Multi-path CAN (Controller Area Network) interface circuit with power supply isolation

Abstract

According to the multipath CAN interface circuit with the power supply isolation function, a solution for performing power supply isolation and ground plane segmentation on the main controller MCU is provided, so that power supply isolation between the MCU controller and the multipath CAN interfaces is realized, the reliability of the CAN interfaces is improved, the more the CAN interfaces are, the more the equipment cost is reduced, the size of the controller is reduced, and the controller is convenient to install. Comprising a power supply isolation circuit which is connected between a system main power supply and an MCU controller and is used for carrying out power supply isolation on the MCU controller and CAN interfaces, the MCU controller is connected with a plurality of CAN interfaces in parallel, and a digital isolation CAN transceiver which is used for carrying out electromagnetic isolation on the MCU controller and the CAN interfaces and an electrostatic protection circuit are connected between the MCU controller and each CAN interface in series; the power supply isolation circuit is formed by connecting an input pi-type filter, an isolation power supply U1, an output pi-type filter and a linear voltage regulator U2 in series.

Description

Technical Field

[0001] The utility model relates to a multi-channel CAN interface circuit with power supply isolation and anti-interference design, belonging to the field of electrical and automation control. Background Art

[0002] CAN bus is a local area network technology widely used in the field of transportation and industrial automation equipment. It has practical characteristics such as high transmission rate, multi-bit addressing and error detection capabilities. Existing AGV / AMR mobile robot control equipment is usually equipped with multiple CAN interfaces to meet the communication connection between different devices, such as high-speed CAN interface for connecting motor drivers, and low-speed CAN interface for connecting batteries, ultrasonic obstacle avoidance sensors and other devices.

[0003] The controller of this type of equipment has high reliability requirements for the CAN bus circuit design. If the CAN fails or the communication is abnormal, it will directly cause the MCU chip and other components to reset abnormally, which will have an adverse effect on the robot's positioning and navigation. In this regard, the existing technology adopts an independent isolation circuit design configured on each CAN interface, but it also significantly increases the equipment cost, controller size and operation and maintenance workload.

[0004] In view of this, this patent application is proposed. Utility Model Content

[0005] The multi-channel CAN interface circuit with power isolation described in the utility model aims to solve the problems existing in the above-mentioned prior art and proposes a solution for power isolation and ground plane division of the main controller MCU, so as to realize power isolation between the MCU controller and the multi-channel CAN interface and improve the reliability of the CAN interface. The more CAN interfaces there are, the more conducive it is to reduce equipment costs and reduce the size of the controller for easy installation.

[0006] To achieve the above-mentioned design purpose, the multi-channel CAN interface circuit with power isolation includes a power isolation circuit connected between the system main power supply and the MCU controller and used to isolate the MCU controller from the CAN interface for power supply. The MCU controller is connected in parallel with multiple CAN interfaces, and a digital isolation CAN transceiver for electromagnetically isolating the MCU controller from the CAN interface, as well as an electrostatic protection circuit, are connected in series between the MCU controller and each CAN interface; the power isolation circuit is composed of an input π-type filter, an isolation power supply U1, an output π-type filter and a linear regulator U2 connected in series.

[0007] Furthermore, in the power isolation circuit, the input +5V power supply is simultaneously connected to the first capacitor C1 and one end of the first inductor L1, the other end of the first capacitor C1 is connected to the input power ground GND, the other end of the first inductor L1 is connected to the second capacitor C2 and the first pin Vin of the isolation power supply U1, and the other end of the second capacitor C2 is connected to the input power ground GND; the first capacitor C1, the second capacitor C2 and the first inductor L1 are connected to form an input π-type filter.

[0008] Furthermore, in the power isolation circuit, the first pin Vin of the isolated power supply U1 is connected to one end of the first inductor L1, the second pin GND is connected to the ground GND of the input power supply and is also connected to the eighth capacitor C8, and the other end of the eighth capacitor C8 is connected to the isolation ground GND_MCU; the fifth pin of the isolated power supply U1 is connected to the other end of the eighth capacitor C8 and is also connected to the isolation ground GND_MCU; the seventh pin of the isolated power supply U1 is simultaneously connected to one end of the third capacitor C3 and one end of the second inductor L2, the other end of the third capacitor C3 is connected to the isolation ground GND_MCU, the other end of the second inductor L2 is simultaneously connected to the fourth capacitor C4, one end of the fifth capacitor C5, and the third pin IN of the linear regulator U2; the other ends of the fourth capacitor C4 and the fifth capacitor C5 are respectively connected to the isolation ground GND_MCU.

[0009] Furthermore, in the power isolation circuit, the third capacitor C3, the fourth capacitor C4 and the second inductor L2 are connected to form an output π-type filter; the output power +5V_MCU of the second inductor L2 and the isolation ground GND_MCU are the power supplies completely isolated from the input.

[0010] Furthermore, in the power isolation circuit, the linear regulator U2 uses the AMS1117-3.3 chip, the fifth capacitor C5 is a 0.1uF filter capacitor, the first pin GND is connected to the isolation ground GND_MCU, the second and fourth pins are respectively connected to one end of the sixth capacitor C6 and the seventh capacitor C7, and the other ends of the sixth capacitor C6 and the seventh capacitor C7 are respectively connected to the isolation ground GND_MCU; 3V3 is the 3.3v voltage after being stepped down by the linear regulator U2, and is filtered by the 10uF sixth capacitor C6 and the 0.1uF seventh capacitor C7 to supply power to the MCU controller.

[0011] In summary, the multi-channel CAN interface circuit with power isolation proposed in the present application has the advantage that it realizes the effective isolation of the MCU controller and the CAN transceiver power supply, including the division of the MCU ground plane, thereby avoiding the separate power supply isolation of each CAN interface. It not only has high economy and multi-channel scalability, but also the present application can be applied to harsh environments and ensure that the MCU controller can operate reliably under all data rates and power supply voltage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present application will now be further described with reference to the following drawings;

[0013] Figure 1 It is a schematic diagram of a multi-channel CAN interface circuit with power isolation described in this application;

[0014] Figure 2 It is a schematic diagram of the power isolation circuit;

[0015] Figure 3 This is the schematic diagram of the MCU controller circuit;

[0016] Figure 4 It is a schematic diagram of the CAN bus interface circuit; DETAILED DESCRIPTION

[0017] Embodiment 1, as Figures 1 to 4 As shown, the present application proposes a multi-channel CAN interface circuit with power isolation that can be applied to AGV / AMR mobile robots, the circuit includes a power isolation circuit connected between the system main power supply and the MCU controller and used to power isolate the MCU controller from the CAN interface, the MCU controller is connected in parallel with multiple CAN interfaces, and a digital isolation CAN transceiver for electromagnetically isolating the MCU controller from the CAN interface, and an electrostatic protection circuit are connected in series between the MCU controller and each CAN interface.

[0018] Among them, Figure 2 As shown, the power isolation circuit is composed of an input π-type filter, an isolated power supply U1, an output π-type filter and a linear regulator U2 connected in series, so as to have the functions of filtering, isolation and voltage reduction;

[0019] The input +5V power supply is connected to one end of the first capacitor C1 and the first inductor L1 at the same time, the other end of the first capacitor C1 is connected to the input power ground GND, the other end of the first inductor L1 is connected to the second capacitor C2 and the first pin Vin of the isolation power supply U1, and the other end of the second capacitor C2 is connected to the input power ground GND; the first capacitor C1 and the second capacitor C2 can use 4.7uF ceramic capacitors, and the first inductor L1 can use 6.8uH inductor; the first capacitor C1, the second capacitor C2 and the first inductor L1 are connected to form an input π-type filter to filter out power input clutter interference;

[0020] The isolated power supply U1 can use the F0505S-2WR3 chip, which has a 2W rated voltage input to isolate the unregulated single output power supply, that is, to achieve 5V / 5V isolation, an isolation voltage of 3000VDC, and a no-load input current as low as 8mA, thus having a continuous short-circuit protection function. The first pin Vin of the isolated power supply U1 is connected to one end of the first inductor L1, the second pin GND is connected to the ground GND of the input power supply and is also connected to the eighth capacitor C8, the other end of the eighth capacitor C8 is connected to the isolated ground GND_MCU, and the eighth capacitor C8 can effectively absorb the high-frequency noise between the input and output ends of the isolated power supply U1; the fifth pin of the isolated power supply U1 is connected to the other end of the eighth capacitor C8 and is also connected to the isolated ground GND_MCU; the seventh pin of the isolated power supply U1 is simultaneously connected to one end of the third capacitor C3 and one end of the second inductor L2, the other end of the third capacitor C3 is connected to the isolated ground GND_MCU, the other end of the second inductor L2 is simultaneously connected to the fourth capacitor C4, one end of the fifth capacitor C5, and the third pin IN of the linear regulator U2; the other ends of the fourth capacitor C4 and the fifth capacitor C5 are respectively connected to the isolated ground GND_MCU;

[0021] The third capacitor C3 and the fourth capacitor C4 can be 10uF ceramic capacitors, and the second inductor L2 can be 6.8uH inductor; the third capacitor C3, the fourth capacitor C4 and the second inductor L2 are connected to form an output π-type filter to filter out output power supply interference; the output power supply +5V_MCU and the isolation ground GND_MCU of the second inductor L2 are the power supply completely isolated from the input;

[0022] The linear regulator U2 can use the AMS1117-3.3 chip, the fifth capacitor C5 is a 0.1uF filter capacitor, the first pin GND is connected to the isolated ground GND_MCU, the second and fourth pins are respectively connected to one end of the sixth capacitor C6 and the seventh capacitor C7, and the other ends of the sixth capacitor C6 and the seventh capacitor C7 are respectively connected to the isolated ground GND_MCU; 3V3 is the 3.3v voltage after being stepped down by the linear regulator U2, and is filtered by the 10uF sixth capacitor C6 and the 0.1uF seventh capacitor C7 to supply power to the MCU controller.

[0023] As shown above, the system total power supply outputs a +5v voltage, which is isolated into a +5V_MCU power supply through a π-type filter and a linear regulator U2. Then, the +5V_MCU power supply is further reduced through an LDO step-down circuit composed of a π-type filter and a linear regulator U2 to obtain a 3V3 power supply. The reduced 3V3 power supply is finally used to supply power to the MCU controller.

[0024] like Figure 3As shown in the figure, the MCU controller includes a power supply circuit, a crystal oscillator circuit, a reset circuit and a startup circuit. Among them, U5A is an STM32F407ZGT6 microcontroller with an ARM Cortex-M4 core from ST, which provides two CAN 2.0B standard CAN controllers with error detection, error notification and error recovery functions; specifically, the 103rd pin CAN1_RX of U5A is connected to Figure 4 The second pin of U3 and the 104th pin of U5A, CAN1_TX, are connected to Figure 4 The 3rd pin of U3 and the 135th pin of U5A CAN2_RX are connected to Figure 4 The 2nd pin of U4 and the 136th pin of U5A, CAN2_RX, are connected to Figure 4The third pin of U4 in the circuit; the 138th startup circuit pin BOOT0 of U5A is connected to one end of the resistor R3, and the other end of R3 is connected to the ground GND_MCU; the 16th, 38th, 51st, 61st, 83rd, 94th, 107th, 120th, 130th pins of U5A are connected to the ground GND_MCU; the 17th, 30th, 39th, 52nd, 62nd, 72nd, 84th, 95th, 108th, 121st, 131st, 144th pins of U5A are connected to the power supply 3V3, and the above pins are also connected to the capacitors C22, C23, C24, C25, One end of C26, C27, C28, C29, C30, C31, C32, and C33, and the other ends of the above capacitors are connected to the ground GND_MCU respectively; the 25th pin of U5A is connected to one end of capacitor C15 and one end of resistor R4, the other end of capacitor C15 is connected to the ground GND_MCU, and the other end of resistor R4 is connected to power supply 3V3 to form a power-on reset circuit; the 23rd pin of U5A is connected to the 3rd pin of crystal oscillator Y1, and is also connected to one end of capacitor C17, and the other end of capacitor C17 is connected to the ground GND_MCU; The 24th pin of U5A is connected to the 1st pin of crystal oscillator Y1, and is also connected to one end of capacitor C16, and the other end of capacitor C16 is connected to ground GND_MCU; the 2nd and 4th pins of crystal oscillator Y1 are connected to ground GND_MCU, forming the crystal oscillator circuit of MCU controller; the 32nd pin of U5A is connected to power supply 3V3, and is also connected to one end of capacitor C18, and the other end of capacitor C18 is connected to ground GND_MCU, thus serving as the internal ADC reference voltage circuit; the 71st pin of U5A is connected to one end of capacitor C19, and the The other end is connected to the ground GND_MCU; the 106th pin of U5A is connected to one end of the capacitor C20, and the other end of the capacitor C20 is connected to the ground GND_MCU; the 33rd pin of U5A is connected to the 120R@100MHz ferrite bead L3, and is also connected to one end of the capacitor C21, the other end of L3 is connected to the power supply 3V3, and the other end of C21 is connected to the ground GND_MCU; the 31st pin of U5A is connected to the ground GND_MCU; the 143rd pin of U5A is connected to one end of the resistor R5, and the other end of R5 is connected to the power supply 3V3.

[0025] like Figure 4As shown in the figure, the CAN interface consists of a digital magnetically isolated CAN transceiver, an electrostatic protection circuit, and a terminal resistor, thereby connecting to the CAN communication port of the external motor driver. Among them, U3 and U4 are two independent digitally isolated CAN transceivers ISO1050D. ISO1050 is an electromagnetically isolated CAN repeater that meets the requirements of ISO11898-2 and has 5000VRMS isolation. When used with an isolated power supply, it can prevent noise currents on the data bus or other circuits from entering the local ground and interfering with and damaging sensitive circuits. It has cross-wire, overvoltage, and ground loss protection (–27 to 40V) as well as overtemperature shutdown functions.

[0026] The first pin VCC1 of the digital isolated CAN transceiver U3 is the digital side power supply voltage (3V-5.5V), which is connected to one end of the filter capacitor C10 and the isolated power supply 3V3. The other end of C10 is connected to the ground GND_MCU. The second pin RXD of U3 is the CAN transmit data input (low level in the dominant bus state; high level in the recessive bus state), which is connected to the 103rd pin CAN1_RX of U5A. The third pin TXD of U3 is the CAN receive data output (low level in the dominant bus state; high level in the recessive bus state), which is connected to the 104th pin CAN1_TX of U5A. The fourth pin GND1 of U3 is the digital side ground, which is connected to the ground GND_MCU of the isolated power supply.

[0027] U3's 8th pin VCC2 is the transceiver side power supply voltage (5V), connected to one end of the filter capacitor C9, and connected to the system's total power supply +5V, and the other end of C9 is connected to the ground GND. U3's 7th pin CANH is the high-level CAN bus, connected to the 2nd pin of the unidirectional TVS diode D1 (PSOT24C), and connected to one end of the terminal resistor R1 (120Ω). U3's 6th pin CANL is the low-level CAN bus, connected to the 1st pin of D1, and connected to the other end of the terminal resistor R1. The 3rd pin of D1 is connected to the system ground GND. U3's 5th pin GND2 is the transceiver side ground connected to the system ground GND, and connected to one end of the 0.01uF capacitor C11, and the other end of C14 is connected to the shielded ground to remove high-frequency noise interference in the power supply. CAN1H and CAN1L are connected to external devices with CAN bus interfaces.

[0028] The first pin VCC1 of the digital isolated CAN transceiver U4 is connected to one end of the filter capacitor C13 and the isolated power supply 3V3. The other end of C13 is connected to the ground GND_MCU. The second pin RXD of U4 is connected to the 135th pin CAN2_RX of U5A. The third pin TXD of U4 is connected to the 136th pin CAN2_TX of U5A. The fourth pin GND1 of U4 is connected to the ground GND_MCU of the isolated power supply.

[0029] The 8th pin VCC2 of U4 is connected to one end of the filter capacitor C12 and to the system total power supply +5V, and the other end of C12 is connected to the ground GND. The 7th pin of U4 is connected to the 2nd pin of TVS tube D2 and to one end of the terminal resistor R2. The 6th pin CANL of U4 is connected to the 1st pin of D2 and to the other end of the terminal resistor R2. The 3rd pin of D2 is connected to the system ground GND. The 5th pin GND2 of U4 is connected to the system ground GND and to one end of the 0.01uF capacitor C14, and the other end of C14 is connected to the shielded ground. CAN2H and CAN2L are connected to external devices with CAN bus interface.

[0030] The above contents and the embodiments given in the accompanying drawings are only preferred solutions for achieving the purpose of the utility model. For those skilled in the art, they can be inspired by this and directly deduce other alternative structures that conform to the design concept of the utility model. Other structural features obtained thereby should also belong to the scope of the solution described in the utility model.

Claims

1. A multi-channel CAN interface circuit with power isolation, characterized in that: It includes a power isolation circuit connected between the system main power supply and the MCU controller and used for isolating the power supply of the MCU controller from the CAN interface. The MCU controller is connected in parallel with multiple CAN interfaces. A digital isolation CAN transceiver for electromagnetically isolating the MCU controller from the CAN interface and an electrostatic protection circuit are connected in series between the MCU controller and each CAN interface; The power isolation circuit is composed of an input π-type filter, an isolation power supply U1, an output π-type filter and a linear regulator U2 connected in series.

2. The multi-channel CAN interface circuit with power isolation according to claim 1, characterized in that: In the power isolation circuit, the input +5V power supply is simultaneously connected to the first capacitor C1 and one end of the first inductor L1, the other end of the first capacitor C1 is connected to the input power ground GND, the other end of the first inductor L1 is connected to the second capacitor C2 and the first pin Vin of the isolation power supply U1, and the other end of the second capacitor C2 is connected to the input power ground GND; the first capacitor C1, the second capacitor C2 and the first inductor L1 are connected to form an input π-type filter.

3. The multi-channel CAN interface circuit with power isolation according to claim 2, characterized in that: The power isolation circuit is as follows: the first pin Vin of the isolated power supply U1 is connected to one end of the first inductor L1, the second pin GND is connected to the ground GND of the input power supply and is also connected to the eighth capacitor C8, and the other end of the eighth capacitor C8 is connected to the isolation ground GND_MCU; the fifth pin of the isolated power supply U1 is connected to the other end of the eighth capacitor C8 and is also connected to the isolation ground GND_MCU; the seventh pin of the isolated power supply U1 is simultaneously connected to one end of the third capacitor C3 and one end of the second inductor L2, the other end of the third capacitor C3 is connected to the isolation ground GND_MCU, the other end of the second inductor L2 is simultaneously connected to the fourth capacitor C4, one end of the fifth capacitor C5, and the third pin IN of the linear regulator U2; the other ends of the fourth capacitor C4 and the fifth capacitor C5 are respectively connected to the isolation ground GND_MCU.

4. The multi-channel CAN interface circuit with power isolation according to claim 1, characterized in that: In the power isolation circuit, the third capacitor C3, the fourth capacitor C4 and the second inductor L2 are connected to form an output π-type filter; the output power +5V_MCU of the second inductor L2 and the isolation ground GND_MCU are the power sources completely isolated from the input.

5. The multi-channel CAN interface circuit with power isolation according to claim 1, characterized in that: In the power isolation circuit, the linear regulator U2 uses the AMS1117-3.3 chip, the fifth capacitor C5 is a 0.1uF filter capacitor, the first pin GND is connected to the isolation ground GND_MCU, the second and fourth pins are respectively connected to one end of the sixth capacitor C6 and the seventh capacitor C7, and the other ends of the sixth capacitor C6 and the seventh capacitor C7 are respectively connected to the isolation ground GND_MCU; 3V3 is the 3.3v voltage after being stepped down by the linear regulator U2, and is filtered by the 10uF sixth capacitor C6 and the 0.1uF seventh capacitor C7 to supply power to the MCU controller.

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