7. Method according to one of claims 1 to 6, characterized in that the modulation signal (M) is amplified before being coupled into the power supply lines (14) or after being coupled out of the power supply lines (14).

8. Device for transmitting data (D) between circuit modules (10) of an electrical device (1), for example a welding device, which circuit modules (10) each contain a control device (11) with a memory (12), a microcontroller and an SPI (Serial Peripheral Interface) interface (13) with a data input (Di) and a data output (Do) as a digital interface and are connected to power supply lines (14), and in each circuit module (10) a coupling circuit (15) is provided and the data (D) can be transmitted via the power supply lines (14), characterized in thatthat the microcontroller of the control device (11) of each circuit module (10) for sending the data (D) for processing the data (D) and for forming a modulation signal (M) via a non-coherent modulation method from the processed data (D' ) with a clock signal (T) and for forwarding the modulation signal (M) via the data output (Do) of the SPI interface (13) and for coupling the modulation signal (M) via the coupling circuit (15) into the power supply lines (14) and, for receiving and decoupling the modulation signal (M) from the power supply lines (14) via the coupling circuit (15), transmitting the modulation signal (M) via the data input (Di) of the SPI interface (13) of the control device (11), demodulating the modulation signal (M) and extracting the data (D) therefrom.

9. Device according to claim 8, characterized in that the coupling circuit (15) is formed by an inductive coupling circuit (16), in particular a transformer (17).

10. Device according to claim 8 or 9, characterized in that the coupling circuit (15) is formed by a capacitive coupling circuit (18).

11. Device according to one of claims 8 to 10, characterized in that in each circuit module (10) a filter (23), in particular a low-pass filter (24) is provided for filtering the modulation signal (M) before coupling into the power supply lines (14) or after coupling out of the power supply lines (14).

12. Device according to one of claims 8 to 11, characterized in that in each circuit module (10) an amplifier (25), in particular an operational amplifier (26), is provided for amplifying the modulation signal (M) before coupling into the power supply lines (14) or after coupling out of the power supply lines (14).

13. Device according to one of claims 8 to 12, characterized in that the power supply lines (14) are formed by direct current power supply lines (19).

14. Device according to one of claims 8 to 12, characterized in that the power supply lines (14) are formed by alternating current power supply lines (20).

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