Switchable communication interface module of transformer area intelligent fusion terminal

Abstract

The utility model discloses a switchable communication interface module of a transformer area intelligent fusion terminal. The switchable communication interface module comprises a power supply decoupling network; a level generation network; the multi-protocol transceiver chip is provided with a data input pin, a data output pin, an enabling control pin, a direction control pin, a mode selection pin and a line interface pin; a bus bias network; the graded surge protection network comprises a first transient suppression diode and a third transient suppression diode which are respectively used for carrying out ground common mode clamping on two signal lines, and a second transient suppression diode is used for realizing inter-line differential mode clamping; and the self-recovery current-limiting protection device comprises a first self-recovery fuse and a second self-recovery fuse, and is connected to an external terminal after being connected in series with the graded surge protection network. The switchable communication interface module of the transformer area intelligent fusion terminal has the characteristics of switchable port protocol, single power supply, graded surge protection, self-recovery current-limiting protection and stable and reliable communication.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of switchable communication interface module of intelligent fusion terminal in transformer area. BACKGROUND

[0002] Intelligent fusion terminal in transformer area usually needs to communicate with electric energy meter, collector, reactive compensation controller, sensor or operation and maintenance debugging equipment.The common communication interface in field is RS485 (used for long line multipoint bus communication) and RS232 (used for near end point-to-point debugging or access).The existing communication interface scheme generally has the following technical problems:

[0003] First, port incompatibility problem.RS485 and RS232 need to be configured with independent hardware interface, which leads to increased number of interfaces on terminal equipment, increased hardware cost, increased PCB area, which is particularly disadvantageous for transformer terminal equipment with limited space.

[0004] Second, power supply and level system complexity problem.RS232 protocol requires positive and negative swing level support.If an independent boost or inverting power module is configured separately, it not only increases the cost of components, but also reduces the overall reliability of the system, increases the risk of electromagnetic interference between power domain and communication domain.

[0005] Third, insufficient anti-interference capability problem.The electromagnetic environment in transformer area is complex, and there are lightning-induced surge, electric fast transient impulse group, power supply ground bounce, long line induction and other interference sources.Ordinary transceiver and simple ESD protection device are easy to fail in strong interference environment, leading to unstable communication or equipment damage.

[0006] Fourth, bus conflict risk problem.In RS485 half-duplex communication mode, if the direction control is improper, it is easy to cause multiple node drive contention, increase error code or transceiver heating damage, affecting the communication reliability in transformer area with complex multi-node wiring scene.

[0007] Therefore, an integrated communication interface module capable of switching between RS485 and RS232 protocols on the same physical port is needed, which has hierarchical surge protection, self-recovery current limiting protection, bus biasing and direction control function, to meet the reliable communication needs of intelligent fusion terminal in transformer area in complex electromagnetic environment. UTILITY MODEL CONTENT

[0008] The utility model aims to provide a kind of switchable communication interface module of intelligent fusion terminal in transformer area.This switchable communication interface module of intelligent fusion terminal in transformer area has the characteristics of port protocol switchable, single power supply, hierarchical surge protection, self-recovery current limiting protection and stable and reliable communication.

[0009] The above technical purpose of the utility model is realized by the following technical scheme:

[0010] A kind of district intelligence fusion terminal switchable communication interface module, comprising: power decoupling network, including first capacitor (C2) and second capacitor (C3) parallel connection between communication power (VCC_485) and communication protection ground (GND1);Level generation network, including inductance (L2) is connected between the communication power (VCC_485) and the switch node (SW) of multi-protocol transceiver chip (U2), third capacitor (C7) is connected between the switch node (SW) and charge pump node (CAP), fourth capacitor (C8) and fifth capacitor (C9) are decoupled to the positive supply rail (VDD) and negative supply rail (VEE) generated inside the multi-protocol transceiver chip (U2) respectively;Multi-protocol transceiver chip (U2), with data input pin (DI), data output pin (RO), enable control pin (SHDN), direction control pin (DE485 / RE485), mode selection pin (485 / 232) and line interface pin (A / DO, B / RI);Bus bias network, including first bias resistor (R3) and second bias resistor (R4), is connected between the line interface pin (A / DO, B / RI) and bias node (FB1, FB2) respectively;Hierarchical surge protection network, including first transient voltage suppressor (TVS1) and third transient voltage suppressor (TVS3) are respectively clamped to common mode to ground for two signal lines, second transient voltage suppressor (TVS2) realizes differential mode clamping between lines;Self-restoring current limiting protection device, including first self-restoring fuse (F1) and second self-restoring fuse (F2), are connected to external terminals (GA1, GB1) after the hierarchical surge protection network.

[0011] The utility model further sets up: the first capacitor (C2) is 100nF ceramic capacitor, the second capacitor (C3) is 10 μF capacitor, and the parallel connection forms wide frequency decoupling structure, and respectively provides high frequency bypass capacity and low frequency energy storage support.

[0012] The utility model further sets up: the inductance of inductance (L2) is 10 μH, the capacitor value of third capacitor (C7) is 220nF, and the internal level conversion circuit of multi-protocol transceiver chip (U2) is cooperated, and the positive and negative swing drive level required for generating RS232 protocol under single communication power input condition.

[0013] The utility model further sets up: the clamping voltage of first transient voltage suppressor (TVS1) and third transient voltage suppressor (TVS3) is 15V, and the clamping voltage of second transient voltage suppressor (TVS2) is 30V, and hierarchical protection configuration of low threshold common mode clamping and high threshold differential mode clamping is formed.

[0014] The utility model further sets up: first self -restoring fuse (F1) and second self -restoring fuse (F2) are PTC type self -restoring fuse, and the resistance is limited when continuing overcurrent, and the on -state is automatically restored after removing the fault.

[0015] The utility model further sets up: the resistance of first bias resistance (R3) and second bias resistance (R4) is 10kΩ, and the certain logic level state of the multi-protocol transceiver chip (U2) receiver input is kept when the external circuit is open or suspended.

[0016] The utility model further sets up: still include pull-up resistance (R150), one end of pull-up resistance (R150) is connected control node, the other end is connected communication power (VCC_485), provides the power-on default state for control signal, avoids the control signal suspension during master control reset and causes the misoperation of transceiver.

[0017] The utility model further sets up: the backflow current of hierarchical surge protection network and power decoupling network is concentrated in communication protection ground (GND1), and the communication protection ground (GND1) forms the partition isolation structure with master control ground, and the surge energy is closed in situ in the communication interface area.

[0018] The utility model further sets up: the multi-protocol transceiver chip (U2) realizes the switching of RS485 differential bus mode and RS232 single -end communication mode through mode selection pin (485 / 232), realizes the on -demand power -on control of port through enable control pin (SHDN).

[0019] The utility model further sets up: the multi-protocol transceiver chip (U2) is under RS485 half duplex mode, and is sent when drive enable is effective and receiving enable is invalid through the coordination control of direction control pin (DE485 / RE485), and drive enable is invalid and receiving enable is effective when receiving, avoids bus drive contention.

[0020] Summarized above, the utility model has following beneficial effect:

[0021] 1. port protocol switchable multiplexing: through the collaborative configuration of mode selection pin (485 / 232) of multi-protocol transceiver chip (U2), enable control pin (SHDN) and direction control pin (DE485 / RE485), realize the software controllable switching of the same physical port between RS485 differential bus mode and RS232 single -end communication mode. Compared with the traditional double transceiver scheme, can reduce a transceiver chip and its supporting decoupling, protection device. Operation and maintenance personnel can switch between meter reading mode and debugging mode without replacing cable or adapter, reduce field maintenance time and operation error risk.

[0022] 2. Single power supply integrated power supply: the level generating network composed of inductance (L2) and third capacitance (C7) generates the positive and negative swing driving level required by RS232 protocol under the condition of single communication power supply (VCC_485) input, without external configuration of independent negative voltage or boost power supply module. Compared with the scheme of using independent DC-DC power supply chip, this structure reduces the number of devices, simplifies the power supply layout, and reduces the electromagnetic interference risk of the power supply domain to the communication domain.

[0023] 3. Graded surge protection capability: the first transient voltage suppression diode (TVS1) and the third transient voltage suppression diode (TVS3) realize common-mode clamping to ground with a 15V clamping voltage, and the second transient voltage suppression diode (TVS2) realizes differential-mode clamping between lines with a 30V clamping voltage, forming a graded protection configuration of low-threshold common-mode clamping and high-threshold differential-mode clamping. This configuration not only ensures that normal communication signals are not disturbed, but also effectively clamps surge energy exceeding the normal range. For lightning-induced surges, the TVS device has a nanosecond-level response speed, which can quickly limit the port voltage within a safe range.

[0024] 4. Self-restoring current limiting protection: the first self-restoring fuse (F1) and the second self-restoring fuse (F2) are PTC type self-restoring fuses connected in series after the TVS device. For continuous overcurrent faults such as misconnection of 220V power frequency power supply, the PTC rises to a high resistance state within hundreds of milliseconds, limiting the current flowing through, protecting the transceiver and TVS from thermal damage. After the fault is removed, the PTC automatically restores conduction without the need for manual replacement, suitable for the protection needs of unattended substation scenarios. This combination of fast clamping and self-restoring current limiting solves the problems of easy thermal breakdown of single TVS and non-recovery of single fuse.

[0025] 5. Improved communication stability: the bus bias network composed of the first bias resistor (R3) and the second bias resistor (R4) maintains a certain logic level when the external line is open or suspended, avoiding random flipping of the receiver due to input suspension, and reducing the suspended state error rate. The pull-up resistor (R150) ensures that the control signal is in a certain state during master reset, avoiding accidental driving of the bus by the transceiver during power-on, and reducing the bus conflict probability in RS485 half-duplex scenarios. The cooperation of the direction control pin (DE485 / RE485) and the enable control pin (SHDN) makes the transceiver drive the bus only when needed, reducing the driving contention risk in multi-node scenarios.

[0026] 6. Protective Ground Zone Isolation: The return current of the hierarchical surge protection network and power decoupling network are concentrated in the communication protective ground (GND1), forming a zone isolation structure with the main control ground and analog sampling ground. Surge energy is closed locally in the communication interface area, reducing the voltage drop interference caused by surge current crossing the main control ground and analog sampling ground, and improving the overall reliability and metering sampling stability of the intelligent fusion terminal in the distribution area.

[0027] 7. Wideband Power Supply Decoupling: The first capacitor (C2) is a 100nF ceramic capacitor providing high-frequency bypass capability, and the second capacitor (C3) is a 10μF capacitor providing low-frequency energy storage and transient response support. Both are connected in parallel near the transceiver power supply pins, effectively suppressing power ripple generated by transceiver switching operations and reducing the propagation of communication noise into the system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall circuit structure of this utility model. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the switchable communication interface module of the intelligent converged terminal for distribution areas disclosed in this utility model can be divided into five functional areas from the perspective of signal flow: power domain, logic interface domain, core transceiver domain, bias network domain, and protection output domain.

[0031] The power supply domain is located on the left side of the module. The first capacitor (C2) is a 100nF ceramic capacitor, and the second capacitor (C3) is a 10μF capacitor. Both are connected in parallel between the communication power supply (VCC_485) and the communication protective ground (GND1). The 100nF ceramic capacitor provides excellent high-frequency bypass capability, suppressing MHz-level high-frequency noise; the 10μF capacitor provides low-frequency energy storage and transient response support, handling the transient current requirements during transceiver switching. Their parallel connection forms a wideband decoupling structure, effectively suppressing power ripple generated by transceiver switching operations.

[0032] The level generating network comprises an inductor (L2), a third capacitor (C7), a fourth capacitor (C8) and a fifth capacitor (C9). The inductor (L2) is selected as a 10 μH inductor, which is connected in series between the communication power supply (VCC_485) and a switch node (SW) of the multi-protocol transceiver chip (U2), and provides energy storage and current smoothing functions. The third capacitor (C7) is selected as a 220 nF capacitor, which is connected between the switch node (SW) and a charge pump node (CAP), and is used for energy transmission and ripple suppression of the switch level conversion circuit. The fourth capacitor (C8) and the fifth capacitor (C9) are both selected as 1 μF capacitors, which are respectively decoupled to a positive power rail (VDD) and a negative power rail (VEE) generated inside the multi-protocol transceiver chip (U2), and are connected back to a communication protection ground (GND1), so as to provide transient current supply capability and ensure stable level swing during RS232 driving. The level generating network can internally generate the positive and negative swing driving levels required by the RS232 protocol under the condition of single 5V or 12V communication power supply input, without the need of externally configuring an independent negative voltage or boost power supply module.

[0033] The core transceiver domain is centered on the multi-protocol transceiver chip (U2). The multi-protocol transceiver chip (U2) can be selected as an LTC2873 or a similar multi-protocol transceiver chip, and has the following function pins: a data input pin (DI) connected to a UART6_TXD signal line of an external host MCU, for receiving serial data sent by the host; a data output pin (RO) connected to a UART6_RXD signal line of the host MCU, for outputting received serial data to the host; an enable control pin (SHDN) connected to an enable control signal of the host, when the SHDN is at a low level, the chip enters an off state, reduces static power consumption and makes the line output high resistance, when the SHDN is at a high level, the chip normally works; a direction control pin (DE485 / RE485) connected to a direction control signal of the host, for switching the receiving and transmitting directions in the RS485 half-duplex mode; a mode selection pin (485 / 232) connected to a mode selection signal of the host, for selecting the RS485 differential bus mode or the RS232 single-end communication mode; and line interface pins (A / DO, B / RI) connected to a bus bias network, as line interfaces for external communication.

[0034] The logic interface domain is located in the left part of the module. The main control MCU sends serial data to the data input pin (DI) of the multi-protocol transceiver chip (U2) through the UART6_TXD signal line. The multi-protocol transceiver chip (U2) converts TTL / CMOS level to corresponding line level output according to the current working mode. When receiving, the external signal enters the line interface pin (A / DO, B / RI) of the multi-protocol transceiver chip (U2) through the protection network, and the chip outputs TTL / CMOS level signal from the data output pin (RO) to the main control UART6_RXD signal line after completing the level conversion. The pull-up resistor (R150) is selected as a 10kΩ resistor, one end of which is connected to the control node, and the other end is connected to the communication power supply (VCC_485), which provides the power-on default state for the control signal, avoiding the control signal suspended during the main control reset, causing the transceiver to malfunction or accidentally drive the bus.

[0035] The bias network domain is composed of a first bias resistor (R3) and a second bias resistor (R4). Both of them are selected as 10kΩ resistors, respectively connected between the line interface pin (A / DO, B / RI) and the bias node (FB1, FB2). The first bias resistor (R3) is pulled up to the communication power supply (VCC_485), and the second bias resistor (R4) is pulled down to the communication protection ground (GND1), forming a bus idle state bias structure. When the external line is open or suspended, the bias network maintains the determined logic level state of the receiver input of the multi-protocol transceiver chip (U2), reducing the false judgment and error code caused by random noise triggering.

[0036] The protection output domain is located in the right part of the module. The hierarchical surge protection network includes three transient voltage suppression diodes: the first transient voltage suppression diode (TVS1) and the third transient voltage suppression diode (TVS3) are both selected as SMBJ15CA type bidirectional TVS devices, with a clamping voltage of 15V, respectively connected between the two signal lines and the communication protection ground (GND1), realizing common mode clamping to ground; the second transient voltage suppression diode (TVS2) is selected as SMBJ30CA type bidirectional TVS device, with a clamping voltage of 30V, connected between the two signal lines, realizing differential mode clamping between lines. This configuration forms a hierarchical protection strategy of low threshold common mode clamping and high threshold differential mode clamping, which not only considers the normal swing range and common mode suppression requirement of RS485 differential signal, ensuring normal communication without interference, but also effectively clamps the surge energy exceeding the normal range.

[0037] The self-recovery current limiting protection device includes a first self-recovery fuse (F1) and a second self-recovery fuse (F2), both of which are selected from MZ11-10A300-600RM type PTC self-recovery fuses. Both are connected in series after the hierarchical surge protection network and before the external terminals (GA1, GB1). When a continuous overcurrent fault occurs, the PTC device rises to a high resistance state within hundreds of milliseconds, limiting the current flowing through, protecting the upstream transceiver and TVS device from continuous power consumption damage. After the fault is removed, the PTC device temperature drops, automatically restoring the on-state, without the need for manual replacement. The external terminals (GA1, GB1) are used to connect external communication lines, and can use standardized plug-in terminal design, facilitating on-site quick connection and replacement.

[0038] In the RS485 working mode, the master MCU enables the port through the enable control pin (SHDN), and selects the RS485 mode through the mode selection pin (485 / 232). The line interface pins (A / DO, B / RI) of the multi-protocol transceiver chip (U2) are used as RS485 differential line outputs or inputs. The master controls the half-duplex direction management through the direction control pin (DE485 / RE485): when sending data, enable the drive enable (DE485 is valid), and close the receive enable (RE485 is invalid); when receiving data, close the drive enable (DE485 is invalid), and open the receive enable (RE485 is valid). This control ensures that only one of sending or receiving is in the same moment, avoiding bus drive contention. After the differential signal is idle biased through the first biasing resistor (R3) and the second biasing resistor (R4), it enters the hierarchical surge protection network, and is output to the external terminals (GA1, GB1) after TVS clamping and PTC current limiting protection.

[0039] In the RS232 working mode, the master MCU switches to the RS232 mode through the mode selection pin (485 / 232). The multi-protocol transceiver chip (U2) internally generates positive and negative swing drive levels adapted to the RS232 protocol with the support of the inductor (L2) and the third capacitor (C7). The line interface pins (A / DO, B / RI) are multiplexed as RS232 send or receive function pins, and are output to the external terminals (GA1, GB1) after passing through the same set of hierarchical surge protection network and self-recovery current limiting protection device, realizing protocol multiplexing of the same physical port.

[0040] Regarding electromagnetic compatibility layout, the inductor (L2) is arranged far away from high-speed digital signal lines and analog sampling circuits, or a shielded inductor package is used to reduce the induced interference of the alternating magnetic field generated during operation on adjacent signal lines. The first capacitor (C2) and the second capacitor (C3) are arranged as close to the power supply pin of the multi-protocol transceiver chip (U2) as possible, so as to reduce the power supply loop area and reduce the high-frequency impedance. The fourth capacitor (C8) and the fifth capacitor (C9) are arranged close to the positive power supply rail (VDD) and the negative power supply rail (VEE) pin respectively, so as to shorten the decoupling loop length. The TVS clamping current of the hierarchical surge protection network should be returned to the communication protection ground (GND1) as soon as possible to avoid passing through the main control ground or the analog sampling area. The communication protection ground (GND1) and the main control ground are preferably connected through a single point or a low-impedance connection to prevent surge current from generating voltage drop interference on the ground plane. The A and B lines of the RS485 differential signal should be parallelly wired, equally matched, and the wiring spacing is 3-5 times the line width, and the differential impedance is controlled within the range of 100-120Ω.

[0041] In order to verify the above technical solutions, the technical effects of the intelligent fusion terminal communication interface module in the transformer area are tested.

[0042] 1. The verification method adopts comparative test, and the traditional double-transceiver independent interface scheme is taken as the control group, and the module of the utility model is taken as the experimental group. The performance index is measured under the same test conditions. The surge test is based on the IEC 61000-4-5 standard, the ESD test is based on the IEC 61000-4-2 standard, and the communication error code test adopts the continuous 72-hour long-time operation mode.

[0043] 2. Technical effect comparison table

[0044]

[0045] 3. Verification conclusion

[0046] Through comparative test verification, the communication interface module of the utility model is significantly better than the traditional scheme. The port protocol multiplexing architecture effectively reduces hardware redundancy; the hierarchical surge protection and self-recovery current limiting combination improves the anti-interference capability to the level of 4kV / 2kA, while realizing fault self-recovery; the bus bias network reduces the suspended error code rate by more than 90%; and the single power supply integrated power supply simplifies the system power supply system. The comprehensive verification results show that the utility model meets the reliable communication requirements of the intelligent fusion terminal in the transformer area in a complex electromagnetic environment.

Claims

1. A transformer area intelligent fusion terminal switchable communication interface module, characterized in that, Comprise: a power decoupling network comprising a first capacitor (C2) and a second capacitor (C3) connected in parallel between a communication power supply (VCC_485) and a communication protective ground (GND1); a level generating network comprising an inductor (L2) connected in series between the communication power supply (VCC_485) and a switching node (SW) of a multi-protocol transceiver chip (U2), a third capacitor (C7) connected between the switching node (SW) and a charge pump node (CAP), and a fourth capacitor (C8) and a fifth capacitor (C9) respectively decoupling a positive power rail (VDD) and a negative power rail (VEE) generated internally by the multi-protocol transceiver chip (U2); the multi-protocol transceiver chip (U2) having a data input pin (DI), a data output pin (RO), an enable control pin (SHDN), a direction control pin (DE485 / RE485), a mode selection pin (485 / 232), and line interface pins (A / DO, B / RI); a bus biasing network comprising a first biasing resistor (R3) and a second biasing resistor (R4) respectively connected between the line interface pins (A / DO, B / RI) and biasing nodes (FB1, FB2); a hierarchical surge protection network comprising a first transient voltage suppressor (TVS1) and a third transient voltage suppressor (TVS3) respectively clamping a common mode to ground for two signal lines, and a second transient voltage suppressor (TVS2) clamping a differential mode between lines; a self-restoring current limiting protection device comprising a first self-restoring fuse (F1) and a second self-restoring fuse (F2) connected in series after the hierarchical surge protection network and connected to external terminals (GA1, GB1).

2. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The first capacitor (C2) is a 100nF ceramic capacitor, and the second capacitor (C3) is a 10μF capacitor, both of which are connected in parallel to form a wide-band decoupling structure, providing high-frequency bypass capability and low-frequency energy storage support, respectively.

3. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The inductance value of the inductor (L2) is 10μH, and the capacitance value of the third capacitor (C7) is 220nF, cooperating with the internal level conversion circuit of the multi-protocol transceiver chip (U2) to generate the positive and negative swing driving levels required by the RS232 protocol under the condition of a single communication power supply input.

4. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The clamping voltage of the first transient voltage suppressor (TVS1) and the third transient voltage suppressor (TVS3) is 15V, and the clamping voltage of the second transient voltage suppressor (TVS2) is 30V, forming a hierarchical protection configuration of low-threshold common-mode clamping and high-threshold differential-mode clamping.

5. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The first self-restoring fuse (F1) and the second self-restoring fuse (F2) are PTC type self-restoring fuses that limit current by increasing resistance when there is a continuous overcurrent, and automatically restore the conduction state after the fault is removed.

6. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The resistance values of the first biasing resistor (R3) and the second biasing resistor (R4) are both 10kΩ, maintaining the determined logic level state of the receiver input of the multi-protocol transceiver chip (U2) when the external line is open or suspended.

7. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, Pull-up resistor (R150) is also included, one end of which is connected to the control node, and the other end is connected to the communication power supply (VCC_485), providing a power-on default state for the control signal, avoiding the control signal suspended during the master reset, leading to the misoperation of the transceiver.

8. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The return current of the hierarchical surge protection network and the power decoupling network is concentrated in the communication protection ground (GND1), which forms a partitioned isolation structure with the master ground, and the surge energy is closed in place in the communication interface area.

9. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, The multi-protocol transceiver chip (U2) realizes the switching between RS485 differential bus mode and RS232 single-ended communication mode through the mode selection pin (485 / 232), and realizes the on-demand power-on control of the port through the enable control pin (SHDN).

10. The transformer area intelligent fusion terminal switchable communication interface module according to claim 1, characterized in that, In the RS485 half-duplex mode, the multi-protocol transceiver chip (U2) is controlled through the direction control pin (DE485 / RE485), and when sending, the drive enable is effective and the receive enable is invalid; when receiving, the drive enable is invalid and the receive enable is effective, avoiding bus drive contention.

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