Signal transmission device and signal transmission system

Abstract

To suppress increase of mode conversion loss due to variability in electric characteristics of electronic components mounted on a P side and an N side when different bias voltages are applied.SOLUTION: A signal transmission device that performs differential transmission comprises: an information processing circuit 9 that performs processing of various kinds of information related to differential transmission; and a power supply circuit 30 including a voltage output circuit that outputs a first application voltage to a first signal wire and outputs a second application voltage to a second signal wire. The information processing circuit 9 includes an output voltage determination unit 41 that determines an instruction value for at least one of the first application voltage and the second application voltage applied by the power supply circuit 30, and delivers the determined instruction value to the power supply circuit 30. The power supply circuit 30 has an output voltage adjustment function 42 for adjusting a parameter of the voltage output circuit so that the first application voltage and the second application voltage reflecting the received instruction value are output to the first signal wire and the second signal wire.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal transmission device and a signal transmission system. [Background technology]

[0002] In recent years, the speed of signal transmission between electronic devices installed in vehicles using twisted pair cables has been increasing. For example, in-vehicle Ethernet has been standardized from the previously main standards of 100BASE-T1, which transmits 100 Mbps, and 1000BASE-T1, which transmits 1 Gbps, to Multi-Gigabit Ethernet (registered trademark) and 25GBASE-T1, which enable transmissions of several Gbps or more. Furthermore, MIPI A-Phy, a communication standard for camera communication, is also standardizing transmission speeds of Gbps or more.

[0003] A challenge with such high-speed in-vehicle cable transmission is maintaining EMC (Electromagnetic Compatibility) performance as frequencies increase. Because the current spectrum used for signal transmission extends to high frequencies above the GHz band, it is necessary to suppress radiation in this high-frequency band. At the same time, because communication LSIs (Large-Scale Integration) have the sensitivity to transmit and receive signals up to the GHz band, it is also necessary to suppress the leakage of GHz-band noise.

[0004] In differential signal transmission, ideally, the positive side (hereafter referred to as "P side") and negative side (hereafter referred to as "N side") transmission lines that make up the differential transmission line (differential wiring) are electrically symmetrical. This allows the magnetic fields generated when currents flow through each transmission line (signal wiring) to be canceled out when currents of opposite phase flow through the differential transmission line, thereby suppressing radiation. Furthermore, when common mode noise is superimposed on both signal wirings, it can be canceled out by the differential receiver, improving resistance to external noise.

[0005] However, the differential balance of the P-side and N-side signal wiring that make up the differential transmission line can be disrupted by variations in electrical characteristics caused by various factors. This disruption of differential balance prevents the benefits of differential transmission from being realized, resulting in a deterioration in EMC performance. The degree of variation in the electrical characteristics of this differential transmission line is defined as mode conversion loss, and is used as a criterion for judging EMC performance, particularly in the high-frequency range above 100 MHz. Mode conversion loss represents the amount of differential mode converted to common mode in differential wiring, or the amount of common mode converted to differential mode. High mode conversion loss can increase radiated noise due to the generation of unintended common mode components, or can reduce noise immunity due to the conversion of common mode components to differential components.

[0006] As background art related to the present invention, the technology described in Patent Document 1 is known. Patent Document 1 discloses a system (Power over Data Line: PoDL) that connects electronic devices with twisted pair cables and transmits differential signals and power superimposed on the twisted pair cables. In this system, a DC blocking capacitor is placed on the signal line, and a filter element such as a common mode choke coil or inductor is inserted as a PoDL filter on the power line. This separates the differential signals and power according to the frequency range of the filter element. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 10 / 594,519 Summary of the Invention [Problem to be solved by the invention]

[0008] The technology described in Patent Document 1 reduces the leakage of common mode noise from the communication circuit on the wiring board to the twisted pair cable by placing a filter element between the communication circuit and the twisted pair cable, and also prevents the common mode noise picked up by the twisted pair cable from propagating to the communication circuit on the wiring board.

[0009] However, when an imbalance in electrical characteristics occurs due to the application of bias voltages with different potential differences from the ground between the P-side and N-side of electronic components that make up the transmission system, the mode conversion loss of the transmission path increases, which can worsen EMC performance. For example, the parasitic capacitance component of the electrostatic protection elements mounted on the signal wiring on both the P-side and N-side can decrease depending on the magnitude of the DC bias. Particularly at high frequencies, this variation in parasitic capacitance contributes to an increase in mode conversion loss, which has been an issue. Mode conversion loss is determined by the "S" parameter, which is a group of parameters that represent the electrical characteristics of a transmission path using mixed mode S-parameters. cd " is expressed in the section.

[0010] Given the above situation, there was a demand for a method to suppress the increase in mode conversion loss caused by variations in the electrical characteristics of the electronic components mounted on the P-side and N-side due to the application of different bias voltages. [Means for solving the problem]

[0011] In order to solve the above problem, a signal transmission device according to one embodiment of the present invention is a signal transmission device comprising: first and second signal wirings that constitute differential wirings; a communication circuit for transmitting differential signals to the differential wirings; an information processing circuit connected to the communication circuit for processing various types of information; a first electronic component arranged between the first signal wiring and a ground wiring; a second electronic component arranged between the second signal wiring and the ground wiring; a power supply circuit having a voltage output circuit that outputs a first applied voltage to the first signal wiring and a second applied voltage to the second signal wiring; and filter components arranged between the power supply circuit and each of the first and second signal wirings. The information processing circuit has an output voltage determination unit that determines an instruction value for at least one of a first applied voltage and a second applied voltage to be applied by the power supply circuit and sends the determined instruction value to the power supply circuit. The power supply circuit has an output voltage adjustment function that adjusts parameters of the voltage output circuit so that the first applied voltage and the second applied voltage that reflect the instruction values ​​received from the output voltage determination unit are output to the first signal wiring and the second signal wiring. [Effects of the Invention]

[0012] According to at least one aspect of the present invention, it is possible to suppress an increase in mode conversion loss due to variations in the electrical characteristics of electronic components mounted on the P side and N side caused by different bias voltages being applied to the differential wiring. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a first embodiment of the present invention is applied. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of an electronic device to which a conventional signal transmission device is applied. [Figure 3] 10 is a graph showing an example of change in mode conversion loss performance depending on whether or not a bias is applied to the output voltage of a power supply circuit (output voltage adjustment). [Figure 4] 10 is a graph showing the bias voltage dependency of the parasitic capacitance of an electrostatic protection element. [Figure 5] FIG. 10 is a diagram showing an example of the configuration of a signal transmission system using an electronic device to which a signal transmission device according to a second embodiment of the present invention is applied. [Figure 6] FIG. 10 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a third embodiment of the present invention is applied. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a fourth embodiment of the present invention is applied. [Figure 8]FIG. 10 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a fifth embodiment of the present invention is applied. [Figure 9] FIG. 10 is a diagram showing an example of the configuration of a signal transmission system using an electronic device to which a signal transmission device according to a sixth embodiment of the present invention is applied. [Figure 10] FIG. 10 is a diagram showing an example of the configuration of a differential-to-single-ended conversion circuit included in an electronic device to which a signal transmission device according to a sixth embodiment of the present invention is applied. [Figure 11] FIG. 13 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a seventh embodiment of the present invention is applied. [Figure 12] FIG. 13 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to an eighth embodiment of the present invention is applied. [Figure 13] FIG. 13 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a ninth embodiment of the present invention is applied. [Figure 14] FIG. 23 is a diagram showing an example of a process for determining an output voltage range in a signal transmission system using an electronic device to which a signal transmission device according to a tenth embodiment of the present invention is applied. [Figure 15] FIG. 20 is a diagram showing an example of a data set obtained using a signal transmission device according to a tenth embodiment of the present invention. [Figure 16] 20 is a flowchart showing an example of a procedure for processing to acquire data on the relationship between the amount of noise and the bias voltage in an electronic device to which a signal transmission device according to a tenth embodiment of the present invention is applied. [Figure 17] FIG. 23 is a diagram showing an example of the configuration and functions for grasping the amount of noise in a noise amount grasping unit of an electronic device to which a signal transmission device according to an eleventh embodiment of the present invention is applied. [Figure 18] FIG. 29 is a diagram showing an example of the configuration and functions for grasping the amount of noise in a noise amount grasping unit of an electronic device to which a signal transmission device according to a twelfth embodiment of the present invention is applied. [Figure 19] FIG. 23 is a diagram showing an example of a process for grasping the amount of noise in a signal transmission system using an electronic device to which a signal transmission device according to a thirteenth embodiment of the present invention is applied. [Figure 20]FIG. 23 is a diagram showing an example of the configuration of a solution system including a signal transmission system using an electronic device to which a signal transmission device according to a fourteenth embodiment of the present invention is applied, and a diagnostic server. [Figure 21] 23A and 23B are diagrams showing examples of data sets and predicted curves of upper limit bias voltages obtained in a signal transmission system using an electronic device to which a signal transmission device according to a fourteenth embodiment of the present invention is applied. [Figure 22] 23 is a flowchart showing an example of the procedure of a maintenance necessary information notification process performed by a solution system including a diagnostic server and a signal transmission system using an electronic device to which a signal transmission device according to a fourteenth embodiment of the present invention is applied. [Figure 23] 23 is a flowchart showing another example of the procedure of the maintenance necessity information notification process by the solution system including the signal transmission system using the electronic device to which the signal transmission device according to the fifteenth embodiment of the present invention is applied. [Figure 24] FIG. 22 is a block diagram showing an example of the functional configuration of an information processing LSI of an electronic device to which a signal transmission device according to a sixteenth embodiment of the present invention is applied. [Figure 25] FIG. 22 is a diagram showing an example of the configuration of a solution system including a signal transmission system using an electronic device to which a signal transmission device according to a seventeenth embodiment of the present invention is applied, an OTA server, and a diagnostic server. [Figure 26] FIG. 22 is a diagram illustrating an example of how to utilize the solution system according to the seventeenth embodiment of the present invention. [Figure 27] 1 is a block diagram showing an example of the hardware configuration of an electronic device to which a signal transmission device according to each embodiment of the present invention is applied, a diagnostic server, and an OTA server computer. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, examples of modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, identical components or components having substantially the same functions will be assigned the same reference numerals, and redundant explanations will be omitted. When there are multiple components having the same or similar functions, they may be described using the same reference numerals with different subscripts. However, when it is not necessary to distinguish between these multiple components, the subscripts may be omitted in the description.

[0015] The following description and drawings are examples for explaining the present invention, and have been omitted or simplified as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0016] In order to facilitate understanding of the invention, the circuit configurations, functional blocks, etc. shown in the drawings may not depict all circuit elements, wiring, functional blocks, etc. Therefore, the present invention is not necessarily limited to the circuit elements, circuit layout, wiring, functional blocks, etc. disclosed in the drawings.

[0017] First Embodiment FIG. 1 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to a first embodiment of the present invention is applied. The electronic device 1 shown in FIG. 1 is connected to a cable consisting of a pair of electric wires (for example, twisted pair cable 8 in FIG. 5) via a cable connector 16, and is connected to another external electronic device (for example, electronic device 1-2 in FIG. 5) for signal transmission. The electronic device 1 includes a communication LSI 2 (an example of a communication circuit) that communicates with the other electronic device by differential transmission via differential wiring 5 connected to the cable connector 16. The communication LSI 2 and the cable connector 16 are connected by differential wiring 5 laid out on a printed wiring board. The differential wiring 5 is composed of a pair of P-side signal wiring 6 (positive side signal wiring) and N-side signal wiring 7 (negative side signal wiring).

[0018] The communication LSI 2 is also connected to an information processing LSI 9 (an example of an information processing circuit). The information processing LSI 9 exchanges data with the communication LSI 2 to process various types of information. The communication LSI 2 includes an output voltage determination unit 41. The output voltage determination unit 41 determines an instruction value for at least one of the voltage to be applied by the power supply circuit 30 to the P-side signal wiring 6 and the voltage to be applied to the N-side signal wiring 7, and sends the determined instruction value to the power supply circuit 30.

[0019] The electronic device 1 further includes a power supply circuit 30 for superimposing a power supply on the P-side signal wiring 6 and the N-side signal wiring 7 of the differential wiring 5, and a power supply superimposition filter 10. For example, the power supply circuit 30 can be configured as a power supply IC equipped with a DC / DC converter. In this embodiment, the power supply circuit 30 includes a voltage output circuit (not shown) that generates and outputs a voltage to be superimposed as a power supply on the P-side signal wiring 6 and the N-side signal wiring 7, and an output voltage adjustment function 42 that outputs an instruction value for adjusting the output voltage of the voltage output circuit. In the power supply circuit 30, an input terminal V IN and the ground terminal GND, the battery voltage V bat The voltage output circuit is connected to the battery voltage V bat The voltage output circuit outputs the generated voltage for the P side to the output terminal V OUTP to the P-side terminal of the power supply superposition filter 10, and the generated N-side voltage is output to the output terminal V OUTN to the N-side terminal of the power supply superposition filter 10.

[0020] The power supply superimposed filter 10 has a function of connecting a power supply line on which a power supply is superimposed and a signal line on which a signal is transmitted. For example, the power supply superimposed filter 10 can be configured using a PoDL filter.

[0021] Between the communication LSI 2 and the cable connector 16, i.e., on the differential wiring 5, there are connected AC coupling capacitors 14P and 14N for cutting DC potential, and a common mode choke coil (CMCC) 15 for reducing common mode noise that deteriorates EMC performance and has flowed into the communication LSI 2. In addition, between the P-side signal wiring 6 and the ground wiring, there is mounted an electrostatic protection element 17P for preventing electrostatic breakdown, and between the N-side signal wiring 7 and the ground wiring, there is mounted an electrostatic protection element 17N.

[0022] Note that the configuration shown in Figure 1 is a general circuit configuration, and components other than those described here (e.g., common mode termination components, filter components, etc.) may be added, and some of the electronic components described here may not be included as components. The layout of the circuit configuration may also differ. For example, a different layout of the circuit configuration may occur when a PoDL filter is inserted between the common mode choke coil and the AC coupling capacitor.

[0023] The features of the components of the electronic device 1 according to the first embodiment of the present invention are that the power supply circuit 30 is provided with an output voltage adjustment function 42, and the information processing LSI 9 is provided with an output voltage determination unit 41 for determining the voltage value of the voltage adjusted by the output voltage adjustment function 42.

[0024] [Conventional electronic devices] FIG. 2 is a diagram showing an example of the configuration of an electronic device to which a conventional signal transmission device is applied. The conventional electronic device 100 shown in FIG. 2 includes an information LSI 90 and a power supply circuit 91. The other components of the electronic device 100 are the same as those of the electronic device 1 shown in FIG. 1. That is, the conventional electronic device 100 does not include the output voltage adjusting function 42 implemented in the power supply circuit 30 of the electronic device 1 and the output voltage determining unit 41 implemented in the information processing LSI 9. The power supply circuit 91 of the electronic device 100 includes a single input terminal V IN and one output terminal V OUT and a ground terminal GND. The power supply circuit 30 has an output terminal V OUTand a P-side terminal of the power supply superimposed filter 10 are connected, and a ground terminal GND of the power supply circuit 30 and an N-side terminal of the power supply superimposed filter 10 are connected.

[0025] Incidentally, mode conversion loss is an index that indicates the EMC performance of the transmission path of the electronic device 1. As a means of evaluating the EMC performance, the mode conversion loss "S" measured from the cable connector 16 using a network analyzer is used. cd,11 The most common method is to measure "S cd,11 " represents the case where the signal input to the input terminal is in differential mode and the output from the output terminal is in common mode. cd,11 By checking whether the " value is smaller than the target value, it is possible to judge whether the EMC performance passes or fails. Examples of such electronic devices include an automobile's automatic driving electronic control unit (AD-ECU) and an advanced driver assistance system electronic control unit (ADAS-ECU).

[0026] Although the present invention will be described in detail in conjunction with an in-vehicle device as an electronic device to which the present invention is applied, the present invention can also be applied to other forms of electronic devices that use similar communication systems. For example, the present invention can be equally effective in communication between an industrial robot and an electronic camera.

[0027] 3 is a graph showing an example of changes in mode conversion loss performance depending on whether or not a bias is applied to the output voltage (output voltage adjustment) of the power supply circuit 30. The horizontal axis represents the frequency [MHz] of the transmission signal, and the vertical axis represents the mode conversion loss [dB]. 4 is a graph showing the bias voltage dependency of the parasitic capacitance of an electrostatic protection element. The horizontal axis represents the bias voltage [V] for the electrostatic protection element, and the vertical axis represents the parasitic capacitance ratio [%].

[0028] For example, if the power supply circuit 30 applies a 10V DC bias voltage (DC voltage) only to the P-side of the differential wiring 5, the electrostatic protection elements 17P and 17N connected to the P-side and N-side of the differential wiring 5 will have DC voltages of 10V and 0V applied to ground, respectively. If we assume that the target electrostatic protection elements 17P and 17N have the bias voltage dependency of parasitic capacitance shown in Figure 4, only the parasitic capacitance of the P-side electrostatic protection element 17P will decrease by approximately 2%. This results in a parasitic capacitance variation ΔC between the P-side electrostatic protection element 17P and the N-side electrostatic protection element 17N, resulting in a characteristic curve similar to the "bias applied (no adjustment)" shown by the dashed line in Figure 3. With characteristics similar to "bias applied (no adjustment)," the mode conversion loss may exceed the target value shown by the solid line, potentially degrading noise performance.

[0029] Therefore, in the present invention, the output voltage adjustment function 42 adjusts the output voltage of the power supply circuit 30, thereby reducing the mode conversion loss of the differential wiring 5. For example, if the output voltage adjustment function 42 has the function of adjusting the output voltage of only the P side of the differential wiring 5, the output voltage adjustment function 42 reduces the output voltage of the power supply circuit 30 connected to the P side signal wiring 6 within a range of voltage values ​​predefined as the output voltage range, so as to increase the parasitic capacitance of the electrostatic protection element 17P. However, it goes without saying that the output voltage adjustment function 42 may also have the function of adjusting the output voltage of the N side.

[0030] The output voltage adjustment function 42 adjusts the output voltage so as to satisfy the conditions for the parasitic capacitance of the electrostatic protection elements 17P, 17N based on output voltage information (for example, the noise amount-bias voltage relationship described later) obtained from an external device (for example, the output voltage determination unit 41 of the information processing LSI 9 or an information processing terminal outside the electronic device 1). This makes it possible to suppress mode conversion loss and satisfy the target value, as shown in the characteristic curve indicated by the dashed dotted line labeled "Bias adjustment according to the present invention" in FIG.

[0031] As described above, the signal transmission device (electronic device 1) according to the first embodiment of the present invention includes a first signal wiring (P side) and a second signal wiring (N side) that constitute a differential wiring, a communication circuit (e.g., communication LSI 2) for transmitting a differential signal to the differential wiring, an information processing circuit (e.g., information processing LSI 9) that is connected to the communication circuit and performs information processing, a first electronic component (e.g., electrostatic protection element 17P) that is arranged between the first signal wiring and the ground wiring, a second electronic component (e.g., electrostatic protection element 17N) that is arranged between the second signal wiring and the ground wiring, a power supply circuit (e.g., power supply circuit 30) that has a voltage output circuit that outputs a first applied voltage to the first signal wiring and a second applied voltage to the second signal wiring, and filter components (e.g., power supply superposition filter 10) that are arranged between the power supply circuit and each of the first signal wiring and the second signal wiring. The information processing circuit has an output voltage determination unit (e.g., output voltage determination unit 41) that determines an instruction value for at least one of the first applied voltage and the second applied voltage to be applied by the power supply circuit and sends the determined instruction value to the power supply circuit. The power supply circuit has an output voltage adjusting function (e.g., output voltage adjusting function 42) that adjusts a parameter of the voltage output circuit so that the first applied voltage and the second applied voltage that reflect the instruction value (e.g., DC bias voltage) received from the output voltage determining unit are output to the first signal wiring and the second signal wiring. This parameter is, for example, the number of steps (amount of change) of voltage change of a circuit having a voltage step-up / step-down function shown in Figures 7 and 8, which will be described later.

[0032] In the signal transmission device (electronic device 1) according to the first embodiment described above, the power supply circuit 30 is provided with an output voltage adjusting function 42, and the information processing LSI 9 is provided with an output voltage determining unit 41. In this embodiment, the output voltage adjusting function 42 and the output voltage determining unit 41 adjust at least one of the output voltage on the P side and the output voltage on the N side of the power supply circuit 30 so as to reduce mode conversion loss caused by variations in electrical characteristics of electronic components mounted on the P side and the N side due to application of different bias voltages to the differential wiring 5. This makes it possible to suppress an increase in mode conversion loss and improve the EMC performance of the signal transmission device (differential transmission path).

[0033] <Second embodiment> FIG. 5 is a diagram showing an example of the configuration of a signal transmission system using an electronic device to which a signal transmission device according to the second embodiment of the present invention is applied. 5 shows an example of a signal transmission system in which an electronic device 1-1 employing the signal transmission device according to the first embodiment (electronic device 1 in FIG. 1) is connected to another external electronic device 1-2 via a twisted pair cable 8. The electronic devices 1-1 and 1-2 have mostly the same configuration, and the same components are given the same reference numerals, but the electronic devices 1-1 and 1-2 are distinguished by adding different suffixes to the same reference numerals. That is, each component of the electronic device 1-1 is given the suffix "-1," and each component of the electronic device 1-2 is given the suffix "-2."

[0034] However, the power supply circuit 30-2 of the electronic device 1-2 is different from the power supply circuit 30-1 of the electronic device 1-1. The power supply circuit 30-2 has an input terminal V IN The power supply circuit 30-2 has a ground terminal GND connected to the N-side terminal of the power supply superposition filter 10-2. The power supply circuit 30-2 also has an output terminal V OUT-1 , the output terminal V that supplies power to the information processing LSI9-2 OUT-2 Equipped with.

[0035] 5, during signal transmission, an output voltage value is determined by an output voltage determination unit 41 of an information processing LSI 9-1 of the electronic device 1-1, and the output voltage is adjusted by an output voltage adjustment function 42 of the power supply circuit 30-1. This makes it possible to improve noise immunity against radiation during signal transmission from a cable (e.g., twisted pair cable 8) originating from the electronic device 1-2, and against external common mode noise in the electronic device 1-2.

[0036] 5, the electronic device 1 to which the signal transmission device according to the first embodiment is applied is only applied to the electronic device 1-1. However, the signal transmission device according to the first embodiment may be applied to both the electronic device 1-1 and the electronic device 1-2.

[0037] <Third embodiment> FIG. 6 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the third embodiment of the present invention is applied. In the third embodiment, a noise amount grasping unit 43 is provided in the information processing LSI 9, and by grasping the amount of noise occurring in the differential wiring 5 of the target signal transmission system, the amount of system noise is reflected in the determination process of the output voltage determining unit 41. In other words, the electronic device 1 according to this embodiment has a function of optimizing the output voltage of the power supply circuit 30 in accordance with the amount of noise.

[0038] A detailed procedure for determining the output voltage using this function will be described later in the tenth embodiment. A more specific configuration and operation of the noise amount grasping unit 43 will be described later in the eleventh embodiment (FIG. 17) and the twelfth embodiment (FIG. 18).

[0039] As described above, in the signal transmission device (electronic device 1) according to the third embodiment, the information processing circuit (information processing LSI 9) has a noise amount grasping unit (noise amount grasping unit 43) that grasps the amount of noise occurring in the first signal wiring and the second signal wiring. Based on the grasping result of the noise amount grasping unit, the output voltage determination unit (output voltage determination unit 41) determines an instruction value (bias voltage) so as to reduce the amount of noise for at least one of the first applied voltage (e.g., P-side) and the second applied voltage (e.g., N-side), and outputs the instruction value to the power supply circuit (output voltage adjustment function 42).

[0040] According to the signal transmission device (electronic device 1) of the third embodiment described above, the bias voltage can be determined based on the results of the noise amount determination unit, so that the output voltage can be dynamically adjusted in accordance with the state of the differential transmission line while the signal transmission system is in operation, thereby achieving dynamic noise reduction. Furthermore, by providing the noise amount determination unit 43 in the information processing LSI 9, the above-described low noise adjustment can be achieved without any additional components.

[0041] <Fourth embodiment> FIG. 7 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the fourth embodiment of the present invention is applied. In the fourth embodiment, the power supply circuit 30 includes an output terminal V OUTP and an output terminal V connected to the N-side terminal of the power supply superposition filter 10. OUTN and a step-up / step-down circuit 44-2 connected to the P-side and N-side, and the output voltages of both are adjusted by an output voltage adjustment function 42. That is, in the electronic device 1 according to this embodiment, the bias voltages applied to the P-side and N-side can be adjusted independently, so that the number of options for the applied bias voltage can be increased even when the potential difference between the P-side and N-side remains the same. This makes it possible to select a setting value for the output voltage that reduces the amount of noise, making it easier to optimize noise reduction.

[0042] The step-up / step-down circuits 44-1 and 44-2 are an example of a voltage output circuit, and can be configured using a step-up charge pump circuit equipped with a function (VCS: Dynamic Voltage Scaling) that can dynamically step up or down the input voltage by register setting, for example. For example, the output voltage can be dynamically changed by appropriately setting the number of voltage change steps (amount of change) as a parameter of the step-up charge pump circuit. Note that in the example of FIG. 7, the output voltage adjustment function 42 and the step-up / step-down circuits 44-1 and 44-2 are shown separately, but the circuit that realizes the output voltage adjustment function 42 may also incorporate the step-up / step-down circuits 44-1 and 44-2.

[0043] <Fifth embodiment> FIG. 8 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the fifth embodiment of the present invention is applied. In the fifth embodiment, the power supply circuit 30 includes an output terminal V OUTP and an output terminal V connected to the N-side terminal of the power supply superposition filter 10. OUTN and an inverting step-up / step-down circuit 45 connected to the P-side, and the output voltages of both are adjusted by an output voltage adjustment function 42. That is, the electronic device 1 according to this embodiment can set a positive bias voltage to be applied to the P-side and a negative bias voltage to be applied to the N-side. Furthermore, it has a function that can independently adjust the bias voltages applied to the P-side and N-side. A feature of the configuration according to this embodiment is that the potential differences from the ground on the P-side and N-side (the absolute values ​​of the two applied bias voltages) can be made approximately the same.

[0044] If the parasitic capacitance of electrostatic protection elements 17P and 17N depends on the potential difference from ground, regardless of the polarity of the bias voltage, applying the same positive and negative potential difference to the P-side signal wiring 6 and the N-side signal wiring 7, as in this configuration, can further reduce imbalances in electrical characteristics. For example, if you want to create a potential difference of 10V between the P-side and N-side, apply a potential of +5V to the P-side and a potential of -5V to the N-side. This means that the same potential difference from ground is applied to electrostatic protection elements 17P and 17N.

[0045] 7 and has a function of dynamically boosting an input voltage to a positive output voltage. The inverting step-up / step-down circuit 45 can be configured using a step-up charge pump circuit having a function (VCS) of dynamically boosting or bucking an input voltage to a negative output voltage by setting a register, for example.

[0046] In the example of FIG. 8, the output voltage adjustment function 42, the step-up / step-down circuit 44, and the inverting step-up / step-down circuit 45 are shown separately, but the circuit that realizes the output voltage adjustment function 42 may also incorporate the step-up / step-down circuit 44 and the inverting step-up / step-down circuit 45.

[0047] As described above, the signal transmission device (electronic device 1) according to the fifth embodiment is configured to adjust the parameters of the voltage output circuit (step-up / step-down circuit 44, inverting step-up / step-down circuit 45) so that a positive voltage is output to the first signal wiring and a negative voltage is output to the second signal wiring using the output voltage adjustment function (output voltage adjustment function 42) of the power supply circuit.

[0048] According to the signal transmission device of this embodiment configured in this manner, it is possible to make the absolute values ​​of the voltages applied to the P-side and N-side electronic components (e.g., electrostatic protection elements) approximately the same, thereby achieving even lower noise compared to the fourth embodiment.

[0049] Sixth Embodiment FIG. 9 is a diagram showing an example of the configuration of a signal transmission system using an electronic device to which a signal transmission device according to the sixth embodiment of the present invention is applied. 9 shows an example of a signal transmission system in which an electronic device 1-1 to which a signal transmission device according to the fifth embodiment (electronic device 1 in FIG. 8) is applied is connected to another external electronic device 1-2 via a twisted pair cable 8. In this signal transmission system, a current supplied from a power supply circuit 30-1 of the electronic device 1-1 is received by a power supply circuit 30-2 of the electronic device 1-2, and the current is distributed to various electronic components mounted on the electronic device 1-2.

[0050] However, the power supply circuit 30-2 (input terminal V IN If the input voltage of the power supply circuit 30-2 (input to the power supply filter 10-2) is specified with respect to ground, the positive and negative voltages output by the power supply circuit 30-1 of the electronic device 1-1 cannot be input as is. For this reason, a feature of this system is that a differential-to-single-ended conversion circuit 46 is interposed between the power supply circuit 30-2 and the power supply superposition filter 10-2 to convert the potential of the differential signal to a potential with respect to ground. By adopting this configuration, it is possible to achieve a noise reduction effect for the entire system. That is, in this embodiment, the electronic device 1-2, which is the communication partner of the electronic device 1-1, is equipped with the differential-to-single-ended conversion circuit 46.

[0051] Fig. 10 is a diagram showing an example of the configuration of a differential-single-ended conversion circuit 46 provided in an electronic device to which a signal transmission device according to a sixth embodiment of the present invention is applied. As shown in Fig. 10, the differential-single-ended conversion circuit 46 can generate a ground-referenced single-ended voltage by utilizing high-precision operational amplifiers 47-1 and 47-2 and a plurality of resistor components 48-1 to 48-5. For example, an example of the differential-single-ended conversion circuit 46 is described on a web page identified by the following URL (Uniform Resource Locator):

[0052] [URL] https: / / www.analog.com / jp / analog-dialogue / raqs / raq-issue-145.html

[0053] In addition, since this circuit configuration has a negative gain, a negative voltage Vin1 is connected to the input terminal V IN3N Then, apply a positive voltage Vin2 to the input terminal V IN3P This circuit configuration is an example of a method for realizing differential-to-single-ended conversion, and may be configured using other circuits having similar functions.

[0054] As described above, the signal transmission system according to the sixth embodiment is a signal transmission system including a first signal transmission device (for example, electronic device 1-1 in FIG. 9) having the configuration of the signal transmission device according to the above-described embodiment, and a second signal transmission device (for example, electronic device 1-2 in FIG. 9) that communicates with the first signal transmission device via a cable (twisted pair cable 8). The second signal transmission device has a third signal wiring (P-side signal wiring 6-2) connected via a cable to a first signal wiring (P-side signal wiring 6-1) to which a first applied voltage of the first signal transmission device is applied, a fourth signal wiring (N-side signal wiring 7-2) connected via a cable to a second signal wiring (N-side signal wiring 7-1) to which a second applied voltage of the first signal transmission device is applied, and a voltage conversion circuit (differential-single-ended conversion circuit 46) that converts the positive and negative differential voltages applied via the third and fourth signal wirings into a voltage referenced to ground.

[0055] In this embodiment configured as above, in a signal transmission device (electronic device 1-2 in FIG. 9) that is the communication partner of the signal transmission device according to the fifth embodiment (electronic device 1-1 in FIG. 9), received power is input to a power circuit via a differential-single-ended conversion circuit on the power receiving side. As a result, according to this embodiment, even when the signal transmission device according to the fifth embodiment is used, the signal transmission system can be established as a power supply system.

[0056] Seventh Embodiment FIG. 11 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the seventh embodiment of the present invention is applied. In the seventh embodiment, the power supply circuit 30 includes an output terminal V OUTP, and the N-side terminal of the power supply superimposing filter 10 is connected to the ground terminal GND, and only the P-side output voltage is adjusted by the output voltage adjustment function 42. That is, in this embodiment, the output voltage is adjusted by the potential of only the P-side, so there is little room for adjusting voltage changes, but the power supply circuit 30 itself can be made of an inexpensive device, so it is a low-cost configuration. However, because a high bias voltage is always applied to the P-side, the parasitic capacitance of the electrostatic protection element 17P tends to be smaller than that of the electrostatic protection element 17N.

[0057] Therefore, a feature of the configuration of this embodiment is that a capacitive load mechanism 18 corresponding to this difference in parasitic capacitance is configured on the printed wiring board. This parasitic capacitance can also be configured as a board pattern on the printed wiring board. That is, if a ground layer is present on the second layer of the printed wiring board, a parallel plate capacitance can be formed by forming an additional electrode structure of a certain size on the top layer. Here, since the capacitance to be adjusted is a small value of 100 fF or less, the size of the board pattern can be a small structure on the order of square millimeters. This capacitive load mechanism can also be configured in other ways as long as it can form a capacitive load.

[0058] As described above, in the signal transmission device (electronic device 1) according to the seventh embodiment, only the parameters related to the first applied voltage (P side) of the voltage output circuit can be adjusted by the output voltage adjustment function (output voltage adjustment function 42) of the power supply circuit, and the potential of the second signal wiring (N side signal wiring 7) is connected to ground.

[0059] According to the signal transmission device of this embodiment having the above configuration, the output voltage of the power supply circuit is adjusted only on the P side, eliminating the need to adjust the output voltage on the N side, thereby achieving low noise with a low-cost configuration. Furthermore, since only one channel of the output of the power supply circuit 30 (power supply IC) is used, an even lower cost configuration can be achieved.

[0060] In this embodiment, the first applied voltage applied to the first signal wiring (P-side signal wiring 6) is higher than the second applied voltage applied to the second signal wiring (N-side signal wiring 7). A capacitive load mechanism (capacitive load mechanism 18) corresponding to the difference in parasitic capacitance between the first electronic component (e.g., electrostatic protection element 17P) and the second electronic component (e.g., electrostatic protection element 17N) is formed on the first signal wiring on the printed wiring board.

[0061] In the present embodiment configured as described above, by adding a capacitive load mechanism to the printed wiring board, it is possible to reduce noise in the differential transmission line with a low-cost configuration.

[0062] Eighth Embodiment FIG. 12 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the eighth embodiment of the present invention is applied. The eighth embodiment is an invention incorporating a function in which a noise amount-bias voltage relationship data storage unit 49 is provided in an information processing LSI 9, a noise amount grasping unit 43 grasps the noise amount of a target signal transmission system when the output voltage is adjusted to the output voltage determined by an output voltage determination unit 41, and the relationship between the set voltage of the output voltage (bias voltage) and the noise amount can be stored as data.

[0063] It should be noted that a nonvolatile memory such as a flash memory can be used for the noise amount-bias voltage relationship data storage unit 49. Alternatively, a volatile memory such as a DRAM can be used for the noise amount-bias voltage relationship data storage unit 49, and the noise amount-bias voltage relationship data can be uploaded to a server outside the vehicle that can communicate with the electronic device 1. The upload destination of this data is not limited to the server, and it may also be a nonvolatile memory (not shown) inside the vehicle. By using a nonvolatile memory inside the vehicle as the storage location for this data, the noise amount-bias voltage relationship data can be managed within the vehicle.

[0064] As described above, the signal transmission device (electronic device 1) according to the eighth embodiment includes a storage unit (e.g., noise amount-bias voltage relationship data storage unit 49) that stores, as correlation data, the relationship between the amount of noise in the differential wiring grasped by the noise amount grasping unit (noise amount grasping unit 43) and the set voltage when communication is performed with at least one of the first applied voltage (P-side signal wiring 6) and the second applied voltage (N-side signal wiring 7) set. Then, the output voltage determination unit (output voltage determination unit 41) determines an instruction value (DC bias voltage) of at least one of the first applied voltage and the second applied voltage based on the relationship between the amount of noise in the differential wiring and the set voltage.

[0065] According to the signal transmission device of this embodiment having the above configuration, by storing data on the relationship between the amount of noise and the set voltage in the memory unit, the output voltage determination unit can retrieve the relationship between the amount of noise and the voltage setting and select an appropriate voltage value for the bias voltage depending on the condition of the differential transmission path.

[0066] <Ninth embodiment> FIG. 13 is a diagram showing an example of the configuration of an electronic device to which a signal transmission device according to the ninth embodiment of the present invention is applied. The ninth embodiment is an invention in which, in addition to the configuration of the eighth embodiment, a signal quality criteria storage unit 50 is provided in the information processing LSI 9, and a function is incorporated to search for a voltage that satisfies the signal quality criteria from the data in the noise amount-bias voltage relationship data storage unit 49, and to define a settable voltage range. Here, the signal quality criteria is information on the noise tolerance of a differential transmission path (for example, differential wiring 5). Details of the processing using this signal quality criteria storage unit 50 will be described in the tenth embodiment of the present invention.

[0067] Similar to the noise amount-bias voltage relationship data storage unit 49, the signal quality criteria storage unit 50 may use a nonvolatile memory or a volatile memory. That is, the signal quality criteria may be managed by the vehicle itself using a nonvolatile memory in the vehicle, or the signal quality criteria may be uploaded or downloaded to or from a server or the like external to the electronic device 1.

[0068] As described above, the signal transmission device (electronic device 1) according to the ninth embodiment includes a storage unit (for example, a signal quality criteria storage unit 50) that stores information about the noise tolerance of the differential wiring. The output voltage determination unit (output voltage determination unit 41) determines an instruction value (bias voltage) of at least one of the first applied voltage (P-side signal wiring 6) and the second applied voltage (N-side signal wiring 7) based on the relationship between the noise amount of the differential wiring and the set voltage and the noise tolerance.

[0069] According to the signal transmission device of this embodiment having the above configuration, it is possible to determine the voltage value of the bias voltage that satisfies the signal quality criteria from the relationship between the noise amount-bias voltage relationship data and the signal quality criteria.

[0070] <Tenth embodiment> FIG. 14 is a diagram showing an example of a process for determining an output voltage range in a signal transmission system using an electronic device to which a signal transmission device according to the tenth embodiment of the present invention is applied. In the tenth embodiment, an invention relating to a process for determining the output voltage range at the time of product shipment or inspection such as a legal vehicle inspection is shown.

[0071] In this embodiment, a reference counterpart device 51 is connected to the electronic device 1 via a twisted pair cable 8, and the two devices communicate with each other. The reference counterpart device 51 is a standard communication module, and serves to relatively evaluate the communication performance of the electronic device 1 connected to this communication module.

[0072] In this state, common noise Nc is applied to the twisted pair cable 8. The applied common noise Nc enters the electronic device 1 via the cable connector 16. The common noise Nc is then converted into differential noise Nd (mode conversion Cm) in accordance with the characteristics of mode conversion loss near the electrostatic protection elements 17N, 17P, and transmitted to the communication LSI 2. The differential noise Nd converted from the common noise Nc increases or decreases according to the output voltage of the power supply circuit 30. By measuring the differential noise Nd transmitted to the communication LSI 2 using the noise amount grasping unit 43 in the information processing LSI 9, it is possible to evaluate the noise performance of the current communication system.

[0073] As described above, the signal transmission system according to the tenth embodiment includes a first signal transmission device (for example, the electronic device 1 in FIGS. 13 and 14) to which the signal transmission device according to the above-described embodiment is applied, and a second signal transmission device (reference opposite device 51 in FIG. 14) that faces the first signal transmission device, and the first signal transmission device and the second signal transmission device are connected by a cable (twisted pair cable 8). Common noise is applied to this cable, and the noise amount is measured by a noise amount grasping unit (noise amount grasping unit 43) of the information processing LSI 9, and the relationship between the noise amount and the set voltage is quantified.

[0074] The process of determining the output voltage range will now be described in more detail with reference to the graph of FIG. 15 and the flow chart of FIG. 15 is a diagram showing an example of a data set obtained using a signal transmission device according to the tenth embodiment of the present invention. In Fig. 15, the horizontal axis represents bias voltage conditions [V], and the vertical axis represents noise amount information. FIG. 16 is a flowchart showing an example of the procedure of a noise amount-bias voltage relationship data acquisition process in an electronic device to which a signal transmission device according to the tenth embodiment of the present invention is applied.

[0075] The information we ultimately want to obtain is a data plot of the relationship between bias voltage conditions and noise amount information, as shown in Figure 15. An example of the procedure for obtaining this information will be explained according to the flowchart in Figure 16. Note that the names of the components used in the explanation of each process in this flowchart refer to those in Figure 14, unless otherwise specified.

[0076] First, in the electronic device 1, the output voltage determination unit 41 of the information processing LSI 9 determines whether the P-side output terminal V OUT The output voltage is set to the lowest value in the settable voltage range using the output voltage adjustment function 42 (step S1).

[0077] Next, communication is started between the electronic device 1 and the reference counterpart device 51 (step S2). In this state, the noise amount grasping unit 43 of the information processing LSI 9 acquires information on the noise amount under this bias voltage condition (hereinafter referred to as "noise amount information") (step S3).

[0078] Next, the output voltage determination unit 41 compares the noise amount information acquired here with the criteria (noise tolerance) stored in the signal quality criteria storage unit 50, and determines whether the noise amount information exceeds the criteria (step S4).

[0079] If the noise amount information exceeds the criteria (YES in step S4), the output voltage determination unit 41 sets the output voltage setting value at that time to the upper limit voltage value (step S5). After the process of step S5, this process ends.

[0080] On the other hand, if the noise amount information is equal to or less than the criterion (NO in step S4), the output voltage determination unit 41 stores the current output voltage and noise amount information in the noise amount-bias voltage relationship data storage unit 49 (step S6).

[0081] Next, the output voltage determination unit 41 increases the output voltage by ΔV, and causes the output voltage adjustment function 42 of the power supply circuit 30 to output the voltage increased by ΔV (step S7).

[0082] Here, the output voltage determination unit 41 compares the output voltage with the settable voltage upper limit (step S8). If the output voltage exceeds the settable voltage upper limit (YES in step S8), this process ends here. On the other hand, if the output voltage is equal to or less than the settable voltage upper limit (NO in step S8), the process returns to step S3 and the operations of steps S3 to S8 are repeated.

[0083] By repeating the above steps S1 to S8, the relationship data between noise amount information and bias voltage shown in FIG. 15 can finally be obtained. Here, two types of data sets, one for product A and one for product B, are shown as examples. For product A, the noise amount information falls below the criterion under all bias voltage conditions within the settable voltage range, resulting in a judgment of no problem (OK). In this case, any voltage value can be selected as the bias voltage for product A. On the other hand, for product B, the noise amount information exceeds the criterion (NG) when the upper limit bias voltage @ bias voltage condition of product B is exceeded. Therefore, under these bias voltage conditions, the settable voltage for product B is determined to be equal to or lower than this upper limit bias voltage @ product B.

[0084] Furthermore, in the signal transmission system according to the tenth embodiment, common noise is applied to a cable (twisted pair cable 8) connecting two signal transmission devices, and the noise amount is measured by a noise amount grasping unit 43 of the information processing LSI 9, and the relationship between the noise amount and the set voltage is quantified. Then, the output voltage determining unit 41 can determine the settable voltage range from the relationship between the noise amount and the set voltage and the noise criteria.

[0085] For ease of understanding, this example has been explained using an example in which the output voltage is adjusted only on the P side, but in reality, by obtaining a similar correlation with combinations of P-side and N-side output voltages, it is possible to determine the settable voltage for combinations of P-side and N-side output voltages. For example, if the potential difference between the P-side and N-side of differential wiring 5 is +10V, if the N-side is non-inverted, the P-side could be set to +12V and the N-side to +2V, and if the N-side is inverted, the P-side could be set to +8V and the N-side to -2V.

[0086] Furthermore, in this embodiment, a simple system has been described in which the amount of noise increases as the bias voltage increases. However, in reality, the relationship between the bias voltage and the amount of noise may be determined by a more complex function. This is because the noise resonance frequency may change, or the relationship between the noise frequency and the noise sensitivity of the device may be complex. Therefore, rather than determining an upper limit bias voltage, it is more practical to find a bias voltage condition that satisfies the criteria by varying the bias voltage value over a range of values, and then set only that bias voltage condition as the settable voltage.

[0087] <Eleventh embodiment> FIG. 17 is a diagram showing an example of the configuration and functions for grasping the amount of noise in a noise amount grasping unit of an electronic device to which a signal transmission device according to an eleventh embodiment of the present invention is applied. The eleventh embodiment shows an example of a method for grasping the amount of noise by the noise amount grasping unit 43 in the information processing LSI 9. Here, a method using an eye waveform monitor circuit 52 (an example of a signal waveform observation circuit) in the communication LSI 2 is shown as an example.

[0088] The eye waveform monitor circuit 52 divides the signal waveform during signal transmission into specific time intervals and overwrites the relationship between the voltage and time of the signal waveform, thereby plotting the relationship between the time of passage and the voltage, forming an eye pattern such as that shown in the lower part of Figure 17. The degree of opening of this eye pattern is the basis for judging the signal quality. All information of such plots can be transmitted to the information processing LSI 9 as eye waveform information 53 to grasp the amount of noise, or only the eye opening voltage V EO and eye opening time T EO It is also possible to extract and utilize only such information.

[0089] As described above, in the signal transmission device according to the twelfth embodiment, the noise amount grasping unit (noise amount grasping unit 43) of the information processing circuit (information processing LSI 9) grasps the noise amount of the differential transmission path by using observation information of the signal waveform observation circuit (eye waveform monitor circuit 52) ​​provided in the communication circuit (communication LSI 2).

[0090] <Twelfth embodiment> FIG. 18 is a diagram showing an example of the configuration and functions for grasping the amount of noise in a noise amount grasping unit of an electronic device to which a signal transmission device according to a twelfth embodiment of the present invention is applied. The twelfth embodiment shows an example of a method for grasping the amount of noise by the noise amount grasping unit 43 in the information processing LSI 9, which is different from that of the eleventh embodiment. Here, a method using a bit error rate evaluation circuit 54 (an example of a communication error rate measurement circuit) in the communication LSI 2 is shown as an example.

[0091] The bit error rate evaluation circuit 54 obtains a bathtub curve as shown in the lower part of FIG. 18 from the bit error occurrence conditions when a signal is transmitted through the differential wiring 5 for a certain period of time. The left graph at the bottom of FIG. 18 is a bathtub curve showing the relationship between the bit error rate and voltage, and the right graph at the bottom of FIG. 18 is a bathtub curve showing the relationship between the bit error rate and time. Information on such a bathtub curve may be transmitted to the information processing LSI 9 as bit error rate information 55 to grasp the amount of noise, or a specific error rate (e.g., BER10) from the bit error rate information 55 may be transmitted to the information processing LSI 9 to grasp the amount of noise. -12 The eye opening voltage V EO and eye opening time T EO It is also possible to extract and utilize only the information such as the eye opening voltage V EO and eye opening time T EO The value of varies depending on the bit error rate. Generally, if the bit error rate is 10 -12 When the value is smaller than , it is determined that the communication quality is maintained.

[0092] In addition, the communication LSI 2 may have a signal quality evaluation function such as SQI (Signal Quality Index), which may be utilized. If there is a similar function that can evaluate the amount of noise and signal quality, it is possible to grasp the amount of noise by utilizing it.

[0093] As described above, in the signal transmission device (electronic device 1) according to the twelfth embodiment, the noise amount grasping unit (noise amount grasping unit 43) of the information processing circuit (information processing LSI 9) grasps the amount of noise in the differential transmission path using measurement information from the communication error rate measuring circuit (bit error rate evaluation circuit 54) provided in the communication circuit (communication LSI 2).

[0094] <Thirteenth embodiment> FIG. 19 is a diagram showing an example of a process for grasping the amount of noise in a signal transmission system using an electronic device to which a signal transmission device according to the thirteenth embodiment of the present invention is applied. The thirteenth embodiment describes an invention relating to a process for determining the amount of noise from the amount of electromagnetic radiation. In this embodiment, a reference opposing device 51 is connected to an electronic device 1 via a twisted pair cable 8, and the two devices communicate with each other. In this state, electromagnetic radiation 56 corresponding to the amount of common noise mode-converted by the electronic device 1 is generated from the twisted pair cable 8. This is measured by an EMI (Electromagnetic Interference) measuring instrument 57 installed outside the electronic device 1, and electromagnetic radiation amount information 58 obtained by this measurement is transmitted to the noise amount determining unit 43. Note that this measurement is preferably performed inside an anechoic chamber to maintain measurement accuracy.

[0095] As described above, the signal transmission system according to the thirteenth embodiment includes a first signal transmission device (for example, the electronic device 1 in FIGS. 12 and 13) to which the signal transmission device according to the above-described embodiment is applied, and a second signal transmission device (reference opposite device 51 in FIG. 19) that faces the first signal transmission device, and the first signal transmission device and the second signal transmission device are connected by a cable (twisted pair cable 8). Electromagnetic noise radiated from this cable is measured by an external measuring device (for example, the EMI measuring device 57), and the noise amount grasping unit (noise amount grasping unit 43) of the information processing LSI 9 calculates the noise amount from the measurement results, thereby quantifying the relationship between the noise amount and the set voltage.

[0096] <Fourteenth embodiment> FIG. 20 is a diagram showing an example of the configuration of a solution system (diagnostic service system) including a signal transmission system using an electronic device to which a signal transmission device according to the fourteenth embodiment of the present invention is applied, and a diagnostic server. In the fourteenth embodiment, a solution is shown in which the present invention is used to determine the output voltage range for a vehicle 59 such as an automobile in operation, and the history of the voltage values ​​of the determined output voltage is stored and managed in a status history memory unit 61 in a diagnostic server 60, thereby utilizing the information for various services such as maintenance and insurance.

[0097] 20, in a vehicle 59, an electronic device 1-2 is connected to an electronic device 1-1 via a twisted pair cable 8, and the two are in communication with each other. In this state, by storing a history of the relationship between bias voltage conditions and noise levels in chronological order, it becomes possible to evaluate the current state of the communication system.

[0098] The process of the diagnostic service in this embodiment will be described in more detail with reference to the graph in FIG. 21 and the flowchart in FIG. FIG. 21 is a diagram showing an example of a data set obtained in a signal transmission system using an electronic device 1-1 to which a signal transmission device according to the 14th embodiment of the present invention is applied, and an example of a predicted curve of the upper limit bias voltage [V]. FIG. 22 is a flowchart showing an example of the procedure for a maintenance requirement information notification process by a solution system (diagnostic service system) including a signal transmission system using an electronic device 1-1 to which a signal transmission device according to the 14th embodiment of the present invention is applied and a diagnostic server 60.

[0099] The information we ultimately want to obtain is a data plot of the relationship between bias voltage conditions and noise amount information, as shown in Fig. 21. An example of the procedure for obtaining this information will be explained according to the flowchart in Fig. 22. Note that the names of the components used in the explanation of each process in this flowchart refer to Fig. 20 unless otherwise specified.

[0100] First, the electronic device 1-1 of the vehicle 59 receives a command to acquire data on the relationship between the amount of noise and the bias voltage from the diagnostic server 60 (step S11).

[0101] Thereafter, the electronic device 1-1 of the vehicle 59 performs control to shift the vehicle 59 to a noise environment initial mode so as to create a constant noise environment (step S12). This vehicle noise environment initial mode refers to shifting the main common noise factors (for example, electric motor control, operation of electric systems such as an air conditioner) to predetermined operation modes so that the external common noise conditions are the same, thereby stabilizing the noise environment.

[0102] In this state, the electronic device 1-1 (output voltage determination unit 41) of the vehicle 59 acquires the noise amount-bias voltage relationship data in accordance with the "procedure for the noise amount-bias voltage relationship data acquisition process" defined in the 10th embodiment (step S13).

[0103] Here, the electronic device 1-1 of the vehicle 59 uploads the acquired data on the relationship between the amount of noise and the bias voltage to the diagnostic server 60 (step S14).

[0104] Next, the diagnostic server 60 adds data acquisition time information to the uploaded noise amount-bias voltage relationship data and stores it in the state history storage unit 61 (step S15). At the same time, the diagnostic server 60 also stores information about the vehicle 59 that is the source of the currently acquired data. Information about the vehicle 59 includes, for example, the vehicle ID. A data set of noise amount-bias voltage relationship data for that specific vehicle is created. An example of this data set is shown in the upper graph of Figure 21. In the upper graph of Figure 21, the horizontal axis represents the bias voltage condition [V] and the vertical axis represents noise amount information. Here, a correlation data set for a certain vehicle A obtained between October 5, 2021 and December 5, 2021 is shown.

[0105] The diagnostic server 60 organizes the feature quantities extracted from the data set of the noise amount-bias voltage relationship data as time-series data and calculates a prediction of future time-series changes (step S16). An example of this time-series change prediction is shown in the graph at the bottom of Fig. 21. In the graph at the bottom of Fig. 21, the horizontal axis represents the test date of the communication test, and the vertical axis represents the upper limit bias voltage [V]. Here, a prediction curve based on the data set of a certain vehicle A is shown.

[0106] Next, the diagnostic server 60 determines whether the period until the maintenance-requiring condition is reached is equal to or less than a certain value based on the result of the above-mentioned prediction calculation (step S17).

[0107] If it is determined in step S17 that the time until the maintenance requirement condition is exceeded (NO in step S17), the diagnostic server 60 determines that there is no problem with the state of the communication system. Then, after a certain period of time has elapsed (step S18), the diagnostic server 60 commands the electronic device 1-1 of the vehicle 59 to perform the data acquisition process of step S11 again.

[0108] On the other hand, if it is determined in step S17 that the period until the maintenance requirement condition is reached is equal to or shorter than the predetermined value (YES in step S17), the diagnostic server 60 notifies the appropriate service provider of the information required for the maintenance (hereinafter referred to as "maintenance requirement information") (step S19). After the processing of step S19, this processing ends.

[0109] For example, by notifying a maintenance company of the necessary maintenance information, the maintenance company can notify the user of the necessary maintenance information. Also, by notifying an insurance company of the necessary maintenance information, the insurance company can take measures such as raising insurance premiums if proper maintenance has not been performed for a long period of time. Also, by notifying a parts company of the necessary maintenance information, it is possible to inform the user of parts that require maintenance.

[0110] As described above, the solution system (diagnostic service system) according to the fourteenth embodiment is a system including, for example, a first signal transmission device (electronic device 1-1) having the configuration of the signal transmission device according to the above-described embodiment, and a second signal transmission device (electronic device 1-2) that communicates with the first signal transmission device via a cable (twisted pair cable 8). The first signal transmission device is mounted on an electronic control unit (ECU) that controls a controlled object. When the electronic control unit is in operation, the electronic device 1-1 uploads data (correlation data) indicating the relationship between the amount of noise in the communication system (differential transmission path) and the set voltage to a diagnostic server (diagnostic server 60). The diagnostic server has a storage unit (status history storage unit 61) that stores the correlation data, a date, and information specific to the electronic control unit (e.g., an ID) as a set. The diagnostic server 60 grasps the status of the communication system based on the history of the correlation data and provides necessary information to various service providers. The diagnostic server also estimates when maintenance is required based on the history of the correlation data, which is data on the relationship between the amount of noise and the set voltage.

[0111] <Fifteenth embodiment> FIG. 23 is a flowchart showing an example of the procedure for maintenance requirement information notification processing by a solution system (diagnostic service system) including a signal transmission system using an electronic device 1-1 to which a signal transmission device according to the fifteenth embodiment of the present invention is applied.

[0112] In the fifteenth embodiment, the present invention is used to determine an output voltage range for a vehicle 59 such as an automobile in operation, and a status history storage unit 61 is provided in the vehicle 59 to store and manage the history of the determined output voltage values, thereby directly indicating the need for maintenance to the driver. In the fourteenth embodiment, data was managed on the diagnostic server 60 side, but the present invention is characterized in that data is managed only by the vehicle 59. The procedure for notifying information about the need for maintenance will be described in detail below using the flowchart in Figure 23.

[0113] First, in the vehicle 59, for example, the electronic device 1-1 starts the engine (step S21).

[0114] Thereafter, the electronic device 1-1 of the vehicle 59 performs control to shift the vehicle 59 to a noise environment initial mode so as to create a constant noise environment (step S22).

[0115] In this state, the electronic device 1-1 (output voltage determination unit 41) of the vehicle 59 acquires the noise amount-bias voltage relationship data in accordance with the "procedure for the noise amount-bias voltage relationship data acquisition process" (Figure 16) defined in the 10th embodiment (step S23).

[0116] Next, the electronic device 1-1 of the vehicle 59 adds data acquisition time information to the acquired noise amount-bias voltage relationship data and stores it in the state history storage unit 61 inside the vehicle 59 (step S24).

[0117] Next, the electronic device 1-1 of the vehicle 59 organizes the feature amounts extracted from the data set of the noise amount-bias voltage relationship data as time-series data, and calculates a prediction of future time-series changes (step S25).

[0118] Next, the electronic device 1-1 determines whether the period until the maintenance-requiring condition is reached is equal to or less than a certain value based on the result of the above-mentioned prediction calculation (step S26).

[0119] If it is determined in step S26 that the time until the maintenance requirement condition is reached exceeds a certain value (NO in step S26), the electronic device 1-1 determines that there is no problem with the state of the communication system. Then, after a certain period of time has elapsed (step S27), the electronic device 1-1 performs the engine start process of step S21 again.

[0120] On the other hand, if it is determined in step S26 that the period until the maintenance-required condition is reached is equal to or shorter than the predetermined value (YES in step S26), the electronic device 1-1 notifies the driver of the maintenance-required information (step S28). After the processing of step S28, this processing ends. Note that the above-described processing in FIG. 23 may be executed by another electronic device instead of the electronic device 1-1.

[0121] As described above, the solution system (diagnostic service system) according to the fifteenth embodiment is a system including, for example, a first signal transmission device (electronic device 1-1) having the configuration of the signal transmission device according to the above-described embodiment, and a second signal transmission device (electronic device 1-2) that communicates with the first signal transmission device via a cable (twisted pair cable 8). The first signal transmission device is mounted on an electronic control unit (ECU) that controls the controlled object. The electronic control unit is in an operational state, and the electronic device 1-1 has a storage unit (e.g., corresponding to the state history storage unit 61 in FIG. 20) that stores data (correlation data) indicating the relationship between the amount of noise in the communication system (differential transmission path) and the set voltage, along with a date. The electronic device 1-1 grasps the state of the communication system based on the history of the correlation data and provides the driver with necessary information. The electronic device 1-1 also estimates when maintenance is required based on the history of the correlation data, which is data on the relationship between the amount of noise and the set voltage.

[0122] <16th embodiment> FIG. 24 is a block diagram showing an example of the functional configuration of an information processing LSI of an electronic device to which a signal transmission device according to the sixteenth embodiment of the present invention is applied. In the embodiments described so far, the output bias voltage is determined based only on the amount of noise in the differential transmission line, but in reality, the bias voltage is also related to the power consumption of the communication system. For example, if the voltage is set low, the supply current in the power supply superimposed on the connected device with a certain power consumption will increase, and as a result, the power consumption due to the resistance loss in the transmission line may increase.

[0123] For this reason, in this embodiment, a power consumption-noise priority determination unit 64 is provided in the information processing LSI 9 so that the relationship between the power consumption and the set voltages of the P-side signal wiring 6 and the N-side signal wiring 7 can be taken into consideration to determine an optimal voltage value overall. The power consumption-noise priority determination unit 64 sends the priority determination results to the output voltage determination unit 41. For example, by providing the power consumption-noise priority determination unit 64 with a determination function that, when noise environment information 63 is input, enables the selection of a set voltage that prioritizes suppression of power consumption if the noise environment is good, it becomes possible to configure a signal transmission system that strikes a balance between the amount of noise and power consumption.

[0124] The noise environment information 63 is information that indicates the noise environment of the vehicle in which the electronic device 1 is mounted. For example, the noise environment information 63 may be map information including information on structures, etc., or an electromagnetic wave map (electromagnetic wave distribution map) that indicates the strength of electromagnetic waves at each location.

[0125] As described above, in the signal transmission device (electronic device) according to the sixteenth embodiment, the output voltage determination unit (output voltage determination unit 41) of the information processing circuit (information processing LSI 9) determines the instruction value of at least one of the first applied voltage (P side) and the second applied voltage (N side) based on the noise environment information and on the priority between the power consumption when communicating via a cable connected to the differential wiring and the amount of noise generated in the differential wiring.

[0126] <Seventeenth embodiment> FIG. 25 is a diagram showing an example of the configuration of a solution system including a signal transmission system using an electronic device to which a signal transmission device according to the seventeenth embodiment of the present invention is applied, an OTA server, and a diagnostic server. The seventeenth embodiment describes a solution that provides a process for re-determining the output voltage range when the noise environment of a vehicle 59, such as an automobile, changes due to a software update, such as over-the-air (OTA), during operation. In this embodiment, a software update is performed on the vehicle 59 from an OTA server 70 via a network 65, such as the Internet. At this time, software update information 71 is transmitted from the OTA server 70 to a diagnostic server 60, and a current profile change determination unit 66 on the diagnostic server 60 side determines whether the current profile associated with noise in the vehicle 59 has changed due to the software update. If it is determined as a result of the determination that the current profile of the vehicle 59 has changed, an optimal bias resetting test command unit 67 issues a command to the vehicle 59 to reset the optimal bias graph (see FIG. 15 ).

[0127] For example, when the noise environment is good (there is little noise), the output voltage determination unit 41 (FIG. 24) sets the output voltage to a value a predetermined number of steps higher than the previous voltage value or the standard value, as a set voltage that prioritizes power consumption.

[0128] FIG. 26 is a diagram showing an example of how to utilize the solution system in the seventeenth embodiment of the present invention. An application example of the solution system according to this embodiment will be described with reference to FIG. 26. The upper graph in FIG. 26 shows the relationship between frequency [MHz] and current [A] contributing to noise. The frequency is the main frequency generated by the vehicle itself, and examples include the rotation speed of the engine or motor. For example, if a software update changes the operation of the DC / DC converter in the vehicle, the rotation frequency of the motor that rotates the drive wheels will change. Before OTA, as indicated by the dashed line, there are peaks at frequency A and frequency C.

[0129] On the other hand, the graph at the bottom of Figure 26 shows the relationship between frequency [MHz] and mode conversion loss [dB] under various bias conditions. In this example, under bias condition A (solid line), the mode conversion loss at frequencies A and C is small, so bias condition A is set as the optimal voltage condition before OTA.

[0130] However, when the software is updated via OTA, we assume that a change occurs such that a peak occurs at frequency B, as shown by the solid line in the upper graph of Fig. 26. In this case, since bias condition A has a mode conversion loss peak at frequency B, it can be seen that after OTA, the voltage becomes inappropriate as a noise condition.

[0131] Therefore, it is desirable to select bias conditions such as bias condition C (dotted line with a narrow pitch) that have peaks at frequencies A and C but no peak at frequency B. By providing an optimal bias resetting test command unit 67 in the diagnostic server 60 and incorporating a process for searching for such bias conditions, it becomes possible to provide a communication system that enables noise optimization even when software is updated.

[0132] As described above, in the solution system (diagnostic service system) according to the seventeenth embodiment, a signal transmission system (communication system) mounted on a mobile object such as a vehicle, a software update management server (OTA server 70) that manages software updates within the vehicle, and a diagnostic server are connected to each other via a network so that they can communicate with each other. In this system, software update information (software update information 71) from the software update management server (OTA server 70) is transmitted to the diagnostic server. The diagnostic server detects a change in the amount of noise from the software update information and, based on the information on the change in the amount of noise, issues a command to an electronic device within the vehicle to reacquire correlation data between the amount of noise and the set voltage.

[0133] <Computer hardware configuration> Next, the hardware configurations of the computers implemented in the electronic devices 1, 1-1, and 1-2 to which the signal transmission devices according to the embodiments are applied, the diagnostic server 60, and the OTA server 70 will be described.

[0134] 27 is a block diagram showing an example of the hardware configuration of a calculator 80. The calculator 80 is an example of hardware used as a computer that realizes the functions of the electronic devices 1, 1-1, and 1-2, the diagnostic server 60, and the OTA server 70 according to this embodiment. Each device and each server according to this embodiment realizes the function of each embodiment by the calculator 80 (computer) executing a program.

[0135] The computer 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, and a RAM (Random Access Memory) 83, which are all connected to a bus. The computer 80 further includes a non-volatile storage 86 and a communication interface 87.

[0136] The CPU 81 reads out program code of software that realizes each function according to the present embodiment from the ROM 82, loads it into the RAM 83, and executes it. Variables, parameters, etc. that arise during the calculation processing of the CPU 81 are temporarily written to the RAM 83, and these variables, parameters, etc. are read out as appropriate by the CPU 81. The CPU 81 executes the program code read out from the ROM 82, thereby realizing each function according to each embodiment. However, other processors such as an MPU (Micro Processing Unit) may be used instead of the CPU 81.

[0137] The nonvolatile storage 86 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), an optical disk, a magneto-optical disk, or a nonvolatile memory. In addition to an operating system (OS) and various parameters, the nonvolatile storage 86 may also store programs for operating the computer 80. The ROM 82 and the nonvolatile storage 86 store programs, data, and the like necessary for the CPU 81 to operate, and are used as an example of a computer-readable non-transitory storage medium that stores programs executed by the computer 80.

[0138] The communication interface 87 may be, for example, a network interface card (NIC), and various data may be transmitted and received between devices via a local area network (LAN) or dedicated line connected to a terminal of the NIC. For example, the interface through which the in-vehicle electronic device 1 etc. acquires sensor data from a sensor and the interface through which the electronic device 1 etc. transmits control commands to actuators are configured by the communication interface 87. Furthermore, data communication between the in-vehicle electronic device 1 etc., the diagnostic server 60, and the OTA server 70 is performed by the communication interface 87.

[0139] <Modification> The above-described embodiments and various modifications are merely examples, and the present invention is not limited to these embodiments and modifications as long as the features of the invention are not impaired. Furthermore, the above-described various embodiments and modifications have been described in detail and specifically to clearly explain the present invention, and are not necessarily limited to those including all of the components described. Other aspects conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0140] Furthermore, the above-described configurations, functions, processing units, etc. may be partially or entirely realized in hardware, for example, by designing them as integrated circuits, etc. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

[0141] In addition, in this specification, processing steps describing chronological processing include not only processing that is performed chronologically in the order described, but also processing that is not necessarily performed chronologically but is performed in parallel or individually (for example, processing by objects).

[0142] In addition, in each of the above-described embodiments, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0143] 1...Electronic device, 2...Communication LSI, 5...Differential wiring, 6...P-side signal wiring, 7...N-side signal wiring, 8...Twisted pair cable, 9...Information processing LSI, 10...Power supply superposition filter, 14N, 14P...AC coupling capacitor, 15...Common mode choke coil (CMCC), 16...Cable connector, 17N, 17P...Electrostatic protection element, 18...Capacitive load mechanism, 30...Power supply circuit, 41...Output voltage determination unit, 42...Output voltage adjustment function, 43...Noise amount grasping unit, 44...Step-up / step-down circuit, 45...Inverting step-up / step-down circuit, 46...Differential-single-ended conversion circuit, 47-1, 47-2...Operational amplifier, 48-1 to 48-5...Resistance component, 49...No Noise amount-bias voltage relationship data storage unit, 50...signal quality criteria storage unit, 51...reference counterpart device, 52...eye waveform monitor circuit, 53...eye waveform information, 54...bit error rate evaluation circuit, 55...bit error rate information, 56...electromagnetic radiation, 57...EMI measuring instrument, 58...electromagnetic radiation amount information, 59...vehicle, 60...diagnosis server, 61...state history storage unit, 62...prediction curve, 63...noise environment information, 64...power consumption-noise priority determination unit, 65...network, 70...OTA server, 71...software update information, 66...current profile change determination unit, 67...optimal bias resetting test command unit

Claims

1. a first signal wiring and a second signal wiring that constitute a differential wiring; a communication circuit for transmitting a differential signal to the differential wiring; an information processing circuit connected to the communication circuit and configured to process various types of information; a first electronic component disposed between the first signal wiring and a ground wiring; a second electronic component disposed between the second signal wiring and the ground wiring; a power supply circuit having a voltage output circuit that outputs a first applied voltage to the first signal wiring and a second applied voltage to the second signal wiring; a filter component disposed between the power supply circuit and each of the first signal wiring and the second signal wiring; A signal transmission device comprising: the information processing circuit has an output voltage determination unit that determines an instruction value of at least one of the first applied voltage and the second applied voltage that are applied by the power supply circuit and sends the determined instruction value to the power supply circuit, and a noise amount grasping unit that grasps an amount of noise occurring in the first signal wiring and the second signal wiring, the output voltage determiner determines the instruction value so as to reduce the amount of noise for at least one of the first applied voltage and the second applied voltage based on the result of the noise amount determination by the noise amount determiner, and outputs the instruction value to the power supply circuit; The power supply circuit has an output voltage adjustment function that adjusts parameters of the voltage output circuit so that the first applied voltage and the second applied voltage that reflect the instruction value received from the output voltage determination unit are output to the first signal wiring and the second signal wiring. Signal transmission device.

2. The output voltage adjusting function of the power supply circuit adjusts a parameter of the voltage output circuit so that a positive voltage is output to the first signal wiring and a negative voltage is output to the second signal wiring.

2. The signal transmission device according to claim 1.

3. a storage unit configured to store, when communication is performed with at least one of the first applied voltage and the second applied voltage set, a relationship between the amount of noise in the differential wiring grasped by the noise amount grasping unit and a set voltage as correlation data; The output voltage determination unit, based on the relationship between the amount of noise in the differential wiring and the set voltage, determining the indicated value of at least one of the first applied voltage and the second applied voltage; 2. The signal transmission device according to claim 1.

4. a storage unit for storing information about the noise tolerance of the differential wiring; The output voltage determination unit determines the indicated value of at least one of the first applied voltage and the second applied voltage based on the relationship between the amount of noise in the differential wiring and the set voltage, and the noise tolerance.

4. The signal transmission device according to claim 3.

5. The noise amount grasping unit grasps the noise amount using observation information of a signal waveform observation circuit provided in the communication circuit.

2. The signal transmission device according to claim 1.

6. The noise amount grasping unit grasps the noise amount using measurement information from a communication error rate measuring circuit included in the communication circuit.

2. The signal transmission device according to claim 1.

7. The output voltage determination unit determines the instruction value of at least one of the first applied voltage and the second applied voltage based on noise environment information and on a priority between power consumption when communication is performed via a cable connected to the differential wiring and an amount of noise generated in the differential wiring.

5. A signal transmission device according to claim 3 or 4.

8. A first signal wiring and a second signal wiring that constitute a differential wiring; a communication circuit for transmitting a differential signal to the differential wiring; an information processing circuit connected to the communication circuit and configured to process various types of information; a first electronic component disposed between the first signal wiring and a ground wiring; a second electronic component disposed between the second signal wiring and the ground wiring; a power supply circuit having a voltage output circuit that outputs a first applied voltage to the first signal wiring and a second applied voltage to the second signal wiring; a filter component disposed between the power supply circuit and each of the first signal wiring and the second signal wiring; A signal transmission device comprising: the information processing circuit has an output voltage determination unit that determines an instruction value of at least one of the first applied voltage and the second applied voltage that are applied by the power supply circuit and sends the determined instruction value to the power supply circuit; the power supply circuit has an output voltage adjustment function that adjusts parameters of the voltage output circuit so that the first applied voltage and the second applied voltage that reflect the instruction value received from the output voltage determination unit are output to the first signal wiring and the second signal wiring, the output voltage adjusting function of the power supply circuit is capable of adjusting only a parameter related to the first applied voltage of the voltage output circuit; The potential of the second signal wiring is connected to ground. Signal transmission device.

9. A signal transmission system including a first signal transmission device having the configuration of the signal transmission device according to claim 2 and a second signal transmission device that communicates with the first signal transmission device via a cable, the second signal transmission device, a third signal wiring connected via the cable to a first signal wiring to which a first applied voltage of the first signal transmission device is applied; a fourth signal wiring connected via the cable to a second signal wiring to which a second applied voltage of the first signal transmission device is applied; a voltage conversion circuit that converts a positive / negative differential voltage applied via the third signal wiring and the fourth signal wiring into a ground-referenced voltage. Signal transmission system.

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