Isolation type RS485 communication module of intelligent fusion terminal in transformer area

Abstract

The utility model discloses a transformer area intelligent fusion terminal isolation type RS485 communication module which comprises a logic side power supply and signal circuit, a field side power supply and bus driving circuit, a port protection circuit and a terminal matching and biasing circuit. The logic side power supply and signal circuit is electrically connected with the field side power supply and bus driving circuit through an isolation type RS485 transceiver (U3); the field side power supply and bus driving circuit is electrically connected with the port protection circuit; and the terminal matching and biasing circuit is electrically connected with the port protection circuit. The transformer area intelligent fusion terminal isolation type RS485 communication module has the characteristics of electrical isolation, ground potential difference resistance, graded surge overcurrent protection and stable and reliable communication.

Description

TECHNICAL FIELD

[0001] The utility model relates to distribution area intelligent fusion terminal communication interface technical field, concretely relates to a distribution area intelligent fusion terminal isolated RS485 communication module. BACKGROUND

[0002] With the further promotion of smart grid construction, distribution area intelligent fusion terminal has become the core equipment of power system terminal information collection and control. This kind of terminal equipment is usually deployed in distribution transformer area, communicates with electric energy meter, collector, reactive power compensation controller, sensor and other field devices through RS485 bus, realizes electric energy information collection, load monitoring, reactive power compensation control and other functions. Because the RS485 bus in the distribution area has the characteristics of long wiring distance and many connection nodes, and is operated in the outdoor strong electromagnetic interference environment for a long time, it puts forward strict technical requirements for the reliability and protection ability of the communication interface.

[0003] The typical interference sources faced by the distribution area include lightning-induced surge, switch operation overvoltage, electromagnetic radiation and ground potential difference. The traditional non-isolated or insufficiently protected RS485 interface has many technical defects: in terms of communication reliability, ground potential difference easily causes communication error or even interface burning, long line reflection and impedance mismatching lead to waveform distortion, and bus idle state uncertainty leads to random triggering and misframe. In terms of device safety, surge and electrostatic discharge easily lead to the breakdown damage of the transceiver. In terms of protection scheme, the scheme of only using TVS transient voltage suppressor is prone to thermal failure under continuous overcurrent condition, and the scheme of only using fuse has the problem of non-recovery, and the maintenance cost is high. UTILITY MODEL CONTENTS

[0004] The utility model aims at providing a distribution area intelligent fusion terminal isolated RS485 communication module. The distribution area intelligent fusion terminal isolated RS485 communication module has the characteristics of electrical isolation, ground potential difference resistance, hierarchical surge overcurrent protection and stable and reliable communication.

[0005] The above technical purpose of the utility model is realized by the following technical scheme:

[0006] A distribution area intelligent fusion terminal isolated RS485 communication module, comprising a logic side power supply and signal circuit, a field side power supply and bus driving circuit, a port protection circuit and a terminal matching and biasing circuit, the logic side power supply and signal circuit are electrically connected with the field side power supply and bus driving circuit through an isolated RS485 transceiver (U3), the field side power supply and bus driving circuit are electrically connected with the port protection circuit, and the terminal matching and biasing circuit are electrically connected with the port protection circuit.

[0007] The utility model further sets up: the logic side power supply and signal circuit includes first decoupling capacitor (C10), second decoupling capacitor (C11) and isolated RS485 transceiver (U3), first decoupling capacitor (C10) with second decoupling capacitor (C11) are connected in parallel between logic side power VCC3V3 and logic side ground GND, the parallel node of first decoupling capacitor (C10) with second decoupling capacitor (C11) is connected to the VDD1 pin of isolated RS485 transceiver (U3), the GND1 pin of isolated RS485 transceiver (U3) is connected to logic side ground GND, and the master control sends signal UART4_TXD is connected to the TXD pin of isolated RS485 transceiver (U3), and the RXD pin of isolated RS485 transceiver (U3) is connected to master control receiving signal UART4_RXD, and direction control signal is connected to the DE pin and RE pin of isolated RS485 transceiver (U3).

[0008] The utility model further sets up: the field side power supply and bus driving circuit include third decoupling capacitor (C12) and fourth decoupling capacitor (C13), third decoupling capacitor (C12) with fourth decoupling capacitor (C13) are connected in parallel between field side power VCC_485 and field side ground GND1, the parallel node of third decoupling capacitor (C12) with fourth decoupling capacitor (C13) is connected to the VDD2 pin of isolated RS485 transceiver (U3), the GND2 pin of isolated RS485 transceiver (U3) is connected to field side ground GND1, the Y pin and A pin of isolated RS485 transceiver (U3) are connected in parallel and form first differential line EA, and the Z pin and B pin of isolated RS485 transceiver (U3) are connected in parallel and form second differential line EB.

[0009] The utility model further sets up: port protection circuit includes EMI suppression unit, surge clamping unit and overcurrent protection unit, EMI suppression unit includes first magnetic pearl (FB5) and second magnetic pearl (FB6), first magnetic pearl (FB5) is connected in series in first difference line EA, second magnetic pearl (FB6) is connected in series in second difference line EB, surge clamping unit includes first TVS pipe (TVS6), second TVS pipe (TVS7) and third TVS pipe (TVS8), first TVS pipe (TVS6), second TVS pipe (TVS7) and third TVS pipe (TVS8) are with the circuit reference of on -the -spot side ground GND1 and carry out surge clamping, overcurrent protection unit includes first PTC self -recovery fuse (F3) and second PTC self -recovery fuse (F4), first PTC self -recovery fuse (F3) is connected in series in first difference line EA close to external terminal EA1 side, second PTC self -recovery fuse (F4) is connected in series in second difference line EB close to external terminal EB1 side.

[0010] The utility model further sets up: terminal matching and bias circuit includes terminal matching resistance (R11), pull -up bias resistance (R16) and pull -down bias resistance (R18), terminal matching resistance (R11) is crossed in first difference line EA and second difference line EB between, pull -up bias resistance (R16) is connected between on -the -spot side power VCC_485 and first difference line EA, pull -down bias resistance (R18) is connected between second difference line EB and on -the -spot ground GND1.

[0011] The utility model further sets up: the signal path of port protection circuit is in proper order first difference line EA and second difference line EB are connected to the bus pin of isolation type RS485 transceiver (U3), first difference line EA and second difference line EB are respectively through first magnetic pearl (FB5) and second magnetic pearl (FB6) and enter surge clamping area, and then are connected to external terminal EA1 and external terminal EB1 through first PTC self -recovery fuse (F3) and second PTC self -recovery fuse (F4) respectively.

[0012] The utility model further sets up: the capacity of first decoupling capacitor (C10) is 100nF, the capacity of second decoupling capacitor (C11) is 10µF, the capacity of third decoupling capacitor (C12) is 100nF, the capacity of fourth decoupling capacitor (C13) is 10µF, the resistance of terminal matching resistance (R11) is 120Ω, the resistance of pull -up bias resistance (R16) is 10kΩ, the resistance of pull -down bias resistance (R18) is 10kΩ.

[0013] The present invention is further configured such that: the isolated RS485 transceiver (U3) adopts ADM2484E, the first ferrite bead (FB5) and the second ferrite bead (FB6) adopt HB-1M2012-102, the first TVS tube (TVS6), the second TVS tube (TVS7) and the third TVS tube (TVS8) adopt SMBJ6.0CA, and the first PTC resettable fuse (F3) and the second PTC resettable fuse (F4) adopt MZ11-10A300-600RM.

[0014] In summary, this utility model has the following beneficial effects:

[0015] 1. Dual power domain isolation architecture: This utility model separates the main control logic ground GND from the field communication ground GND1 through an isolated RS485 transceiver (U3). The logic side operates in the VCC3V3 / GND power domain, and the field side operates in the VCC_485 / GND1 power domain. Electrical isolation is achieved between the two domains, which significantly reduces the impact of ground potential difference and surge backflow on the main control system. It also reduces the probability of reset, bit error and damage caused by ground potential difference at the system level.

[0016] 2. Hierarchical Energy Management Protection Link: This utility model constructs a three-level protection link consisting of magnetic bead speed limiting, TVS clamping, and PTC current limiting. The first magnetic bead (FB5) and the second magnetic bead (FB6) suppress high-frequency spikes and reduce voltage rise time to make clamping more stable. The first TVS tube (TVS6), the second TVS tube (TVS7), and the third TVS tube (TVS8) quickly clamp transient overvoltages. The first PTC self-resetting fuse (F3) and the second PTC self-resetting fuse (F4) thermally limit continuous overcurrents. The three work together to solve the problem of transient and continuous combined interference in the transformer area, which is significantly better than a single protection scheme of only TVS or only fuse.

[0017] 3. Local closing of interface return current: This utility model uses GND1 to carry the TVS discharge circuit on the field side, so that the surge current does not pass through the main control ground, and the surge energy is discharged and closed on the field side, effectively protecting the main control system from surge impact.

[0018] 4. Integrated Termination Matching and Idle Bias: This utility model achieves differential termination matching through a termination matching resistor (R11), reducing reflection and ringing, and lowering the bit error rate. An idle bias network is formed through pull-up bias resistors (R16) and pull-down bias resistors (R18), which keeps the differential pairs in a defined idle state when the external bus is disconnected, unloaded, or when multiple nodes are at full high impedance, improving the ability to resist noise and false triggering, and adapting to common working conditions in the field where cables are suspended or have poor contact.

[0019] 5. Self-resetting overcurrent protection: This utility model uses a PTC self-resetting fuse for overcurrent protection. When there is continuous overcurrent, the riser current limiting protection protects the downstream circuit. After the fault is cleared, it can automatically resume conduction, reducing the probability of on-site replacement and maintenance. It is suitable for long-life, unattended deployment scenarios of transformer terminals. Attached Figure Description

[0020] Figure 1 This is the overall circuit schematic diagram of this utility model. Detailed Implementation

[0021] In the description of this utility model, it should be noted that the terms logical side, field side, internal, external, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0022] like Figure 1 As shown, this utility model provides an isolated RS485 communication module for a distribution area intelligent fusion terminal. This module is suitable for distribution area intelligent fusion terminals and is used to realize isolated communication between the main control system and the field RS485 bus, while providing graded surge and overcurrent protection. The module consists of four parts: logic-side power supply and signal circuit, field-side power supply and bus drive circuit, port protection circuit, and terminal matching and biasing circuit.

[0023] The logic-side power supply and signal circuit is located on the left side of the circuit and operates in the VCC3V3 / GND power domain. It is used to complete the digital transmission and reception and direction control between the main control MCU and the isolated RS485 transceiver (U3). This circuit includes a first decoupling capacitor (C10), a second decoupling capacitor (C11), and the isolated RS485 transceiver (U3). The first decoupling capacitor (C10) is a surface-mount capacitor with a capacitance of 100nF, used to suppress high-frequency spikes. The second decoupling capacitor (C11) is a surface-mount capacitor with a capacitance of 10µF, used to provide low-frequency energy support. The first decoupling capacitor (C10) and the second decoupling capacitor (C11) are connected in parallel between the logic-side power supply VCC3V3 and the logic-side ground GND. The parallel configuration of the two capacitors reduces the VDD1 fluctuation caused by the transient current on the digital side of the isolated RS485 transceiver (U3). The parallel node is connected to the VDD1 pin of the isolated RS485 transceiver (U3) to power its logic side. The GND1 pin of the isolated RS485 transceiver (U3) is connected to the logic side ground GND. The isolated RS485 transceiver (U3) uses the ADM2484E model, which has electrically isolated power supply domains of logic side VDD1 / GND1 and field side VDD2 / GND1 for differential drive, differential reception, and electrical isolation functions. The master control transmits data through the UART4_TXD signal line to the TXD pin of the isolated RS485 transceiver (U3) as a logic transmit input. The RXD pin of the isolated RS485 transceiver (U3) is connected to the UART4_RXD signal line as a logic receive output to the master control. The direction control signal PB12_GPIO_4851_DIR is connected to the DE and RE pins of the isolated RS485 transceiver (U3) to switch the transmit and receive directions.

[0024] The field-side power supply and bus drive circuit is located in the middle of the circuit, operating in the VCC_485 / GND1 power domain. It provides differential bus drive and differential reception functions after isolation, using GND1 as the surge discharge and protection return current reference. This circuit includes a third decoupling capacitor (C12) and a fourth decoupling capacitor (C13). The third decoupling capacitor (C12) is a surface-mount capacitor with a capacitance of 100nF, used to suppress high-frequency spikes. The fourth decoupling capacitor (C13) is a surface-mount capacitor with a capacitance of 10µF, used to ensure stable power supply on the isolation side. The third decoupling capacitor (C12) and the fourth decoupling capacitor (C13) are connected in parallel between the field-side power supply VCC_485 and the field-side ground GND1. This decoupling configuration ensures stable bus-side drive current and receiver comparator power supply after isolation, preventing long-line interference from causing bit errors through power coupling. The parallel node is connected to the VDD2 pin of the isolated RS485 transceiver (U3) to provide power to its field side. The GND2 pin of the isolated RS485 transceiver (U3) is connected to the field-side ground GND1 as the field-side reference ground. The bus-related pins of the isolated RS485 transceiver (U3) are connected using the engineering practice of two-wire half-duplex RS485, with the transmit output and receive input connected in parallel to the same line. Specifically, the Y pin and the A pin are connected in parallel to form the first differential line EA, and the Z pin and the B pin are connected in parallel to form the second differential line EB.

[0025] The port protection circuit is located on the right side of the circuit, providing multi-level protection from the bus pins of the isolated RS485 transceiver (U3) to the external terminals. This circuit includes an EMI suppression unit, a surge clamping unit, and an overcurrent protection unit. The EMI suppression unit includes a first ferrite bead (FB5) and a second ferrite bead (FB6), both using the HB-1M2012-102 model, which are high-frequency impedance components that present high impedance to high-frequency interference, suppressing the high-frequency components and radiated coupling of external surges. The first ferrite bead (FB5) is connected in series to the first differential line EA, and the second ferrite bead (FB6) is connected in series to the second differential line EB. The surge clamping unit includes a first TVS diode (TVS6), a second TVS diode (TVS7), and a third TVS diode (TVS8), all using the SMBJ6.0CA model bidirectional transient voltage suppressor, with field-side ground GND1 as the loop reference for surge clamping. The distribution of multiple devices enables multipath suppression of common-mode and differential-mode signals, quickly clamping overvoltages of the wire pair to GND1 during surges or electrostatic discharge, thus improving withstand capability and redundancy. The overcurrent protection unit includes a first PTC resettable fuse (F3) and a second PTC resettable fuse (F4), both using the MZ11-10A300-600RM model. The first PTC resettable fuse (F3) is connected in series on the first differential line EA near the external terminal EA1, and the second PTC resettable fuse (F4) is connected in series on the second differential line EB near the external terminal EB1. During normal operation, the PTC resettable fuses exhibit a low-impedance state, allowing normal signal transmission. During continuous overcurrent, they increase resistance to limit current and protect the downstream circuitry. They automatically resume conduction after the fault is cleared.

[0026] The signal path of the port protection circuit is as follows: The bus pins of the isolated RS485 transceiver (U3) are connected to the first differential line EA and the second differential line EB. The first differential line EA and the second differential line EB first pass through the first ferrite bead (FB5) and the second ferrite bead (FB6) for EMI suppression, respectively. Then, they enter the surge clamping zone where the first TVS diode (TVS6), the second TVS diode (TVS7), and the third TVS diode (TVS8) perform overvoltage clamping. Finally, they are connected to the external terminals EA1 and EB1 via the first PTC resettable fuse (F3) and the second PTC resettable fuse (F4), respectively. This signal path achieves graded energy management protection through ferrite bead speed limiting, TVS clamping, and PTC current limiting.

[0027] The termination matching and biasing circuit is used to implement differential termination matching and idle biasing functions. This circuit includes a termination matching resistor (R11), a pull-up bias resistor (R16), and a pull-down bias resistor (R18). The termination matching resistor (R11) has a resistance of 120Ω and is connected between the first differential line EA and the second differential line EB to form differential termination matching. When this module acts as a bus terminator, it can significantly reduce reflections and ringing, and improve the eye diagram and bit error rate. The pull-up bias resistor (R16) has a resistance of 10kΩ and is connected between the field-side power supply VCC_485 and the first differential line EA, providing pull-up bias for the first differential line EA. The pull-down bias resistor (R18) has a resistance of 10kΩ and is connected between the second differential line EB and the field-side ground GND1, providing pull-down bias for the second differential line EB. The pull-up bias resistor (R16) and the pull-down bias resistor (R18) work together to form a differential idle state bias network. When the external bus is disconnected, unloaded, or when multiple nodes are at full high impedance, the first differential line EA and the second differential line EB maintain a defined differential idle state, which improves the ability to resist noise and false triggering and adapts to common working conditions such as suspended or poorly connected cables in the field.

[0028] The working principle of this utility model is as follows:

[0029] During reception, the signal is transmitted from the fieldbus to the main control system after undergoing multiple levels of protection. The external bus signal enters the circuit through external terminals EA1 and EB1, first passing through the first and second PTC resettable fuses (F3 and F4) for overcurrent protection. Under normal operation, the PTC exhibits a low-impedance state, allowing the signal to pass normally. When an abnormal current occurs, the PTC increases its resistance to limit the current, protecting the subsequent circuitry. Then, the signal enters the surge clamping region, where the first TVS diode (TVS6), second TVS diode (TVS7), and third TVS diode (TVS8) quickly clamp overvoltage spikes to the field-side ground (GND1), suppressing overvoltage to ground and protecting the transceiver from transient overvoltage damage. Next, the signal undergoes EMI suppression via the first ferrite bead (FB5) and second ferrite bead (FB6). After high-frequency interference is suppressed, the signal reaches the bus pin of the isolated RS485 transceiver (U3). Finally, the isolated RS485 transceiver (U3) decodes the differential signals on the first differential line EA and the second differential line EB into logic levels in the receive-enabled state. After passing through the internal isolation channel, the logic level is output from the RXD pin to the UART4_RXD signal line and finally sent to the main control MCU.

[0030] During transmission, the signal is transmitted from the main control system to the fieldbus after isolation. The main control MCU controls the isolated RS485 transceiver (U3) to enter the transmit state through the direction control signal PB12_GPIO_4851_DIR, enabling the DE pin and disabling the RE pin. Simultaneously, it outputs the data to be transmitted to the TXD pin of the isolated RS485 transceiver (U3) through the UART4_TXD signal line. The isolated RS485 transceiver (U3) transmits the logic level signal received by the TXD pin to the field side through the internal isolation channel and converts it into differential drive signals, which are output to the first differential line EA and the second differential line EB. The differential signal reaches the protection zone through the first ferrite bead (FB5) and the second ferrite bead (FB6), and then is output to the external terminals EA1 and EB1 through the first PTC resettable fuse (F3) and the second PTC resettable fuse (F4). In the event of an external surge or misconnection, the first TVS diode (TVS6), the second TVS diode (TVS7), the third TVS diode (TVS8), the first PTC resettable fuse (F3), and the second PTC resettable fuse (F4) will preferentially absorb and limit energy, protecting the isolated RS485 transceiver (U3) from direct impact by overvoltage or overcurrent.

[0031] Direction control is achieved through the PB12_GPIO_4851_DIR signal, which connects to both the DE and RE pins of the isolated RS485 transceiver (U3). By using a single-direction signal or complementary logic, half-duplex switching is achieved: driving is enabled and receiving is disabled during transmission, and driving is disabled and receiving is enabled during reception. This effectively avoids bus contention, signal backflow, and false triggering.

[0032] This utility model discloses an isolated RS485 communication module for a distribution transformer intelligent fusion terminal. It achieves electrical isolation between the main control logic ground and the field communication ground through a dual power domain isolation architecture. It provides protection against transient and continuous composite interference through a graded energy management protection link consisting of ferrite bead speed limiting, TVS clamping, and PTC current limiting. It ensures waveform quality and determines the idle state through a terminal matching resistor and an idle state bias network. This module solves the reliability and protection problems of the RS485 communication interface in a strong interference environment in the distribution transformer field, and realizes high-reliability field communication for the distribution transformer intelligent fusion terminal. It has good application value.

Claims

1. A transformer area intelligent fusion terminal isolated RS485 communication module, characterized in that, Comprise: Logic side power supply and signal circuit, field side power supply and bus driving circuit, port protection circuit and terminal matching and biasing circuit; The logic side power supply and signal circuit and the field side power supply and bus driving circuit are electrically connected through an isolated RS485 transceiver (U3); The field side power supply and bus driving circuit is electrically connected with the port protection circuit; The terminal matching and biasing circuit is electrically connected with the port protection circuit.

2. The intelligent fusion terminal isolation RS485 communication module for a transformer area according to claim 1, characterized in that, The logic side power supply and signal circuit comprises a first decoupling capacitor (C10), a second decoupling capacitor (C11) and an isolated RS485 transceiver (U3), the first decoupling capacitor (C10) and the second decoupling capacitor (C11) are connected in parallel between the logic side power supply VCC3V3 and the logic side ground GND, the parallel node of the first decoupling capacitor (C10) and the second decoupling capacitor (C11) is connected to the VDD1 pin of the isolated RS485 transceiver (U3), and the GND1 pin of the isolated RS485 transceiver (U3) is connected to the logic side ground GND; The master sending signal UART4_TXD is connected to the TXD pin of the isolated RS485 transceiver (U3), the RXD pin of the isolated RS485 transceiver (U3) is connected to the master receiving signal UART4_RXD, and the direction control signal is connected to the DE pin and RE pin of the isolated RS485 transceiver (U3).

3. The intelligent fusion terminal isolation RS485 communication module for a transformer area according to claim 2, characterized in that, The field side power supply and bus driving circuit comprises a third decoupling capacitor (C12) and a fourth decoupling capacitor (C13), the third decoupling capacitor (C12) and the fourth decoupling capacitor (C13) are connected in parallel between the field side power supply VCC_485 and the field side ground GND1, the parallel node of the third decoupling capacitor (C12) and the fourth decoupling capacitor (C13) is connected to the VDD2 pin of the isolated RS485 transceiver (U3), and the GND2 pin of the isolated RS485 transceiver (U3) is connected to the field side ground GND1; The Y pin and the A pin of the isolated RS485 transceiver (U3) are connected in parallel to form a first differential line EA, and the Z pin and the B pin of the isolated RS485 transceiver (U3) are connected in parallel to form a second differential line EB.

4. The district intelligence fusion terminal isolated RS485 communication module according to claim 3, characterized in that, The port protection circuit comprises an EMI suppression unit, a surge clamping unit and an overcurrent protection unit; The EMI suppression unit comprises a first magnetic bead (FB5) and a second magnetic bead (FB6), the first magnetic bead (FB5) is connected in series to the first differential line EA, and the second magnetic bead (FB6) is connected in series to the second differential line EB; The surge clamping unit comprises a first TVS tube (TVS6), a second TVS tube (TVS7) and a third TVS tube (TVS8), the first TVS tube (TVS6), the second TVS tube (TVS7) and the third TVS tube (TVS8) perform surge clamping with the field side ground GND1 as the loop reference; The overcurrent protection unit comprises a first PTC self-resetting fuse (F3) and a second PTC self-resetting fuse (F4), the first PTC self-resetting fuse (F3) is connected in series on the first differential line EA close to the external terminal EA1 side, and the second PTC self-resetting fuse (F4) is connected in series on the second differential line EB close to the external terminal EB1 side.

5. The district intelligence fusion terminal isolated RS485 communication module according to claim 4, characterized in that, The terminal matching and biasing circuit comprises a terminal matching resistor (R11), a pull-up biasing resistor (R16) and a pull-down biasing resistor (R18); The terminal matching resistor (R11) is connected across the first differential line EA and the second differential line EB; The pull-up biasing resistor (R16) is connected between the field side power supply VCC_485 and the first differential line EA; The pull-down biasing resistor (R18) is connected between the second differential line EB and the field side ground GND1.

6. The intelligent fusion terminal isolation RS485 communication module for a transformer area according to claim 5, characterized in that, The signal path of the port protection circuit is: the bus pin of the isolation RS485 transceiver (U3) is connected to the first differential line EA and the second differential line EB, the first differential line EA and the second differential line EB respectively enter the surge clamping area through the first magnetic bead (FB5) and the second magnetic bead (FB6), and then are connected to the external terminal EA1 and the external terminal EB1 through the first PTC self-resetting fuse (F3) and the second PTC self-resetting fuse (F4) respectively.

7. The district intelligence fusion terminal isolated RS485 communication module according to claim 6, characterized in that, The capacitance of the first decoupling capacitor (C10) is 100nF, the capacitance of the second decoupling capacitor (C11) is 10µF, the capacitance of the third decoupling capacitor (C12) is 100nF, and the capacitance of the fourth decoupling capacitor (C13) is 10µF; The resistance of the terminal matching resistor (R11) is 120Ω, the resistance of the pull-up biasing resistor (R16) is 10kΩ, and the resistance of the pull-down biasing resistor (R18) is 10kΩ.

8. The intelligent fusion terminal isolation RS485 communication module for a transformer area according to claim 7, characterized in that, The isolation RS485 transceiver (U3) adopts ADM2484E; the first magnetic bead (FB5) and the second magnetic bead (FB6) adopt HB-1M2012-102 model; the first TVS tube (TVS6), the second TVS tube (TVS7) and the third TVS tube (TVS8) adopt SMBJ6.0CA model; and the first PTC self-resetting fuse (F3) and the second PTC self-resetting fuse (F4) adopt MZ11-10A300-600RM model.

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