Double-isolation double-path R485 circuit

Abstract

The utility model provides a double-isolation double-path R485 circuit, comprising an isolation power supply and two paths of R485 circuits respectively connected with the isolation power supply, the two paths of R485 circuits are the same, and each of the two paths of R485 circuits comprises a 485 communication chip and a communication isolation circuit; the isolation power supply comprises a transformer driver chip and two isolation transformers, the input of the transformer driver chip is connected with the analog power supply, and the output of the transformer driver chip serves as an isolation power supply I and an isolation power supply II through the two isolation transformers and supplies power to the two R485 circuits respectively; a pin A and a pin B of the 485 communication chip are respectively connected with a 485 communication interface, and a pin R and a pin D of the 485 communication chip are communicated with the MCU through the communication isolation circuit.

Description

Technical Field

[0001] The utility model relates to an R485 circuit, in particular to a double-isolated dual-path R485 circuit. Background Art

[0002] With the rapid development of electronic technology, various electronic devices have emerged. These devices have brought great changes to people's production and life, and at the same time, the operating environment of current electronic products has become more complex - especially the electromagnetic environment has become more and more complex. This requires that the designed products must have the ability to operate without failure in complex electromagnetic environments.

[0003] RS485 bus is a universal serial communication bus that uses balanced transmission and differential reception to achieve communication. It is widely used in various fields such as industrial intelligent instruments and communication equipment. With the increasing intelligence of industrial intelligent instruments and communication equipment, more and more integrated system equipment has led to more and more complex equipment on-site monitoring. The interconnection of instrument equipment is the general trend under the new situation. In order to meet the increasingly complex industrial needs, dual-channel RS485 communication technology has emerged. Circuits with 485 communication are easily affected by external interference factors, making communication unstable, which has a serious impact on the operation of electronic equipment.

[0004] Existing solutions to achieve RS485 circuit isolation include using optocoupler isolation to achieve RS485 circuit isolation, using digital isolators to achieve RS485 circuit isolation, and using optocoupler + digital isolation to achieve RS485 circuit isolation, etc., but these only isolate the signal transmission part. In fact, the power supply crosstalk and instability of the RS485 circuit are the biggest interference sources affecting 485 communication. How to reduce the interference of the power supply has become a problem that needs to be solved.

[0005] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the invention

[0006] The utility model aims to provide a dual-isolation dual-path R485 circuit in view of the deficiencies in the prior art.

[0007] In order to achieve the above object, the technical solution adopted by the utility model is: to provide a dual-isolated dual-way R485 circuit, including an isolated power supply and two R485 circuits respectively connected to the isolated power supply, the two R485 circuits are the same, both including a 485 communication chip and a communication isolation circuit;

[0008] The isolated power supply includes a transformer driver chip and two isolation transformers, the input of the transformer driver chip is connected to the analog power supply, and the output of the transformer driver chip is used as an isolated power supply I and an isolated power supply II after passing through two isolation transformers to supply power to two R485 circuits respectively;

[0009] The A and B pins of the 485 communication chip are respectively connected to the 485 communication interface, and the R and D pins of the 485 communication chip communicate with the MCU through the communication isolation circuit.

[0010] In one embodiment, the communication isolation R485 circuit includes a dual-channel digital isolation chip and a photoelectric isolator; VIA and VOB of the dual-channel digital isolation chip are connected to the R and D pins of the 485 communication chip; VIB and V0A of the dual-channel digital isolation chip are connected to the MCU; the cathode of the photoelectric isolator is connected to the MCU, and the emitter of the photoelectric isolator is connected to the RE and DE pins of the 485 communication chip.

[0011] The utility model has substantial characteristics and progress compared with the prior art. Specifically, the utility model arranges a transformer driver chip and two isolation transformers to form an isolated power supply, thereby realizing power supply isolation of two 485 circuits; arranges a dual-channel digital isolation chip and a photoelectric isolator to form a communication isolation R485 circuit, thereby realizing communication isolation of two 485 circuits, and the transmission rate is improved, and the system complexity is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a principle block diagram of the utility model.

[0013] Figure 2 It is a circuit diagram of the isolated power supply of the utility model.

[0014] Figure 3 It is a circuit diagram of the R485 circuit of the utility model. DETAILED DESCRIPTION

[0015] The technical solution of the utility model is further described in detail below through specific implementation methods.

[0016] Example 1

[0017] This embodiment provides a dual-isolation dual-path R485 circuit, such as Figure 1 As shown, it includes an isolated power supply and two R485 circuits respectively connected to the isolated power supply, and the two R485 circuits are the same, both including a 485 communication chip and a communication isolation circuit;

[0018] The isolated power supply includes a transformer driver chip and two isolation transformers, the input of the transformer driver chip is connected to the analog power supply, and the output of the transformer driver chip is used as an isolated power supply I and an isolated power supply II through two isolation transformers to supply power to two R485 circuits respectively;

[0019] The A and B pins of the 485 communication chip are respectively connected to the 485 communication interface, and the R and D pins of the 485 communication chip communicate with the MCU through the communication isolation circuit.

[0020] like Figure 2 As shown, the model of the transformer driver chip is VPS8504B, and the model of the isolation transformer is VPT85BB-01; the VIN pin of the VPS8504B is connected to the analog power supply, the EN pin of the VPS8504B is connected to the analog power supply through a resistor R94, and is connected to the analog ground through a capacitor C59. Capacitors C57 and C58 are also provided between the analog power supply and the analog ground, and the CLK pin and GND pin of the VPS8504B are grounded; the VD1, VD2, and VIN pins of the VPS8504B are respectively connected to the primary side pins of two VPT85BB-01s; the secondary sides of the two VPT85BB-01s output +5.0VA and +5.0VB isolation voltages through anti-reverse diodes and limiting resistors R95 to respectively power the two R485 circuits, and at the same time, the analog ground pin GND is also isolated into GND-A and GND-B through capacitors C208, C209, C210, and C211.

[0021] VPS8504B is a push-pull transformer driver specially designed for small-volume, low standby power consumption micro-power isolated power supply. It has an internal integrated oscillator, providing a pair of high-precision complementary signals to drive two N-channel MOSFETs. The chip is designed according to a symmetrical structure, which can effectively ensure the high symmetry of the two power MOSFETs and avoid the circuit from being magnetically biased during operation. By setting input and output filter capacitors, isolation transformers and rectifier circuits on its periphery, an isolated power supply with 5V input, 5V output and output power of 1~3W is realized. The VPS8504B chip also has an enable pin EN, and two different operating frequencies can be selected by leaving the CLK pin floating or grounding. In this embodiment, the CLK pin is grounded.

[0022] like Figure 3As shown, the communication isolation R485 circuit includes a dual-channel digital isolation chip and a photoelectric isolator, the model of the dual-channel digital isolation chip is NS18221N1-DSPR, the photoelectric isolator is OR-3H7C-TP-G and the model of the 485 communication chip is TP8485E-SR; the A and B pins of the TP8485E-SR are respectively connected to the 485 communication interface; the R and D pins of the TP8485E-SR are connected to the VIA and VOB of the NS18221N1-DSPR; the VIB and V0A of the NS18221N1-DSPR are connected to the MCU; the cathode of the OR-3H7C-TP-G is connected to the MCU, and the emitter of the OR-3H7C-TP-G is connected to the RE and DE pins of the TP8485E-SR.

[0023] The working principle is as follows: the 485 signal is transmitted to the NS18221N1-DSPR through the TP8485E-SR to isolate the power supply and signal at the input and output ends. It has the characteristics of low power consumption, high electromagnetic immunity and low radiation, which improves the reliability and stability of use; the isolated 485 signal RS485_RX is transmitted to the MCU for analysis and processing; similarly, the 485 signal RS485_TX is transmitted from the MCU to the TP8485E-SR after isolation by the NS18221N1-DSPR, and finally connected to the peripheral devices. At the same time, the signal output of the MCU is isolated using a signal optocoupler isolation device and then input into the TP8485E-SR. Compared with the traditional optocoupler circuit, the system transmission rate is improved and the system complexity is reduced.

[0024] Furthermore, the communication isolation R485 circuit also includes an electrostatic protection device, and the A and B pins of the 485 communication chip are respectively connected to the electrostatic protection device. Figure 3 As shown, the electrostatic protection device is an ESD electrostatic diode SDT23C24L02.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the utility model can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the utility model, which should be included in the scope of the technical solution for protection of the utility model.

Claims

1. A dual-isolated dual-path R485 circuit, characterized in that: It includes an isolated power supply and two R485 circuits respectively connected to the isolated power supply, and the two R485 circuits are the same, both including a 485 communication chip and a communication isolation circuit; The isolated power supply includes a transformer driver chip and two isolation transformers, the input of the transformer driver chip is connected to the analog power supply, and the output of the transformer driver chip is used as an isolated power supply I and an isolated power supply II after passing through two isolation transformers to supply power to two R485 circuits respectively; The A and B pins of the 485 communication chip are respectively connected to the 485 communication interface, and the R and D pins of the 485 communication chip communicate with the MCU through the communication isolation circuit.

2. A dual-isolated dual-path R485 circuit according to claim 1, characterized in that: The communication isolation R485 circuit includes a dual-channel digital isolation chip and a photoelectric isolator; VIA and VOB of the dual-channel digital isolation chip are connected to the R and D pins of the 485 communication chip; VIB and V0A of the dual-channel digital isolation chip are connected to the MCU; the cathode of the photoelectric isolator is connected to the MCU, and the emitter of the photoelectric isolator is connected to the RE and DE pins of the 485 communication chip.

3. A dual-isolated dual-path R485 circuit according to claim 2, characterized in that: The communication isolation R485 circuit also includes an electrostatic protection device, and the A and B pins of the 485 communication chip are respectively connected to the electrostatic protection device.

4. A dual-isolated dual-path R485 circuit according to claim 2, characterized in that: The model of the 485 communication chip is TP8485E-SR, the model of the dual-channel digital isolation chip is NS18221N1-DSPR, the model of the transformer driver chip is VPS8504B, the model of the isolation transformer is VPT85BB-01; the photoelectric isolator is OR-3H7C-TP-G.

5. A dual-isolated dual-path R485 circuit according to claim 3, characterized in that: The electrostatic protection device is an ESD electrostatic diode SDT23C24L02.

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