CAN bus communication circuit with high reliability and high applicability

Abstract

The utility model discloses a CAN bus communication circuit with high reliability and high applicability, which comprises an isolation CAN chip U1, a ground surge protection circuit, a common mode interference suppression circuit and a differential signal surge and short circuit protection circuit, and is characterized in that the output end of the isolation CAN chip U1 is electrically connected with the input end of the ground surge protection circuit; the output end of the ground surge protection circuit is electrically connected with the input end of the common-mode interference suppression circuit. According to the CAN bus communication circuit with high reliability and high applicability provided by the utility model, a plurality of module CAN nodes are connected in parallel, and the communication waveform is still good; meanwhile, the CAN bus surge and short circuit protection function is achieved, and a CAN chip cannot be damaged when surge and short circuit occur on the CAN bus; the anti-common-mode interference capability is high, and stable operation is still realized in a scene with large common-mode interference.

Description

Technical Field

[0001] The utility model relates to the technical field of CAN bus communication, and particularly relates to a CAN bus communication circuit with high reliability and high applicability. Background Technique

[0002] As the core component of new energy products, the power electronic conversion device needs to have the characteristics of strong maintainability, high reliability, strong anti-interference ability, etc. to operate stably in a complex external environment. The modular concept can reduce the pressure on a single power device of a high-power power electronic conversion device, achieve power redundancy between multiple modules, and enable maintenance without shutting down, greatly improving the reliability of high-power (such as MW-level systems) new energy products.

[0003] Currently, inside common high-power new energy products, several to dozens of smaller-power power modules are connected in parallel to jointly bear the system load power. Communication is required between the power modules to achieve data interaction, such as the load power borne by each module, so as to evenly distribute the load power, etc. Once the communication fails, it will affect the system operation performance and even cause the system to shut down. The communication between modules often adopts the CAN bus communication method. The CAN bus is widely used in the wired communication of power electronic products because of its long transmission distance and fast transmission speed. To improve the reliability of communication between modules, a CAN bus communication circuit suitable for multiple CAN node scenarios, with surge and short-circuit protection functions, and strong common-mode interference resistance, a CAN bus communication circuit with high reliability and high applicability is proposed. Content of the Utility Model

[0004] The purpose of the utility model is to provide a CAN bus communication circuit with high reliability and high applicability. When multiple module CAN nodes are connected in parallel, the communication waveform is still good; it has the CAN bus surge and short-circuit protection functions, and the CAN chip will not be damaged when there are surges and short-circuits on the CAN bus; it has strong common-mode interference resistance and can still operate stably in scenarios with large common-mode interference, so as to solve the problems of reporting errors when the CAN recognizes incorrect levels when multiple module CAN nodes are connected in parallel, damage to the CAN chip when there are surges and short-circuits on the CAN bus, and inability to communicate normally in scenarios with large common-mode interference proposed in the above background technique.

[0005] To achieve the above object, the present utility model provides the following technical solution: a CAN bus communication circuit with high reliability and high applicability, including an isolated CAN chip U1, a ground surge protection circuit, a common-mode interference suppression circuit, and a surge and short-circuit protection circuit for differential signals. The output end of the isolated CAN chip U1 is electrically connected to the input end of the ground surge protection circuit, the output end of the ground surge protection circuit is electrically connected to the input end of the common-mode interference suppression circuit, the output end of the common-mode interference suppression circuit is electrically connected to the input end of the surge and short-circuit protection circuit for differential signals, and the output end of the surge and short-circuit protection circuit for differential signals is connected to the CANH terminal and the CANL terminal for output.

[0006] Preferably, the 2nd terminal of the isolated CAN chip U1 is connected in series with a resistor R1 and then connected to the CAN-RX terminal for input signal. The output end of the resistor R1 is connected to the output end of the resistor R3, and the input end of the resistor R3 is connected to the DVCC power supply terminal for input; the 3rd terminal of the isolated CAN chip U1 is connected in series with a resistor R2 and then connected to the CAN-TX terminal for input signal. The output end of the resistor R2 is connected to the output end of the resistor R4, and the input end of the resistor R4 is connected to the DVCC power supply terminal for input; the 1st terminal of the isolated CAN chip U1 is connected to the DVCC power supply terminal for input. The DVCC power supply terminal is connected to the input ends of a capacitor C1, a capacitor C2, and a capacitor C3. The output ends of the capacitor C1, the capacitor C2, and the capacitor C3 are connected to the 4th terminal of the isolated CAN chip U1 and then grounded.

[0007] Preferably, the ground surge protection circuit includes diodes D1 - D5. The 1st pin of the diode D1, the 2nd pin of the diode D5, and the 1st pin of the diode D4 are connected together and then connected to the 5th pin of the isolated CAN chip U1, and are connected to the output ends of a capacitor C4 and a capacitor C5. The input ends of the capacitor C4 and the capacitor C5 are connected to the 8th pin of the isolated CAN chip U1 and then connected to the VCC-CAN power supply terminal for input; the 2nd pin of the diode D1 is connected to the 1st pin of the diode D2 and is connected to the output end of a resistor R5. The input end of the resistor R5 is connected to the 7th pin of the isolated CAN chip U1; the 2nd pin of the diode D4 is connected to the 1st pin of the diode D3 and is connected to the output end of a resistor R6. The input end of the resistor R6 is connected to the 6th pin of the isolated CAN chip U1; the 2nd pins of the diode D2 and the diode D3 are connected together and then connected to the 1st pin of the diode D5; both ends of the diode D4 are connected in parallel with a capacitor C7.

[0008] Preferably, the common-mode interference suppression circuit includes capacitors C8 - C11, resistors R7 - R12, and a common-mode inductor L1. The input terminal of capacitor C9 is connected to the input terminal of resistor R12 and then connected to pin 5 of the isolated CAN chip U1. The output terminal of capacitor C9 is connected to the input terminal of resistor R8, and the output terminal of resistor R8 is grounded. The output terminal of resistor R12 is sequentially connected in series with resistors R11 and R10, and the output terminal of resistor R10 is connected to the output terminal of capacitor C9. The input terminal of capacitor C8 is also connected to resistor R9, the output terminal of resistor R9 is sequentially connected in series with resistors R8 and R7, and the output terminal of resistor R7 is connected to the output terminal of capacitor C8. Pin 3 of the common-mode inductor L1 is connected to the output terminal of resistor R5, pin 4 of the common-mode inductor L1 is connected to the output terminal of resistor R6, pin 2 of the common-mode inductor L1 is connected to the input terminal of resistor R13 and is also connected to the input terminal of capacitor C10, and the output terminal of capacitor C10 is grounded. Pin 1 of the common-mode inductor L1 is connected to the output terminal of resistor R13 and is also connected to the input terminal of capacitor C11, and the output terminal of capacitor C11 is grounded.

[0009] Preferably, the surge and short-circuit protection circuit for the differential signal includes a self-resetting fuse F1, a self-resetting fuse F2, and a gas discharge tube F3. The input terminal of the self-resetting fuse F1 is connected to pin 2 of the common-mode inductor L1, the output terminal of the self-resetting fuse F1 is connected to pin 2 of the gas discharge tube F3 and is connected to the CANH terminal for output. The input terminal of the self-resetting fuse F2 is connected to pin 1 of the common-mode inductor L1, the output terminal of the self-resetting fuse F2 is connected to pin 1 of the gas discharge tube F3 and is connected to the CANL terminal for output, and pin 3 of the gas discharge tube F3 is grounded.

[0010] Compared with the prior art, the beneficial effects of the present utility model are:

[0011] This high-reliability and high-applicability CAN bus communication circuit uses multiple modular CAN nodes in parallel, and the communication waveform is still good. At the same time, it has the functions of surge and short-circuit protection for the CAN bus, and the CAN chip will not be damaged when surges and short circuits occur on the CAN bus. It has strong anti-common-mode interference ability and can still operate stably in scenarios with large common-mode interference. Description of the Drawings

[0012] Figure 1 It is the circuit schematic diagram of the present utility model. Detailed Embodiments

[0013] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0014] Please refer to Figure 1 , a high-reliability and high-applicability CAN bus communication circuit, including an isolated CAN chip U1, a ground surge protection circuit, a common-mode interference suppression circuit, and a surge and short-circuit protection circuit for differential signals. The output end of the isolated CAN chip U1 is electrically connected to the input end of the ground surge protection circuit, the output end of the ground surge protection circuit is electrically connected to the input end of the common-mode interference suppression circuit, the output end of the common-mode interference suppression circuit is electrically connected to the input end of the surge and short-circuit protection circuit for differential signals, and the output end of the surge and short-circuit protection circuit for differential signals is connected to the CANH terminal and the CANL terminal for output.

[0015] Among them: The No. 2 terminal of the isolated CAN chip U1 is connected in series with the resistor R1 and then connected to the CAN-RX terminal to input a signal. The output end of the resistor R1 is connected to the output end of the resistor R3, and the input end of the resistor R3 is connected to the DVCC power supply terminal for input; The No. 3 terminal of the isolated CAN chip U1 is connected in series with the resistor R2 and then connected to the CAN-TX terminal to input a signal. The output end of the resistor R2 is connected to the output end of the resistor R4, and the input end of the resistor R4 is connected to the DVCC power supply terminal for input; The No. 1 terminal of the isolated CAN chip U1 is connected to the DVCC power supply terminal for input. The DVCC power supply terminal is connected to the input ends of the capacitor C1, the capacitor C2, and the capacitor C3. The output ends of the capacitor C1, the capacitor C2, and the capacitor C3 are connected to the No. 4 terminal of the isolated CAN chip U1 and then grounded.

[0016] The above CAN_RX and CAN_TX are ground communication signals sent by the controller. Since they are low-valid, they are pulled up to DVCC through the resistors R3 and R4. The communication circuit requires a certain amount of current, generally 20 - 100 mA, when the level flips. The resistors R1 and R2 mainly play a role in series current limiting. The DVCC supplies transient current to DGND through the capacitors C1 - C3, which has a certain filtering effect. After passing through the CAN isolation chip U1, CAN_RX and CAN_TX are converted into differential signals CANH and CANL. VCC_CAN is similar to DVCC, and supplies transient current to GND_CAN through the capacitors C4 and C5, which has a certain filtering effect; The resistors R5 and R6 mainly play a role in series current limiting. The capacitor C6 filters the signal between CANH and GND_CAN, and the capacitor C7 filters the signal between CANL and GND_CAN.

[0017] Among them, the ground surge protection circuit includes diodes D1 - D5. The pin 1 of diode D1, the pin 2 of diode D5, and the pin 1 of diode D4 are connected and then connected to the pin 5 of the isolated CAN chip U1, and also connected to the output terminals of capacitors C4 and C5. The input terminals of capacitors C4 and C5 are connected to the pin 8 of the isolated CAN chip U1 and then connected to the input of the VCC - CAN power terminal; the pin 2 of diode D1 is connected to the pin 1 of diode D2 and also connected to the output terminal of resistor R5, and the input terminal of resistor R5 is connected to the pin 7 of the isolated CAN chip U1; the pin 2 of diode D4 is connected to the pin 1 of diode D3 and also connected to the output terminal of resistor R6, and the input terminal of resistor R6 is connected to the pin 6 of the isolated CAN chip U1; the pin 2 of diode D2 and the pin 2 of diode D3 are connected and then connected to the pin 1 of diode D5; both ends of diode D4 are shunted with capacitor C7.

[0018] When the signal between CANH and GND_CAN is positive and exceeds the breakdown voltage of diode D5 (the parameter can be selected by 2 times the normal CANH to CAN_GND level value), CANH conducts through diodes D2 and D5 to CAN_GND. When the signal between CANH and GND_CAN is negative, GND_CAN clamps CANH to zero level through diode D1, protecting the other circuit components; when the signal between CANL and GND_CAN is positive and exceeds the breakdown voltage of diode D5 (the parameter can be selected by 2 times the normal CANL to CAN_GND level value), CANL conducts through diodes D3 and D5 to CAN_GND. When the signal between CANL and GND_CAN is negative, GND_CAN clamps CANL to zero level through diode D4, protecting the other circuit components.

[0019] Among them: The common-mode interference suppression circuit includes capacitors C8 - C11, resistors R7 - R12, and a common-mode inductor L1. The input terminal of capacitor C9 is connected to the input terminal of resistor R12 and then connected to pin 5 of the isolated CAN chip U1. The output terminal of capacitor C9 is connected to the input terminal of resistor R8, and the output terminal of resistor R8 is grounded; the output terminal of resistor R12 is sequentially connected in series with resistor R11 and resistor R10, and the output terminal of resistor R10 is connected to the output terminal of capacitor C9; the input terminal of capacitor C8 is also connected to resistor R9, the output terminal of resistor R9 is sequentially connected in series with resistor R8 and resistor R7, and the output terminal of resistor R7 is connected to the output terminal of capacitor C8; pin 3 of the common-mode inductor L1 is connected to the output terminal of resistor R5, pin 4 of the common-mode inductor L1 is connected to the output terminal of resistor R6, pin 2 of the common-mode inductor L1 is connected to the input terminal of resistor R13 and connected to the input terminal of capacitor C10, and the output terminal of capacitor C10 is grounded; pin 1 of the common-mode inductor L1 is connected to the output terminal of resistor R13 and connected to the input terminal of capacitor C11, and the output terminal of capacitor C11 is grounded.

[0020] The above capacitors C8, C9, and resistors R7 - R12 form a series-parallel RC filter to filter the common-mode interference signal between GND_CAN and PE; the common-mode inductor L1, capacitor C10, and inductor C11 form an LC filter for the common-mode interference signal of CANH and CANL to PE to filter the CAN bus; resistor R13 is the CAN node termination resistor, and its resistance value can be flexibly configured according to the number of nodes. It can be configured according to the formula R13 / N = 120Ω, where N is the number of CAN bus nodes.

[0021] Among them: The surge and short-circuit protection circuit for differential signals includes a self-recovery fuse F1, a self-recovery fuse F2, and a gas discharge tube F3. The input terminal of the self-recovery fuse F1 is connected to pin 2 of the common-mode inductor L1, and the output terminal of the self-recovery fuse F1 is connected to pin 2 of the gas discharge tube F3 and connected to the CANH terminal output; the input terminal of the self-recovery fuse F2 is connected to pin 1 of the common-mode inductor L1, and the output terminal of the self-recovery fuse F2 is connected to pin 1 of the gas discharge tube F3 and connected to the CANL terminal output, and pin 3 of the gas discharge tube F3 is grounded.

[0022] When there is a short circuit between the differential signals above, the front-end circuit can be protected by disconnecting the self-recovery fuse F1 and the self-recovery fuse F2. When there is a surge voltage between the differential signals, the gas discharge tube F3 can be closed to protect the front-end circuit. The gas discharge tube F3 uses a 3-pin package, and the middle pin 3 is connected to PE to further filter the common-mode interference.

[0023] This high-reliability and high-applicability CAN bus communication circuit. The isolated CAN chip U1 mainly converts the CAN_TX and CAN_RX signals to the ground into differential CANH and CANL signals, and has a certain isolation effect between the primary and secondary sides. The power supply for the isolated primary side is DVCC and DGND, and the power supply for the isolated secondary side is VCC_CAN and GND_CAN. The voltage of the power supply determines the digital conversion logic of the CAN chip. Generally, a supply voltage > 0.7 is considered high level, and a supply voltage < 0.3 is considered low level. When there is a surge voltage between CANH or CANL and GND_CAN, diodes D1 to D5 form an energy discharge path to prevent the CAN chip U1 from being damaged by overvoltage. Capacitors C8, C9, and resistors R7 to R12 provide a common-mode interference discharge path from GND_CAN to PE. Capacitor C10 provides a common-mode interference discharge path from CANH to PE, and capacitor C11 provides a common-mode interference discharge path from CANL to PE. The common-mode inductor L1 is mainly used to suppress the common-mode interference signal between CANH and CANL. When the differential signals are short-circuited, the front-end circuit can be protected by disconnecting the self-resetting fuses F1 and F2. When there is a surge voltage between the differential signals, the front-end circuit can be protected by closing the gas discharge tube F3. The reason for using a gas discharge tube (usually a few pF) instead of a TVS tube (usually a few hundred pF) for the gas discharge tube F3 is that the parasitic capacitance of the TVS tube is relatively large. When there are many CAN bus nodes, the parasitic capacitance of the TVS tube will affect the rise and fall times of the differential signals, resulting in the CAN node recognizing an incorrect level and reporting an error. When using a TVS tube, the communication waveform quality is good.

[0024] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A CAN bus communication circuit with high reliability and high applicability, including an isolated CAN chip U1, a ground surge protection circuit, a common-mode interference suppression circuit, and a surge and short-circuit protection circuit for differential signals, characterized in that: The output terminal of the isolated CAN chip U1 is electrically connected to the input terminal of the ground surge protection circuit. The output terminal of the ground surge protection circuit is electrically connected to the input terminal of the common-mode interference suppression circuit. The output terminal of the common-mode interference suppression circuit is electrically connected to the input terminal of the surge and short-circuit protection circuit for differential signals. The output terminal of the surge and short-circuit protection circuit for differential signals is connected to the CANH terminal and the CANL terminal for output.

2. The high-reliability and high-applicability CAN bus communication circuit according to claim 1, characterized in that: The 2nd terminal of the isolated CAN chip U1 is connected to the CAN-RX terminal for input signal after being connected in series with the resistor R1. The output terminal of the resistor R1 is connected to the output terminal of the resistor R3. The input terminal of the resistor R3 is connected to the DVCC power supply terminal for input. The 3rd terminal of the isolated CAN chip U1 is connected to the CAN-TX terminal for input signal after being connected in series with the resistor R2. The output terminal of the resistor R2 is connected to the output terminal of the resistor R4. The input terminal of the resistor R4 is connected to the DVCC power supply terminal for input. The 1st terminal of the isolated CAN chip U1 is connected to the DVCC power supply terminal for input. The DVCC power supply terminal is connected to the input terminals of the capacitor C1, the capacitor C2, and the capacitor C3. The output terminals of the capacitor C1, the capacitor C2, and the capacitor C3 are connected to the 4th terminal of the isolated CAN chip U1 and then grounded.

3. A high-reliability and high-applicability CAN bus communication circuit according to claim 1, characterized in that: The ground surge protection circuit includes diodes D1 - D5. The 1st pin of the diode D1, the 2nd pin of the diode D5, and the 1st pin of the diode D4 are connected together and then connected to the 5th pin of the isolated CAN chip U1, and are also connected to the output terminals of the capacitor C4 and the capacitor C5. The input terminals of the capacitor C4 and the capacitor C5 are connected to the 8th pin of the isolated CAN chip U1 and then connected to the VCC-CAN power supply terminal for input. The 2nd pin of the diode D1 is connected to the 1st pin of the diode D2 and is also connected to the output terminal of the resistor R5. The input terminal of the resistor R5 is connected to the 7th pin of the isolated CAN chip U1. The 2nd pin of the diode D4 is connected to the 1st pin of the diode D3 and is also connected to the output terminal of the resistor R6. The input terminal of the resistor R6 is connected to the 6th pin of the isolated CAN chip U1. The 2nd pin of the diode D2 and the 2nd pin of the diode D3 are connected together and then connected to the 1st pin of the diode D5. Capacitor C7 is connected in parallel across the two ends of the diode D4.

4. The high-reliability and high-applicability CAN bus communication circuit according to claim 1, characterized in that: The common-mode interference suppression circuit includes capacitors C8 - C11, resistors R7 - R12, and a common-mode inductor L1. The input end of capacitor C9 is connected to the input end of resistor R12 and then connected to pin 5 of the isolated CAN chip U1. The output end of capacitor C9 is connected to the input end of resistor R8, and the output end of resistor R8 is grounded; the output end of resistor R12 is sequentially connected in series with resistors R11 and R10, and the output end of resistor R10 is connected to the output end of capacitor C9; the input end of capacitor C8 is also connected to resistor R9, the output end of resistor R9 is sequentially connected in series with resistors R8 and R7, and the output end of resistor R7 is connected to the output end of capacitor C8; pin 3 of the common-mode inductor L1 is connected to the output end of resistor R5, pin 4 of the common-mode inductor L1 is connected to the output end of resistor R6, pin 2 of the common-mode inductor L1 is connected to the input end of resistor R13 and is connected to the input end of capacitor C10, and the output end of capacitor C10 is grounded; pin 1 of the common-mode inductor L1 is connected to the output end of resistor R13 and is connected to the input end of capacitor C11, and the output end of capacitor C11 is grounded.

5. The high-reliability and high-applicability CAN bus communication circuit according to claim 1, characterized in that: The surge and short-circuit protection circuit for the differential signal includes a self-resetting fuse F1, a self-resetting fuse F2, and a gas discharge tube F3. The input end of the self-resetting fuse F1 is connected to pin 2 of the common-mode inductor L1, and the output end of the self-resetting fuse F1 is connected to pin 2 of the gas discharge tube F3 and is connected to the CANH terminal for output; the input end of the self-resetting fuse F2 is connected to pin 1 of the common-mode inductor L1, and the output end of the self-resetting fuse F2 is connected to pin 1 of the gas discharge tube F3 and is connected to the CANL terminal for output, and pin 3 of the gas discharge tube F3 is grounded.

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