Protection circuit suitable for RS485 communication

Abstract

The protection circuit comprises an RS485 circuit, a communication isolation circuit, an isolation power supply circuit, an over-current protection circuit and an ESD protection circuit, the isolation power supply circuit is respectively connected with the communication isolation circuit and the RS485 circuit, the isolation power supply circuit is used for providing isolation voltage, the communication isolation circuit is connected with the RS485 circuit, the over-current protection circuit is connected with the communication isolation circuit, and the ESD protection circuit is connected with the communication isolation circuit. The communication isolation circuit is used for interactive isolation of communication data, the RS485 circuit is connected with the over-current protection circuit, the over-current protection circuit is connected with the ESD protection circuit, the over-current protection circuit is used for current limiting and over-current protection, and the ESD protection circuit is used for transient voltage surge electrostatic protection. The utility model has the advantages of over-current and over-voltage protection function, strong anti-interference capability, suitability for complex working environment and the like.

Description

Technical Field

[0001] The utility model belongs to the technical field of RS485 communication circuits, and in particular relates to a protection circuit suitable for RS485 communication. Background Art

[0002] Since the current RS485 communication circuit only has electrostatic protection but not overvoltage protection and overcurrent protection, it is extremely easy to cause the RS485 chip and other circuit components to burn out. For example, during data interaction between the battery swap cabinet and the battery (48V), and during data interaction between the battery (48V), the electric vehicle controller, the electric vehicle intelligent central control and the electric vehicle instrument, the RS485 chip and the system MCU will often be burned out. Therefore, the RS485 communication circuit needs to be improved. Utility Model Content

[0003] In order to solve the deficiencies in the prior art, the utility model provides a protection circuit suitable for RS485 communication with overvoltage and overcurrent protection functions.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A protection circuit suitable for RS485 communication includes an RS485 circuit, a communication isolation circuit, an isolation power supply circuit, an overcurrent protection circuit, and an ESD protection circuit. The isolation power supply circuit is respectively connected to the communication isolation circuit and the RS485 circuit. The isolation power supply circuit is used to provide an isolation voltage. The communication isolation circuit is connected to the RS485 circuit. The communication isolation circuit is used to isolate communication data from each other. The RS485 circuit is connected to the overcurrent protection circuit. The overcurrent protection circuit is connected to the ESD protection circuit. The overcurrent protection circuit is used for current limiting and overcurrent protection. The ESD protection circuit is used for transient voltage surge and electrostatic protection.

[0006] Preferably, the isolated power supply circuit includes an isolated power supply U1, a first capacitor C1 and a third resistor R3, one end of the first capacitor C1 is connected to the +Vo end of the isolated power supply U1, the other end of the first capacitor C1 is connected to the 0V end of the first power supply U1, one end of the third resistor R3 is connected to the +Vo end of the isolated power supply U1, and the other end of the third resistor R3 is connected to the 0V end of the first power supply U1.

[0007] Preferably, the communication isolation circuit includes an isolation chip U2, an isolation optocoupler O1, a first resistor R1, a second resistor R2, a fourth resistor R4, a fifth resistor R5, a second capacitor C2 and a third capacitor C3, the positive input terminal of the isolation optocoupler O1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the VDD end of the isolation chip U2, the first end of the second capacitor C2 is connected to the second end of the second resistor R2, the second end of the second capacitor C2 is grounded, the output collector of the isolation optocoupler O1 is connected to one end of the first resistor R1, the other end of the first resistor R1 is connected to the +Vo end of the isolation power supply U1, the GND end of the isolation chip U2 is grounded, the VDD2 end of the isolation chip U2 is connected to the +Vo end of the isolation power supply U1, the first end of the third capacitor C3 is connected to the VDD2 end of the isolation chip U2, and the second end of the third capacitor C3 is connected to the GND2 end of the isolation chip U2.

[0008] Preferably, the RS485 circuit includes an RS485 chip U3, an eighth resistor R8, a ninth resistor R9, an eleventh resistor R11, a fifth capacitor C5 and a terminal P1, the RO terminal of the RS485 chip U3 is connected to one end of the eighth resistor R8, the other end of the eighth resistor R8 is connected to the INA terminal of the isolation chip U2, the RE terminal and the DE terminal of the RS485 chip U3 are both connected to one end of the ninth resistor R9, the other end of the ninth resistor R9 is connected to the output collector of the isolation optocoupler O1, the DI terminal of the RS485 chip U3 is connected to one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is connected to the OUTB terminal of the isolation chip U2, the VCC terminal of the RS485 chip U3 is respectively connected to the +Vo terminal of the isolation power supply U1 and the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is respectively connected to the 0V terminal of the first power supply U1, the output emitter of the isolation optocoupler O1, the second end of the third capacitor C3 and the first port of the terminal P1.

[0009] Preferably, the overcurrent protection circuit includes a sixth resistor R6, a seventh resistor R7, a first fuse F1 and a second fuse F2, one end of the sixth resistor R6 is connected to the A end of the RS485 chip U3, the other end of the sixth resistor R6 is connected to the first end of the first fuse F1, the second end of the first fuse F1 is connected to the third port of the terminal P1, one end of the seventh resistor R7 is connected to the B end of the RS485 chip U3, the other end of the seventh resistor R7 is connected to the first end of the second fuse F2, and the second end of the second fuse F2 is connected to the second port of the terminal P1.

[0010] Preferably, the ESD protection circuit includes a first transient diode D1 and a second transient diode D2, one end of the first transient diode D1 is connected to the second port of the terminal P1, and the other end of the first transient diode D1 is respectively connected to the second end of the fifth capacitor C5 and the GND end of the RS485 chip U3, one end of the second transient diode D2 is connected to the third port of the terminal P1, and the other end of the second transient diode D2 is respectively connected to the second end of the fifth capacitor C5 and the GND end of the RS485 chip U3.

[0011] By adopting the above technical solution, the utility model has the following beneficial effects:

[0012] Compared with the existing traditional RS485 communication circuit, the utility model adds an RS485 chip, a communication isolation circuit, an overcurrent protection circuit and an ESD protection circuit. When used, it has overcurrent and overvoltage protection functions, improves the protection characteristics of the communication circuit, has strong anti-interference ability, and is suitable for complex working environments;

[0013] In summary, the utility model has the advantages of overcurrent and overvoltage protection functions, strong anti-interference ability, and suitability for complex working environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a block diagram of the utility model;

[0015] Figure 2 It is a circuit principle diagram of the utility model. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0017] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention.

[0018] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0019] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0021] Example 1

[0022] In this embodiment, a protection circuit suitable for RS485 communication is proposed, which has better overcurrent and overvoltage protection based on the existing technology.

[0023] like Figure 1 and Figure 2 As shown, in one embodiment of the present invention, a protection circuit suitable for RS485 communication of the present invention includes an RS485 circuit 101, a communication isolation circuit 102, an isolation power supply circuit 103, an overcurrent protection circuit 104 and an ESD protection circuit 105. The isolation power supply circuit 103 is respectively connected to the communication isolation circuit 102 and the RS485 circuit 101, and the isolation power supply circuit 103 is used to provide an isolation voltage. The communication isolation circuit 102 is connected to the RS485 circuit 101, and the communication isolation circuit 102 is used for interactive isolation of communication data. The RS485 circuit 101 is connected to the overcurrent protection circuit 104, and the overcurrent protection circuit 104 is connected to the ESD protection circuit 105. The overcurrent protection circuit 104 is used for current limiting and overcurrent protection, and the ESD protection circuit 105 is used for transient voltage surge and electrostatic protection.

[0024] Specifically, the isolated power supply circuit 103 includes an isolated power supply U1, a first capacitor C1 and a third resistor R3, one end of the first capacitor C1 is connected to the +Vo end of the isolated power supply U1, the other end of the first capacitor C1 is connected to the 0V end of the first power supply U1, one end of the third resistor R3 is connected to the +Vo end of the isolated power supply U1, the other end of the third resistor R3 is connected to the 0V end of the first power supply U1, the isolated power supply can select B0505S-1WR2, in the circuit, the isolated power supply U1 (B0505S-1WR2) provides a stable 5V isolation voltage for the entire circuit, the communication isolation circuit 102 It includes an isolation chip U2, an isolation optocoupler O1, a first resistor R1, a second resistor R2, a fourth resistor R4, a fifth resistor R5, a second capacitor C2 and a third capacitor C3. The positive electrode of the input end of the isolation optocoupler O1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the VDD end of the isolation chip U2, the first end of the second capacitor C2 is connected to the second end of the second resistor R2, and the second end of the second capacitor C2 is grounded. The collector of the output end of the isolation optocoupler O1 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the +Vo end of the isolation power supply U1. The GN of the isolation chip U2 The D terminal is grounded, the VDD2 terminal of the isolation chip U2 is connected to the +Vo terminal of the isolation power supply U1, the first end of the third capacitor C3 is connected to the VDD2 terminal of the isolation chip U2, the second end of the third capacitor C3 is connected to the GND2 terminal of the isolation chip U2, the RS485 circuit 101 includes the RS485 chip U3, the eighth resistor R8, the ninth resistor R9, the eleventh resistor R11, the fifth capacitor C5 and the terminal P1, the RO terminal of the RS485 chip U3 is connected to one end of the eighth resistor R8, the other end of the eighth resistor R8 is connected to the INA terminal of the isolation chip U2, and the RE terminal of the RS485 chip U3 is connected to the INA terminal of the isolation chip U2. The DE terminal and the DE terminal are both connected to one end of the ninth resistor R9, the other end of the ninth resistor R9 is connected to the output collector of the isolation optocoupler O1, the DI terminal of the RS485 chip U3 is connected to one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is connected to the OUTB terminal of the isolation chip U2, the VCC terminal of the RS485 chip U3 is respectively connected to the +Vo terminal of the isolated power supply U1 and the first end of the fifth capacitor C5, the second end of the fifth capacitor C5 is respectively connected to the 0V terminal of the first power supply U1, the output emitter of the isolation optocoupler O1, the second end of the third capacitor C3 and the first port of the terminal P1;

[0025] The isolation chip U2 can select NIRS21, the RS485 chip U3 can select SN65HVD1781DR, and the isolation optocoupler O1 can select CT357B (T1). In the present invention, the isolation chip U2 and the isolation optocoupler O1 play the role of isolating the communication data interaction. After the RS485 chip selects SN65HVD1781D, its internal structure has the characteristics of high-voltage resistance below 70V, which improves the protection characteristics of the communication circuit, and has strong anti-interference ability, and can work in a variety of complex environments.

[0026] Continue to refer to Figure 2 The overcurrent protection circuit 104 includes a sixth resistor R6, a seventh resistor R7, a first fuse F1 and a second fuse F2, one end of the sixth resistor R6 is connected to the A end of the RS485 chip U3, the other end of the sixth resistor R6 is connected to the first end of the first fuse F1, the second end of the first fuse F1 is connected to the third port of the terminal P1, one end of the seventh resistor R7 is connected to the B end of the RS485 chip U3, the other end of the seventh resistor R7 is connected to the first end of the second fuse F2, the second end of the second fuse F2 is connected to the second port of the terminal P1, the ESD protection circuit 105 includes a first transient diode D1 and a second transient diode D2, one end of the first transient diode D1 is connected to the second port of the terminal P1, The other end of the transient diode D1 is respectively connected to the second end of the fifth capacitor C5 and the GND terminal of the RS485 chip U3. One end of the second transient diode D2 is connected to the third port of the terminal P1. The other end of the second transient diode D2 is respectively connected to the second end of the fifth capacitor C5 and the GND terminal of the RS485 chip U3. In this application, the negative electrode of the input end of the isolation optocoupler O1 is connected to RS485EN, which is used to control whether the RS485 chip is in a data sending state or a data receiving state. The OUTA terminal of the isolation chip U2 is connected to one end of a fourth resistor R4, the other end of the fourth resistor R4 is connected to the RS485RX terminal. The INB terminal of the isolation chip U2 is connected to one end of a fifth resistor R5, the other end of the fifth resistor R5 is connected to the RS485TX terminal.

[0027] In the present invention, the first fuse F1 and the second fuse F2 are both JK-nSMD005 / 60, the first transient diode D1 and the second transient diode D2 are both SMBJ43CA, and the sixth resistor R6 and the seventh resistor R7 are both 10Ω, which have a current limiting function. The first fuse F1 and the second fuse F2 provide overcurrent protection, and the first transient diode D1 and the second transient diode D2 provide transient voltage surge and electrostatic protection.

[0028] In the present invention, it is connected to other system MCUs. When the system MCU sends serial port data through the isolation chip U2 (NIRS21), the isolation chip U2 (NIRS21) filters and isolates the noise in the serial port data, obtains high-quality serial port data and gives it to the RS485 chip (SN65HVD1781DR), and the RS485 chip (SN65HVD1781DR) converts the serial port data into RS485 communication data, which is limited by the sixth resistor R6 and the seventh resistor R7, and then passes through the first fuse F1 and the second fuse F2 and is transmitted from the port of the terminal P1 to the external slave or host. Due to the complex environment of the external slave or host, the RS485 communication data returned is very likely to be mixed with an effective voltage below 70V or higher and a transient electrostatic voltage. When the returned data passes through the terminal P1, the transient voltage will be blocked by the first transient diode D1 and the second transient diode D2 (S MBJ43CA) is suppressed. When the RS485 data bus is connected to an effective voltage below 70V for other reasons, the high-voltage protection characteristics of the RS485 chip (SN65HVD1781DR) can well protect the entire circuit. When the RS485 data bus is connected to an effective voltage of more than 70V or even higher for other reasons, it can be seen from the volt-ampere characteristics that the RS485 chip (SN65HVD1781DR) must exceed 100mA in order to be burned out. However, when the bus current exceeds 50mA, the first fuse F1 and the second fuse F2 (JK-nSMD005 / 60) will burn out directly to protect the RS485 chip and the subsequent circuit in the circuit, thereby achieving overvoltage and overcurrent protection. The RS485 data is converted into serial port data after passing through the RS485 chip, and then transmitted to the MCU through the isolation chip U2 (NIRS21). The entire communication work is completed.

[0029] The isolated power supply U1 (B0505S-1WR2) can prevent the RS485 circuit 101 of this application from short-circuiting and pulling the external voltage, causing the external circuit to fail to work. At the same time, it can also ensure that after the RS485 circuit 101 of this application is broken down by a higher voltage, it will be connected in series with the external circuit, causing other components of the external circuit to burn out. The isolation chip U2 and the isolation optocoupler O1 play the role of communication isolation, isolate the internal and external communication data interaction, improve the circuit data stability, and have higher anti-interference ability.

[0030] This application sets up an isolated power supply circuit 103 to make the transmission data more stable, with strong anti-interference ability, and with overvoltage and overcurrent protection functions. It can be effectively used in scenarios such as data interaction between the battery swap cabinet and the battery (48V), the battery (48V), the electric vehicle controller, the electric vehicle intelligent central control and the electric vehicle instrument, and can effectively reduce the product defective rate.

[0031] This embodiment does not impose any formal restrictions on the shape, material, structure, etc. of the utility model. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the utility model are within the scope of protection of the technical solution of the utility model.

Claims

1. A protection circuit suitable for RS485 communication, characterized in that: It includes an RS485 circuit, a communication isolation circuit, an isolation power supply circuit, an overcurrent protection circuit and an ESD protection circuit. The isolation power supply circuit is connected to the communication isolation circuit and the RS485 circuit respectively. The isolation power supply circuit is used to provide isolation voltage. The communication isolation circuit is connected to the RS485 circuit. The communication isolation circuit is used for interactive isolation of communication data. The RS485 circuit is connected to the overcurrent protection circuit. The overcurrent protection circuit is connected to the ESD protection circuit. The overcurrent protection circuit is used for current limiting and overcurrent protection. The ESD protection circuit is used for transient voltage surge and electrostatic protection.

2. A protection circuit suitable for RS485 communication according to claim 1, characterized in that: The isolated power supply circuit includes an isolated power supply U1, a first capacitor C1 and a third resistor R3, one end of the first capacitor C1 is connected to the +Vo terminal of the isolated power supply U1, the other end of the first capacitor C1 is connected to the 0V terminal of the first power supply U1, one end of the third resistor R3 is connected to the +Vo terminal of the isolated power supply U1, and the other end of the third resistor R3 is connected to the 0V terminal of the first power supply U1.

3. A protection circuit suitable for RS485 communication according to claim 2, characterized in that: The communication isolation circuit includes an isolation chip U2, an isolation optocoupler O1, a first resistor R1, a second resistor R2, a fourth resistor R4, a fifth resistor R5, a second capacitor C2 and a third capacitor C3. The positive input terminal of the isolation optocoupler O1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the VDD end of the isolation chip U2, the first end of the second capacitor C2 is connected to the second end of the second resistor R2, and the second end of the second capacitor C2 is grounded. The collector output terminal of the isolation optocoupler O1 is connected to one end of the first resistor R1, the other end of the first resistor R1 is connected to the +Vo end of the isolation power supply U1, the GND end of the isolation chip U2 is grounded, the VDD2 end of the isolation chip U2 is connected to the +Vo end of the isolation power supply U1, the first end of the third capacitor C3 is connected to the VDD2 end of the isolation chip U2, and the second end of the third capacitor C3 is connected to the GND2 end of the isolation chip U2.

4. A protection circuit suitable for RS485 communication according to claim 3, characterized in that: The RS485 circuit includes an RS485 chip U3, an eighth resistor R8, a ninth resistor R9, an eleventh resistor R11, a fifth capacitor C5 and a terminal P1. The RO terminal of the RS485 chip U3 is connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is connected to the INA terminal of the isolation chip U2. The RE terminal and DE terminal of the RS485 chip U3 are both connected to one end of the ninth resistor R9, and the other end of the ninth resistor R9 is connected to the output collector of the isolation optocoupler O1. The DI terminal of the RS485 chip U3 is connected to one end of the eleventh resistor R11, and the other end of the eleventh resistor R11 is connected to the OUTB terminal of the isolation chip U2. The VCC terminal of the RS485 chip U3 is respectively connected to the +Vo terminal of the isolated power supply U1 and the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is respectively connected to the 0V terminal of the first power supply U1, the output emitter of the isolation optocoupler O1, the second end of the third capacitor C3 and the first port of the terminal P1.

5. A protection circuit suitable for RS485 communication according to claim 4, characterized in that: The overcurrent protection circuit includes a sixth resistor R6, a seventh resistor R7, a first fuse F1 and a second fuse F2. One end of the sixth resistor R6 is connected to the A end of the RS485 chip U3, the other end of the sixth resistor R6 is connected to the first end of the first fuse F1, the second end of the first fuse F1 is connected to the third port of the terminal P1, one end of the seventh resistor R7 is connected to the B end of the RS485 chip U3, the other end of the seventh resistor R7 is connected to the first end of the second fuse F2, and the second end of the second fuse F2 is connected to the second port of the terminal P1.

6. A protection circuit suitable for RS485 communication according to claim 5, characterized in that: The ESD protection circuit includes a first transient diode D1 and a second transient diode D2, one end of the first transient diode D1 is connected to the second port of the terminal P1, and the other end of the first transient diode D1 is respectively connected to the second end of the fifth capacitor C5 and the GND end of the RS485 chip U3, one end of the second transient diode D2 is connected to the third port of the terminal P1, and the other end of the second transient diode D2 is respectively connected to the second end of the fifth capacitor C5 and the GND end of the RS485 chip U3.

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