Optical fiber transmission circuit, equipment and system for CAN bus signal

Abstract

The utility model provides an optical fiber transmission circuit, equipment and system for CAN bus signals. The optical fiber transmission circuit comprises N electro-optical conversion circuits, N photoelectric conversion circuits and a CAN bus differential driving circuit, the input ends of the electro-optical conversion circuits are connected with the output end of the CAN bus differential driving circuit, and the output ends of the photoelectric conversion circuits are connected with the input end of the CAN bus differential driving circuit; wherein N is greater than or equal to 1, and N is a positive integer; the electro-optical conversion circuit is used for receiving the first CAN bus differential signal and outputting a corresponding optical fiber transmitting signal under the driving of the first CAN bus differential signal; the photoelectric conversion circuit is used for performing photoelectric conversion on the received optical fiber receiving signal to obtain a CAN bus differential driving signal; and the CAN bus differential driving circuit is used for outputting a second CAN bus differential signal under the driving of the CAN bus differential driving signal. The equipment can reduce the time delay of signal propagation and the equipment cost.

Description

Technical Field

[0001] The utility model relates to the technical field of communication, and more specifically to an optical fiber transmission circuit, equipment and system for CAN bus signals. Background Art

[0002] Compared with traditional cable communication, optical fiber communication has higher anti-interference ability, longer transmission distance and stronger isolation performance. The Controller Area Network (CAN) bus is a serial communication network that effectively supports distributed control and real-time control. It has the characteristics of low cost, high speed, real-time performance and high reliability. It is widely used in many fields such as automobile industry, automation control, medical equipment, etc.

[0003] The traditional CAN bus belongs to cable communication, including two wires, CAN_H and CAN_L. On the CAN bus, the signal is in the form of voltage, and the CAN signal is represented by the potential difference between the CAN_H and CAN_L lines, that is, the differential signal. Due to the defects of cable communication itself, the CAN bus is difficult to be used in long-distance, ultra-harsh electromagnetic environments, and ultra-high voltage environments. Therefore, optical fiber transmission equipment is required to convert CAN signals into optical fiber signal transmission. The existing optical fiber transmission equipment converts the differential signal on the CAN bus into the logic level CAN_TX and CAN_RX used to represent the digital signal through the CAN transceiver at the transmitting end, and then realizes the conversion of CAN_TX and CAN_RX into optical pulse signals. At the receiving end, the optical pulse signal is first converted into the logic level CAN_TX and CAN_RX, and then the CAN_TX and CAN_RX are converted into differential signals on the CAN bus through the CAN transceiver. Since the entire CAN signal transmission process undergoes multiple conversions, the signal propagation delay and equipment cost are increased. Utility Model Content

[0004] The present invention is proposed in view of the above problems. The present invention provides an optical fiber transmission circuit, device and system for CAN bus signals, which can effectively reduce the delay of signal propagation and the cost of equipment.

[0005] The first aspect of the utility model provides an optical fiber transmission circuit for a CAN bus signal, the optical fiber transmission circuit comprising: N electro-optical conversion circuits, N photoelectric conversion circuits and a CAN bus differential drive circuit, the input end of the electro-optical conversion circuit is connected to the output end of the CAN bus differential drive circuit, the output end of the photoelectric conversion circuit is connected to the input end of the CAN bus differential drive circuit; wherein N≥1, and N is a positive integer;

[0006] The electro-optical conversion circuit is used to receive the first CAN bus differential signal and output a corresponding optical fiber transmission signal under the drive of the first CAN bus differential signal;

[0007] The photoelectric conversion circuit is used to perform photoelectric conversion on the received optical fiber receiving signal to obtain a CAN bus differential drive signal;

[0008] The CAN bus differential driving circuit is used to output a second CAN bus differential signal under the drive of the CAN bus differential driving signal.

[0009] In one embodiment of the present invention, the CAN bus differential driving circuit includes a CAN bus differential driver.

[0010] In one embodiment of the utility model, when N≥2, the CAN bus differential driving circuit also includes a line and logic circuit, the output ends of the N photoelectric conversion circuits are respectively connected to the input ends of the line and logic circuit, and the output end of the line and logic circuit is connected to the input end of the CAN bus differential driver.

[0011] In one embodiment of the utility model, the CAN bus differential driver includes an emitter follower, a complementary switch circuit, a first drive circuit and a second drive circuit;

[0012] The input end of the emitter follower is connected to the output end of the photoelectric conversion circuit, the output end of the emitter follower is connected to the input end of the complementary switch circuit, the two output ends of the complementary switch circuit are respectively connected to the control ends of the first drive circuit and the second drive circuit, and the output ends of the first drive circuit and the second drive circuit are used to output the CAN bus differential drive signal.

[0013] In one embodiment of the utility model, the electro-optical conversion circuit includes a differential amplifier, a photoelectric emission driver and a photoelectric emission tube connected in sequence;

[0014] The differential amplifier is used to differentially amplify the first CAN bus differential signal to obtain two complementary voltage drive signals;

[0015] The photoelectric emission driver is used to convert the voltage drive signal into a first current pulse signal and output it to the photoelectric emission tube;

[0016] The photoelectric transmitting tube is used to output a corresponding optical fiber transmitting signal under the drive of the first current pulse signal.

[0017] In one embodiment of the present utility model, the differential amplifier comprises: a first transistor, a second transistor, a first resistor, a second resistor, a third resistor and a fourth resistor;

[0018] The first end of the first resistor is used to connect to a circuit power supply, and the second end of the first resistor is connected to the collector of the first transistor and serves as a first output end for outputting the voltage drive signal;

[0019] The first end of the second resistor is connected to the collector of the second transistor and serves as a second output end for outputting the voltage driving signal; the second end of the second resistor is grounded;

[0020] The first end of the third resistor serves as the first input end of the first CAN bus differential signal, and the second end of the third resistor is connected to the base of the first transistor;

[0021] The first end of the fourth resistor serves as the second input end of the first CAN bus differential signal, and the second end of the fourth resistor is connected to the base of the second transistor;

[0022] An emitter of the first transistor is connected to an emitter of the second transistor.

[0023] In one embodiment of the present invention, the output end of the photoelectric conversion circuit is also connected to the control end of the photoelectric emission driver.

[0024] In one embodiment of the present utility model, the photoelectric emission driver includes: a third transistor, a fourth transistor, a fifth transistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor;

[0025] The first end of the fifth resistor is connected to the circuit power supply and to the emitter of the third transistor, the first end of the sixth resistor serves as the first input end of the two complementary voltage drive signals, and the second end of the fifth resistor and the second end of the sixth resistor are both connected to the base of the third transistor;

[0026] The second end of the eighth resistor is grounded and connected to the emitter of the fourth transistor, the first end of the seventh resistor serves as the second input end of the two complementary voltage drive signals, and the second end of the seventh resistor and the first end of the eighth resistor are both connected to the base of the fourth transistor;

[0027] The collector of the third transistor is connected to the first end of the photoelectric emission tube, the collector of the fourth transistor is connected to the emitter of the fifth transistor, the collector of the fifth transistor is connected to the second end of the photoelectric emission tube, and the base of the fifth transistor is connected to the output end of the photoelectric conversion circuit.

[0028] In one embodiment of the utility model, the photoelectric conversion circuit includes a photoelectric receiving tube and a photoelectric receiving amplification and shaping circuit connected to each other;

[0029] The photoelectric receiving tube is used to convert the optical fiber receiving signal into a second current pulse signal;

[0030] The photoelectric receiving amplifying and shaping circuit is used to convert the second current pulse signal into a voltage pulse signal, and obtain the CAN bus differential driving signal after shaping and amplifying.

[0031] In one embodiment of the utility model, the photoelectric receiving amplification and shaping circuit includes a first-stage amplification circuit, a second-stage amplification circuit and a waveform shaping circuit connected in sequence;

[0032] The first-stage amplifier circuit and the second-stage amplifier circuit are common-emitter amplifier circuits, and the waveform shaping circuit is a Schmitt trigger circuit.

[0033] A second aspect of the utility model provides an optical fiber transmission system for CAN bus signals, wherein the optical fiber transmission system comprises a plurality of optical fiber transmission devices as described in the first aspect above, and the optical fiber transmission devices are connected via optical fibers.

[0034] The optical fiber transmission circuit of the CAN bus signal in the embodiment of the utility model realizes direct driving of the differential signal on the CAN bus to generate an optical fiber transmission signal through an electro-optical conversion circuit, directly obtains the CAN bus differential drive signal after photoelectric conversion through a photoelectric conversion circuit, and obtains the corresponding CAN bus differential signal through the CAN bus differential drive circuit. During the signal conversion process, there is no need to convert the differential signal into the logic level of the digital signal, thereby reducing the number of signal conversions, thereby reducing the signal propagation delay and equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and other purposes, features and advantages of the present invention will become more apparent by describing the embodiments of the present invention in more detail in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0036] Figure 1 It is a schematic structural diagram of an optical fiber transmission circuit of a CAN bus signal according to an embodiment of the utility model;

[0037] Figure 2 is a circuit diagram of a differential amplifier according to an embodiment of the utility model;

[0038] Figure 3 is a circuit diagram of a photoelectric emission driver according to an embodiment of the utility model;

[0039] Figure 4 is a circuit diagram of a CAN bus differential driver according to an embodiment of the utility model;

[0040] Figure 5 is a circuit diagram of a two-input line AND logic circuit according to an embodiment of the utility model;

[0041] Figure 6 It is a circuit diagram of a photoelectric receiving amplifying and shaping circuit according to an embodiment of the utility model;

[0042] Figure 7 is a schematic structural diagram of an optical fiber transmission circuit according to another embodiment of the utility model;

[0043] Figure 8 It is a schematic structural diagram of an optical fiber transmission system for CAN bus signals according to an embodiment of the utility model. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the utility model more obvious, the exemplary embodiments according to the utility model will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments of the utility model, and it should be understood that the utility model is not limited to the exemplary embodiments described here. Based on the embodiments of the utility model described in the utility model, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the utility model.

[0045] First, refer to Figure 1 The optical fiber transmission circuit of the CAN bus signal according to the embodiment of the utility model is described. The optical fiber transmission circuit of the CAN bus signal of the utility model is used to connect with an electronic device having a CAN bus port, so as to realize long-distance CAN bus signal transmission. The optical fiber transmission circuit of the utility model can support the high-speed CAN communication standard, with a transmission rate of up to 1Mbps and a bus length of ≤40 meters; it can also support the low-speed CAN communication standard, with a transmission rate of 40kbps and a bus length of up to 1000 meters.

[0046] like Figure 1 As shown, the present application proposes an optical fiber transmission circuit for CAN bus signals, the optical fiber transmission circuit comprising: N electro-optical conversion circuits 101, N photoelectric conversion circuits 102 and a CAN bus differential drive circuit 103, the input end of the electro-optical conversion circuit 101 is connected to the output end of the CAN bus differential drive circuit 103, the output end of the photoelectric conversion circuit 102 is connected to the input end of the CAN bus differential drive circuit 103; wherein, N≥1, and N is a positive integer.

[0047] The electro-optical conversion circuit 101 is used to receive the first CAN bus differential signal and output a corresponding optical fiber transmission signal under the drive of the first CAN bus differential signal;

[0048] The photoelectric conversion circuit 102 is used to perform photoelectric conversion on the received optical fiber receiving signal to obtain a CAN bus differential drive signal;

[0049] The CAN bus differential driving circuit is used to output a second CAN bus differential signal under the drive of the CAN bus differential driving signal.

[0050] In this application, the first CAN bus differential signal and the second CAN bus differential signal are expressed in voltage form. Since the CAN bus structure has two lines, CAN_H and CAN_L, the CAN signal is represented by the potential difference between the CAN_H and CAN_L lines, which are divided into two types: dominant level and recessive level. The dominant level is logic 0, and the recessive level is logic 1.

[0051] In the optical fiber transmission circuit of the present invention, the input end of the electro-optical conversion circuit 101 and the output end of the CAN bus differential driving circuit 103 are connected through two wires CAN_H and CAN_L, so that both can be connected to and communicate with the electronic equipment of the CAN bus port.

[0052] The optical fiber transmission circuit of the CAN bus signal in the embodiment of the utility model realizes direct driving of the differential signal on the CAN bus to generate an optical fiber transmission signal through an electro-optical conversion circuit, directly obtains the CAN bus differential drive signal after photoelectric conversion through a photoelectric conversion circuit, and obtains the corresponding CAN bus differential signal through the CAN bus differential drive circuit. During the signal conversion process, there is no need to convert the differential signal into the logic level of the digital signal, thereby reducing the number of signal conversions, thereby reducing the signal propagation delay and equipment cost.

[0053] In one embodiment of the present application, the electro-optical conversion circuit includes a differential amplifier, a photoelectric emission driver, and a photoelectric emission tube connected in sequence;

[0054] A differential amplifier, used for differentially amplifying the first CAN bus differential signal to obtain two complementary voltage drive signals;

[0055] A photoelectric emission driver, used for converting a voltage drive signal into a first current pulse signal and outputting it to the photoelectric emission tube;

[0056] The photoelectric transmitting tube is used to output a corresponding optical fiber transmitting signal under the drive of the first current pulse signal.

[0057] Next, refer to Figure 2A differential amplifier according to an embodiment of the present invention is described below.

[0058] like Figure 2 As shown, in the embodiment of the present application, the differential amplifier includes: a first transistor Q1, a second transistor Q2, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4.

[0059] Specifically, the first transistor Q1 and the second transistor Q2 are NPN and PNP transistors respectively, which are key components of the differential amplifier and play a role in signal amplification.

[0060] The first end of the first resistor R1 is used to connect the circuit power supply Vcc, the second end of the first resistor R1 is connected to the collector of the first transistor Q1, and serves as the first output end Dout_H of the output voltage drive signal; the first end of the second resistor R2 is connected to the collector of the second transistor Q2, and serves as the second output end Dout_L of the output voltage drive signal; the second end of the second resistor R2 is grounded; the first end of the third resistor R3 serves as the first input end of the first CAN bus differential signal, and is used to be connected to CAN_H, and the second end of the third resistor R3 is connected to the base of the first transistor Q1; the first end of the fourth resistor R4 serves as the second input end of the first CAN bus differential signal, and is used to be connected to the CAN_L line, and the second end of the fourth resistor R4 is connected to the base of the second transistor Q2; the emitter of the first transistor Q1 is connected to the emitter of the second transistor Q2.

[0061] The whole circuit constitutes a complementary common-emitter amplifier circuit with floating reference. As a common-emitter amplifier circuit, the emitter of the transistor is the signal common terminal. Since there is no external connection line to the emitter, the voltage of the emitter to the ground will change with the input and load, so the emitter becomes a floating reference to the ground.

[0062] Preferably, the differential amplifier further includes a seventh capacitor C7 and an eighth capacitor C8. C7 is connected in parallel with R3, and C8 is connected in parallel with R4. The CAN bus signal is a digital signal with very steep edge changes. Adding C7 and C8 acceleration capacitors can improve the frequency response of the differential amplifier and improve the voltage waveform after amplification, thereby playing a role in signal acceleration.

[0063] The CAN bus differential signal is connected from the third resistor R3 and the fourth resistor R4, and output from the collector of the first transistor Q1 and the second transistor Q2; the current of the differential signal flows into the third resistor R3 and flows out from the fourth resistor R4, and is amplified by the triode current-controlled amplifier of the first transistor Q1 and the second transistor Q2 on the way. The amplified current is output from the collector of the first transistor Q1 and the second transistor Q2, flows through the first resistor R1 and the second resistor R2 and generates a voltage drop, converting the current signal into a voltage signal. Since the other end of the first resistor R1 is connected to the power supply VCC, the voltage drop of the first resistor R1 causes the collector voltage of the first transistor Q1 to drop to the ground; since the other end of the second resistor R2 is connected to GND, the voltage drop of the second resistor R2 causes the collector voltage of the second transistor Q2 to rise to the ground; in this way, the collector voltage of the first transistor Q1 to the ground and the collector voltage of the second transistor Q2 to the ground form a pair of complementary symmetrical voltages. When the CAN bus is at a dominant level, the voltage difference between CAN_H and CAN_L is greater than 1.4V, the first transistor Q1 and the second transistor Q2 are turned on, the collector of the first transistor Q1 is pulled low, and the collector of the second transistor Q2 is pulled high; when the first transistor Q1 and the second transistor Q2 are saturated and turned on, their collector voltages are close, approximately equal to half of VCC. When the CAN bus is at a recessive level, the voltage difference between CAN_H and CAN_L is less than 1.4V, the first transistor Q1 and the second transistor Q2 are turned off, and under the pull-up action of the first resistor R1 and the pull-down action of the second resistor R2, the collector of the first transistor Q1 is pulled high, and the collector of the second transistor Q2 is pulled low.

[0064] The level signal of the CAN bus is amplified and output by the differential amplifier to form two complementary and symmetrical voltage signals, which are output to the input terminal pair of the photoelectric transmitter driver.

[0065] Next, refer to Figure 3 A photoelectric emission driver according to an embodiment of the present invention is described.

[0066] like Figure 3 As shown, the photoelectric emission driver includes: a third transistor Q3, a fourth transistor Q4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8.

[0067] Specifically, the third transistor Q3 and the fourth transistor Q4 are NPN and PNP transistors, which are key components of the driver and play the role of current amplification and switching.

[0068] The first end of the fifth resistor R5 is connected to the circuit power supply Vcc and to the emitter of the third transistor Q3. The first end of the sixth resistor R6 serves as the first input end of two complementary voltage drive signals. The second end of the fifth resistor R5 and the second end of the sixth resistor R6 are both connected to the base of the third transistor Q3.

[0069] The fifth resistor R5 and the sixth resistor R6 form a series voltage divider, which divides the voltage signal input from the fifth resistor R5. The voltage divider output is connected to the base of the third transistor Q3 to control the on and off of the third transistor Q3. At the same time, the sixth resistor R6 has a shunt effect to reduce the current flowing through the base of the third transistor Q3, thereby preventing the third transistor Q3 from being damaged by excessive current and heating.

[0070] The second end of the eighth resistor R8 is grounded and connected to the emitter of the fourth transistor Q4. The first end of the seventh resistor R7 serves as the second input end of the two complementary voltage drive signals. The second end of the seventh resistor R7 and the first end of the eighth resistor R8 are both connected to the base of the fourth transistor Q4.

[0071] The seventh resistor R7 and the eighth resistor R8 form a series voltage divider, which divides the voltage signal input from the seventh resistor R7. The voltage divider output is connected to the base of the fourth transistor Q4 to control the on and off of the fourth transistor Q4. The eighth resistor R8 has a shunting effect to reduce the current flowing through the base of the fourth transistor Q4 to avoid damage to the fourth transistor Q4 due to excessive current.

[0072] The collector of the third transistor Q3 is connected to the first end of the photoelectric emitting tube D1 , and the collector of the fourth transistor Q4 is connected to the other end of the photoelectric emitting tube D1 .

[0073] Specifically, the photoelectric emitting tube D1 is a photoelectric emitting diode. When sufficient current passes through D1, D1 will emit infrared light.

[0074] Preferably, the collector of the third transistor Q3 is connected to the first end of the photoelectric emission tube D1 via a ninth resistor R9, and the ninth resistor R9 is a current limiting resistor, thereby preventing the device from being damaged due to excessive current.

[0075] Preferably, the output terminal of the photoelectric conversion circuit is also connected to the control terminal of the photoelectric emission driver. Then the photoelectric emission driver further includes: a fifth transistor Q5 and a tenth resistor R10.

[0076] Specifically, the fifth transistor Q5 is an NPN triode, which works in a cut-off and saturation state and acts as a switch for turning off or on the photocurrent output.

[0077] At this time, the collector of the fourth transistor Q4 is connected to the emitter of the fifth transistor Q5, the collector of the fifth transistor Q5 is connected to the second end of the photoelectric emission tube, and the base of the fifth transistor Q5 is connected to the output end of the photoelectric conversion circuit through the tenth resistor R10.

[0078] The output end of the photoelectric conversion circuit is also connected to the control end of the photoelectric transmitter driver to realize the function of "receive lock send". When the CAN dominant signal is received from the optical path, only the optical path of the opposite row is allowed to be relayed, and the optical path of the same row is prohibited to be relayed, thereby eliminating the phenomenon of optical path locking caused by repeated relaying between points.

[0079] Preferably, the photoelectric emission driver further includes a twelfth capacitor C12 and a thirteenth capacitor C13. The twelfth capacitor C12 is connected in parallel with the sixth resistor R6, and the thirteenth capacitor C13 is connected in parallel with the seventh resistor R7. The two capacitors play an accelerating role, thereby improving the high-frequency characteristics of the driver.

[0080] The working process of the photoelectric emission driver is as follows: the complementary voltage signal pair from the differential amplifier is connected from the sixth resistor R6 and the seventh resistor R7, and after being enhanced and converted by the driver, a current signal is output from the loop composed of the third transistor Q3, the fourth transistor Q4, the fifth transistor Q5, and the ninth resistor R9 to drive the photoelectric emission tube D1 load diode to emit light. If the signal voltage of the sixth resistor R6 is high, due to symmetry, the signal voltage at the seventh resistor R7 must be low; after the series voltage divider circuit steps down the voltage, the bases of the third transistor Q3 and the fourth transistor Q4 obtain a very small differential voltage, the third transistor Q3 and the fourth transistor Q4 are turned off, the output loop is disconnected, there is no current output, and the photoelectric emission tube D1 does not emit light; if the signal voltage of the sixth resistor R6 is low, then the signal voltage of the seventh resistor R7 must be high, after the series voltage divider circuit steps down the voltage, the bases of the third transistor Q3 and the fourth transistor Q4 obtain a large differential voltage, and the third transistor Q3 and the fourth transistor Q4 are turned on; when the third transistor Q3 and the fourth transistor Q4 are turned on, if the fifth transistor Q5 is turned on, the output loop is fully connected, and the current passes through the ninth resistor R9 and the photoelectric emission tube D1, so that the photoelectric emission tube D1 emits light; if the fifth transistor Q5 is turned off, the output loop is not fully connected, and the photoelectric emission tube D1 does not emit light.

[0081] In one embodiment of the present application, the CAN bus differential driving circuit includes a CAN bus differential driver.

[0082] Next, refer to Figure 4 A CAN bus differential driver according to an embodiment of the present invention is described.

[0083] like Figure 4 As shown, the CAN bus differential driver includes an emitter follower 401 , a complementary switch circuit 402 , a first drive circuit 403 and a second drive circuit 404 .

[0084] The input end of the emitter follower 401 is connected to the output end of the photoelectric conversion circuit, and the output end of the emitter follower 401 is connected to the input end of the complementary switch circuit 402. The two output ends of the complementary switch circuit 402 are respectively connected to the control ends of the first drive circuit 403 and the second drive circuit 404. The output ends of the first drive circuit 403 and the second drive circuit 404 are used to output CAN bus differential drive signals.

[0085] The tenth transistor Q10, the sixth resistor R16 and the third resistor R13 form an emitter follower. The signal is input from the base of the tenth transistor Q10 and output from the emitter. Using the emitter follower as the input electrode can increase the input impedance, reduce the output resistance, and enhance the current output capability.

[0086] The eighth transistor Q8 and the ninth transistor Q9 form a complementary switch circuit 402. The signal output by the emitter follower is limited by the eleventh resistor R11 and the twelfth resistor R12, and is connected to the complementary switch circuit 402 composed of the eighth transistor Q8 and the ninth transistor Q9. At the same time, only one of the eighth transistor Q8 and the ninth transistor Q9 can be turned on, and the other can be turned off; when the input is a high level, the eighth transistor Q8 is turned on, and the ninth transistor Q9 is turned off; when the input is a low level, the ninth transistor Q9 is turned on, and the eighth transistor Q8 is turned off; the output signal of the complementary switch circuit 402 composed of the eighth transistor Q8 and the ninth transistor Q9 is output from their emitters and collectors, and is connected to the first drive circuit 403 composed of the sixth transistor Q6 and the second drive circuit 404 composed of the seventh transistor Q7, that is, a symmetrical drive pair. Since the bases of the sixth transistor Q6 and the seventh transistor Q7 are connected together through the fourteenth resistor R14, the fifteenth resistor R15, and the ninth transistor Q9 series branch, the sixth transistor Q6 and the seventh transistor Q7 can only be turned on and off at the same time. If the input signal turns on the ninth transistor Q9 and turns off the eighth transistor Q8, the sixth transistor Q6 and the seventh transistor Q7 are turned on, and the collectors of the sixth transistor Q6 and the seventh transistor Q7 are unidirectionally guided by the fifth diode D5 and the sixth diode D6 to output a driving current to the CAN bus, so that the CAN bus presents a dominant state; if the input signal turns off the ninth transistor Q9 and turns on the eighth transistor Q8, the sixth transistor Q6 and the seventh transistor Q7 are turned off, and the CAN bus loses the driving current and presents a recessive level state. The seventeenth resistor R17 and the twentieth resistor R20 are the output load resistors of the ninth transistor Q9, which can increase the turn-off speed of the ninth transistor Q9; the sixth transistor Q6, the seventh transistor Q7, the eighteenth resistor R18, and the nineteenth resistor R19 are the output loads of the eighth transistor Q8. In addition, the eighteenth resistor R18 and the nineteenth resistor R19 are also used to set the reference voltage of the recessive level of the CAN bus, and the resistance values ​​of the eighteenth resistor R18 and the nineteenth resistor R19 must be equal. In order to make the circuit performance symmetrical, the resistance values ​​of the fourteenth resistor R14 and the fifteenth resistor R15 must be equal, the resistance values ​​of the seventeenth resistor R17 and the twentieth resistor R20 must be equal, the resistance values ​​of the eleventh resistor R11 and the twelfth resistor R12 must be equal. The capacitance values ​​of the nineteenth capacitor C19 and the twentieth capacitor C20 must be equal, the capacitance values ​​of the eighteenth capacitor C18 and the seventeenth capacitor C17 must be equal, and the resistance of the third resistor R3 is much smaller than that of the eleventh resistor R11 and the twelfth resistor R12.

[0087] In one embodiment of the present application, when N≥2, the CAN bus differential drive circuit also includes a line and logic circuit, the output ends of the N photoelectric conversion circuits are respectively connected to the input ends of the line and logic circuit, and the output end of the line and logic circuit is connected to the input end of the CAN bus differential driver.

[0088] The number of input paths of the wire-AND logic circuit should be equal to N. For example, when N=2, the wire-AND logic circuit is a two-input logic "AND" circuit; when N=3, the wire-AND logic circuit is a three-input logic "AND" circuit.

[0089] Next, refer to Figure 5 A two-input wire-AND logic circuit according to an embodiment of the present invention is described.

[0090] like Figure 5 As shown, the line-and-logic circuit is composed of a third diode D3, a fourth diode D4 and a thirty-ninth resistor R39, a fortieth resistor R40 and a forty-first resistor R41. The first ends of the thirty-ninth resistor R39, the fortieth resistor R40 and the forty-first resistor R41 are all connected to the circuit power supply Vcc, the second end of the fortieth resistor R40 is connected to the anode of the third diode D3, and the second end of the forty-first resistor R41 is connected to the cathode of the third diode D3; the second end of the thirty-ninth resistor R39 is connected to the anode of the fourth diode D4, and the second end of the forty-first resistor R41 is connected to the cathode of the fourth diode D4.

[0091] The two input signals are LTRcvOut_Up and LTRcvOut_Dn, which are the output signals from the uplink and downlink optical fiber interface circuits, respectively. CAN_Drv_In is the output signal, and the logical relationship is CAN_Drv_In=LTRcvOut_Dn<RcvOut_Up.

[0092] In one embodiment of the present application, the photoelectric conversion circuit includes a photoelectric receiving tube and a photoelectric receiving amplification and shaping circuit connected to each other;

[0093] A photoelectric receiving tube, used for converting the optical fiber receiving signal into a second current pulse signal;

[0094] The photoelectric receiving amplifying and shaping circuit is used to convert the second current pulse signal into a voltage pulse signal, and obtain a CAN bus differential driving signal after shaping and amplifying.

[0095] Specifically, the photoelectric receiving amplification and shaping circuit may include a first-stage amplification circuit, a second-stage amplification circuit and a waveform shaping circuit connected in sequence; wherein the first-stage amplification circuit and the second-stage amplification circuit are common-emitter amplification circuits, and the waveform shaping circuit is a Schmitt trigger circuit.

[0096] Next, refer to Figure 6 To describe the photoelectric receiving amplification and shaping circuit according to an embodiment of the utility model.

[0097] like Figure 6As shown, the eleventh transistor Q11, the twelfth transistor Q12, the thirteenth transistor Q13, and the fifteenth transistor Q15 form a two-stage amplification circuit and a waveform shaping circuit. Among them, the eleventh transistor Q11, the twelfth transistor Q12, the thirteenth transistor Q13, and the fifteenth transistor Q15 are all NPN transistors.

[0098] The eleventh transistor Q11, the twenty-first resistor R21, the twenty-second resistor R22, the twenty-third resistor R23, the twenty-fourth resistor R24, the twenty-sixth resistor R26, the twenty-seventh resistor R27, the first capacitor C1, the first inductor L1, and the photoelectric receiving tube D2 form a first stage amplifying circuit 601.

[0099] The twenty-ninth resistor R29 , the thirtieth resistor R30 , the thirty-first resistor R31 , the thirty-second resistor R32 , the twelfth transistor Q12 , and the second capacitor C2 form a second-stage amplifier circuit 602 .

[0100] The thirty-third resistor R33, the thirty-fourth resistor R34, the thirty-fifth resistor R35, the thirty-sixth resistor R36, the forty-fifth resistor R45, the forty-sixth resistor R46, the third capacitor C3, the fifteenth capacitor C15, the thirteenth transistor Q13, and the fifteenth transistor Q15 form a waveform shaping circuit 603.

[0101] The fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 are bypass capacitors of each level of the circuit, which play a role in power supply filtering and reduce circuit noise; the twenty-fifth resistor R25, the twenty-eighth resistor R28, and the thirty-seventh resistor R37 are power supply isolation resistors, which play a role in blocking power supply noise of each level of the circuit and preventing amplifier self-oscillation caused by power supply crosstalk.

[0102] In the first-stage amplifier circuit 601, the twenty-first resistor R21, the twenty-third resistor R23, the twenty-fourth resistor R24, the twenty-sixth resistor R26, the twenty-seventh resistor R27 and the eleventh transistor Q11 form a common-emitter amplifier circuit. The twenty-sixth resistor R26 is the load resistor of the common-emitter amplifier circuit, which converts the current signal after the transistor amplification into a voltage signal; R27 is a negative feedback resistor, which can improve the stability of the circuit; the twenty-first resistor R21, the twenty-third resistor R23, and the twenty-fourth resistor R24 ​​are input resistors, which are combined with the R27 feedback resistor to set the static operating point of the Q11 transistor, so that the eleventh transistor Q11 transistor is in the best amplification state. The photoelectric receiving tube D2 is a photoelectric receiving diode, which converts the optical signal into a weak electrical signal. The first capacitor C1 is an accelerating capacitor, which improves the high-frequency response of the amplifier circuit. The first inductor L1 is a high-frequency enhancement inductor, which prevents high-frequency current from flowing through GND, bypasses low-frequency signals and DC signals, prevents low-frequency and DC from entering the amplifier, and improves the high-frequency characteristics of the amplifier. The twenty-second resistor R22 and the first inductor L1 are connected in parallel to limit the upper limit of high-frequency impedance and avoid noise problems caused by infinite high-frequency impedance. The twenty-second resistor R22 and the first inductor L1 are connected in parallel and then connected in series with the twenty-third resistor R23 to form a load impedance circuit of the photoelectric receiving tube D2, which converts the photocurrent of the photoelectric receiving tube D2 into a voltage signal. When infrared light irradiates the photoelectric receiving tube D2, a photoelectric effect occurs, and the photoelectric receiving tube D2 generates a weak photocurrent. The current flows through the impedance circuit, generating a voltage drop, and the current signal is converted into a voltage signal. Since the photocurrent generated by the photoelectric effect is very weak, generally only about 5 to 50uA, and the dark current of the photodiode is between 0.1uA and 5uA, in order to distinguish the photocurrent from the dark current, this circuit sets the lower limit of the identifiable photocurrent to 10uA. By adjusting the ratio of the 26th resistor R26 and the 27th resistor R27, the amplifier gain is set to 30; the 21st resistor R21, the 23rd resistor R23, and the 24th resistor R24 ​​are adjusted to set the collector voltage of the 11th transistor Q11 to about 1 / 2VCC, so that the amplifier is in the best state; the total load impedance of the photoelectric receiving tube D2 is set to about 330 ohms. When the photoelectric receiving tube D2 generates a current of 10uA, a signal voltage of 3.3mV is generated, and the first-stage amplifier outputs a voltage signal of about 100mV.

[0103] In the second-stage amplifier circuit 602, the twenty-ninth resistor R29, the thirtieth resistor R30, the thirty-first resistor R31, the thirty-second resistor R32 and the twelfth transistor Q12 form a common-emitter amplifier circuit, and the second capacitor C2 is an acceleration capacitor to improve the frequency response of the amplifier. The thirty-first resistor R31 is the load of the common-emitter amplifier circuit, the thirty-second resistor R32 is a negative feedback resistor to improve the stability of the amplifier circuit, and the twenty-ninth resistor R29 and the thirtieth resistor R30 are input resistors for adjusting the static operating point of the amplifier. The resistance values ​​of the twenty-ninth resistor R29, the thirtieth resistor R30, and the thirty-second resistor R32 are adjusted to set the collector voltage of the twelfth transistor Q12 to be approximately 1V. The resistance ratio of the thirty-second resistor R32 and the thirty-first resistor R31 is adjusted to set the amplifier's amplification factor to be approximately 10, and the emitter voltage of the twelfth transistor Q12 to be approximately 0.1V. When a voltage signal of 100mV is input, the collector of the twelfth transistor Q12 outputs a voltage signal of 1V after passing through the amplifier.

[0104] In the waveform shaping circuit 603, the thirteenth transistor Q13, the fifteenth transistor Q15 and the thirty-third resistor R33, the thirty-fourth resistor R34, the thirty-fifth resistor R35, the thirty-sixth resistor R36, the forty-fifth resistor R45, and the forty-sixth resistor R46 form a basic Schmitt trigger circuit, and the third capacitor C3 and C15 are acceleration capacitors to improve the high-frequency response speed of the circuit. The signal is input from the parallel branch of the thirty-third resistor R33 and the third capacitor C3, and is output from the collector of the thirteenth transistor Q13, and the output waveform is a rectangular wave. The hysteresis voltage difference is set to 0.7V, and the threshold voltage is set to 1.9V and 1.2V. When the input voltage reaches 1.9V or above, the trigger outputs a low level, and when the input voltage is lower than 1.2V, the trigger outputs a high level.

[0105] Next, refer to Figure 7 The optical fiber transmission circuit according to another embodiment of the present utility model is described.

[0106] like Figure 7 As shown, this embodiment includes two electro-optical conversion circuits 701 , two photoelectric conversion circuits 702 and a CAN bus differential driving circuit 703 .

[0107] Among them, the electro-optical conversion circuit 701 is composed of a differential amplifier, a photoelectric transmitting driver, and a photoelectric transmitting tube. The photoelectric conversion circuit 702 is composed of a photoelectric receiving tube and a photoelectric receiving amplification and shaping circuit. The CAN bus differential drive circuit 703 is composed of a CAN bus driver and a line-and-logic circuit.

[0108] This embodiment uses two identical photoelectric transmitting tubes, two identical photoelectric transmitting drivers, two identical differential amplifiers, two identical photoelectric receiving tubes, and two identical photoelectric receiving amplification and shaping circuits to form two completely symmetrical optical fiber interface circuits for uplink and downlink, respectively connected to the uplink and downlink optical fibers, to achieve the function of bridging the upper and lower optical paths. In order to simplify the circuit, this embodiment uses a line-and-logic circuit to merge the receiving signals of the uplink and downlink optical fiber interface circuits into one receiving signal output, thereby reducing the use of one CAN bus driver.

[0109] Specifically, a photoelectric transmitting tube is a device that can convert a current signal into a light signal; for example, a common light emitting diode, an infrared light emitting diode, a light emitting transistor, a laser diode, etc. A photoelectric receiving tube is a device that can convert a light signal into an electrical signal, for example, a photodiode, a phototransistor, a photoresistor, etc.

[0110] The photoelectric receiving tube, the photoelectric receiving amplifying and shaping circuit, the line and logic circuit, and the CAN bus driver are connected in sequence to form an "optical-electrical" conversion loop, which realizes the function of converting the optical pulse signal into the dominant and recessive signals of the CAN bus. When the optical pulse signal is received from the optical path, the photoelectric receiving tube converts the optical pulse signal into a weak current pulse signal and connects it to the photoelectric receiving amplifying and shaping circuit. The photoelectric receiving amplifying and shaping circuit converts the weak current pulse signal into a voltage signal, amplifies and shapes the signal, outputs a rectangular wave signal, and then connects it to the line and logic circuit. The line and logic circuit couples the single-ended signals output by the uplink and downlink receiving circuits together to realize the "AND" logic function of the single-ended signal, and the output signal of the line and logic circuit is connected to the CAN bus driver. The CAN bus driver converts the input single-ended signal into the HL differential signal of the CAN bus, controls the voltage of the HL line, and makes the CAN bus present a dominant or recessive level. When the input signal is logic "0", the CAN driver outputs a dominant level; when the input signal is logic "1", the CAN driver outputs a recessive level. To put it simply, when the laser is sensed, a logic "0" signal is output, making the CAN bus present a dominant level state; when the laser is not sensed, a logic "1" signal is output, making the CAN bus present a recessive level state.

[0111] The differential amplifier, the photoelectric emission driver, and the photoelectric emission tube are connected in sequence to form an electro-optical conversion circuit 701, which converts the dominant and recessive level signals of the CAN bus into optical pulse signals. In the process of circuit electro-optical conversion, the differential amplifier differentially amplifies the dominant and recessive level signals of the CAN bus, outputs two complementary drive signals (Dout_H and Dout_L), and then connects to the photoelectric emission driver. The photoelectric emission driver further amplifies and strengthens the input signal pair, and converts it into a current pulse signal, which is connected to the photoelectric emission tube. The photoelectric emission tube converts the current pulse signal into an optical pulse signal and projects it onto the optical fiber port. When the CAN bus is at a dominant level, the driver controls the photoelectric emission tube to emit laser; when the CAN bus is at a recessive level, the driver controls the photoelectric emission tube to stop emitting laser.

[0112] The photoelectric conversion circuit 701 and the electro-optical conversion circuit 702 are connected together on the CAN bus to form an optical-electrical-optical conversion loop, thereby realizing the bridging function of the upstream optical path and the downstream optical path. Since the entire optical-electrical-optical conversion process is completely symmetrical, it can be ensured that the logic signal remains consistent after conversion of multiple nodes.

[0113] The single-ended signal output by the photoelectric receiving amplification shaping circuit (i.e., the LTRcvOut signal in the figure) has two branches, one branch is connected to the line and logic circuit, and the other branch is connected to the photoelectric transmitting driver of the same optical path, realizing the receiving locking transmitting function, thereby realizing the function of prohibiting the same optical path and retransmitting the different optical paths. When the optical-electric conversion loop receives the laser signal, the LTRcvOut signal is logic "0", controlling the photoelectric transmitting driver of the same optical path to stop emitting the laser, realizing the function of prohibiting the retransmission of the same optical path; at the same time, the logic "0" of the LTRcvOut signal also makes the line and logic circuit output the logic "0" signal, controlling the CAN bus driver to output the dominant level; then, the dominant level signal of the CAN bus enters the electrical-optical conversion loop of the different optical path, and outputs the laser signal from the different optical path port, thereby realizing the function of retransmitting the different optical path.

[0114] The optical fiber transmission circuit in this embodiment can provide two optical fiber interfaces, upstream and downstream, to realize the optical path bridging function and realize bus-type network structure networking. The optical fiber transmission circuit directly converts the CAN differential signal into an optical pulse signal without decoding the CAN packet and changing the CAN timing, so the transmission is more real-time; the optical fiber transmission circuit uses all discrete components, which is lower in application cost than integrated circuits; no control algorithm is required, so the circuit is simpler.

[0115] An embodiment of the present application also provides an optical fiber transmission device for CAN bus signals, including the optical fiber transmission circuit as described in any of the above embodiments.

[0116] The embodiment of the present application also provides a fiber optic transmission system for CAN bus signals, the fiber optic transmission system comprising a plurality of fiber optic transmission devices as described in any of the above embodiments, the fiber optic transmission devices being connected by optical fibers. The fiber optic transmission device comprises N electro-optical conversion circuits, N photoelectric conversion circuits and a CAN bus differential drive circuit.

[0117] Specifically, the optical fiber transmission system may include two optical fiber transmission devices, and the optical fiber transmission circuit in each optical fiber transmission device includes an electro-optical conversion circuit, a photoelectric conversion circuit, and a CAN bus differential drive circuit, and the two optical fiber transmission devices communicate point-to-point.

[0118] The optical fiber transmission system may also include 3 or more optical fiber transmission devices, each of which includes 2 electro-optical conversion circuits, 2 photoelectric conversion circuits and 1 CAN bus differential drive circuit, and multiple transmission devices use a bus-type network structure to communicate; among these optical fiber transmission devices, one optical fiber transmission device may include 2 or more electro-optical conversion circuits, 2 or more photoelectric conversion circuits and 1 CAN bus differential drive circuit, and other optical fiber transmission devices may include 1 electro-optical conversion circuit, 1 photoelectric conversion circuit and CAN bus differential drive circuit. In this case, the optical fiber transmission device including 2 or more electro-optical conversion circuits and 2 or more photoelectric conversion circuits serves as a central node, and the optical fiber transmission device including 1 electro-optical conversion circuit and 1 photoelectric conversion circuit serves as an access node, forming a star network structure with the central node for communication.

[0119] Next, refer to Figure 8 The optical fiber transmission system of the CAN bus signal according to the embodiment of the utility model is described. In the embodiment of the utility model, the optical fiber transmission circuit N in the optical fiber transmission device is 2, that is, each optical fiber transmission device includes 2 electro-optical conversion circuits, 2 photoelectric conversion circuits and a CAN bus differential drive circuit.

[0120] like Figure 8 As shown, in the embodiment of the utility model, the optical fiber transmission device bridges the CAN communication buses of two upper and lower adjacent battery management unit (BMU) modules in the battery management system (BMS) through an optical fiber bus. The BMU module includes a processor and a CAN transceiver. The processor interacts with the CAN transceiver through digital logic signals TX and RX. The CAN transceiver interacts with the optical fiber transmission device through the CAN bus signals on the H and L lines. The optical fiber transmission device converts the electrical pulse signal into an optical pulse signal, so that the signal propagation is transferred from the dielectric medium to the optical medium, thereby improving the reliability of signal propagation.

[0121] The upper and lower BMS modules are bridged by the optical fiber transmission device of this embodiment to form a hand-in-hand linear bus topology, which can reduce the use of optical fibers in applications and reduce material costs. Because optical fiber media is used instead of traditional cable media, the CAN bus signal does not pass through the cable that transmits electrical signals during the transmission process, thus avoiding external electromagnetic interference and improving the electrical isolation strength and anti-interference performance of the CAN bus.

[0122] The optical fiber transmission device of this embodiment can also be used in other CAN bus devices, such as a battery cluster management unit (BCMU). This embodiment does not specifically limit the application scenario of the optical fiber transmission device.

[0123] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present invention thereto. A person of ordinary skill in the art may make various changes and modifications therein without departing from the scope and spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as required by the appended claims.

[0124] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0125] Similarly, it should be understood that in order to streamline the present invention and help understand one or more of the various aspects of the present invention, in the description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present invention should not be interpreted as reflecting the following intention: the claimed invention requires more features than the features explicitly stated in each claim. More specifically, as reflected in the corresponding claims, its utility model point is that the corresponding technical problem can be solved with less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby explicitly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

[0126] It will be understood by those skilled in the art that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this specification may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0127] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0128] It should be noted that the above embodiments illustrate the utility model rather than limit the utility model, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets should not be constructed as a limitation to the claims. The word "comprising" does not exclude the existence of elements or steps not listed in the claims. The word "one" or "an" before an element does not exclude the existence of multiple such elements. The utility model can be implemented by means of hardware including several different elements and by means of appropriately programmed computers. In a unit claim that lists several devices, several of these devices can be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words can be interpreted as names.

[0129] The above is only a specific implementation or description of the specific implementation of the utility model, and the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the utility model, which should be included in the protection scope of the utility model. The protection scope of the utility model shall be based on the protection scope of the claims.

Claims

1. An optical fiber transmission circuit for CAN bus signals, characterized in that: The optical fiber transmission circuit comprises: N electro-optical conversion circuits, N photoelectric conversion circuits and a CAN bus differential drive circuit, wherein the input end of the electro-optical conversion circuit is connected to the output end of the CAN bus differential drive circuit, and the output end of the photoelectric conversion circuit is connected to the input end of the CAN bus differential drive circuit; wherein N≥1, and N is a positive integer; The electro-optical conversion circuit is used to receive the first CAN bus differential signal and output a corresponding optical fiber transmission signal under the drive of the first CAN bus differential signal; The photoelectric conversion circuit is used to perform photoelectric conversion on the received optical fiber receiving signal to obtain a CAN bus differential drive signal; The CAN bus differential driving circuit is used to output a second CAN bus differential signal under the drive of the CAN bus differential driving signal.

2. The optical fiber transmission circuit of the CAN bus signal according to claim 1, characterized in that: The CAN bus differential driving circuit includes a CAN bus differential driver.

3. The optical fiber transmission circuit for CAN bus signals according to claim 2, characterized in that: When N≥2, the CAN bus differential drive circuit further includes a line and logic circuit, the output ends of the N photoelectric conversion circuits are respectively connected to the input ends of the line and logic circuit, and the output end of the line and logic circuit is connected to the input end of the CAN bus differential driver.

4. The optical fiber transmission circuit for CAN bus signals according to claim 2, characterized in that: The CAN bus differential driver includes an emitter follower, a complementary switch circuit, a first drive circuit and a second drive circuit; The input end of the emitter follower is connected to the output end of the photoelectric conversion circuit, the output end of the emitter follower is connected to the input end of the complementary switch circuit, the two output ends of the complementary switch circuit are respectively connected to the control ends of the first drive circuit and the second drive circuit, and the output ends of the first drive circuit and the second drive circuit are used to output the CAN bus differential drive signal.

5. The optical fiber transmission circuit for CAN bus signals according to claim 1, characterized in that: The electro-optical conversion circuit includes a differential amplifier, a photoelectric emission driver and a photoelectric emission tube, wherein the output end of the differential amplifier is connected to the input end of the photoelectric emission driver, and the output end of the photoelectric emission driver is connected to the input end of the photoelectric emission tube; The differential amplifier is used to differentially amplify the first CAN bus differential signal to obtain two complementary voltage drive signals; The photoelectric emission driver is used to convert the voltage drive signal into a first current pulse signal and output it to the photoelectric emission tube; The photoelectric transmitting tube is used to output a corresponding optical fiber transmitting signal under the drive of the first current pulse signal.

6. The optical fiber transmission circuit for CAN bus signals according to claim 5, characterized in that: The differential amplifier includes: a first transistor, a second transistor, a first resistor, a second resistor, a third resistor and a fourth resistor; The first end of the first resistor is used to connect to a circuit power supply, and the second end of the first resistor is connected to the collector of the first transistor and serves as a first output end for outputting the voltage drive signal; The first end of the second resistor is connected to the collector of the second transistor and serves as a second output end for outputting the voltage driving signal; the second end of the second resistor is grounded; The first end of the third resistor serves as the first input end of the first CAN bus differential signal, and the second end of the third resistor is connected to the base of the first transistor; The first end of the fourth resistor serves as the second input end of the first CAN bus differential signal, and the second end of the fourth resistor is connected to the base of the second transistor; An emitter of the first transistor is connected to an emitter of the second transistor.

7. The optical fiber transmission circuit for CAN bus signals according to claim 5, characterized in that: The output end of the photoelectric conversion circuit is also connected to the control end of the photoelectric emission driver.

8. The optical fiber transmission circuit for CAN bus signals according to claim 7, characterized in that: The photoelectric emission driver includes: a third transistor, a fourth transistor, a fifth transistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor; The first end of the fifth resistor is connected to the circuit power supply and to the emitter of the third transistor, the first end of the sixth resistor serves as the first input end of the two complementary voltage drive signals, and the second end of the fifth resistor and the second end of the sixth resistor are both connected to the base of the third transistor; The second end of the eighth resistor is grounded and connected to the emitter of the fourth transistor, the first end of the seventh resistor serves as the second input end of the two complementary voltage drive signals, and the second end of the seventh resistor and the first end of the eighth resistor are both connected to the base of the fourth transistor; The collector of the third transistor is connected to the first end of the photoelectric emission tube, the collector of the fourth transistor is connected to the emitter of the fifth transistor, the collector of the fifth transistor is connected to the second end of the photoelectric emission tube, and the base of the fifth transistor is connected to the output end of the photoelectric conversion circuit.

9. The optical fiber transmission circuit for CAN bus signals according to claim 1, characterized in that: The photoelectric conversion circuit includes a photoelectric receiving tube and a photoelectric receiving amplification and shaping circuit, and the output end of the photoelectric receiving tube is connected to the input end of the photoelectric receiving amplification and shaping circuit; The photoelectric receiving tube is used to convert the optical fiber receiving signal into a second current pulse signal; The photoelectric receiving amplifying and shaping circuit is used to convert the second current pulse signal into a voltage pulse signal, and obtain the CAN bus differential driving signal after shaping and amplifying.

10. The optical fiber transmission circuit for CAN bus signals according to claim 9, characterized in that: The photoelectric receiving amplification and shaping circuit comprises a first-stage amplification circuit, a second-stage amplification circuit and a waveform shaping circuit connected in sequence; The first-stage amplifier circuit and the second-stage amplifier circuit are common-emitter amplifier circuits, and the waveform shaping circuit is a Schmitt trigger circuit.

11. An optical fiber transmission device for CAN bus signals, characterized in that: The optical fiber transmission circuit comprises the optical fiber transmission circuit according to any one of claims 1 to 10.

12. An optical fiber transmission system for CAN bus signals, characterized in that: The optical fiber transmission system comprises a plurality of optical fiber transmission devices according to claim 11, and the optical fiber transmission devices are connected via optical fibers.

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