Vehicle-mounted CAN port protection circuit and PCB

Abstract

The embodiment of the utility model provides a vehicle-mounted CAN port protection circuit and a PCB, the vehicle-mounted CAN port protection circuit comprises a common-mode inductor L1, a CAN signal matching circuit, a first-stage filter circuit and a second-stage filter circuit, a pin 2 of the common-mode inductor L1 is connected with a low-voltage wiring chip port, a pin 3 of the common-mode inductor L1 is connected with a high-voltage wiring chip port, and a pin 3 of the common-mode inductor L1 is connected with a high-voltage wiring chip port. The common-mode inductor L1 is connected with a chip IO interface through a chip port of a low-voltage wire and a chip port of a high-voltage wire, the CAN signal matching circuit is connected with a pin 1 and a pin 4 of the common-mode inductor L1, the first-stage filter circuit serves as a first-stage filter, the second-stage filter circuit serves as a second-stage filter, and the first-stage filter circuit and the second-stage filter circuit serve as a second-stage filter. The CAN signal matching circuit, the second-stage filter circuit and the first-stage filter circuit are connected in sequence, and the first-stage filter circuit is connected with a connector through a connector port of a low-voltage wire and a connector port of a high-voltage wire and is connected with a whole vehicle wire harness through the connector.

Description

Technical Field

[0001] The utility model relates to the technical field of PCB boards, and in particular to a vehicle-mounted CAN port protection circuit and a PCB board. Background Art

[0002] CAN (Controller Area Network) signals are one of the primary communication signals in the automotive industry. Hundreds of electronic components throughout a vehicle exchange information with the vehicle and other components via CAN signals. Vehicles must have a CAN diagnostic port to support complete vehicle fault analysis. However, every time information is manually read through a peripheral connector, the CAN port becomes a high-frequency discharge point for human static electricity. This instantaneous discharge of static electricity, with voltages ranging from several kilovolts to over ten kilovolts, can easily damage electronic components within the circuit and cause signal distortion. Utility Model Content

[0003] The present application provides a vehicle-mounted CAN port protection circuit and PCB board. Through the reasonable design of the port circuit, the electrostatic protection function is realized, the anti-static ability and the anti-interference ability of the CAN signal are improved, damage to the circuit electronic components and signal distortion are avoided, and the service life of the circuit electronic components is increased.

[0004] In a first aspect, according to an embodiment of the present application, a vehicle-mounted CAN port protection circuit is provided, comprising: a common-mode inductor L1, a CAN signal matching circuit, a first-stage filtering circuit, and a second-stage filtering circuit;

[0005] Pin 2 of the common-mode inductor L1 is connected to the chip port CAN1_1_L with low voltage wiring, and pin 3 of the common-mode inductor L1 is connected to the chip port CAN1_1_H with high voltage wiring. The common-mode inductor L1 is connected to the chip IO interface through the chip port CAN1_1_L with low voltage wiring and the chip port CAN1_1_H with high voltage wiring. The CAN signal matching circuit is respectively connected to pin 1 and pin 4 of the common-mode inductor L1. The first-stage filter circuit serves as the first-stage filter, and the second-stage filter circuit serves as the second-stage filter. The CAN signal matching circuit is connected to the second-stage filter circuit, and the second-stage filter circuit is connected to the first-stage filter circuit. The first-stage filter circuit is respectively connected to the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and the first-stage filter circuit is connected to the connector through the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and is connected to the vehicle wiring harness through the connector.

[0006] In some embodiments of the present application, the CAN signal matching circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6 and a capacitor C1, one end of the resistor R3 is respectively connected to pin 4 of the common-mode inductor L1 and the high-voltage wiring connector port CAN1H, the other end of the resistor R3 is respectively connected to one end of the resistor R4 and one end of the capacitor C1, the other end of the resistor R4 is respectively connected to pin 1 of the common-mode inductor L1 and the low-voltage wiring connector port CAN1L, one end of the resistor R5 is respectively connected to pin 4 of the common-mode inductor L1 and the high-voltage wiring connector port CAN1H, the other end of the resistor R5 is respectively connected to one end of the resistor R6 and one end of the capacitor C1, the other end of the resistor R6 is respectively connected to pin 1 of the common-mode inductor L1 and the low-voltage wiring connector port CAN1L, and the other end of the capacitor C1 is grounded.

[0007] In some embodiments of the present application, the second-stage filtering circuit includes a clamping diode D1, wherein pin 1 of the clamping diode D1 is respectively connected to pin 4 of the common-mode inductor L1 and the connector port CAN1H for the high-voltage wiring, pin 2 of the clamping diode D1 is respectively connected to pin 1 of the common-mode inductor L1 and the connector port CAN1L for the low-voltage wiring, and pin 3 of the clamping diode D1 is grounded.

[0008] In some embodiments of the present application, the first-stage filtering circuit includes a capacitor C2 and a capacitor C3, one end of the capacitor C2 is respectively connected to pin 4 of the common-mode inductor L1 and the connector port CAN1H of the high-voltage wiring, and the other end of the capacitor C2 is grounded, one end of the capacitor C3 is respectively connected to pin 1 of the common-mode inductor L1 and the connector port CAN1L of the low-voltage wiring, and the other end of the capacitor C3 is grounded.

[0009] In some embodiments of the present application, it further includes: a resistor R1 and a resistor R2, one end of the resistor R1 is connected to the chip port CAN1_1_H with high voltage wiring, one end of the resistor R2 is connected to the chip port CAN1_1_L with low voltage wiring, and the other end of the resistor R1 and the other end of the resistor R2 are respectively connected to the CAN signal matching circuit.

[0010] In a second aspect, according to an embodiment of the present application, a PCB board is provided, comprising: the vehicle-mounted CAN port protection circuit described in the first aspect.

[0011] In some embodiments of the present application, the pin 3 of the clamping diode D1 is connected to the entire GND copper layer of the PCB board.

[0012] In some embodiments of the present application, the ground terminal of the capacitor C2, the ground terminal of the capacitor C3, and the pin 3 of the clamping diode D1 are all connected to the MGND (battery negative pole - vehicle body ground) pad of the PCB board.

[0013] In some embodiments of the present application, the ground terminal of the negative electrode of the vehicle battery is connected to the MGND pad of the PCB board.

[0014] The beneficial effects of the embodiments of the present application are as follows:

[0015] A reasonable on-board CAN port protection circuit design is adopted to implement electrostatic protection function, improve anti-static ability and CAN signal anti-interference ability, avoid damage to circuit electronic components and signal distortion, and increase the service life of circuit electronic components. In addition, it is combined with the optimized layout of various components on the PCB board to reduce the effect of performance derating caused by the parasitic parameters of the PCB board, further improving the anti-interference ability of the CAN signal in the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a circuit schematic diagram of a vehicle-mounted CAN port protection circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this utility model, not all of them. Based on the embodiments of this utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this utility model.

[0019] It should be noted that the terms "including," "having," and any variations thereof in the embodiments and drawings of this application are intended to cover non-exclusive inclusions. For example, "including" is not limited to the listed structures, but may optionally include structures not listed, or may optionally include other components inherent to those structures.

[0020] The present application discloses an in-vehicle CAN port protection circuit that, through the rational design of the port circuit, implements an electrostatic protection function, prevents damage to electronic components in the circuit and signal distortion, and thus increases the service life of electronic components in the circuit. Detailed descriptions are given below.

[0021] Figure 1 FIG. 1 shows a vehicle-mounted CAN port protection circuit provided according to an embodiment of the present application. Figure 1 As shown, the in-vehicle CAN port protection circuit primarily includes a common-mode inductor L1, a CAN signal matching circuit, a first-stage filter circuit, and a second-stage filter circuit. The common-mode inductor L1 utilizes both common-mode and differential-mode inductance to divide the voltage of the electrostatic signal, thereby suppressing common-mode interference and protecting the IO port of the downstream chip. The common-mode inductor L1 includes pins 1, 2, 3, and 4. Pin 1 is the output terminal of the first winding of the common-mode inductor L1, pin 2 is the input terminal of the first winding of the common-mode inductor L1, pin 3 is the input terminal of the second winding of the common-mode inductor L1, and pin 4 is the output terminal of the second winding of the common-mode inductor L1. Specifically, pin 2 of the common-mode inductor L1 is connected to the chip port CAN1_1_L with low voltage wiring, pin 3 of the common-mode inductor L1 is connected to the chip port CAN1_1_H with high voltage wiring, and the common-mode inductor L1 is connected to the chip IO interface through the chip port CAN1_1_L with low voltage wiring and the chip port CAN1_1_H with high voltage wiring. The CAN signal matching circuit is respectively connected to pin 1 and pin 4 of the common-mode inductor L1, the first-stage filtering circuit serves as the first-stage filtering, the second-stage filtering circuit serves as the second-stage filtering, the CAN signal matching circuit is connected to the second-stage filtering circuit, the second-stage filtering circuit is connected to the first-stage filtering circuit, the first-stage filtering circuit is respectively connected to the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and the first-stage filtering circuit is connected to the connector through the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and is connected to the vehicle wiring harness through the connector.

[0022] Furthermore, the vehicle-mounted CAN port protection circuit also includes resistors R1 and R2. One end of resistor R1 is connected to the high-voltage chip port CAN1_1_H, and one end of resistor R2 is connected to the low-voltage chip port CAN1_1_L. The other ends of resistors R1 and R2 are respectively connected to the CAN signal matching circuit. Resistors R1 and R2 perform the same function as common-mode inductor L1. The vehicle-mounted CAN port protection circuit can be implemented in either of two ways. In a specific implementation, resistors R1 and R2 are surface-mount components with specifications of R0402 and a resistance value of 0R.

[0023] In some embodiments, as Figure 1As shown, the CAN signal matching circuit includes resistors R3, R4, R5, R6, and C1. Specifically, one end of resistor R3 is connected to pin 4 of common-mode inductor L1 and the high-voltage connector port CAN1H, respectively. The other end of resistor R3 is connected to one end of resistor R4 and one end of capacitor C1, respectively. The other end of resistor R4 is connected to pin 1 of common-mode inductor L1 and the low-voltage connector port CAN1L, respectively. One end of resistor R5 is connected to pin 4 of common-mode inductor L1 and the high-voltage connector port CAN1H, respectively. The other end of resistor R5 is connected to one end of resistor R6 and one end of capacitor C1, respectively. The other end of resistor R6 is connected to pin 1 of common-mode inductor L1 and the low-voltage connector port CAN1L, respectively. The other end of capacitor C1 is grounded. Thus, the arrangement of resistors R3, R4, R5, R6, and C1 improves signal quality and anti-interference capabilities, reduces electromagnetic interference on the bus, matches the bus characteristic impedance, and controls the propagation speed of the bus signal. In a specific implementation process, the surface mount device specification of the resistors R3, R4, R5, and R6 is R0805, and the resistance value is 120R.

[0024] In other embodiments, Figure 1As shown, capacitors C2 and C3 are used as the first-stage filter circuit to discharge static electricity to the ground, and a clamping diode D1 is used as the second-stage filter circuit package to discharge static electricity to the ground. At the same time, voltage clamping is used to accurately protect the subsequent circuit. Among them, the clamping diode D1 is composed of four Zener diodes (i.e., a first Zener diode, a second Zener diode, a third Zener diode, and a fourth Zener diode). The positive electrode of the first Zener diode is connected to the positive electrode of the second Zener diode, the positive electrode of the third Zener diode is connected to the positive electrode of the fourth Zener diode, and the cathode of the second Zener diode is connected to the cathode of the third Zener diode. The clamping diode D1 includes pins 1, 2, and 3. Pin 1 is the negative terminal of the first Zener diode, pin 2 is the negative terminal of the fourth Zener diode, and pin 3 is the connecting end of the negative electrode of the second Zener diode and the negative electrode of the third Zener diode. Specifically, pin 1 of clamping diode D1 is connected to pin 4 of common-mode inductor L1 and high-voltage connector port CAN1H, respectively. Pin 2 of clamping diode D1 is connected to pin 1 of common-mode inductor L1 and low-voltage connector port CAN1L, respectively. Pin 3 of clamping diode D1 is grounded. One end of capacitor C2 is connected to pin 4 of common-mode inductor L1 and high-voltage connector port CAN1H, respectively. The other end of capacitor C2 is grounded. One end of capacitor C3 is connected to pin 1 of common-mode inductor L1 and low-voltage connector port CAN1L, respectively. The other end of capacitor C3 is grounded. In a specific implementation, the model of clamping diode D1 is PESD2IVN24-UX, and the models of capacitors C2 and C3 are both C0402, with a capacitance of 47 pF.

[0025] like Figure 1 As shown in the figure, the low-voltage connector port CAN1L and the high-voltage connector port CAN1H on the right side of the vehicle CAN port protection circuit are connected to the vehicle wiring harness via connectors. The low-voltage chip port CAN1_1_L and the high-voltage chip port CAN1_1_H on the left side are connected to the internal chip IO. The static electricity propagation path in this circuit is when the human body (static source) contacts the vehicle wiring harness / connector port pins, and then transfers from the right side to the chip IO on the left side. During this process, the circuit design of the first-stage filtering circuit, the second-stage filtering circuit, the CAN signal matching circuit, and the common-mode inductor L1 reduces the impact of static electricity, achieving ESD protection, preventing damage to the circuit's electronic components and signal distortion, thereby increasing the service life of the circuit's electronic components.

[0026] In addition, if Figure 1 As shown, the vehicle-mounted CAN port protection circuit is further provided with detection points TP100, TP101, TP102, TP103 and TP104 to facilitate circuit detection.

[0027] The embodiment of the present application further discloses a printed circuit board (PCB), which includes: a vehicle-mounted CAN port protection circuit, wherein the vehicle-mounted CAN port protection circuit is the vehicle-mounted CAN port protection circuit provided in the above embodiment, such as Figure 1 As shown, its components and principles are the same as those in the above embodiment. For the sake of brief description, the content of the vehicle-mounted CAN port protection circuit is not repeated in this embodiment. Please refer to the content in the above embodiment of the vehicle-mounted CAN port protection circuit.

[0028] Although the PCB circuit structure of the PCB board can reduce the influence of static electricity through the circuit design of the above-mentioned vehicle-mounted CAN port protection circuit, it cannot completely eliminate the influence. Based on this, in some specific embodiments, the pin 3 of the clamping diode D1 is connected to the entire layer of GND copper foil of the PCB board. In the prior art, the ground pin of the clamping diode is generally connected to GND through a via. The parasitic resistance and inductance of the via increase the impedance of the discharge path, which will cause the electrostatic capacity of the clamping diode to be reduced. The ground pin of the clamping diode D1 in the present application is connected to the entire layer of GND (copper foil), which greatly reduces the impedance of the discharge path and can effectively ensure that the discharge path is unobstructed.

[0029] In other specific embodiments, the ground terminal of capacitor C2, the ground terminal of capacitor C3, and pin 3 of clamping diode D1 in the PCB board are all connected to the MGND (battery negative pole - vehicle body ground) pad of the PCB board. Furthermore, the ground terminal of the negative pole of the vehicle battery is connected to the MGND pad of the PCB board. The GND copper foil in the prior art is not directly connected to the MGND, resulting in a blocked discharge path. However, the PCB board in the embodiment of the present application adjusts the capacitor C2, capacitor C3, clamping diode D1, and the electrostatic discharge ground (GND) to a unified GND with the MGND, ensuring a smooth discharge path.

[0030] The PCB board in the embodiment of the present application adopts a reasonable vehicle-mounted CAN port protection circuit design, and combined with the above-mentioned PCB circuit structure adjustment, during the experiment, static electricity was injected into the CAN signal, the equipment worked normally, and the impact was completely eliminated, and it is highly practical.

[0031] In summary, the present application discloses a vehicle-mounted CAN port protection circuit and PCB board, which adopts a reasonable vehicle-mounted CAN port protection circuit design to realize electrostatic protection function, improve anti-static ability and CAN signal anti-interference ability, avoid damage to circuit electronic components and signal distortion, etc., and increase the service life of circuit electronic components. In addition, it cooperates with the optimized layout of various components on the PCB board to reduce the effect derating caused by the parasitic parameters of the PCB board, and further improves the anti-interference ability of the CAN signal on the entire vehicle.

[0032] Those skilled in the art will understand that the drawings are merely schematic diagrams of one embodiment, and that the components shown in the drawings are not necessarily essential to the practice of the present invention. It should also be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it need not be further defined or explained in subsequent drawings.

[0033] In the description of the embodiments of this application, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0034] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection described in the claims.

Claims

1. A vehicle-mounted CAN port protection circuit, characterized in that: include: Common mode inductor L1, CAN signal matching circuit, first stage filter circuit and second stage filter circuit; Pin 2 of the common-mode inductor L1 is connected to the chip port CAN1_1_L with low voltage wiring, and pin 3 of the common-mode inductor L1 is connected to the chip port CAN1_1_H with high voltage wiring. The common-mode inductor L1 is connected to the chip IO interface through the chip port CAN1_1_L with low voltage wiring and the chip port CAN1_1_H with high voltage wiring. The CAN signal matching circuit is respectively connected to pin 1 and pin 4 of the common-mode inductor L1. The first-stage filter circuit serves as the first-stage filter, and the second-stage filter circuit serves as the second-stage filter. The CAN signal matching circuit is connected to the second-stage filter circuit, and the second-stage filter circuit is connected to the first-stage filter circuit. The first-stage filter circuit is respectively connected to the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and the first-stage filter circuit is connected to the connector through the connector port CAN1L with low voltage wiring and the connector port CAN1H with high voltage wiring, and is connected to the vehicle wiring harness through the connector.

2. The vehicle-mounted CAN port protection circuit according to claim 1, characterized in that: The CAN signal matching circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6 and a capacitor C1. One end of the resistor R3 is respectively connected to pin 4 of the common-mode inductor L1 and the high-voltage wiring connector port CAN1H, the other end of the resistor R3 is respectively connected to one end of the resistor R4 and one end of the capacitor C1, the other end of the resistor R4 is respectively connected to pin 1 of the common-mode inductor L1 and the low-voltage wiring connector port CAN1L, one end of the resistor R5 is respectively connected to pin 4 of the common-mode inductor L1 and the high-voltage wiring connector port CAN1H, the other end of the resistor R5 is respectively connected to one end of the resistor R6 and one end of the capacitor C1, the other end of the resistor R6 is respectively connected to pin 1 of the common-mode inductor L1 and the low-voltage wiring connector port CAN1L, and the other end of the capacitor C1 is grounded.

3. The vehicle-mounted CAN port protection circuit according to claim 2, characterized in that: The second-stage filtering circuit includes a clamping diode D1, wherein pin 1 of the clamping diode D1 is respectively connected to pin 4 of the common-mode inductor L1 and the high-voltage wiring connector port CAN1H, pin 2 of the clamping diode D1 is respectively connected to pin 1 of the common-mode inductor L1 and the low-voltage wiring connector port CAN1L, and pin 3 of the clamping diode D1 is grounded.

4. The vehicle-mounted CAN port protection circuit according to claim 3, characterized in that: The first-stage filtering circuit includes a capacitor C2 and a capacitor C3. One end of the capacitor C2 is respectively connected to pin 4 of the common-mode inductor L1 and the connector port CAN1H for the high-voltage wiring, and the other end of the capacitor C2 is grounded. One end of the capacitor C3 is respectively connected to pin 1 of the common-mode inductor L1 and the connector port CAN1L for the low-voltage wiring, and the other end of the capacitor C3 is grounded.

5. The vehicle-mounted CAN port protection circuit according to claim 4, characterized in that: Also includes: Resistor R1 and resistor R2, one end of the resistor R1 is connected to the chip port CAN1_1_H with the high voltage wiring, one end of the resistor R2 is connected to the chip port CAN1_1_L with the low voltage wiring, and the other end of the resistor R1 and the other end of the resistor R2 are respectively connected to the CAN signal matching circuit.

6. A PCB board, characterized in that: include: The vehicle-mounted CAN port protection circuit according to claim 5.

7. The PCB board according to claim 6, characterized in that: Pin 3 of the clamping diode D1 is connected to the entire GND copper layer of the PCB board.

8. The PCB board according to claim 6, characterized in that: The ground terminal of the capacitor C2, the ground terminal of the capacitor C3, and the pin 3 of the clamping diode D1 are all connected to the MGND pad of the PCB board.

9. The PCB board according to claim 8, characterized in that: The ground terminal of the negative electrode of the vehicle battery is connected to the MGND pad of the PCB board.

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