CN111294263A - CAN bus circuit - Google Patents
CAN bus circuit Download PDFInfo
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- CN111294263A CN111294263A CN201811503888.5A CN201811503888A CN111294263A CN 111294263 A CN111294263 A CN 111294263A CN 201811503888 A CN201811503888 A CN 201811503888A CN 111294263 A CN111294263 A CN 111294263A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40006—Architecture of a communication node
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0423—Input/output
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/21—Pc I-O input output
- G05B2219/21063—Bus, I-O connected to a bus
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L2012/40208—Bus networks characterized by the use of a particular bus standard
- H04L2012/40215—Controller Area Network CAN
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L2012/4026—Bus for use in automation systems
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- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Computer Networks & Wireless Communication (AREA)
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- Dc Digital Transmission (AREA)
Abstract
The invention discloses a CAN bus circuit, comprising: the ground terminal of the control module is connected with a first reference ground; the grounding end of the CAN transceiving module is connected with a second reference ground; the first isolation side of the digital isolation module is connected with the control module, the second isolation side of the digital isolation module is connected with the CAN transceiving module, the grounding end of the first isolation side is connected with a first reference ground, and the grounding end of the second isolation side is connected with a second reference ground; and the isolation power supply module is respectively connected with the control module, the first isolation side, the second isolation side and the CAN transceiving module so as to provide first power supply voltage for the control module and the first isolation side and provide second power supply voltage for the second isolation side and the CAN transceiving module. The CAN bus circuit realizes the electrical isolation of the control system and the CAN communication interface, thereby effectively solving the problem of interference caused by ground potential difference.
Description
Technical Field
The invention relates to the technical field of circuits, in particular to a CAN bus circuit.
Background
A Controller Area Network (CAN) is a bus protocol widely used in the world, and has the characteristics of low cost, high speed, good real-time performance, high reliability and the like, and a plurality of large companies in related industries at home and abroad support the related development of the CAN protocol. The CANopen protocol is an application layer protocol of the CAN protocol, and has been written into the IEC (International electrotechnical commission) standard as a communication standard in the rail transit industry, and there are a lot of application cases in the rail transit industry at home and abroad.
The length of the engineering application CAN bus is often hundreds of meters or even thousands of meters, and many engineers connect the reference ground of each node to the ground as shown in fig. 1, but this method has great hidden trouble. Since a ground potential difference always exists between different ground points, there is usually a large ground potential difference when the distance is long, which is superimposed on the output signal of the CAN transceiver to form common mode noise, which, once exceeding the common mode noise tolerance of the CAN transceiver chip, CAN cause damage to the device.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the present invention is directed to a CAN bus circuit, which CAN effectively solve the problem of interference caused by a ground potential difference.
In order to achieve the above object, the present invention provides a CAN bus circuit, including: the ground terminal of the control module is connected with a first reference ground; the grounding end of the CAN transceiving module is connected with a second reference ground; the digital isolation module is provided with a first isolation side and a second isolation side, the first isolation side is connected with the control module, the second isolation side is connected with the CAN transceiving module, the grounding end of the first isolation side is connected with the first reference ground, and the grounding end of the second isolation side is connected with the second reference ground; the isolation power supply module is provided with a first power supply end and a second power supply end, the first power supply end is respectively connected with the control module and the first isolation side so as to provide first power supply voltage for the control module and the first isolation side, and the second power supply end is respectively connected with the second isolation side and the CAN transceiver module so as to provide second power supply voltage for the second isolation side and the CAN transceiver module.
According to the CAN bus circuit provided by the embodiment of the invention, an electrical isolation design is adopted, and the grounding end of the communication end of the equipment is not connected with the ground, so that common-mode interference caused by grounding to the CAN transceiver module is avoided. And two completely independent power supplies are adopted to supply power to the control module and the CAN transceiving module, and the digital isolation module is adopted to electrically isolate digital transmission signals between the CAN transceiving module and the control module, so that the electrical isolation between the control system and the CAN communication interface is realized, and the problem of interference caused by ground potential difference is effectively solved.
In addition, the CAN bus circuit according to the embodiment of the present invention may further have the following additional technical features:
according to an embodiment of the present invention, the isolated power supply module includes a first isolation circuit and a second isolation circuit, the first isolation circuit includes the first power supply terminal, the second isolation circuit includes the second power supply terminal, the first isolation circuit is configured to provide the first power supply voltage, the second isolation circuit is configured to provide the second power supply voltage, and the first isolation circuit and the second isolation circuit are configured to achieve isolation between the first power supply voltage and the second power supply voltage.
According to one embodiment of the invention, the first isolation circuit comprises: a first power supply unit having a + VIN pin and a-VIN pin, wherein the-VIN pin is connected to the first reference ground; one end of the first inductor is connected with the + VIN pin, the other end of the first inductor is connected with a preset power supply and serves as the first power supply end, and the voltage of the preset power supply is the first power supply voltage; one end of the first capacitor is connected with the other end of the first inductor, and the other end of the first capacitor is connected with the first reference ground; and one end of the second capacitor is connected with one end of the first inductor, and the other end of the second capacitor is connected with the first reference ground.
According to an embodiment of the invention, the second isolation circuit comprises: a second power supply unit having a + VOUT pin and a-VOUT pin, wherein the + VOUT pin is used as the second power supply terminal, and the-VOUT pin is connected to the second reference ground; one end of the third capacitor is connected with the + VOUT pin, and the other end of the third capacitor is connected with the second reference ground; one end of the fourth capacitor is connected with the + VOUT pin, and the other end of the fourth capacitor is connected with the second reference ground; one end of the first resistor is connected with the + VOUT pin, and the other end of the first resistor is connected with the second reference ground.
According to an embodiment of the present invention, the first isolation side of the digital isolation module includes a third isolation circuit, and the second isolation side of the digital isolation module includes a fourth isolation circuit, where the third isolation circuit and the fourth isolation circuit are configured to implement isolation between data output/received by the control module and data received/output by the CAN transceiver module.
According to one embodiment of the invention, the digital isolation module comprises: the third isolation circuit includes: the first digital unit is provided with a VCC1 pin, an INB pin, an OUTA pin and a GND1 pin, wherein the VCC1 pin is connected with the first power supply end, the GND1 pin is connected with the first reference ground, and the INB pin and the OUTA pin are both connected with the control module; one end of the fifth capacitor is connected with the VCC1 pin, and the other end of the fifth capacitor is connected with the first reference ground; one end of the second resistor is connected with the VCC1 pin, and the other end of the second resistor is connected with the INB pin; and one end of the third resistor is connected with the VCC1 pin, and the other end of the third resistor is connected with the OUTA pin.
According to an embodiment of the invention, the fourth isolation circuit comprises: the second digital unit is provided with a VCC2 pin, an INA pin, an OUTB pin and a GND2 pin, wherein the VCC2 pin is connected with the second power supply end, the GND2 pin is connected with the second reference ground, and the INA pin and the OUTB pin are both connected with the CAN transceiving module; and one end of the sixth capacitor is connected with the VCC2 pin, and the other end of the sixth capacitor is connected with the second reference ground.
According to one embodiment of the present invention, the CAN transceiver module includes: a CAN transceiver having a TXD pin, a GND pin, a VDD pin, a RXD pin, a RS pin, a CANH pin, a CANL pin and a VREF pin, wherein the TXD pin is connected with the OUTB pin, the GND pin is connected with the second reference ground, the VDD pin is connected with the second power supply terminal, the RXD pin is connected with the INA pin, the RS pin is connected with the second reference ground, the CANH pin and the CANL pin are both connected with the CAN bus, and the VREF pin is connected with the second power supply terminal; one end of the seventh capacitor is connected with the first power supply end, and the other end of the seventh capacitor is connected with the second reference ground; and one end of the eighth capacitor is connected with the first power supply end, and the other end of the eighth capacitor is connected with the second reference ground.
According to an embodiment of the present invention, the CAN-bus circuit further includes: the protection module is connected between the CAN bus and the CAN transceiver and used for filtering and denoising differential signals output to the CAN bus and differential signals from the CAN bus.
According to one embodiment of the invention, the protection module comprises: one end of the first magnetic bead is connected with the CANH pin, and one end of the second magnetic bead is connected with the CANL pin; a first end of the common mode inductor is connected with the other end of the first magnetic bead, and a second end of the common mode inductor is connected with the other end of the second magnetic bead; a first end of the bridge protection circuit is connected with a third end of the common-mode inductor, and a second end of the bridge protection circuit is connected with a fourth end of the common-mode inductor; the anode of the first diode is connected with the third end of the bridge protection circuit, and the cathode of the first diode is connected with the second reference ground; the anode of the second diode is connected with the second reference ground, and the cathode of the second diode is connected with the fourth end of the bridge protection circuit; one end of the fourth resistor is connected with the third end of the common-mode inductor, and the other end of the fourth resistor is connected with the first signal end of the CAN bus; one end of the fifth resistor is connected with the fourth end of the common-mode inductor, and the other end of the fifth resistor is connected with the second signal end of the CAN bus; one end of the filter circuit is connected with the first reference ground, and the other end of the filter circuit is connected with the second reference ground.
According to an embodiment of the present invention, the bridge protection circuit includes: the anode of the third diode is connected with the third end of the common-mode inductor and the cathode of the fourth diode respectively, the cathode of the third diode is connected with the cathode of the second diode and the cathode of the sixth diode respectively, the anode of the fourth diode is connected with the anode of the first diode and the anode of the fifth diode respectively, and the cathode of the second diode is connected with the fourth end of the common-mode inductor and the anode of the sixth diode respectively; and one end of the TVS diode is connected with the anode of the first diode, and the other end of the TVS diode is connected with the cathode of the second diode.
According to one embodiment of the present invention, the filter circuit includes: one end of the sixth resistor is connected with the first reference ground, and the other end of the sixth resistor is connected with the second reference ground; and one end of the ninth capacitor is connected with the first reference ground, and the other end of the ninth capacitor is connected with the second reference ground.
According to one embodiment of the invention, the protection module further comprises: and a first pole of the gas discharge tube is connected with the first signal end of the CAN bus, a second pole of the gas discharge tube is connected with the second signal end of the CAN bus, and a third pole of the gas discharge tube is connected with the second reference ground.
According to one embodiment of the invention, the first supply voltage and the second supply voltage are both +5V, the first reference ground is ground, and the second reference ground is CAN shield ground.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
FIG. 1 is a schematic diagram of a CAN bus circuit in the related art;
FIG. 2 is a block diagram of a CAN bus circuit according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of an isolated power supply module according to one embodiment of the invention;
FIG. 4 is a circuit diagram of a digital isolation module and a CAN transceiver module according to one embodiment of the present invention;
FIG. 5 is a block diagram of a CAN bus circuit according to another embodiment of the present invention;
FIG. 6 is a circuit diagram of a protection module according to one embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
A CAN bus circuit of an embodiment of the present invention is described below with reference to the drawings.
Fig. 2 is a block diagram of a CAN bus circuit according to an embodiment of the present invention. As shown in fig. 2, the circuit 100 includes: the circuit 100 CAN be used in a rail transit system, wherein a rail vehicle in the rail transit system CAN be a tram, a monorail train, an APM (automated peer move systems), a subway, or the like.
Referring to fig. 2, the ground terminal of the control module 10 is connected to the first ground reference GND1, and the ground terminal of the CAN transceiver module 20 is connected to the second ground reference GND 2; the digital isolation module 30 has a first isolation side and a second isolation side, the first isolation side is connected with the control module 10, the second isolation side is connected with the CAN transceiver module 20, a ground terminal of the first isolation side is connected with a first reference ground GND1, and a ground terminal of the second isolation side is connected with a second reference ground GND 2; the isolation power module 40 has a first power terminal connected to the control module 10 and the first isolation side, respectively, to provide a first supply voltage to the control module and the first isolation side, and a second power terminal connected to the second isolation side and the CAN transceiver module 20, respectively, to provide a second supply voltage to the second isolation side and the CAN transceiver module 20.
The first power supply voltage may be +5V, the second power supply voltage may be +5V, the first reference ground is ground, and the second reference ground is a CAN shield ground. Optionally, for the same node of the CAN bus in the rail transit system, a single-point grounding method CAN be adopted during grounding; for different nodes of the CAN bus in the rail transit system, a multipoint grounding method CAN be adopted during grounding.
It should be noted that the first power supply terminal and the second power supply terminal are two different ports, and are isolated from each other, so that the first power supply voltage and the second power supply voltage are also isolated from each other. For convenience of illustration, the first supply voltage may be referred to as +5V1 and the second supply voltage may be referred to as +5V 2.
The CAN shield may be a CAN shield layer, and in some cases, FG may be used. Specifically, a conductor wrapped outside the conductor is called a shield wire, a wrapped conductor is called a shield layer, which is generally a braided copper mesh or copper foil (aluminum), and the shield layer needs grounding treatment to ensure that an external interference signal CAN be guided into the ground by the shield layer, that is, the shield layer after grounding treatment is the CAN shield ground.
In this embodiment, the data output by the control module 10 passes through the digital isolation module 30 and then is transmitted to the CAN transceiver module 20, so that the data is transmitted to the CAN bus in the form of differential signals through the CAN transceiver module 20, and the differential signals from the CAN bus pass through the CAN transceiver module 20 and then are transmitted to the digital isolation module 30, so that the data is transmitted to the control module 10 through the digital isolation module 30.
According to the CAN bus circuit provided by the embodiment of the invention, two completely independent power supplies are adopted to supply power to the control module and the CAN transceiver module, and the digital isolation module is adopted to electrically isolate digital transmission signals between the CAN transceiver module and the control module, so that the electrical isolation between the control system and the CAN communication interface is realized, and the problem of interference caused by ground potential difference is effectively solved.
In an embodiment of the present invention, the isolated power supply module 40 includes a first isolation circuit and a second isolation circuit, the first isolation circuit includes a first power supply terminal, the second isolation circuit includes a second power supply terminal, the first isolation circuit is configured to provide a first power supply voltage, the second isolation circuit is configured to provide a second power supply voltage, and the first isolation circuit and the second isolation circuit are configured to implement isolation between the first power supply voltage and the second power supply voltage.
In this embodiment, as shown in fig. 3, the first isolation circuit includes a first power supply unit, a first inductor L1, a first capacitor C1, and a second capacitor C2, and the second isolation circuit includes a second power supply unit, a third capacitor C3, a fourth capacitor C4, and a first resistor R1.
Referring to fig. 3, the first power supply unit and the second power supply unit together constitute an isolation power supply 41, and the isolation power supply 41 has a + VIN pin, a + VOUT pin, a-VIN pin, and a-VOUT pin, wherein the first power supply unit has the + VIN pin and the-VIN pin, the second power supply unit has the + VOUT pin and the-VOUT pin, the + VOUT pin serves as a second power supply terminal, the-VIN pin is connected to a first ground GND1, and the-VOUT pin is connected to a second ground GND 2. One end of the first inductor L1 is connected to the + VIN pin, and the other end of the first inductor L1 is connected to a preset power supply, and serves as a first power supply end, where the voltage of the preset power supply is a first power supply voltage. One end of the first capacitor C1 is connected to the other end of the first inductor L1, and the other end of the first capacitor C1 is connected to the first ground reference GND 1. One end of the second capacitor C2 is connected to one end of the first inductor L1, and the other end of the second capacitor C2 is connected to the first ground reference GND 1. One end of the third capacitor C3 is connected to the + VOUT pin, and the other end of the third capacitor C3 is connected to the second ground reference GND 2. One end of the fourth capacitor C4 is connected to the + VOUT pin, and the other end of the fourth capacitor C4 is connected to the second ground GND 2. One end of the first resistor R1 is connected to the + VOUT pin, and the other end of the first resistor R1 is connected to the second ground GND 2.
Alternatively, referring to fig. 3, the isolation power supply 41 may employ RECOM isolation power supply chip RP0505S, but the isolation power supply 41 may employ other isolation power supply chips, such as RP0524S, RP1212S, RP1215S, RP-0512D, etc.
Further, in an embodiment of the present invention, the first isolation side of the digital isolation module 30 includes a third isolation circuit, and the second isolation side of the digital isolation module 30 includes a fourth isolation circuit, where the third isolation circuit and the fourth isolation circuit are configured to implement isolation between data output/received by the control module 10 and data received/output by the CAN transceiver module 20.
As shown in fig. 4, the third isolation circuit includes a first digital unit, a fifth capacitor C5, a second resistor R2, and a third resistor R3, and the fourth isolation circuit includes a second digital unit and a sixth capacitor C6.
Referring to fig. 4, the first digital unit and the second digital unit together form a digital isolator 31, the digital isolator 31 has a VCC1 pin, an INB pin, an OUTA pin, a GND1 pin, a VCC2 pin, an INA pin, an OUTB pin, and a GND2 pin, wherein the first digital unit has the VCC1 pin, the INB pin, the OUTA pin, and a GND1 pin, the second digital unit has the VCC2 pin, the INA pin, the OUTB pin, and a GND2 pin, the VCC1 pin is connected to a first power supply terminal, the VCC2 pin is connected to a second power supply terminal, the GND1 pin is connected to a first ground GND1, the GND2 pin is connected to a second ground GND2, the INB pin and the OUTA pin are both connected to a control module, and the INA pin and the OUTB pin are both connected to an isolation transceiver module. One end of the fifth capacitor C5 is connected to the pin VCC1, and the other end of the fifth capacitor C5 is connected to the first ground reference GND 1. One end of the second resistor R2 is connected to the VCC1 pin, and the other end of the second resistor R2 is connected to the INB pin. One end of the third resistor R3 is connected to the VCC1 pin, and the other end of the third resistor R3 is connected to the OUTA pin. One end of the sixth capacitor C6 is connected to the pin VCC2, and the other end of the sixth capacitor C6 is connected to the second ground reference GND 2.
Alternatively, referring to fig. 4, the digital isolator 31 may be an ISO7421 chip, in which two channels are in opposite directions, one channel is used for transmitting signals and the other channel is used for receiving signals.
As shown in fig. 4, the CAN transceiver module 20 includes: CAN transceiver 21, seventh capacitor C7 and eighth capacitor C8.
Referring to fig. 4, the CAN transceiver 21 has a TXD pin, a GND pin, a VDD pin, an RXD pin, an RS pin, a CANH pin, a CANL pin, and a VREF pin, wherein the TXD pin is connected to the OUTB pin, the GND pin is connected to the second ground reference GND2, the VDD pin is connected to the second power supply terminal, the RXD pin is connected to the INA pin, the RS pin is connected to the second ground reference GND2, the CANH pin and the CANL pin are connected to the CAN bus, and the VREF pin is connected to the second power supply terminal. One end of the seventh capacitor C7 is connected to the first power terminal, and the other end of the seventh capacitor C7 is connected to the second ground reference GND 2. One end of the eighth capacitor C8 is connected to the first power terminal, and the other end of the eighth capacitor C8 is connected to the second ground GND 2.
Alternatively, referring to fig. 4, the CAN transceiver 21 may employ an HVD5511 chip.
In one embodiment of the present invention, the control module 10 may be a DSP (Digital Signal Processing) chip.
Specifically, referring to fig. 3 and 4, in order to realize electrical isolation between the DSP and the CAN bus, the RECOM isolation power supply module RP0505 is used to isolate the power supply of the DSP and the CAN chip in the present invention. The DSP side of the digital isolator ISO7421 is powered by +5V1, and the CAN chip side of the digital isolator ISO7421 is powered by +5V 2.
Referring to fig. 4, differential signals are transmitted on the CAN bus, two signal lines are "CANH" and "CANL", respectively, and when the bus is static, both signal lines are about 2.5V, which is called "recessive" and represents logic "1"; when the bus is "dominant", CANH and CANL are around 3.5V and around 1.5V, respectively, and this state represents a logical "0".
The serial port signal TXD of the DSP is transmitted to a CAN physical interface chip HVD551 after being isolated by the capacitor through ISO7421, and finally converted into a differential signal on a CAN bus to be transmitted; differential signals from the CAN bus are demodulated by the HVD551, then are converted into digital signals, and enter an RXD pin of the DSP after passing through capacitance isolation by the ISO7421, the DSP supplies power by adopting +5V1, the reference ground is GND1, the HVD551 supplies power by adopting +5V2, and the reference ground is GND2, so that the electrical isolation of the DSP and the CAN bus is realized. Thereby, the problem of interference due to the ground potential difference in fig. 1 can be solved.
In an embodiment of the present invention, as shown in fig. 5, the CAN bus circuit 100 further includes a protection module 50, wherein the protection module 50 is connected between the CAN bus and the CAN transceiver 21, and the protection module 50 is configured to perform filtering and noise reduction on the differential signal output to the CAN bus and the differential signal from the CAN bus.
Specifically, as shown in fig. 6, the protection module 50 includes: the circuit comprises a first magnetic bead CZ1, a second magnetic bead CZ2, a common mode inductor L2, a bridge protection circuit 51, a first diode D1, a second diode D2, a fourth resistor R4 and a filter circuit 52.
Referring to fig. 6, one end of the first bead CZ1 is connected to the CANH pin and one end of the second bead CZ2 is connected to the CANL pin. The first end of common mode inductance L2 links to each other with the other end of first magnetic bead, and the second end of common mode inductance links to each other with the other end of second magnetic bead. The first terminal of the bridge protection circuit 51 is connected to the third terminal of the common mode inductor L2, and the second terminal of the bridge protection circuit 51 is connected to the fourth terminal of the common mode inductor L2. The anode of the first diode D1 is connected to the third terminal of the bridge protection circuit 51, and the cathode of the first diode D1 is connected to the second ground GND 2. The anode of the second diode D2 is connected to the second ground reference GND2, and the cathode of the second diode D2 is connected to the fourth terminal of the bridge protection circuit 51. One end of the fourth resistor R4 is connected to the third end of the common mode inductor L2, and the other end of the fourth resistor R4 is connected to the first signal terminal CANH of the CAN bus. One end of the fifth resistor R5, one end of the fifth resistor R5 is connected to the fourth end of the common mode inductor L2, and the other end of the fifth resistor R5 is connected to the second signal end CANL of the CAN bus. One end of the filter circuit 52 is connected to the first ground reference GND1, and the other end of the filter circuit 52 is connected to the second ground reference GND 2.
The common-mode inductor and the magnetic beads can eliminate the influence of interference of specific frequency.
In one example, as shown in fig. 6, the bridge protection circuit 51 includes third to sixth diodes D3 to D6 and TVS (Transient Voltage Suppressor) diodes.
Referring to fig. 6, anodes of the third diode D3 are respectively connected to the third terminal of the common mode inductor L3 and the cathode of the fourth diode D4, the cathode of the third diode D3 is respectively connected to the cathode of the second diode D2 and the cathode of the sixth diode D6, the anode of the fourth diode D4 is respectively connected to the anode of the first diode D1 and the anode of the fifth diode D5, and the cathode of the second diode D2 is respectively connected to the fourth terminal of the common mode inductor L2 and the anode of the sixth diode D6. One end of the TVS diode is connected to the anode of the first diode D1, and the other end of the TVS diode is connected to the cathode of the second diode D2.
In one example, as shown in fig. 6, the filter circuit 52 includes: a sixth resistor R6 and a ninth capacitor C9. One end of the sixth resistor R6 is connected to the first ground reference GND1, and the other end of the sixth resistor R6 is connected to the second ground reference GND 2; one end of the ninth capacitor C9 is connected to the first ground reference GND1, and the other end of the ninth capacitor C9 is connected to the second ground reference GND 2.
Further, as shown in fig. 6, the protection module 50 further includes a gas discharge tube GDT, wherein a first pole of the gas discharge tube GDT is connected to the first signal terminal CANH of the CAN bus, a second pole of the gas discharge tube GDT is connected to the second signal terminal CANL of the CAN bus, and a third pole of the gas discharge tube GDT is connected to the second reference ground GND 2.
When the protection module shown in fig. 6 is used, in the CAN communication process, if a lightning strike occurs, the TVS diode which is extremely fast in action time will act first in a few nanoseconds, and differential mode and common mode interference from the CAN bus are limited within a safe range. If the surge is maintained for a long time and the energy is large, the gas discharge tube with a slow speed but a strong discharge capacity starts a protection function to discharge the energy to the ground, so that the communication interface is protected from being damaged. Therefore, the gas discharge tube GDT and the TVS tube are adopted for two-stage protection, and the CAN bus interface is not damaged when reaching 2000V surge.
In summary, according to the CAN bus circuit of the embodiment of the invention, two sets of completely independent power supplies are used to supply power to the DSP and the CAN communication physical interface chip, and the digital isolation device is used to electrically isolate the digital transmission signal between the CAN communication physical interface chip and the DSP, thereby avoiding the ground backflow from burning the circuit board or limiting the amplitude of interference, and improving the reliability of the system. In addition, a lightning-proof surge protection circuit is arranged at the port of the CAN bus, and a common-mode inductor and a magnetic bead are added, so that the influence of specific frequency interference CAN be effectively weakened, and the surge interference on the CAN bus is prevented from damaging a post-stage system.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (14)
1. A CAN bus circuit, comprising:
the ground terminal of the control module is connected with a first reference ground;
the grounding end of the CAN transceiving module is connected with a second reference ground;
the digital isolation module is provided with a first isolation side and a second isolation side, the first isolation side is connected with the control module, the second isolation side is connected with the CAN transceiving module, the grounding end of the first isolation side is connected with the first reference ground, and the grounding end of the second isolation side is connected with the second reference ground;
the isolation power supply module is provided with a first power supply end and a second power supply end, the first power supply end is respectively connected with the control module and the first isolation side so as to provide first power supply voltage for the control module and the first isolation side, and the second power supply end is respectively connected with the second isolation side and the CAN transceiver module so as to provide second power supply voltage for the second isolation side and the CAN transceiver module.
2. The CAN-bus circuit of claim 1 wherein the isolated power module comprises a first isolation circuit comprising the first power supply terminal and a second isolation circuit comprising the second power supply terminal, the first isolation circuit for providing the first supply voltage and the second isolation circuit for providing the second supply voltage, wherein the first isolation circuit and the second isolation circuit are arranged to effect isolation of the first supply voltage from the second supply voltage.
3. The CAN bus circuit of claim 1, wherein the first isolation circuit comprises:
a first power supply unit having a + VIN pin and a-VIN pin, wherein the-VIN pin is connected to the first reference ground;
one end of the first inductor is connected with the + VIN pin, the other end of the first inductor is connected with a preset power supply and serves as the first power supply end, and the voltage of the preset power supply is the first power supply voltage;
one end of the first capacitor is connected with the other end of the first inductor, and the other end of the first capacitor is connected with the first reference ground;
and one end of the second capacitor is connected with one end of the first inductor, and the other end of the second capacitor is connected with the first reference ground.
4. The CAN bus circuit of claim 3 wherein the second isolation circuit comprises:
a second power supply unit having a + VOUT pin and a-VOUT pin, wherein the + VOUT pin is used as the second power supply terminal, and the-VOUT pin is connected to the second reference ground;
one end of the third capacitor is connected with the + VOUT pin, and the other end of the third capacitor is connected with the second reference ground;
one end of the fourth capacitor is connected with the + VOUT pin, and the other end of the fourth capacitor is connected with the second reference ground;
one end of the first resistor is connected with the + VOUT pin, and the other end of the first resistor is connected with the second reference ground.
5. The CAN bus circuit of any of claims 1-4, wherein the first isolated side of the digital isolation module comprises a third isolation circuit and the second isolated side of the digital isolation module comprises a fourth isolation circuit, wherein the third isolation circuit and the fourth isolation circuit are configured to enable isolation between data output/received by the control module and data received/output by the CAN transceiver module.
6. The CAN-bus circuit of claim 5, wherein the third isolation circuit comprises:
the first digital unit is provided with a VCC1 pin, an INB pin, an OUTA pin and a GND1 pin, wherein the VCC1 pin is connected with the first power supply end, the GND1 pin is connected with the first reference ground, and the INB pin and the OUTA pin are both connected with the control module;
one end of the fifth capacitor is connected with the VCC1 pin, and the other end of the fifth capacitor is connected with the first reference ground;
one end of the second resistor is connected with the VCC1 pin, and the other end of the second resistor is connected with the INB pin;
and one end of the third resistor is connected with the VCC1 pin, and the other end of the third resistor is connected with the OUTA pin.
7. The CAN bus circuit of claim 6 wherein the fourth isolation circuit comprises:
the second digital unit is provided with a VCC2 pin, an INA pin, an OUTB pin and a GND2 pin, wherein the VCC2 pin is connected with the second power supply end, the GND2 pin is connected with the second reference ground, and the INA pin and the OUTB pin are both connected with the CAN transceiving module;
and one end of the sixth capacitor is connected with the VCC2 pin, and the other end of the sixth capacitor is connected with the second reference ground.
8. The CAN bus circuit of claim 7 wherein the CAN transceiver module comprises:
a CAN transceiver having a TXD pin, a GND pin, a VDD pin, a RXD pin, a RS pin, a CANH pin, a CANL pin and a VREF pin, wherein the TXD pin is connected with the OUTB pin, the GND pin is connected with the second reference ground, the VDD pin is connected with the second power supply terminal, the RXD pin is connected with the INA pin, the RS pin is connected with the second reference ground, the CANH pin and the CANL pin are both connected with the CAN bus, and the VREF pin is connected with the second power supply terminal;
one end of the seventh capacitor is connected with the first power supply end, and the other end of the seventh capacitor is connected with the second reference ground;
and one end of the eighth capacitor is connected with the first power supply end, and the other end of the eighth capacitor is connected with the second reference ground.
9. The CAN bus circuit of claim 8, further comprising:
the protection module is connected between the CAN bus and the CAN transceiver and used for filtering and denoising differential signals output to the CAN bus and differential signals from the CAN bus.
10. The CAN bus circuit of claim 8 wherein the protection module comprises:
one end of the first magnetic bead is connected with the CANH pin, and one end of the second magnetic bead is connected with the CANL pin;
a first end of the common mode inductor is connected with the other end of the first magnetic bead, and a second end of the common mode inductor is connected with the other end of the second magnetic bead;
a first end of the bridge protection circuit is connected with a third end of the common-mode inductor, and a second end of the bridge protection circuit is connected with a fourth end of the common-mode inductor;
the anode of the first diode is connected with the third end of the bridge protection circuit, and the cathode of the first diode is connected with the second reference ground;
the anode of the second diode is connected with the second reference ground, and the cathode of the second diode is connected with the fourth end of the bridge protection circuit;
one end of the fourth resistor is connected with the third end of the common-mode inductor, and the other end of the fourth resistor is connected with the first signal end of the CAN bus;
one end of the fifth resistor is connected with the fourth end of the common-mode inductor, and the other end of the fifth resistor is connected with the second signal end of the CAN bus;
one end of the filter circuit is connected with the first reference ground, and the other end of the filter circuit is connected with the second reference ground.
11. The CAN bus circuit of claim 10 wherein the bridge protection circuit comprises:
the anode of the third diode is connected with the third end of the common-mode inductor and the cathode of the fourth diode respectively, the cathode of the third diode is connected with the cathode of the second diode and the cathode of the sixth diode respectively, the anode of the fourth diode is connected with the anode of the first diode and the anode of the fifth diode respectively, and the cathode of the second diode is connected with the fourth end of the common-mode inductor and the anode of the sixth diode respectively;
and one end of the TVS diode is connected with the anode of the first diode, and the other end of the TVS diode is connected with the cathode of the second diode.
12. The CAN bus circuit of claim 8 wherein the filter circuit comprises:
one end of the sixth resistor is connected with the first reference ground, and the other end of the sixth resistor is connected with the second reference ground;
and one end of the ninth capacitor is connected with the first reference ground, and the other end of the ninth capacitor is connected with the second reference ground.
13. The CAN bus circuit of claim 8 wherein the protection module further comprises:
and a first pole of the gas discharge tube is connected with the first signal end of the CAN bus, a second pole of the gas discharge tube is connected with the second signal end of the CAN bus, and a third pole of the gas discharge tube is connected with the second reference ground.
14. The CAN bus circuit of claim 1 wherein the first supply voltage and the second supply voltage are both +5V, the first reference ground is ground, and the second reference ground is CAN shield ground.
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| CN201811503888.5A CN111294263A (en) | 2018-12-10 | 2018-12-10 | CAN bus circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811503888.5A CN111294263A (en) | 2018-12-10 | 2018-12-10 | CAN bus circuit |
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| CN111294263A true CN111294263A (en) | 2020-06-16 |
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