An RS485 and CAN switchable communication interface for an electricity information acquisition terminal

Abstract

This utility model discloses an RS485 and CAN switchable communication interface for an electricity information acquisition terminal, comprising: a control processing unit, a dual-mode transceiver unit, an isolated power supply unit, and a bus protection circuit. The mode switching control input terminal of the dual-mode transceiver unit is electrically connected to the mode switching signal output terminal of the control processing unit, and the data port of the dual-mode transceiver unit is electrically connected to the data interaction port of the control processing unit. The isolated power supply output terminal of the isolated power supply unit is electrically connected to the isolated power supply input terminal of the dual-mode transceiver unit. The first terminal of the bus protection circuit is electrically connected to the bus pin of the dual-mode transceiver unit, and the second terminal of the bus protection circuit is connected to an external bus. This utility model solves the problems of hardware redundancy, incomplete isolation domain, and weak protection capability in traditional solutions, and has the advantages of high integration, strong anti-interference capability, and high reliability.

Description

Technical Field

[0001] This utility model belongs to the field of communication for electricity information collection terminals, and in particular, it is a switchable RS485 and CAN communication interface for electricity information collection terminals. Background Technology

[0002] To adapt to equipment from different manufacturers and diverse application scenarios, the communication interface of a terminal must possess high flexibility and compatibility. Among these, the RS485 bus, with its long transmission distance and simple networking, is widely used in industrial control and data acquisition; while the CAN bus, with its high reliability, strong anti-interference capability, and good real-time performance, occupies an important position in power automation and vehicle systems. Therefore, developing a communication interface capable of flexibly switching between RS485 and CAN protocols and operating reliably for extended periods in complex power grid environments is of significant research importance for improving the applicability and system stability of power consumption information acquisition terminals.

[0003] Currently, existing technical solutions for supporting both RS485 and CAN protocols typically employ a hardware redundancy design. These solutions mount two independent physical layer circuits in parallel on the circuit board: one RS485 transceiver chip (such as the MAX485 series) and one CAN transceiver chip (such as the TJA1050 series). Each circuit requires independent power filtering and bus protection components. To enable protocol switching on a single physical connector (such as a DB9 or terminal block), designers often add an additional set of analog switches (such as multiplexer chips) or relay arrays between the outputs of the two circuits and the connector. When protocol switching is required, the main control unit (MCU) sends control signals to the analog switches to select whether to connect the RS485 or CAN bus to the external network. Regarding EMC (electromagnetic compatibility) design, to prevent interference on the bus side from damaging the main control unit, the conventional approach is to use optocouplers or digital isolation chips to isolate the data (TX / RX) channels of the two transceivers separately.

[0004] However, the aforementioned traditional solutions have significant technical bottlenecks in terms of hardware topology, signal integrity, and electrical reliability. Specifically, these bottlenecks are mainly reflected in the degradation of signal integrity due to complex hardware switching topologies, and insufficient common-mode immunity due to incomplete isolation domain design. Utility Model Content

[0005] Purpose of the utility model: To provide an RS485 and CAN switchable communication interface for an electricity information collection terminal, so as to solve the above-mentioned problems existing in the prior art.

[0006] Technical solution: An RS485 and CAN switchable communication interface for an electricity consumption information collection terminal, comprising:

[0007] The control processing unit has a mode switching signal output terminal and a data interaction port;

[0008] The 2-in-1 transceiver unit features a mode switching control input, a data port, bus pins, and an isolated power input.

[0009] The mode switching control input terminal of the dual-in-one transceiver unit is electrically connected to the mode switching signal output terminal of the control processing unit, and the data port of the dual-in-one transceiver unit is electrically connected to the data interaction port of the control processing unit.

[0010] An isolated power supply unit has an isolated power supply output terminal, which is electrically connected to the isolated power supply input terminal of a two-in-one transceiver unit.

[0011] The bus protection circuit has its first terminal electrically connected to the bus pin of the dual-transceiver unit, and its second terminal connected to the external bus.

[0012] According to one aspect of this application, a signal isolation unit is also included, which is disposed between the control processing unit and the dual transceiver unit;

[0013] The mode switching signal output terminal and data interaction port of the control processing unit are electrically connected to the mode switching control input terminal and data port of the dual-in-one transceiver unit via a signal isolation unit.

[0014] According to one aspect of this application, the signal isolation unit includes:

[0015] A data isolation channel, whose input is electrically connected to the data interaction port of the control processing unit, and whose output is electrically connected to the data port of the dual-mode transceiver unit; and,

[0016] The control isolation channel has its input terminal electrically connected to the mode switching signal output terminal of the control processing unit, and its output terminal electrically connected to the mode switching control input terminal of the dual-transceiver unit.

[0017] According to one aspect of this application, the control processing unit is connected to a first ground;

[0018] The dual-function transceiver unit and bus protection circuit are connected to a second ground;

[0019] The isolated power supply unit provides power to the second ground that is isolated from the first ground;

[0020] The signal isolation unit is connected between the first ground and the second ground to achieve signal isolation between the control processing unit and the dual transceiver unit.

[0021] According to one aspect of this application, the dual-transceiver unit includes a multi-protocol transceiver chip;

[0022] The multi-protocol transceiver chip has a mode control pin, which constitutes the mode switching control input of the two-in-one transceiver unit.

[0023] According to one aspect of this application, the multi-protocol transceiver chip further includes at least one pair of common bus pins, which constitute the bus pins of the dual-transceiver unit;

[0024] The shared bus pins are multiplexed into RS485 bus interfaces or CAN bus interfaces within the multi-protocol transceiver chip, depending on the level signal of the mode control pin.

[0025] According to one aspect of this application, the data interaction port of the control processing unit includes a UART transmitter and a UART receiver;

[0026] The data port of the 2-in-1 transceiver unit includes data input pins and data output pins;

[0027] The data isolation channel of the signal isolation unit electrically connects the UART transmitter to the data input pin and the data output pin to the UART receiver.

[0028] According to one aspect of this application, the bus protection circuit includes: at least one overcurrent protection element;

[0029] Overcurrent protection components are connected in series on at least one line of the bus pins of the dual-transceiver unit.

[0030] According to one aspect of this application, the bus protection circuit further includes at least one transient voltage suppression diode.

[0031] According to one aspect of this application, at least one transient voltage suppression diode comprises:

[0032] The first transient voltage suppressor diode is connected across the two lines of the bus pin;

[0033] The second transient voltage suppressor diode is electrically connected between the first line of the bus pin and the second ground; and,

[0034] The third transient voltage suppressor diode is electrically connected between the second line of the bus pin and the second ground.

[0035] Beneficial effects: This utility model solves the problems of hardware redundancy, incomplete isolation domain and weak protection capability by using a complete electrical isolation topology and highly integrated transceiver chip. It has the advantages of high integration, strong anti-interference capability and high reliability. Attached Figure Description

[0036] Figure 1 This utility model provides a system structure block diagram of an RS485 and CAN switchable communication interface for an electricity information collection terminal.

[0037] Figure 2 A circuit diagram of an isolated power supply unit provided in an embodiment of this utility model.

[0038] Figure 3 A circuit diagram of the signal isolation unit provided in an embodiment of this utility model.

[0039] Figure 4 The circuit diagram of the two-in-one transceiver unit and bus protection circuit provided for the embodiments of this utility model. Detailed Implementation

[0040] The research revealed that the switching scheme using two independent transceivers in conjunction with external analog switches introduces additional signal paths. These analog switches themselves have on-resistance and parasitic capacitance, which can easily cause signal attenuation, reflection, and impedance mismatch at high-speed communication (e.g., 10Mbps), leading to decreased signal integrity and limiting communication distance and the number of nodes. Simultaneously, these additional discrete components (transceivers, switches) increase PCB layout area and hardware costs, reducing system integration. Furthermore, existing isolation designs suffer from incomplete isolation domains. Many schemes, while isolating TX / RX data signals, neglect the mode switching signal used to control the analog switches. The mode switching signal is often directly provided by the cold-side MCU, with its signal ground connected to the cold-side ground. When the hot-side bus experiences a high-energy common-mode surge, the surge current may form a creeping path through the control pins of the analog switches, coupling back to the cold-side MCU, causing MCU logic malfunction or even physical damage. This vulnerability caused by the lack of isolation of the control channel poses a significant hazard in complex power grid environments.

[0041] like Figure 1 As shown, an RS485 and CAN switchable communication interface for an electricity information acquisition terminal is proposed, including: a control processing unit, a signal isolation unit, an isolation power supply unit, a dual-transceiver unit, and a bus protection circuit. In terms of circuit connections: the control processing unit is electrically connected to the signal isolation unit to provide data signals and mode switching signals. The signal isolation unit is electrically connected to the dual-transceiver unit to transmit isolated data signals and mode switching signals. The isolation output terminal of the isolation power supply unit is electrically connected to the hot-side power input of the signal isolation unit and the power input terminal of the dual-transceiver unit, respectively. The bus-side pins of the dual-transceiver unit are electrically connected to the first terminal of the bus protection circuit. The second terminal of the bus protection circuit is connected to an external RS485 or CAN bus.

[0042] Functionally, the control processing unit is used to output mode switching signals and process communication data. In this embodiment, the control processing unit can be implemented by a microcontroller (MCU). An isolated power supply unit provides isolated power to the signal isolation unit and the dual-mode transceiver unit. For example, a 5V±0.5V isolated power supply can be provided, with an isolation voltage up to 3000V. This achieves electrical isolation between the control processing unit side (cold end) and the bus side (hot end) to meet the EMC (electromagnetic compatibility) anti-interference performance requirements of the power information acquisition terminal. A signal isolation unit is located between the control processing unit and the dual-mode transceiver unit; electrical isolation prevents surges or electrical faults on the bus side from damaging the cold-end control processing unit. The dual-mode transceiver unit receives mode switching signals from the signal isolation unit and selectively operates in RS485 mode or CAN mode according to the mode switching signal. A bus protection circuit provides electrostatic discharge (ESD) protection, overvoltage protection, and high-frequency interference filtering functions for the interface to resist electrostatic discharge, surges, and high-frequency interference from the external bus, ensuring the reliability of the interface in complex power grid environments.

[0043] In one exemplary embodiment, the interface circuitry is divided into two ground (GND) domains by an electrical isolation boundary: the first ground (cold end ground) is the common ground to which the control processing unit (i.e., MCU) is connected. The second ground (hot end ground or isolation ground) is 485G. The hot end of the dual-mode transceiver unit, the signal isolation unit, and the bus protection circuitry are all electrically connected to 485G.

[0044] According to one aspect of this application, the data interaction port of the control processing unit includes a UART transmitter and a UART receiver;

[0045] The data ports of the 2-in-1 transceiver unit include a data input pin (TX) and a data output pin (RX);

[0046] The data isolation channel of the signal isolation unit electrically connects the UART transmitter to the data input pin and the data output pin to the UART receiver.

[0047] like Figure 2 As shown, the isolated power supply unit is implemented by an isolated DC-DC module U2 (e.g., F0505S-1W). The input terminals (VIN, GND) of the isolated DC-DC module U2 are electrically connected to the power supply and first ground of the cold end; a capacitor C41 is connected in series between the power supply and first ground of the cold end; the output terminals (+VO, 0V) of the isolated DC-DC module U2 are electrically connected to the isolated power supply voltage VCC485 and the isolated ground; a capacitor C42 is connected in series between the power supply voltage VCC485 and the isolated ground. This provides electrically isolated power to all circuits on the hot end (including the hot end of the signal isolation unit and the dual-transceiver unit).

[0048] A signal isolation unit is disposed between the control processing unit and the dual-mode transceiver unit (D10), bridging the first ground and the second ground (485G). The signal isolation unit includes: a data isolation channel, the input of which is electrically connected to the data interaction port of the control processing unit, and the output of which is electrically connected to the data port of the dual-mode transceiver unit; and a control isolation channel, the input of which is electrically connected to the mode switching signal output of the control processing unit, and the output of which is electrically connected to the mode switching control input of the dual-mode transceiver unit.

[0049] For example, such as Figure 3 and Figure 4 As shown, the signal isolation unit is mainly composed of a signal isolation chip D11 (e.g., PA162U61). Pin 1 of the signal isolation chip D11 is connected to both capacitor C47 and the power supply, with the other end of capacitor C47 connected to the first ground. Pin 2 (cold-end data input) of the signal isolation chip D11 outputs the isolated data signal TXD1, which is electrically connected to the UART transmitter of the control processing unit. The mode switching signal output of the control processing unit (e.g., GPIO pin, SW 485 / CAN 1) is electrically connected to pin 4 (cold-end control input) of the signal isolation chip D11. Pin 7 (cold-end isolated data output) of the signal isolation chip D11 outputs the isolated data signal RXD1, which is electrically connected to the UART receiver of the control processing unit. Pin 8 of the signal isolation chip D11 is connected to the first ground. Pin 9 of the signal isolation chip D11 is connected to the second ground. Pin 13 (hot-end isolated control output) of the signal isolation chip D11 outputs the isolated mode switching signal CAN 5V. A 5V circuit is electrically connected to the mode switching control input of the dual-transceiver unit D10, i.e., pin 4 (RS485 / CAN) of the dual-transceiver unit D10; pin 14 of the signal isolation chip D11 outputs signal 485RTS1, which is electrically connected to pins 6 and 7 of the dual-transceiver unit D10; pin 15 (hot-end isolated data output) of the signal isolation chip D11 outputs the isolated data signal 485TXD1, which is electrically connected to pin 5 (data input) of the dual-transceiver unit D10; pin 16 of the signal isolation chip D11 is connected to both capacitor C48 and the power supply, with the other end of capacitor C48 connected to a second ground; pin 8 of the dual-transceiver unit D10 outputs data signal 485RXD1, which is electrically connected to the hot-end data input pin 10 of the signal isolation chip D11.

[0050] This embodiment constructs a complete electrical isolation domain by isolating the power supply unit and the signal isolation unit. Electrical isolation is achieved between the cold-end control processing unit and the hot-end bus transceiver circuit at three levels: power, data (TX / RX), and control (SW 485 / CAN 1). This effectively blocks common-mode interference and surges from the bus side, improving the reliability and anti-interference capability of the interface.

[0051] According to another aspect of this application, a dual-protocol transceiver unit includes a multi-protocol transceiver chip. The multi-protocol transceiver chip has a mode control pin, which constitutes a mode switching control input for the dual-protocol transceiver unit. For example, the multi-protocol transceiver chip is model SCCK28001B. The multi-protocol transceiver chip also includes at least one pair of common bus pins, which constitute the bus pins of the dual-protocol transceiver unit; these common bus pins are internally multiplexed as an RS485 bus interface or a CAN bus interface according to the level signal of the mode control pin.

[0052] Regarding power connections, power pins 15 and 16 of the dual-transceiver unit D10 are electrically connected to the isolated power supply VCC485 provided by the isolated power supply unit U2. Power pin 15 of the dual-transceiver unit D10 is also connected to one end of capacitor C46, ​​with the other end of capacitor C46 connected to the second ground. Power pin 16 of the dual-transceiver unit D10 is also connected to one end of capacitor C45, with the other end of capacitor C45 connected to the second ground. Pin 14 of the dual-transceiver unit D10 is connected to one end of resistor R46, with the other end of resistor R46 connected to the power supply. Pin 11 of the dual-transceiver unit D10 is connected to one end of resistor R48, with the other end of resistor R48 connected to the second ground. Pins 9 and 10 of the dual-transceiver unit D10 are simultaneously connected to the second ground. Pin 4 of the dual-transceiver unit D10 is the mode control pin, i.e., RS485 / CAN, which constitutes the mode switching control input of the dual-transceiver unit. The RS485 / CAN is electrically connected to the isolation control signal CAN5V from the signal isolation unit, and is used to receive mode selection commands from the control processing unit (e.g., high level selects CAN mode, low level selects RS485 mode). The dual-transceiver unit D10 has a pair of common bus pins, namely pin 13 (A / CANH) and pin 12 (B / CANL).

[0053] Optionally, the dual-mode transceiver unit D10 integrates a set of analog switches. The control terminals of these analog switches are electrically connected to pin 4 (RS485 / CAN) of the dual-mode transceiver unit D10. Based on the level signal received at pin 4 of the dual-mode transceiver unit D10, these analog switches selectively connect the shared bus pins A / CANH and B / CANL to either the integrated RS485 transceiver or the integrated CAN transceiver within the dual-mode transceiver unit D10, thereby achieving physical layer function multiplexing of the bus pins. Externally, the shared bus pins A / CANH and B / CANL, as output terminals of the dual-mode transceiver unit, are electrically connected to the bus protection circuit.

[0054] This embodiment uses the SCCK28001B chip (D10) topology to integrate the RS485 transceiver, CAN transceiver, and mode switching logic into one unit, reusing the same pair of bus pins. Compared to solutions requiring two independent transceivers and external switching circuitry, this embodiment offers high integration, reducing PCB (printed circuit board) area and lowering hardware costs.

[0055] In one possible implementation, a bus protection circuit is located between the common bus pin of the dual-transceiver unit D10 and the external bus connector P1. The bus protection circuit includes at least one overcurrent protection element; this overcurrent protection element is connected in series on at least one line of the bus pins of the dual-transceiver unit. Preferably, the overcurrent protection element is a positive temperature coefficient thermistor R47 (PTC). In terms of circuit connection, the PTC thermistor R47 is connected in series between the A / H line and the external bus RS485A / CANH line.

[0056] Furthermore, the bus protection circuit also includes three transient voltage suppressor diodes (TVS): a first TVS diode F16, a second TVS diode F15, and a third TVS diode F17. These TVS diodes can be selected from the SMBJ series (e.g., SMBJ6.5A). In the TVS connection topology: the first TVS diode F16 (for differential mode protection) is connected across the A / H line and the B / L line. The second TVS diode F15 (for common mode protection) is electrically connected between the A / H line and the second ground 485G. The third TVS diode F17 (for common mode protection) is electrically connected between the B / L line and the second ground 485G.

[0057] The bus protection circuit in this embodiment combines a positive temperature coefficient thermistor with a transient voltage suppressor diode to construct a multi-level protection topology that simultaneously provides overcurrent protection, differential mode overvoltage protection, and common mode overvoltage protection. This effectively resists electrostatic discharge (ESD), surges, and overcurrent impacts from the external bus, ensuring the reliability of the 2-in-1 transceiver unit in complex power grid environments.

[0058] It should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this utility model will not describe the various possible combinations separately.

Claims

1. A switchable RS485 and CAN communication interface for an electricity information collection terminal, characterized in that, include: The control processing unit has a mode switching signal output terminal and a data interaction port; The 2-in-1 transceiver unit features a mode switching control input, a data port, bus pins, and an isolated power input. The mode switching control input terminal of the dual-in-one transceiver unit is electrically connected to the mode switching signal output terminal of the control processing unit, and the data port of the dual-in-one transceiver unit is electrically connected to the data interaction port of the control processing unit. An isolated power supply unit has an isolated power supply output terminal, which is electrically connected to the isolated power supply input terminal of a two-in-one transceiver unit. The bus protection circuit has its first terminal electrically connected to the bus pin of the dual-transceiver unit, and its second terminal connected to the external bus.

2. The RS485 and CAN switchable communication interface according to claim 1, characterized in that, It also includes a signal isolation unit, which is disposed between the control processing unit and the dual transceiver unit; The mode switching signal output terminal and data interaction port of the control processing unit are electrically connected to the mode switching control input terminal and data port of the dual-in-one transceiver unit via a signal isolation unit.

3. The RS485 and CAN switchable communication interface according to claim 2, characterized in that, The signal isolation unit includes: A data isolation channel, whose input is electrically connected to the data interaction port of the control processing unit, and whose output is electrically connected to the data port of the dual-mode transceiver unit; and, The control isolation channel has its input terminal electrically connected to the mode switching signal output terminal of the control processing unit, and its output terminal electrically connected to the mode switching control input terminal of the dual-transceiver unit.

4. The RS485 and CAN switchable communication interface according to claim 2, characterized in that: The control processing unit is connected to the first ground; The dual-function transceiver unit and bus protection circuit are connected to a second ground; The isolated power supply unit provides power to the second ground that is isolated from the first ground; The signal isolation unit is connected between the first ground and the second ground to achieve signal isolation between the control processing unit and the dual transceiver unit.

5. The RS485 and CAN switchable communication interface according to claim 1, characterized in that, The 2-in-1 transceiver unit includes a multi-protocol transceiver chip; The multi-protocol transceiver chip has a mode control pin, which constitutes the mode switching control input of the two-in-one transceiver unit.

6. The RS485 and CAN switchable communication interface according to claim 5, characterized in that, The multi-protocol transceiver chip also includes at least one pair of shared bus pins, which constitute the bus pins of the dual-transceiver unit; The shared bus pins are multiplexed into RS485 bus interfaces or CAN bus interfaces within the multi-protocol transceiver chip, depending on the level signal of the mode control pin.

7. The RS485 and CAN switchable communication interface according to claim 3, characterized in that, The data interaction ports of the control processing unit include a UART transmitter and a UART receiver; The data port of the 2-in-1 transceiver unit includes data input pins and data output pins; The data isolation channel of the signal isolation unit electrically connects the UART transmitter to the data input pin and the data output pin to the UART receiver.

8. The RS485 and CAN switchable communication interface according to claim 4, characterized in that, The bus protection circuit includes at least one overcurrent protection element; Overcurrent protection components are connected in series on at least one line of the bus pins of the dual-transceiver unit.

9. The RS485 and CAN switchable communication interface according to claim 8, characterized in that, The bus protection circuit also includes at least one transient voltage suppression diode.

10. The RS485 and CAN switchable communication interface according to claim 9, characterized in that, At least one transient voltage suppressor diode includes: The first transient voltage suppressor diode is connected across the two lines of the bus pin; The second transient voltage suppressor diode is electrically connected between the first line of the bus pin and the second ground; and, The third transient voltage suppressor diode is electrically connected between the second line of the bus pin and the second ground.

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