KR20200137687A - Vehicular communication system including a vibration suppression circuit - Google Patents

Abstract

The present invention relates to a vehicle communication system including a shaking suppression circuit, which can reduce a shaking phenomenon due to a state change in a vehicle network environment. According to an embodiment of the present invention, a controller area network (CAN) transceiver operated in a CAN comprises: a CAN controller; a CAN transceiver connected to the CAN controller; and a selective shaking suppression circuit including a capacitor and a shaking magnitude suppressing circuit serially connected to the capacitor. The selective shaking suppression circuit is disposed between CAN-H and CAN-L lines, and the capacitor can be short-circuited when a first communication state is converted into a second communication state. According to another embodiment of the present invention, the vehicle communication system configuring a CAN comprises: a CAN controller; a CAN transceiver connected to the CAN controller; and a selective shaking suppression circuit including a switch control unit, a switch controlled by the switch control unit; and a shaking magnitude suppression circuit serially connected to the switch. The selective shaking suppression circuit is disposed between the CAN-H and CAN-L lines. Also, a switch controller can be controlled to turn on the switch when the first communication state is converted into the second communication state on the basis of an input signal (TxD) of the CAN transceiver.

Description

Vehicle communication system including a vibration suppression circuit

The present invention relates to a communication system for a vehicle including a vibration suppression circuit capable of reducing a vibration phenomenon due to a state change in a vehicle network environment.

In recent years, electronic equipment systems mounted on vehicles are increasing day by day, and their complexity is also increasing. As the number of controllers increases, the number of inputs/outputs also increases significantly. In the past, many communication wires were used for input/output between remote controllers, but as the complexity increases, there are limitations in cost, space, and weight increase due to the increase in physical wires. Therefore, what was introduced is a wired communication interface such as CAN (Controller Area Network).

The CAN communication method is a method in which each controller is connected in parallel with two wires (CAN LOW, CAN HIGH) and exchanges data through a specified CAN protocol (data transmission method, data transmission rate, priority, etc.). Because a lot of information can be exchanged between controllers with just two wires, the CAN communication method is a method that has improved the vehicle system dramatically. Recently, a flexible data-rate (CAN-FD) method has also been introduced for faster data transmission.

The CAN (Controller Area Network) protocol constituting the backbone network of the vehicle network is implemented by the CAN controller 120 and the CAN transceiver 130.

Referring to FIG. 1, the CAN protocol includes a CAN controller 120 and a CAN transceiver 130. In addition, the CAN protocol is connected to a microcomputer (hereinafter referred to as MCU; 110). The CAN controller 120 has an internal buffer and transmits it to the MCU 110 to determine whether data is valid for a received message transmitted from the transceiver. In the case of a transmission message, the data to be transmitted from the MCU 110 is transmitted to the CAN transceiver 130.

The CAN transceiver 130 converts transmission/reception data transmitted from the CAN bus line or the MCU 110 into an electrical signal. That is, the CAN transceiver 130 converts data transmitted from the MCU 110 into CAN communication data, and converts the CAN communication data transmitted from the CAN bus line into data for transmission/reception of the MCU 110.

The structure of the CAN transceiver 130 will be described in detail with reference to FIG. 2. 2 shows an example of a typical CAN transceiver structure.

Referring to FIG. 2, the CAN transceiver 130 may include a controller 131, an output terminal 132, and an input terminal 133. The output terminal 132 includes two transistors (Tr1, Tr2) connected to the CAN-H and CAN-L lines, respectively, and the controller 131 controls the transistors (Tr1, Tr2) to operate the CAN transceiver 130. The state can be changed from a dominant state (corresponding to 0) to a recessive state (corresponding to 1) or vice versa. For example, in the dominant state, the transistors Tr1 and Tr2 are turned on, so that a current flowing from the CAN-H line to the CAN-L line may be supplied. Therefore, a voltage difference may occur between the CAN-H line and the CAN-L line. Conversely, in the recessive state, the transistors Tr1 and Tr2 are turned off, so that no current flows from the CAN-H line to the CAN-L line.

3 shows the configuration of a general CAN bus line. FIG. 4 shows a terminated CAN node of the CAN bus line shown in FIG. 3, and FIG. 5 shows an unterminated CAN node of the CAN bus line shown in FIG. 3.

3 to 5, a CAN bus line generally has a large inductance component due to a long bus line, but with respect to a terminated CAN node 200 operating as a transmitter The CAN bus line acts as an inductive load. However, if current is supplied between the CAN-H line and the CAN-L line in the dominant state, and the recessive state is also converted, the current changes to '0' in a short moment. In this case, when the current i flowing through the inductive load changes for a short time dt, a negative transient voltage (Vind) is generated.

Here, L is the inductance of the CAN bus line, which is proportional to the length of the bus line and inversely proportional to the thickness, the amount of current change di is a negative current (-I) having a size of usually tens mA, and the time change dt is several tens. From ns to hundreds of ns, it is small enough to make di/dt large enough. Therefore, it occurs when a relatively large negative voltage is converted from the dominant state to the recessive state. The generated negative voltage (Vind) proceeds along the CAN bus line branch line and causes waveform reflection due to impedance mismatching at the branch point connected to the main line. In this case, as the number of branch lines connected to the branch point increases, the size of the reflected waveform increases. Meanwhile, the waveform reflected from the branch point is reflected back by impedance mismatching at the input terminal of the CAN node. However, at the branch point, the reflection coefficient has a negative sign, and at the input of the CAN node, the reflection coefficient has a positive sign. As a result, the generated voltage (Vind) is reflected from the branch point and the input terminal of the CAN node because the phase is reversed, thereby forming a ringing waveform.

When the vibration phenomenon occurs according to the above-described principle, especially when the data communication speed is high such as CAN-FD, when the sampling time is short, it is difficult to stably measure the signal state. In order to suppress such vibration, a method of connecting a resistor controlled by a switch to the CAN-H line and CAN-L line is also suggested, but the resistance connection method not only reduces the number of connectable CAN nodes and reduces the bus voltage level. Rather, it is based on the measurement of the bus voltage level, which causes a delay due to switch control.

In the CAN network as described above, a problem may occur due to impedance mismatching. Impedance mismatching is i) a branch point where the main line and the branch line of the CAN bus line are connected, ii) an Unterminated CAN node 300 that does not have a termination resistor that absorbs the CAN bus line and transmission energy. ) Can occur at the input of the CAN node. In the case of i), the degree of impedance mismatching is determined by the number of branches connected to one branch point, and in the case of ii), it may be determined by the input impedance (Z _C ) of the CAN node viewed from the CAN bus line.

However, the input impedance Z _C of the CAN node viewed from the CAN bus line may vary depending on the operating state of the CAN transceiver 130 described above. For example, in the dominant state, the transistors Tr1 and Tr2 are turned on as described above with reference to FIG. 2, and the impedance of the output terminal acts in parallel with the impedance of the input terminal 133 in the transceiver. Accordingly, the input impedance is substantially lowered, and the degree of impedance mismatching is not large. However, in the recessive state, the transistors Tr1 and Tr2 are turned off, so that only the input impedance of the input terminal is visible. Consequently, in the recessive state, since the input impedance is relatively high, the degree of impedance mismatching increases.

Therefore, when the dominant state is converted to the recessive state (dominant-to-recessive state), the impedance mismatching at the input terminal of the CAN node becomes the greatest, so that the reflected wave due to the voltage difference between the two states increases, resulting in ringing. There is a problem that the phenomenon occurs. In particular, the vibration phenomenon is the biggest problem that occurs when the CAN node connected to the branch line operates as a transmitter.

The present invention is to provide a communication system for a vehicle including a vibration suppression circuit capable of suppressing a vibration phenomenon in a CAN communication environment.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems that are not mentioned will be clearly understood by those of ordinary skill in the technical field to which the present invention belongs from the following description. I will be able to.

CAN controller for solving the above problems; A CAN transceiver connected to the CAN controller; And a capacitor, an optional vibration suppression circuit including a vibration magnitude suppression circuit connected in series with the capacitor, wherein the selective vibration suppression circuit is disposed between the CAN-H and CAN-L lines, and the capacitor is in a first communication state. When converted to the second communication state, it may be shorted.

In addition, a communication system for a vehicle according to another embodiment of the present invention includes a CAN controller; A CAN transceiver connected to the CAN controller; And a switch control unit, a switch controlled by the switch control unit, and an optional vibration suppression circuit including a vibration size suppression circuit connected in series to the switch, wherein the selective vibration suppression circuit is between the CAN-H and CAN-L lines. And the switch controller may control the switch to be turned on when it is converted from a first communication state to a second communication state based on an input signal TxD of the CAN transceiver.

According to at least one embodiment of the present invention, there are the following effects.

Vibration can be suppressed by acting on an unterminated CAN node operating as a transmitter, which causes the greatest vibration problem during CAN bus operation in a vehicle network.

In particular, the capacitor-based selective vibration suppression circuit has a very simple structure because an additional circuit is simple and no control is required.

In addition, the switch-based selective vibration suppression circuit has the advantage of short delay time and optimal timing control by using the Tx signal directly.

The effects that can be obtained in the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those of ordinary skill in the art from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are provided to aid understanding of the present invention and provide embodiments of the present invention together with a detailed description. However, the technical features of the present invention are not limited to a specific drawing, and features disclosed in each drawing may be combined with each other to constitute a new embodiment.
1 is a simple implementation example of the CAN protocol.
2 shows an example of a typical CAN transceiver structure.
3 shows an example of a general CAN bus.
4 shows a typical terminated CAN node.
5 shows a typical unterminated CAN node.
6 shows an example of a vehicle network configuration provided with a capacitor-based selective vibration size suppression circuit according to an embodiment of the present invention.
7 shows an example of a network configuration for a vehicle equipped with a switch-based selective vibration size suppression circuit according to an embodiment of the present invention.
8 is a diagram showing the configuration of each vibration amplitude suppression circuit according to an embodiment of the present invention.

Hereinafter, an apparatus and various methods to which embodiments of the present invention are applied will be described in more detail with reference to the drawings. The suffixes "module" and "unit" for components used in the following description are given or used interchangeably in consideration of only the ease of preparation of the specification, and do not have meanings or roles that are distinguished from each other by themselves.

In the description of the embodiment, in the case of being described as being formed in "top (top) or bottom (bottom)", "before (front) or after (back)" of each component, "top (top) or bottom (Bottom)" and "Before (front) or after (back)" include both components formed by direct contact with each other or one or more other components disposed between the two components.

In addition, in describing the constituent elements of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the component is not limited by the term. When a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected or connected to that other component, but another component between each component It should be understood that elements may be “connected”, “coupled” or “connected”.

In addition, the terms such as "include", "consist of" or "have" described above mean that the corresponding component may be embedded unless otherwise stated, excluding other components Rather, it should be interpreted as being able to further include other components. All terms, including technical or scientific terms, unless otherwise defined, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms commonly used, such as terms defined in the dictionary, should be interpreted as being consistent with the meaning in the context of the related technology, and are not interpreted as ideal or excessively formal meanings unless explicitly defined in the present invention.

6 shows an example of a vehicle network configuration provided with a capacitor-based selective vibration size suppression circuit according to an embodiment of the present invention.

6, the configuration of the CAN controller 120 and the CAN transceiver 130 itself may be a general configuration. However, the optional vibration suppression circuit 400 including the capacitor C and the vibration amplitude suppression circuit 140 connected in series to the capacitor C may be disposed between the CAN-H line and the CAN-L line.

In this case, when the CAN transceiver 130 is in a dominant state, a current may flow when the potential difference from the CAN-H line to the CAN-L line is greater than or equal to the turn-on voltage.

Thereafter, when the CAN transceiver 130 is converted from the dominant state to the recessive state, the capacitor C is shorted, and the vibration amplitude suppression circuit 140 is connected to the CAN-H line and the CAN-L line. Then, the vibration size suppression circuit 140 operates.

In this case, the capacitor C may have an appropriate capacity to be short when converting from a dominant state to a recessive state in consideration of the transition time of the CAN bus line signal.

Meanwhile, when the CAN transceiver 130 is in a steady-state after completion of the telephone operation, the capacitor C is opened and the CAN-H, CAN-L and the vibration suppression circuit 140 are separated. It will be. Due to this, the vibration amplitude suppression circuit 140 does not affect the CAN bus signal.

The selective vibration suppression circuit 400 including the capacitor C may have an advantage of simple circuit configuration and application.

7 shows an example of a network configuration for a vehicle equipped with a switch-based selective vibration size suppression circuit according to an embodiment of the present invention.

7 shows the configuration of the CAN controller 120 and the CAN transceiver 130 itself may be a general configuration.

The optional vibration size suppression circuit 500 may include a switch control unit 141, a switch SW controlled by the switch control unit 141, and a vibration size suppression circuit 140 connected in series to the switch SW. .

Here, the switch SW and the vibration level suppression circuit 140 are disposed between the CAN-H line and the CAN-L line. Therefore, when the switch (SW) is turned off, current can flow when the potential difference from the CAN-H line to the CAN-L line is more than the turn-on voltage, and vice versa, the CAN-H line Current cannot flow in the -L line direction. In addition, the switch controller 141 may control the switch SW between the CAN controller 120 and the CAN transceiver 130 based on the input signal TxD of the CAN transceiver 130.

Accordingly, when the selective vibration magnitude suppression circuit 500 is converted from the dominant state to the recessive state, the switch control unit 141 may determine the conversion time based on the input signal TxD. Thereafter, the switch control unit 141 may turn on the switch SW through a switch control signal. At this time, the switch SW may be maintained in the on state for a time when the shaking is a problem.

On the other hand, when the CAN transceiver 130 is in a steady-state after completion of the telephone operation, the switch (SW) is turned off to separate the CAN-H, CAN-L and the vibration suppression circuit 140 It will be. Due to this, the vibration amplitude suppression circuit 140 does not affect the CAN bus signal.

The selective vibration suppression circuit 500 including the switch SW has the advantage of being able to precisely control the operation of the vibration amplitude suppression circuit, and can be connected only when the dominant state is converted to the recessive state.

8 is a diagram showing the configuration of each vibration amplitude suppression circuit according to an embodiment of the present invention.

Referring to FIG. 8, a diagram showing a vibration amplitude suppression circuit including a resistor according to an embodiment of the present invention.

The vibration amplitude suppression circuit 140 illustrated in FIG. 8A may include a resistance having the same size Zc as the characteristic impedance of the CAN bus line. When the vibration amplitude suppression circuit 140 is connected to the CAN bus line, a resistor of size Zc is connected between CAN-H and CAN-L, and the resistance matches the input terminal impedance of the unterminated CAN node 300. do. Accordingly, the resistance-based vibration size suppression circuit matches the impedance of the input terminal of the unterminated CAN node with the characteristic impedance of the bus line to prevent the generation of additional reflected waves and suppress the vibration.

Meanwhile, the vibration size suppression circuit 140 shown in FIG. 8(b) is mostly similar to that of 8(a), but may include a diode D. When the vibration amplitude suppression circuit 140 is connected to the CAN bus, a resistor and a diode D having the same size Zc as the characteristic impedance between CAN-H and CAN-L may be configured in parallel connection. That is, the anode of the diode D may be connected to the CAN-H line, and the cathode may be connected to the CAN-L line. Therefore, the anode of the diode D can limit the positive voltage difference (Vdiff = CAN-H voltage-CAN-L voltage).

Meanwhile, the vibration size suppression circuit 140 shown in FIG. 8(c) is mostly similar to that of 8(b), but may include a plurality of diodes D1 and D2. When the vibration amplitude suppression circuit 140 is connected to the CAN bus, a resistance having the same size (Zc) as the characteristic impedance, a first diode, and a second diode may be connected in parallel between CAN-H and CAN-L.

In this case, the anode of the first diode D1 may be connected to the CAN-H line, and the cathode may be connected to the CAN-L line. That is, the first diode D! may be connected to the CAN-H line and the CAN-L line in a forward direction.

In addition, the anode of the second diode D2 may be connected to the CAN-L line, and the cathode may be connected to the CAN-H line. That is, the second diode D2 may be connected in a reverse direction to the CAN-H line and the CAN-L line.

Accordingly, the plurality of diodes D1 and D2 can limit both the positive voltage difference Vdiff and the negative voltage difference Vdiff.

Hereinafter, a method of controlling each selective vibration amplitude suppression circuit shown in FIG. 8 will be described. According to FIG. 8, when the dominant state is converted to the recessive state in common, the connection can be made at an appropriate time and for an appropriate time. In the following description, it is assumed that the forward voltage drop (VF) of the diodes (D, D1, D2) has a value smaller than the detection level in the recessive state, and if necessary, a small resistance in series with the diode is It is assumed that it may be connected.

At this time, in the case of FIG. 8(a), the resistance is connected from the CAN-H line to the CAN-L line. A negative voltage is generated in the transmitter, and the phase is reversed at the branch point, and a reflected wave having a positive magnitude is generated. The reflected wave thus generated reaches the input terminal of the transmitter, and impedance matching is performed by the resistance of the vibration amplitude suppression circuit. In this case, by matching the impedance of the input terminal of the unterminated CAN node 300 for a certain period of time, generation of additional reflected waves may be suppressed. That is, the reflected wave generated at the branch point is transmitted without generating the reflected wave, and vibration after the reflected wave at the branch point of the CAN bus line can be prevented.

Next, referring to FIG. 8(b), a diode D and a resistor connected from the CAN-H line to the CAN-L line and in the forward direction are connected in parallel.

As shown in FIG. 8B, the resistance matches the impedance of the input terminal of the unterminated CAN node 300 to suppress generation of additional reflected waves.

The diode D may limit a bus voltage having a positive magnitude reflected by a negative signal to be less than or equal to the forward voltage (VF) of the diode D. Accordingly, state transition due to the shaking phenomenon is prevented, and asymmetry and settling time of a transition time can be minimized.

Next, referring to FIG. 8(c), a first diode D1 connected in a forward direction from a CAN-H line to a CAN-L line, a second diode D2 connected in a reverse direction, and a resistor are connected in parallel.

As shown in FIG. 8C, the resistance matches the impedance of the input terminal of the unterminated CAN node 300 to suppress the generation of additional reflected waves.

The first diode D1 may limit the magnitude of a positive reflected wave due to mismatching of the input terminal impedance of the unterminated CAN node to less than or equal to the forward voltage of the first diode. That is, the first diode D1 may limit a bus voltage having a positive magnitude reflected by a negative signal to be less than or equal to the forward voltage (VF) of the diode.

The second diode D2 may limit the magnitude of the negative reflected wave to less than or equal to the positive voltage of the second diode. That is, the second diode D2 may limit the size of the reflected wave to less than or equal to the positive voltage of the second diode D2 so that the bus voltage does not fall below zero due to a negative signal.

As a result, since both the maximum value and the minimum value of the bus voltage difference Vdiff are limited, state change due to shaking is prevented, and asymmetry and settling time of a transition time can be minimized.

The following effects can be expected due to the configuration of the transmitter output stage according to the present embodiment.

The general ringing suppression method reduces vibration by minimizing reflected waves by reducing the impedance of the CAN node when a negative transient voltage (Vind, negative transient voltage) is applied to the CAN node.

However, the method according to the present embodiment may limit the size of the vibration waveform to a level below the detection level by using a rectifying principle. That is, in a recessive state through a diode having a positive voltage drop (VF) value smaller than a detection level, the bus voltage difference (Vdiff) is limited to be less than the positive voltage drop (VF) value of the diode. Therefore, state re-change due to shaking does not occur. In addition, by acting on the CAN node operating as a transmitter that causes the vibration, the time delay until the vibration suppression operation is short, and the effect of the vibration on other CAN nodes can be minimized.

On the other hand, it is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Therefore, the detailed description above should not be construed as restrictive in all respects and should be considered as illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

The method according to the above-described embodiment may be produced as a program to be executed on a computer and stored in a computer-readable recording medium. Examples of computer-readable recording media include ROM, RAM, CD-ROM, and magnetic There are tapes, floppy disks, and optical data storage systems. The computer-readable recording medium is distributed over a computer system connected by a network, and computer-readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the above-described method can be easily inferred by programmers in the technical field to which the embodiment belongs.

110: MCU
120: CAN controller
130: CAN transceiver
140: vibration amplitude suppression circuit
400,500: selective vibration suppression circuit

Claims (20)

In a vehicle communication system constituting a CAN (Controller Area Network) network,
CAN controller;
A CAN transceiver connected to the CAN controller; And
Including a capacitor, an optional vibration suppression circuit comprising a vibration amplitude suppression circuit connected in series with the capacitor,
The selective vibration suppression circuit is disposed between the CAN-H and CAN-L lines,
The vehicle communication system is short-circuited when the capacitor is converted from the first communication state to the second communication state. The method of claim 1,
The vibration magnitude suppression circuit includes a resistor,
The resistance is a vehicle communication system connected in series with the capacitor. The method of claim 2,
The resistance is
Vehicle communication system for suppressing the generation of reflected waves by matching the impedance of the input terminal of the unterminated CAN node. The method of claim 3,
The resistance is
Vehicle communication system with the same size as the characteristic impedance of the CAN bus line. The method of claim 1,
The vibration magnitude suppression circuit includes a resistor and a diode,
The resistor and the diode are connected in parallel
The diode is a vehicle communication system connected in a forward direction with respect to the CAN-H line and the CAN-L line. The method of claim 5
The diode is
A communication system for a vehicle that limits the magnitude of a positive reflected wave according to an input impedance mismatch of an unterminated CAN node to a forward voltage (VF) or less of the diode. The method of claim 2,
The vibration magnitude suppression circuit includes a resistor, and a first diode and a second diode,
The resistor, the first diode, and the second diode are connected in parallel,
The first diode is connected in a forward direction with respect to the CAN-H line and the CAN-L line,
The second diode is a communication system for a vehicle that is connected in a reverse direction to a CAN-H line and a CAN-L line. The method of claim 7,
The first diode limits the magnitude of a positive reflected wave according to an impedance mismatch of the input terminal of the unterminated CAN node to be less than or equal to the positive voltage of the first diode,
The second diode is a vehicle communication system for limiting the magnitude of a negative reflected wave according to an impedance mismatch of an input terminal of an unterminated CAN node to less than or equal to the positive voltage of the second diode. The method of claim 1,
The first communication state includes a dominant state,
The second communication state includes a recessive state. The selective vibration suppression circuit according to claims 1 to 9
After communication conversion, the capacitor is opened and the vibration suppression circuit is separated from CAN-H and CAN-L. In a vehicle communication system constituting a CAN (Controller Area Network) network,
CAN controller;
A CAN transceiver connected to the CAN controller; And
Including a switch control unit, a switch controlled by the switch control unit, and a selective vibration suppression circuit including a vibration amplitude suppression circuit connected in series with the switch,
The selective vibration suppression circuit is disposed between the CAN-H and CAN-L lines,
The switch controller controls the switch to be turned on when it is converted from a first communication state to a second communication state based on the input signal TxD of the CAN transceiver. The method of claim 11,
The vibration magnitude suppression circuit includes a resistor,
The resistance is a vehicle communication system connected in series with the capacitor. The method of claim 12,
The resistance is
Vehicle communication system that suppresses the generation of additional reflected waves by matching the impedance of the input terminal of the unterminated CAN node. The method of claim 13,
The resistance is
Vehicle communication system with the same size as the characteristic impedance of the CAN bus line. The method of claim 11,
The vibration magnitude suppression circuit includes a resistor and a diode,
The resistor and the diode are connected in parallel
The diode is a vehicle communication system connected in a forward direction with respect to the CAN-H line and the CAN-L line. The method of claim 15
The diode is
A communication system for a vehicle that limits the magnitude of a positive reflected wave according to an input impedance mismatch of an unterminated CAN node to a forward voltage (VF) or less of the diode. The method of claim 11,
The vibration magnitude suppression circuit includes a resistor, and a first diode and a second diode,
The resistor, the first diode, and the second diode are connected in parallel,
The first diode is connected in a forward direction with respect to the CAN-H line and the CAN-L line,
The second diode is a communication system for a vehicle that is connected in a reverse direction to a CAN-H line and a CAN-L line. The method of claim 17,
The first diode limits the magnitude of a positive reflected wave according to an impedance mismatch of the input terminal of the unterminated CAN node to be less than or equal to the positive voltage of the first diode,
The second diode is a vehicle communication system for limiting the magnitude of a negative reflected wave according to an impedance mismatch of an input terminal of an unterminated CAN node to less than or equal to the positive voltage of the second diode. The method of claim 11,
The first communication state includes a dominant state,
The second communication state includes a recessive state. The selective vibration suppression circuit according to claims 11 to 19
After communication conversion, the switch is turned off to separate the vibration amplitude suppression circuit from CAN-H and CAN-L.

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