CN216700023U

CN216700023U - CAN bus protection and control circuit

Info

Publication number: CN216700023U
Application number: CN202122471064.8U
Authority: CN
Inventors: 陈聪; 徐信; 刘申君; 王亚琼
Original assignee: Jiangsu Aviation Technical College
Current assignee: Jiangsu Aviation Technical College
Priority date: 2021-10-14
Filing date: 2021-10-14
Publication date: 2022-06-07
Anticipated expiration: 2031-10-14

Abstract

The utility model discloses a CAN bus protection and control circuit. It is including the MCU that has CAN controller and IO port and the CAN transceiver circuitry who has the CANH output and the CANL output, thereby MCU's CAN controller through the two-channel digital isolator with CAN transceiver circuitry be connected with CAN transceiver circuitry between carry out information communication, CAN transceiver circuitry's CANH output and CANL output are connected with common mode choke circuit, common mode choke circuit is connected to CAN communication bus through the protection control circuit who has terminal resistance circuit and protection circuit on, be connected with the solid state relay that CAN carry out on-off control to terminal resistance circuit between MCU's IO port and the terminal resistance circuit. The beneficial effects are that: the CAN communication terminal CAN be effectively electrically isolated, noise interference is suppressed, surge protection is realized, the anti-interference and protection capabilities are remarkably improved, whether the terminal resistor circuit is accessed or not CAN be timely selected according to different CAN communication environments, and CAN communication application occasions are widened.

Description

CAN bus protection and control circuit

Technical Field

The utility model relates to a circuit structure in a CAN communication system, in particular to a CAN bus protection and control circuit which CAN be used for communication of an automobile electronic controller.

Background

The CAN (controller Area network) bus protocol is a serial communication bus based on a message broadcasting mode invented by BOSCH, is used for realizing reliable communication between Electronic Control Units (ECUs) in automobiles at first, and is widely applied to other fields of industrial automation, ships, medical treatment and the like due to the characteristics of simplicity, practicability, reliability and the like.

In the current automobile application field, the number of the ECUs in the automobile CAN be up to 70, subsystems such as a transmission control subsystem, an air bag subsystem, an ABS (anti-lock brake system), a cruise control subsystem, an EPS (electric power system), a sound system subsystem, a door and window control subsystem and a battery management subsystem exist besides an engine control unit, and the CAN bus CAN meet the requirements of data transmission of the subsystems. Before the automobile leaves a factory, the ECU needs to perform repeated communication tests, so the reliability, flexibility and anti-interference performance of test equipment influence the test flow and test effect of the ECU, however, in the existing automobile ECU communication test, because the control circuit is unreasonable in design, the anti-interference and protection capabilities are poor and the controllability is poor, so the test reliability is reduced, in addition, the existing control circuit can only be applied to a specific certain occasion according to specific environment, and the application range is narrow.

Disclosure of Invention

The utility model aims to solve the technical problem of providing a CAN bus protection and control circuit which has strong anti-interference capability and good controllability, thereby ensuring the test reliability.

In order to solve the technical problem, the CAN bus protection and control circuit comprises an MCU with a CAN controller and an I/O port and a CAN transceiver circuit with a CANH output end and a CANL output end, wherein the CAN controller of the MCU is connected with the CAN transceiver circuit through a dual-channel digital isolator so as to carry out information communication with the CAN transceiver circuit, the CANH output end and the CANL output end of the CAN transceiver circuit are connected with a common mode choke coil circuit, the common mode choke coil circuit is connected to a CAN communication bus through a protection control circuit with a terminal resistance circuit and a protection circuit, and a solid-state relay capable of controlling the on-off of the terminal resistance circuit is connected between the I/O port of the MCU and the terminal resistance circuit.

Pins VOA and VIB of the dual-channel digital isolator are respectively connected with RX and TX of the CAN controller, and pins VIA and VOB are respectively connected with RXD and TXD of the CAN transceiver circuit.

The dual-channel digital isolator adopts an ADUM1201 chip.

The CAN transceiver circuit consists of a CAN transceiver and a Y-type filter circuit consisting of two capacitors, and the CAN transceiver adopts an SN65HVD1050 chip.

The common mode choke coil circuit is composed of a common mode choke coil and a Y-shaped filter circuit composed of two capacitors.

The protection control circuit adopts a double common anode Zener transient voltage suppressor.

The solid-state relay adopts an ASSR1228 double-channel solid-state relay chip.

The solid-state relay ASSR1228 chip has 8 pins, the pins 1 and 3 are connected with the I/O port, the pins 2 and 4 are grounded, the pins 5 and 6 are connected to one terminal resistor in series, and the pins 7 and 8 are connected to the other terminal resistor in series.

Compared with the prior art, the utility model has the beneficial effects that:

the digital isolator is arranged between the CAN controller and the transceiver of the MCU, so that the high-speed CMOS and the single-chip transformer technology are integrated through the digital isolator, the performance of the digital isolator is superior to that of an optical coupling device, effective electrical isolation, noise interference suppression and surge protection CAN be realized in a CAN communication field, the anti-interference and protection capabilities are remarkably improved, especially, a terminal resistance circuit is specially designed in a protection control circuit, and a solid-state relay is connected between an I/O port of the MCU and the terminal resistance circuit, so that the terminal resistance circuit is controlled by the optical coupling solid-state relay which is high in sensitivity, high in conversion speed and small in electromagnetic interference, whether the terminal resistance circuit is accessed or not CAN be timely selected according to different CAN communication environments, and the CAN communication application occasions are widened.

Drawings

FIG. 1 is a schematic block diagram of a CAN bus protection and control circuit of the present invention;

fig. 2 is a circuit diagram of a CAN bus protection and control circuit according to the present invention.

Detailed Description

The CAN bus protection and control circuit of the present invention will be described in further detail with reference to the accompanying drawings and the detailed description.

The CAN bus protection and control circuit CAN be used in the fields of automobile ECU communication test or other CAN communication application, as shown in the figure, the CAN bus protection and control circuit comprises a MCU with a CAN controller and an I/O port and a CAN transceiver circuit with a CANH output end and a CANL output end, wherein the CAN controller of the MCU is connected with the CAN transceiver circuit through a double-channel digital isolator circuit so as to carry out information communication with the CAN transceiver circuit, the digital isolator chip, the CAN controller, the CAN transceiver and other circuits jointly form an isolation transceiver circuit, the CANH output end and the CANL output end of the CAN transceiver circuit are connected with a common mode choke coil circuit, and the common mode choke coil is connected to a CAN communication bus through a protection control circuit with a terminal resistance circuit and a protection circuit.

In this embodiment, the digital isolator selects an ADUM1201 dual-channel digital isolator chip with high common mode transient immunity and high data rate, the ADUM1201 chip has 8 pins, the pins VOA and VIB 2 and 3 are respectively connected with a CAN receiving signal and a CAN sending signal, the CAN sending and receiving signal is led out from an MCU with a CAN controller, the ADUM1201 chip 6, the pin VOB and the pin VIA such as an MCU selectable STM32 series are connected with the sending and receiving pins of the CAN transceiver, the pin 1 is connected with a power supply voltage same as that of the MCU, and if the MCU with 3.3V power supply is selected, the pin 1 is connected with a 3.3V voltage; pin 8 is connected with the same power supply voltage as the CAN transceiver, a voltage of 3.3V is connected, different reference grounds are selected for pins 4 and 5 GND1 and GND2 of the ADUM1201 chip, and a decoupling capacitor of 100nF is connected between the power supply and the ground. Specifically, as shown in fig. 2, pins VOA and VIB of the isolator chip are respectively connected to RX and TX of the CAN controller, pins VIA and VOB are respectively connected to RXD and TXD of the CAN transceiver, pin VDD1 is connected to the 3.3V dc power supply, pin VDD2 is connected to the 3.3V dc power supply, and decoupling capacitors are respectively disposed between the power supply and ground.

The CAN transceiver circuit is composed of a CAN transceiver and a Y-type filter circuit composed of two capacitors, wherein the CAN transceiver in the CAN transceiver circuit selects an anti-electromagnetic interference SN65HVD1050 chip with excellent performance, the chip has 8 pins, the 1 and 4 pins are connected with input and output pins of a digital isolator chip, CANH and CANL signals are led out from the 6 and 7 pins, a Y-type capacitor filter circuit is connected to a signal line, the capacitor selects 47pF, the 8 pin is grounded, and a 100nF decoupling capacitor is arranged between a power supply and the ground.

The common mode choke circuit is composed of a common mode choke coil and a Y-shaped filter circuit composed of two capacitors, as CAN be seen from fig. 2, the common mode choke coil circuit is connected in series with a CAN communication bus, the common mode choke coil adopts a B82793 chip of EPCOS company, the Y-shaped capacitor filter circuit connected behind the common mode choke coil is used for filtering a low-frequency part of common mode current, and the capacitance value is 47 pF.

Through the circuit structure design, a CAN communication bus transceiving signal is led out from an MCU with a CAN controller, and is sent to a CAN transceiver chip SN65HVD1050 through a dual-channel digital isolator ADUM1201 chip isolated by a planar magnetic field, CANH and CANL signals output by the CAN transceiver are transmitted to the CAN communication bus through a common mode choke coil and a protection control circuit, the protection control circuit plays a role in preventing surge on the CAN communication bus, and the protection control circuit is formed by a double common anode Zener transient voltage suppressor MMBZ33VA chip; the MCU takes an I/O port to drive the double-channel solid-state relay so as to control whether a terminal resistor circuit is accessed or not, concretely, the solid-state relay is connected between the I/O port of the MCU and the terminal resistor circuit, the solid-state relay adopts a double-channel solid-state relay ASSR1228 chip, the normally open end of the solid-state relay is connected to the terminal resistor circuit to carry out on-off control, therefore, the on-off control of whether the terminal resistor circuit is accessed or not on a CAN bus CAN be provided at any time, namely, the on-off control of the terminal resistor circuit is controlled by the double-channel solid-state relay, as CAN be seen from the figure, the common end of the double-channel solid-state relay is respectively connected with the I/O port of the MCU and the ground, the two normally open ports are respectively connected with a terminal resistor to jointly control whether the two terminal resistors are accessed or not, when the other side of the CAN communication port is provided with the terminal resistor circuit, the relay is controlled to be disconnected, and when the other side of the CAN communication port is not provided with a terminal resistor circuit, the relay is controlled to be closed.

Furthermore, the terminal resistor circuit is formed by connecting two 61.9 ohm resistors in series at the CAN bus terminal to realize the impedance matching of the CAN bus terminal, and a 100nF capacitor is indirectly arranged between the two resistors to filter out the common mode current.

Furthermore, the solid-state relay ASSR1228 chip has 8 pins, pins 1 and 3 are connected with the I/O port, and pins 2 and 4 are grounded. 5. Pin No. 6 is connected in series to one terminal resistor, and pins No. 7 and No. 8 are connected in series to the other terminal resistor. When the I/O port outputs a high level, the relay is closed, and the terminal resistance circuit is connected into the CAN bus; when the I/O port outputs low level, the relay is opened, and the terminal resistance circuit is disconnected from the CAN bus.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.

Claims

1. A CAN bus protection and control circuit, including MCU and CAN transceiver circuitry that has CAN controller and IO port and has CANH output and CANL output, its characterized in that: thereby MCU's CAN controller through the double-channel digital isolator with CAN transceiver circuit be connected with CAN transceiver circuit between carry out information communication, CAN transceiver circuit's CANH output and CANL output are connected with common mode choke coil circuit, common mode choke coil circuit is connected to CAN communication bus on through the protection control circuit who has terminal resistance circuit and protection circuit, be connected with the solid state relay that CAN carry out on-off control to terminal resistance circuit between MCU's IO port and the terminal resistance circuit.

2. The CAN bus protection and control circuit of claim 1, wherein: pins VOA and VIB of the dual-channel digital isolator are respectively connected with RX and TX of the CAN controller, and pins VIA and VOB are respectively connected with RXD and TXD of the CAN transceiver circuit.

3. The CAN-bus protection and control circuit according to claim 1 or 2, wherein: the dual-channel digital isolator adopts an ADUM1201 chip.

4. The CAN bus protection and control circuit of claim 3, wherein: the CAN transceiver circuit consists of a CAN transceiver and a Y-shaped filter circuit consisting of two capacitors, and the CAN transceiver adopts an SN65HVD1050 chip.

5. The CAN-bus protection and control circuit according to claim 1, 2 or 4, wherein: the common mode choke coil circuit is composed of a common mode choke coil and a Y-shaped filter circuit composed of two capacitors.

6. The CAN bus protection and control circuit of claim 5, wherein: the protection control circuit adopts a double common anode Zener transient voltage suppressor.

7. The CAN-bus protection and control circuit of claim 1, 2, 4 or 6, wherein: the solid-state relay adopts an ASSR1228 double-channel solid-state relay chip.

8. The CAN bus protection and control circuit of claim 7, wherein: the solid-state relay ASSR1228 chip has 8 pins, the pins 1 and 3 are connected with the I/O port, the pins 2 and 4 are grounded, the pins 5 and 6 are connected to one terminal resistor in series, and the pins 7 and 8 are connected to the other terminal resistor in series.