Electric energy meter communication module

Abstract

The utility model discloses an electric energy meter communication module, comprising a control side circuit having a power supply end and a reference ground end; the isolation side circuit is provided with a power supply end and a reference ground end and is used for connecting a bus; a first optocoupler; a second optocoupler; a third optocoupler; a transceiver; a first transistor; the second transistor is arranged on the isolation side circuit, the base electrode of the second transistor is connected with the output end of the second optocoupler, and the collector electrode of the second transistor is connected with the sending input end of the transceiver; the bidirectional transient voltage suppressor is connected to the differential signal input / output end of the transceiver; and the self-recovery fuse is connected in series between the differential signal input / output end of the transceiver and the bus. The electric energy meter communication module has the following beneficial effects that the electric energy meter communication module has the characteristics of high anti-interference capability, high reliability, high safety and convenience in maintenance.

Description

Technical Field

[0001] The utility model relates to an electric energy meter communication module. Background Art

[0002] RS-485 is a widely used communication interface standard in industrial settings. Its differential transmission method offers strong immunity to common-mode interference and a long transmission distance. In the field of electric energy meters, the RS-485 interface is often used to connect multiple devices to form a network system. However, in practical applications, electric energy meter communication presents a number of problems, as follows:

[0003] 1. The industrial field environment is complex and there are a large number of electromagnetic interference sources, such as transient interference and common-mode noise generated by motor start-up and shutdown, high-voltage switch switching, etc., which can easily lead to communication errors or communication interruptions.

[0004] 2. There may be ground potential differences between field devices. If the controller is directly connected to the RS-485 bus, the ground potential difference may be transmitted to the controller through the bus, endangering system safety.

[0005] 3. In half-duplex communication, the switching between sending and receiving directions requires precise control. Improper control timing can easily cause bus contention and data conflicts.

[0006] 4. High-energy pulses such as electrostatic discharge, lightning induction, and power surges in the field environment may be transmitted to the inside of the device through the communication lines, damaging the transceiver chip and subsequent circuits.

[0007] 5. In multi-node networks, the determination of the bus idle state often becomes unstable due to line noise, leading to false triggering and incorrect judgment.

[0008] Existing technologies typically use simple RS-485 transceivers to directly connect to controllers, or optocouplers for signal isolation without signal shaping. These solutions suffer from poor reliability in environments with high noise and large ground potential differences, and are susceptible to interference and damage. Therefore, a highly reliable energy meter communication module that can address these issues is urgently needed. Utility Model Content

[0009] The purpose of the utility model is to provide an electric energy meter communication module, which has the characteristics of high anti-interference ability, high reliability, high safety and easy maintenance.

[0010] The above technical objectives of the present invention are achieved through the following technical solutions:

[0011] An electric energy meter communication module comprises: a control side circuit having a power supply terminal (VCM) and a reference ground terminal (GND) for connecting to a controller; a 485 isolation side circuit having a power supply terminal (V485) and a reference ground terminal (G485) for connecting to an RS-485 bus; a first optical coupler (U17) for isolating a receiving signal between the control side circuit and the 485 isolation side circuit; a second optical coupler (U18) for isolating a transmitting signal between the control side circuit and the 485 isolation side circuit; a third optical coupler (U19) for isolating a direction control signal between the control side circuit and the 485 isolation side circuit; an RS-485 transceiver (U20) provided on the 485 isolation side circuit and having a differential signal input / output terminal (A, B), a receiving output terminal (RO), a transmitting input terminal (DI), a transmitting enable terminal ( DE) and a receiving enable terminal (RE_); a first transistor (Q11), arranged in the control side circuit, with its base connected to the output terminal of the first optocoupler (U17), and its collector connected to the power supply terminal (VCM) of the control side circuit through a pull-up resistor (R220); a second transistor (Q12), arranged in the 485 isolation side circuit, with its base connected to the output terminal of the second optocoupler (U18), and its collector connected to the transmitting input terminal (DI) of the RS-485 transceiver (U20); a bidirectional transient voltage suppressor (TVS1), connected to the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20); and a resettable fuse (PTC1), connected in series between the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20) and the RS-485 bus.

[0012] The utility model is further configured such that the output end of the third optical coupler (U19) is simultaneously connected to the transmit enable end (DE) and the receive enable end (RE_) of the RS-485 transceiver (U20), thereby realizing synchronous control of the transmit and receive states through a single control signal.

[0013] The utility model is further configured to include: a first pull-up resistor (R232) and a first pull-down resistor (R233) arranged on the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20), for providing fail-safe bias.

[0014] The utility model is further configured as follows: the resistance of the first pull-up resistor (R232) and the first pull-down resistor (R233) is 20kΩ.

[0015] The utility model is further configured as follows: the collector of the first transistor (Q11) is connected to the receiving data line (485RXD1) of the control side circuit, the base of the second transistor (Q12) is connected to the output end of the second optical coupler (U18) via a base current limiting resistor (R227), and the base of the second transistor (Q12) is also connected to a base feedback resistor (R228).

[0016] The utility model is further configured to include: an RC shaping network, wherein the RC shaping network includes a first resistor (R229) connected in series with the input end of the first optocoupler (U17), and a first capacitor (C221) and a second resistor (R222) connected in parallel with the base of the first transistor (Q11); and also includes a second capacitor (C226) connected in parallel with the collector of the second transistor (Q12).

[0017] The utility model is further configured to include a decoupling capacitor (C83) arranged between the power supply terminal (V485) and the reference ground terminal (G485) of the RS-485 transceiver (U20).

[0018] The utility model is further configured as follows: the LED side of the first optocoupler (U17) is connected to the receiving output end (RO) of the RS-485 transceiver (U20), the LED side of the second optocoupler (U18) is connected to the sending data line (485TXD1) of the control side circuit, and the LED side of the third optocoupler (U19) is connected to the direction control line (485CTL1) of the control side circuit.

[0019] The utility model is further configured as follows: the transistor side of the first optocoupler (U17) is connected to the power supply end (V485) of the 485 isolation side circuit through a second pull-up resistor (R224), the transistor side of the second optocoupler (U18) is connected to the power supply end (V485) of the 485 isolation side circuit through a third pull-up resistor (R226), and the transistor side of the third optocoupler (U19) is connected to the power supply end (V485) of the 485 isolation side circuit through a fourth pull-up resistor (R231).

[0020] In summary, the present invention has the following beneficial effects:

[0021] 1. Improved Anti-Interference Performance: A three-channel fully optically isolated architecture completely isolates the control-side circuit from the 485 isolation-side circuit, effectively blocking the propagation path of common-mode interference. This isolation structure enables the system to withstand high common-mode voltage differences, significantly improving system safety. The optocoupler + transistor dual-stage shaping structure restores signal drive capability, and the RC shaping network finely shapes signal edges, ensuring stable communication at high baud rates.

[0022] 2. Enhanced communication reliability: Directional single-line isolation control reduces the risk window caused by misalignment between wiring and logic timing, lowering the probability of bus contention. A weak bias network makes the idle state determinable and minimizes bus load, significantly reducing false triggering and misjudgment in multi-node networks. A shaping network suppresses reflections, significantly reducing communication bit error rates, especially over long cables and in high-noise environments.

[0023] 3. Improved safety: The fully isolated architecture prevents dangerous voltages from being transmitted between the MCU and the 485 bus, enhancing the system's isolation from external electrical faults. The multi-layered protection design includes TVS diodes to suppress high-voltage pulses, PTC diodes to limit abnormal currents, and common-mode suppressors to filter out common-mode noise. This creates a layered protection chain from port to chip, ensuring link stability in lightning, ESD, and conducted disturbance scenarios.

[0024] 4. Improved ease of use: Single-wire directional control reduces the number of control interfaces, reduces interface wiring complexity, and simplifies PCB layout and software control logic. Multi-layer protection and self-recovery mechanisms reduce the need for manual intervention and reduce system maintenance frequency. The overall compact structure facilitates application in space-constrained environments and requires fewer components than discrete implementations. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the circuit structure of the utility model electric energy meter communication module;

[0026] Figure numerals: 1. Control side circuit; 2. 485 isolation side circuit; 3. VCM; 4. GND; 5. V485; 6. G485; 7. First optocoupler (U17); 8. Second optocoupler (U18); 9. Third optocoupler (U19); 10. RS, 485 transceiver (U20); 11. First transistor (Q11); 12. Second transistor (Q12); 13. Bidirectional transient voltage suppressor (TVS1); 14. Resettable fuse (PTC1); 15. Receive data line (485RXD1); 16. Transmit data line (485TXD1); 17. Direction control Line (485CTL1); 24, pull-up resistor (R220); 25, base current limiting resistor (R227); 26, base feedback resistor (R228); 27, first pull-up resistor (R232); 28, first pull-down resistor (R233); 29, first resistor (R229); 30, first capacitor (C221); 31, second resistor (R222); 32, second capacitor (C226); 33, decoupling capacitor (C83); 35, second pull-up resistor (R224); 36, third pull-up resistor (R226); 37, fourth pull-up resistor (R231). DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, the present invention provides an electric energy meter communication module, including a control-side circuit 1 and a 485 isolation-side circuit 2. The control-side circuit 1 has a power supply terminal VCM 3 and a reference ground terminal GND 4 for connecting to a controller; the 485 isolation-side circuit 2 has a power supply terminal V485 5 and a reference ground terminal G485 6 for connecting to an RS-485 bus.

[0029] Three optocouplers are provided between control-side circuit 1 and 485 isolation-side circuit 2: the first optocoupler (U17) 7, the second optocoupler (U18) 8, and the third optocoupler (U19) 9. These are used to achieve complete electrical isolation between the two circuit domains. The first optocoupler (U17) 7 isolates the receive signal, the second optocoupler (U18) 8 isolates the transmit signal, and the third optocoupler (U19) 9 isolates the direction control signal.

[0030] An RS-485 transceiver (U20) 10 is provided in the 485 isolation side circuit 2, which has differential signal input / output terminals A and B, a receive output terminal (RO), a transmit input terminal (DI), a transmit enable terminal (DE) and a receive enable terminal (RE_).

[0031] In the receiving link, a first transistor (Q11) 11 is provided in the control-side circuit 1, with its base connected to the output terminal of the first optocoupler (U17) 7, and its collector connected to the power supply terminal VCM3 of the control-side circuit 1 through a pull-up resistor (R220) 24, and connected to the receiving data line (485RXD1) 15. The LED side of the first optocoupler (U17) 7 is connected to the receiving output terminal (RO) 20 of the RS-485 transceiver (U20) 10, and the transistor side of the first optocoupler (U17) 7 is connected to the power supply terminal V485 5 of the 485 isolation-side circuit 2 through a second pull-up resistor (R224) 35.

[0032] The device also includes an RC shaping network, which includes a first resistor (R229) 29 connected in series with the input terminal of the first optocoupler (U17) 7, and a first capacitor (C221) 30 and a second resistor (R222) 31 connected in parallel with the base of the first transistor (Q11) 11. These components together constitute a shaping circuit for the received signal, which is used to suppress glitches and improve signal quality.

[0033] In the transmit link, a second transistor (Q12) 12 is provided in the 485 isolation side circuit 2, with its base connected to the output of the second optocoupler (U18) 8, and its collector connected to the transmit input (DI) of the RS-485 transceiver (U20) 10. The LED side of the second optocoupler (U18) 8 is connected to the transmit data line (485TXD1) 16 of the control side circuit 1, and the transistor side of the second optocoupler (U18) 8 is connected to the power supply terminal V485 5 of the 485 isolation side circuit 2 via a third pull-up resistor (R226) 36.

[0034] The base of the second transistor (Q12) 12 is connected to the output terminal of the second optocoupler (U18) 8 via a base current-limiting resistor (R227) 25. The base of the second transistor (Q12) 12 is also connected to a base feedback resistor (R228) 26. A second capacitor (C226) 32 connected in parallel with the collector of the second transistor (Q12) 12 is used to optimize signal edges and improve signal quality.

[0035] In the direction control section, the LED side of the third optocoupler (U19) 9 is connected to the direction control line (485CTL1) 17 of the control-side circuit 1, and the transistor side of the third optocoupler (U19) 9 is connected to the power supply terminal V485 5 of the 485 isolation-side circuit 2 through the fourth pull-up resistor (R231) 37. The output end of the third optocoupler (U19) 9 is simultaneously connected to the transmit enable terminal (DE) and receive enable terminal (RE_) of the RS-485 transceiver (U20) 10, achieving synchronous control of the transmit and receive states through a single control signal, simplifying the control logic and reducing the risk of timing conflicts.

[0036] The present invention also includes a multi-layer bus protection structure. A bidirectional transient voltage suppressor (TVS1) 13 is connected to the differential signal input / output terminals A and B of the RS-485 transceiver (U20) 10 to suppress electrostatic discharge and surge spikes. A resettable fuse (PTC1) 14 is connected in series between the differential signal input / output terminals A and B of the RS-485 transceiver (U20) 10 and the RS-485 bus to limit abnormal current. A first pull-up resistor (R232) 27 and a first pull-down resistor (R233) 28 are also provided on the differential signal line, each with a resistance of 20kΩ, to provide a fail-safe bias to ensure the stability of the bus idle state.

[0037] Common-mode suppression devices are installed between the RS-485 transceiver (U20) 10's differential signal input / output terminals A and B and the RS-485 bus to reduce common-mode noise and radiation, improving EMC performance. Decoupling capacitors (C83) 33 are installed between the RS-485 transceiver (U20) 10's power supply terminal V485 5 and reference ground terminal G485 6 for local decoupling, suppressing high-frequency ripple and spikes on the transceiver's power supply side.

[0038] When the utility model is working, the signal flow is as follows:

[0039] In the receive direction (bus to MCU), the differential signal of the RS10-485 bus first passes through the protection of PTC1, TVS1, and common-mode suppression devices before entering the A / B ports of the RS10-485 transceiver (U20). The RS10-485 transceiver (U20) converts the differential signal to single-ended TTL levels and outputs it to the RO port. The signal from the RO port drives the LED of the first optocoupler (U17 transmit data line (485TXD1)). The first optocoupler (U17 transmit data line (485TXD1)) optically isolates the signal and transmits it to control-side circuit 1. The output of the first optocoupler (U17 transmit data line (485TXD1)) is processed by the first transistor (Q114 bidirectional transient voltage suppressor (TVS1) 85 transceiver (U20)) and an RC shaping network to form a clean digital signal. This signal is then sent to the receive data line (485RXD1) of control-side circuit 1 and connected to the controller.

[0040] In the transmit direction (MCU to bus), data from the controller drives the LED of the second optocoupler (U18) via the transmit data line (485TXD1). The second optocoupler (U18) transmits the signal through optical isolation to the 485 isolation side circuit 2. The output of the second optocoupler (U18) is processed by the second transistor (Q12) and the first transistor (Q11) and the associated shaping network before being sent to the DI port of the RS10-485 transceiver (U20). When the transmit enable signal is valid, the RS10-485 transceiver (U20) converts the single-ended signal into a differential signal and outputs it to the RS10-485 bus through the A / B port.

[0041] Direction control (transmit / receive switching) is implemented by the controller via the direction control line (485CTL1). This signal, isolated by a third optocoupler (U19), simultaneously controls the DE and RE_ ports of the RS10-485 transceiver (U20), switching between transmit and receive states. This single-line synchronous control design simplifies control logic and reduces the risk of timing conflicts.

[0042] The electric energy meter communication module of this utility model significantly improves the anti-interference capability, communication reliability, safety and ease of use of the electric energy meter communication through designs such as a three-channel fully optically isolated architecture, an optocoupler + transistor two-stage shaping structure, directional single-line isolation control, multi-layer protection and EMC design, and a weak bias and high-resistance sampling structure. It is particularly suitable for industrial application scenarios with complex electromagnetic environments, large ground potential differences, and high reliability requirements.

[0043] In order to verify the technical effects of the above technical solutions, the technical effects of the utility model for testing the communication module of the electric energy meter are as follows: anti-interference performance, communication reliability, electrical safety and ease of use.

[0044] 1. Using a comparative test method, the circuit of this utility model is compared with a traditional non-isolated RS-485 circuit and a single optocoupler isolation circuit. The test environment is set to simulate an industrial field environment, including interference sources such as motor start-stop and high-voltage switching, as well as simulated ground potential differences, electrostatic discharge, and surge interference.

[0045] The test evaluates performance through the following key indicators: common mode interference immunity, signal integrity at high baud rates, data transmission error rate, half-duplex switching reliability, electrical isolation effect, and protection capability.

[0046] 2. Technical Effect Comparison Table

[0047]

[0048] 3. Verification methods and results

[0049] Common-mode interference testing: Common-mode voltages of varying amplitudes were applied across the RS-485 bus, and the maximum acceptable common-mode voltage was recorded. The utility model circuit maintained stable communication at common-mode voltages of ±1500V, while conventional circuits failed at ±7V, and single-optocoupler isolation circuits degraded at ±50V.

[0050] High-speed communication testing: Continuous data transmission was conducted at a baud rate of 115.2 kbps, and the bit error rate (BER) was measured. The BER of the circuit was below 0.01%, significantly better than the 0.5% of conventional circuits and the 0.2% of single-optocoupler isolation circuits. Even at a transmission rate of 460.8 kbps, the BER remained below 0.05%.

[0051] Half-duplex switching test: Simulates a fast transmit / receive switching scenario and measures the bus conflict rate. The single-wire synchronous control scheme adopted by this utility model controls the conflict rate to below 0.5%, while the conflict rate of traditional two-wire control schemes is as high as 5%.

[0052] Anti-interference capability test: ESD, electrical fast transients, and surge pulses complying with IEC 61000-4-2 / 4 / 5 standards were applied to the RS-485 interface. The circuit of the utility model continued to operate normally after the 15kV ESD test, while the traditional circuit was damaged after the 4kV test.

[0053] Multi-node network testing: Measured idle state false trigger rate in a 32-node RS-485 network. The 20kΩ weak bias design of this utility model controlled the false trigger rate to below 0.3%, demonstrating good network compatibility.

[0054] 4. Verify the conclusion

[0055] Test results demonstrate that this utility model's energy meter communication module offers significant advantages over traditional technologies. The three-channel fully optically isolated architecture significantly enhances common-mode interference resistance; the optocoupler + transistor dual-stage shaping structure significantly improves signal quality; the single-wire directional isolation control simplifies the interface and improves reliability; the multi-layer protection design significantly enhances the system's anti-interference capabilities; and the weak bias design balances multi-node network compatibility and idle state stability. In summary, this utility model is suitable for industrial applications with complex electromagnetic environments, large ground potential differences, and high reliability requirements, and has broad application prospects.

Claims

1. An electric energy meter communication module, characterized in that: include: The control side circuit has a power supply terminal (VCM) and a reference ground terminal (GND) for connecting to the controller; 485 isolation side circuit, with power supply terminal (V485) and reference ground terminal (G485), used to connect to RS-485 bus; A first optical coupler (U17), used to isolate the receiving signal between the control side circuit and the 485 isolation side circuit; A second optical coupler (U18) is used to isolate the transmission signal between the control side circuit and the 485 isolation side circuit; A third optical coupler (U19) is used to isolate the direction control signal between the control side circuit and the 485 isolation side circuit; An RS-485 transceiver (U20), provided in the 485 isolation side circuit, having differential signal input / output terminals (A, B), a receiving output terminal (RO), a transmitting input terminal (DI), a transmitting enable terminal (DE) and a receiving enable terminal (RE_); a first transistor (Q11), arranged in the control side circuit, with its base connected to the output end of the first optical coupler (U17), and its collector connected to the power supply end (VCM) of the control side circuit via a pull-up resistor (R220); A second transistor (Q12) is provided in the 485 isolation side circuit, a base of which is connected to the output end of the second optical coupler (U18), and a collector of which is connected to the transmitting input end (DI) of the RS-485 transceiver (U20); a bidirectional transient voltage suppressor (TVS1), connected to the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20); A resettable fuse (PTC1) is connected in series between the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20) and the RS-485 bus.

2. The electric energy meter communication module according to claim 1, characterized in that: The output end of the third optical coupler (U19) is simultaneously connected to the transmit enable end (DE) and the receive enable end (RE_) of the RS-485 transceiver (U20), thereby achieving synchronous control of the transmit and receive states through a single control signal.

3. The electric energy meter communication module according to claim 1, characterized in that: The invention also includes a first pull-up resistor (R232) and a first pull-down resistor (R233) arranged on the differential signal input / output terminals (A, B) of the RS-485 transceiver (U20) for providing fail-safe bias.

4. The electric energy meter communication module according to claim 3, characterized in that: The resistance of the first pull-up resistor (R232) and the first pull-down resistor (R233) is 20 kΩ.

5. The electric energy meter communication module according to claim 1, characterized in that: The collector of the first transistor (Q11) is connected to the receiving data line (485RXD1) of the control side circuit, the base of the second transistor (Q12) is connected to the output end of the second optical coupler (U18) via a base current limiting resistor (R227), and the base of the second transistor (Q12) is also connected to a base feedback resistor (R228).

6. The electric energy meter communication module according to claim 1, characterized in that: The invention also includes an RC shaping network, which includes a first resistor (R229) connected in series with the input end of the first optocoupler (U17), a first capacitor (C221) and a second resistor (R222) connected in parallel with the base of the first transistor (Q11); and a second capacitor (C226) connected in parallel with the collector of the second transistor (Q12).

7. The electric energy meter communication module according to claim 1, characterized in that: It also includes a decoupling capacitor (C83) arranged between the power supply terminal (V485) and the reference ground terminal (G485) of the RS-485 transceiver (U20).

8. The electric energy meter communication module according to claim 1, characterized in that: The LED side of the first optocoupler (U17) is connected to the receiving output end (RO) of the RS-485 transceiver (U20), the LED side of the second optocoupler (U18) is connected to the transmitting data line (485TXD1) of the control side circuit, and the LED side of the third optocoupler (U19) is connected to the direction control line (485CTL1) of the control side circuit.

9. The electric energy meter communication module according to claim 1, characterized in that: The transistor side of the first optocoupler (U17) is connected to the power supply end (V485) of the 485 isolation side circuit through a second pull-up resistor (R224), the transistor side of the second optocoupler (U18) is connected to the power supply end (V485) of the 485 isolation side circuit through a third pull-up resistor (R226), and the transistor side of the third optocoupler (U19) is connected to the power supply end (V485) of the 485 isolation side circuit through a fourth pull-up resistor (R231).

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