A RS485 interface circuit based on self-powered magnetic isolation

Abstract

The utility model belongs to communication technical field discloses a kind of RS485 interface circuit based on self-powered electromagnetic isolation, including first equipment and second equipment, and first equipment and second equipment all include RS485 communication controller, first self-powered electromagnetic isolation device and second self-powered electromagnetic isolation device, first equipment is connected with first self-powered electromagnetic isolation device and second self-powered electromagnetic isolation device respectively by receiving switch RDEN and sending switch TDEN, first equipment is connected with first self-powered electromagnetic isolation device by data end, and is connected with second self-powered electromagnetic isolation device by clock end, two first self-powered electromagnetic isolation devices are connected by isolated ground, two second self-powered electromagnetic isolation devices are connected by isolated ground, isolated ground of between first equipment and second equipment is common ground, in the case where performance and reliability are promoted, component cost drops by 83%, communication rate can reach 16Mbps at most, compared with opto-coupler transmission, 8 times are improved.

Description

Technical Field

[0001] This utility model belongs to the field of communication technology and relates to an RS485 interface circuit based on self-powered electromagnetic isolation. Background Technology

[0002] RS485 is a serial data interface standard. Based on RS422, the transceiver uses balanced drive and differential reception, possessing the ability to suppress common-mode interference and providing multi-point, bidirectional communication capabilities. The RS485 standard only specifies the electrical characteristics of the interface and does not cover connectors, cables, or protocols; users can build their own higher-level communication protocols on this basis. Existing aircraft RS485 bus communication... Figure 1 As shown, the seeker, inertial measurement unit, main control computer, transponder, electrical control devices, and other equipment are connected via an RS485 serial bus. The aircraft's main control computer is the master station, and the other devices are slave stations. The master station is responsible for the entire network and schedules and manages the other slave devices. The master station can select any slave station for communication, forming a communication pair. The selected slave station can both receive information from and send information to the master station, thus constituting the communication process of the aircraft's RS485 bus. The aircraft's RS485 bus topology mainly adopts the FLY_BY topology structure, such as... Figure 2 As shown, since the various devices of the aircraft are not in the same compartment, the cable network needs to pass through the compartment. The common-mode interference of the cable network is large, and the signals of the various devices are not grounded. Therefore, in practical applications, the RS485 interface needs to be isolated.

[0003] like Figure 3 As shown, the existing isolated RS485 interface uses optocouplers for isolation. 1) Optocoupler isolation requires the main control computer to provide a dedicated isolation power supply, which increases the overall power consumption. 2) Because optocouplers are current-transmission devices with low transmission rates, the maximum transmission rate of high-speed optocouplers is 2Mbps. The impedance of the transmission cable itself will reduce the differential amplitude at the receiving end, limiting the communication rate and transmission distance of the RS485 interface. The actual cable network length cannot exceed 3m. 3) One RS485 interface on a single device requires one isolation power supply, two level conversion chips, three high-speed optocouplers, one differential transmitter chip, and one differential receiver chip. The cost of selecting all domestically produced components is about 15,000 yuan.

[0004] In summary, existing isolated RS485 interfaces suffer from low transmission speed, require separate isolated power supplies, and have high costs associated with domestic design. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide an RS485 interface circuit based on self-powered electromagnetic isolation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This utility model provides an RS485 interface circuit based on self-powered electromagnetic isolation, including a first device and a second device. Both the first and second devices include an RS485 communication controller, a first self-powered electromagnetic isolation device, and a second self-powered electromagnetic isolation device. The first device is connected to the first and second self-powered electromagnetic isolation devices through a receive switch RDEN and a transmit switch TDEN, respectively. The first device is connected to the first self-powered electromagnetic isolation device through a data terminal and to the second self-powered electromagnetic isolation device through a clock terminal. The two first self-powered electromagnetic isolation devices are connected through an isolation ground, and the two second self-powered electromagnetic isolation devices are connected through an isolation ground. The isolation grounds of the first device and the second device are common.

[0008] Furthermore, the data terminal includes a single-ended transmit signal TXD and a single-ended receive signal RXD. The RS485 communication controller is connected to the first self-powered electromagnetic isolation device through the single-ended transmit signal TXD, and the first self-powered electromagnetic isolation device is connected to the RS485 communication controller through the single-ended receive signal RXD.

[0009] Furthermore, the clock terminal includes a transmitting clock terminal TXC and a receiving clock terminal RXC. The RS485 communication controller is connected to the second self-powered electromagnetic isolation device through the transmitting clock terminal TXC, and the second self-powered electromagnetic isolation device is connected to the RS485 communication controller through the receiving clock terminal RXC.

[0010] Furthermore, the single-ended transmitting signal TXD operates synchronously with the transmitting clock terminal TXC, and the single-ended receiving signal RXD operates synchronously with the receiving clock terminal RXC. The single-ended transmitting signal TXD transmits data bit by bit from the transmitting data terminal according to the frequency of the transmitting clock terminal TXC, and the single-ended receiving signal RXD samples the received data according to the frequency of the receiving clock terminal RXC.

[0011] Furthermore, the single-ended transmit signal TXD of the RS485 communication controller of the first device is converted into differential transmit signals TXD+ and TXD- through the first self-powered electromagnetic isolation device; the transmit clock terminal TXC is converted into clock signals TXC+ and TXC-.

[0012] Furthermore, the differential transmit signal TXD+ of the first device is connected to the differential receive signal RXD+ of the second device, and the differential transmit signal TXD- of the first device is connected to the differential receive signal RXD- of the second device; the clock signal TXC+ of the first device is connected to the clock signal RXC+ of the second device, and the clock signal TXC- of the first device is connected to the clock signal RXC- of the second device.

[0013] Furthermore, the communication rate of the first self-powered electromagnetic isolation device and the second self-powered electromagnetic isolation device is less than or equal to 16 Mbps.

[0014] Furthermore, the power supply for the first and second self-powered electromagnetic isolation devices is 3.3V or 5V.

[0015] Furthermore, the first and second self-powered electromagnetic isolation devices are LM2682C, with a quality grade of H.

[0016] Furthermore, the first and second self-powered electromagnetic isolation devices are LM2682P, with a quality grade of N1.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] This invention relates to an RS485 interface circuit based on self-powered electromagnetic isolation. The first and second self-powered electromagnetic isolation devices can generate their own isolated power supplies, and are compatible with 3.3V and 5V. While improving performance and reliability, the component cost is reduced by 83%, and the communication rate can reach up to 16Mbps, which is 8 times higher than that of optocoupler transmission. This invention solves the problems of low transmission speed, the need for separate isolated power supplies, and high cost of domestic design in existing isolated RS485 interfaces. Attached Figure Description

[0019] Figure 1 A schematic diagram of existing aircraft RS485 bus communication;

[0020] Figure 2 This is a schematic diagram of the existing RS485 bus topology for aircraft.

[0021] Figure 3 This is a schematic diagram of an existing isolated RS485 interface;

[0022] Figure 4 This is a schematic diagram of the RS485 interface circuit based on self-powered electromagnetic isolation according to this utility model;

[0023] Figure 5 This is the isolated RS485 interface of the remote aircraft master computer in this embodiment.

[0024] Figure label:

[0025] 1-RS485 communication controller; 2-First self-powered electromagnetic isolation device; 3-Second self-powered electromagnetic isolation device. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0027] Example 1

[0028] An RS485 interface circuit based on self-powered electromagnetic isolation includes a first device and a second device. Both the first device and the second device include an RS485 communication controller 1, a first self-powered electromagnetic isolation device 2, and a second self-powered electromagnetic isolation device 3. The first device is connected to the first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3 through a receive switch RDEN and a transmit switch TDEN, respectively. The first device is connected to the first self-powered electromagnetic isolation device 2 through a data terminal and to the second self-powered electromagnetic isolation device 2 through a clock terminal. The two first self-powered electromagnetic isolation devices 2 are connected through an isolation ground, and the two second self-powered electromagnetic isolation devices 3 are connected through an isolation ground.

[0029] This invention uses only two self-powered electromagnetic isolation interface devices, namely the first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3, to achieve isolated RS485 communication with a maximum communication rate of 16Mbps, which is 8 times higher than that of optocoupler transmission. The first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3 can generate isolated power independently, and are compatible with 3.3V and 5V, without the need for the whole machine to provide isolated power.

[0030] The data end includes a single-ended transmit signal TXD and a single-ended receive signal RXD, and the clock end includes a transmit clock end TXC and a receive clock end RXC. The single-ended transmit signal TXD operates synchronously with the transmit clock end TXC, and the single-ended receive signal RXD operates synchronously with the receive clock end RXC. The single-ended transmit signal TXD transmits data bit by bit from the data end according to the frequency of the transmit clock end TXC, and the single-ended receive signal RXD samples the received data according to the frequency of the receive clock end RXC.

[0031] The first device, RS485 communication controller 1, is connected to the first self-powered electromagnetic isolator 2 via a single-ended transmit signal TXD. The first self-powered electromagnetic isolator 2 is connected to the RS485 communication controller 1 via a single-ended receive signal RXD. The RS485 communication controller 1 is connected to the second self-powered electromagnetic isolator 3 via a transmit clock terminal TXC. The second self-powered electromagnetic isolator 3 is connected to the RS485 communication controller 1 via a receive clock terminal RXC.

[0032] Similarly, the second device, RS485 communication controller 1, is connected to the first self-powered electromagnetic isolator 2 via a single-ended transmit signal TXD, and the first self-powered electromagnetic isolator 2 is connected to the RS485 communication controller 1 via a single-ended receive signal RXD. The RS485 communication controller 1 is connected to the second self-powered electromagnetic isolator 3 via a transmit clock terminal TXC, and the second self-powered electromagnetic isolator 3 is connected to the RS485 communication controller 1 via a receive clock terminal RXC.

[0033] like Figure 4 As shown, TDEN is the transmit switch and RDEN is the receive switch. The first device RS485 communication controller 1 is connected to the first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3 through the transmit switch TDEN; the RS485 communication controller is connected to the first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3 through the receive switch RDEN.

[0034] Two first self-powered electromagnetic isolation devices 2 are connected through isolation ground GLGND, and two second self-powered electromagnetic isolation devices 3 are connected through isolation ground GLGND. The single-ended transmission signal TXD of the RS485 communication controller 1 of the first device is converted into differential transmission signals TXD+ and TXD- through the first self-powered electromagnetic isolation device 2; the transmission clock terminal TXC is converted into clock signals TXC+ and TXC-.

[0035] The differential transmit signal TXD+ of the first device is connected to the differential receive signal RXD+ of the second device, and the differential transmit signal TXD- of the first device is connected to the differential receive signal RXD- of the second device; the clock signal TXC+ of the first device is connected to the clock signal RXC+ of the second device, and the clock signal TXC- of the first device is connected to the clock signal RXC- of the second device.

[0036] Similarly, the differential transmit signal TXD+ of the second device is connected to the differential receive signal RXD+ of the first device, the differential transmit signal TXD- of the second device is connected to the differential receive signal RXD- of the first device, the clock signal TXC+ of the second device is connected to the clock signal RXC+ of the first device, and the clock signal RXC- of the second device is connected to the clock signal TXC- of the first device.

[0037] Among them, the first self-powered electromagnetic isolation device 2 and the second self-powered electromagnetic isolation device 3 are selected from the LM2682 series. The ceramic packaged LM2682C with quality grade H can be selected, or the plastic packaged LM2682P with quality grade N1 can be selected.

[0038] like Figure 5 As shown, the isolated RS485 interface of the remote-controlled aircraft's main control computer is in synchronous half-duplex mode. The control signals come from the FPGA, and differential clock, differential data, and isolation ground signals are output. Through physical testing and communication waveform measurement, the RS485 interface circuit design based on self-powered electromagnetic isolation technology can meet the communication requirements of the aircraft's seeker, inertial measurement unit, main control computer, transponder, and electrical control devices via the RS485 serial bus.

[0039] Table 1 shows a cost comparison between existing isolated RS485 interfaces and the RS485 interface circuit based on self-powered electromagnetic isolation of this invention.

[0040] Table 1

[0041]

[0042] Compared with the cost of existing isolated RS485 interfaces, the cost of components in this invention is reduced by more than 80%, and it can meet the current design requirements of isolated RS485 interface circuits between various devices in aircraft.

[0043] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

Claims

1. An RS485 interface circuit based on self-powered electromagnetic isolation, characterized in that: The device includes a first device and a second device. Both the first device and the second device include an RS485 communication controller (1), a first self-powered electromagnetic isolation device (2), and a second self-powered electromagnetic isolation device (3). The first device is connected to the first self-powered electromagnetic isolation device (2) and the second self-powered electromagnetic isolation device (3) through a receive switch RDEN and a transmit switch TDEN, respectively. The first device is connected to the first self-powered electromagnetic isolation device (2) through a data terminal and to the second self-powered electromagnetic isolation device (3) through a clock terminal. The two first self-powered electromagnetic isolation devices (2) are connected through an isolation ground, and the two second self-powered electromagnetic isolation devices (3) are connected through an isolation ground. The isolation grounds between the first device and the second device are common.

2. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 1, characterized in that: The data terminal includes a single-ended transmit signal TXD and a single-ended receive signal RXD. The RS485 communication controller (1) is connected to the first self-powered electromagnetic isolation device (2) through the single-ended transmit signal TXD. The first self-powered electromagnetic isolation device (2) is connected to the RS485 communication controller (1) through the single-ended receive signal RXD.

3. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 2, characterized in that: The clock terminal includes a transmitting clock terminal TXC and a receiving clock terminal RXC. The RS485 communication controller (1) is connected to the second self-powered electromagnetic isolation device (3) through the transmitting clock terminal TXC. The second self-powered electromagnetic isolation device (3) is connected to the RS485 communication controller (1) through the receiving clock terminal RXC.

4. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 3, characterized in that: The single-ended transmitting signal TXD operates synchronously with the transmitting clock TXC, and the single-ended receiving signal RXD operates synchronously with the receiving clock RXC. The single-ended transmit signal TXD transmits data bit by bit from the transmit data end according to the frequency of the transmit clock end TXC, and the single-ended receive signal RXD samples the received data according to the frequency of the receive clock end RXC.

5. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 4, characterized in that: The single-ended transmit signal TXD of the RS485 communication controller (1) of the first device is converted into differential transmit signals TXD+ and TXD- through the first self-powered electromagnetic isolation device (2); the transmit clock terminal TXC is converted into clock signals TXC+ and TXC-.

6. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 5, characterized in that: The differential transmit signal TXD+ of the first device is connected to the differential receive signal RXD+ of the second device, and the differential transmit signal TXD- of the first device is connected to the differential receive signal RXD- of the second device; The clock signal TXC+ of the first device is connected to the clock signal RXC+ of the second device, and the clock signal TXC- of the first device is connected to the clock signal RXC- of the second device.

7. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 1, characterized in that: The communication rate of the first self-powered electromagnetic isolation device (2) and the second self-powered electromagnetic isolation device (3) is less than or equal to 16Mbps.

8. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 7, characterized in that: The power supply for the first self-powered electromagnetic isolation device (2) and the second self-powered electromagnetic isolation device (3) is 3.3V or 5V.

9. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 8, characterized in that: The first self-powered electromagnetic isolation device (2) and the second self-powered electromagnetic isolation device (3) are LM2682C, with a quality grade of H.

10. The RS485 interface circuit based on self-powered electromagnetic isolation according to claim 8, characterized in that: The first self-powered electromagnetic isolation device (2) and the second self-powered electromagnetic isolation device (3) are LM2682P, with a quality grade of N1.

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