CN101383084B - An Isolated Bus Power Supply Communication System - Google Patents

Abstract

The isolated bus power supply communication system disclosed in the present invention includes a power supply module connected to the power supply/communication bus and N communication modules, N being at least 2, the power supply module includes a power switch circuit and a switch control circuit, and the communication module includes an isolation transformer, Rectification and stabilization circuit, data sending circuit, data receiving circuit and communication control circuit, the transmission of each data bit of the communication module on the power supply/communication bus includes 4 stages: positive power supply stage, negative power supply stage, magnetic reset stage and data communication stage. The bus power supply communication system of the present invention has a simple circuit structure, simultaneously realizes the functions of power supply and data signal transmission on a pair of transmission buses, and realizes signal isolation through a single transformer, which greatly simplifies the complexity of the circuit and reduces the cost. When forming a multi-node bus communication mode, it supports master-slave communication and peer-to-peer communication.

Description

An Isolated Bus Power Supply Communication System

technical field

The invention relates to an isolated bus power supply communication system, in particular to a system for transmitting power and data through a single bus isolated and transmitted by a transformer, and belongs to the technical field of field bus communication.

Background technique

In the fields of industrial control, intelligent buildings, equipment monitoring, etc., there are a large number of requirements for connecting scattered detection points and control points through the bus. Currently commonly used bus technologies are RS485, CAN, ProfiBus and so on. Compared with the centralized star connection, the bus mode can greatly reduce the total length of the connection and the complexity of wiring. The interface of each bus module requires a pair of power lines and a pair of signal lines.

In order to further reduce the wiring and consider the intrinsic safety characteristics of the equipment, there are currently many technologies that only need to transmit signals and power simultaneously through a pair of wires, such as the IEC1158-2 standard adopted by ProfiBus-PA. This technology uses Manchester encoding to superimpose the baseband data signal on the power line before transmission.

ProfiBus-PA is widely used in the field of industrial control. However, ProfiBus-PA, like RS485 and CAN, has a disadvantage: the bus is not isolated from the communication controller. Bus isolation. In addition, the controller power supply is isolated from the bus through a DC/DC isolation circuit, which requires a large number of peripheral circuits.

Contents of the invention

The purpose of the present invention is to provide an isolated bus power supply communication system with simple structure and capable of simultaneously realizing power supply and data transmission on a pair of power supply/communication buses.

The isolated bus-powered communication system of the present invention is characterized in that it includes a power supply module connected to the power supply/communication bus and N communication modules, where N is at least 2, wherein:

The power module includes a power switch circuit and a switch control circuit, the input terminal of the power switch circuit is connected to the power supply, the output terminal is connected to the power supply/communication bus, and the switch control circuit is connected to the power switch circuit;

The communication module includes an isolation transformer, a rectification and stabilization circuit, a data transmission circuit, a data reception circuit and a communication control circuit. The primary winding of the isolation transformer is connected to the power supply/communication bus, and the secondary winding of the isolation transformer is respectively connected to the input of the rectification and stabilization circuit. The input end of the data receiving circuit and the output end of the data sending circuit are connected, the input end of the data sending circuit is connected with the data sending end of the communication control circuit, the output end of the data receiving circuit is connected with the data receiving end of the communication control circuit, and the rectification The output terminal of the voltage stabilizing circuit provides power to the data sending circuit, data receiving circuit and communication control circuit; the transmission of each data bit of the communication module on the power supply/communication bus includes 4 stages: positive power supply stage, negative power supply stage, Magnetic reset phase and data communication phase.

The transmission process of a bit signal in this system includes 4 stages: positive power supply stage, negative power supply stage, magnetic reset stage and data communication stage. In the positive power supply stage, the power module outputs positive voltage; in the negative power supply stage, the power supply/communication bus has a negative voltage, which can be output by the power supply module or automatically generated by the primary excitation current of the isolation transformer of the communication module. In the phase of magnetic reset, the output of the power supply module is turned off, and the data transmission circuit of the communication module does not output voltage, so as to ensure that the excitation current of the isolation transformer returns to zero during this phase. In the data communication stage, the power supply module turns off the output. When the communication module sends data "0", the data transmission circuit outputs voltage, which is coupled by the isolation transformer and generates a voltage pulse on the power supply/communication bus, indicating "logic 0". In the data communication stage, the data receiving circuit detects the input voltage, and when its value is greater than the fixed threshold Vref, it is judged that the bus is "logic 0", otherwise it is "logic 1".

On the basis of realizing bit transmission, this system can realize the mutual communication between communication nodes by defining the corresponding frame format.

The bus power supply communication system of the present invention has a simple circuit structure, simultaneously realizes the functions of power supply and data signal transmission on a pair of transmission buses, and realizes signal isolation through a single transformer, which greatly simplifies the complexity of the circuit and reduces the cost. When forming a multi-node bus communication mode, it supports master-slave communication and peer-to-peer communication.

Description of drawings

Figure 1 is a block diagram of an isolated bus-powered communication system;

Figure 2 is a block diagram of the communication module;

Fig. 3 is a circuit example of a specific power supply module;

Fig. 4 is a kind of circuit example of concrete communication module;

Figure 5 is a timing diagram for transmitting one bit of data on the bus.

Specific implementation method

Further illustrate the present invention below in conjunction with accompanying drawing

Referring to Fig. 1 and Fig. 2, the isolated bus-powered communication system of the present invention includes a power supply module 1 and N communication modules 2 connected to the power supply/communication bus, and N is at least 2, wherein:

The power module 1 includes a power switch circuit 3 and a switch control circuit 4, the input terminal of the power switch circuit 3 is connected to the power supply, the output terminal is connected to the power supply/communication bus, and the switch control circuit 4 is connected to the power switch circuit 3;

The communication module 2 includes an isolation transformer 5, a rectification and voltage stabilization circuit 6, a data transmission circuit 7, a data reception circuit 8, and a communication control circuit 9. The primary winding of the isolation transformer 5 is connected to the power supply/communication bus, and the secondary winding of the isolation transformer 5 Respectively connected to the input end of the rectification voltage stabilizing circuit 6, the input end of the data receiving circuit 8 and the output end of the data sending circuit 7, the input end of the data sending circuit 7 is connected with the data sending end of the communication control circuit 9, and the data receiving circuit 8 The output end of the communication control circuit 9 is connected to the data receiving end, and the output end of the rectification and voltage stabilization circuit 6 provides power to the data sending circuit 7, the data receiving circuit 8 and the communication control circuit 9.

Fig. 3 is a circuit example of a specific power supply module. In this example, the power switch circuit 3 is a full-bridge inverter circuit composed of power MOS transistors T1, T2, T3, and T4. The switch control circuit 4 consists of a microcontroller U2 and The driver U1 of the power MOS tube is composed of the driver U1 of the power MOS tube. Here, the driver U1 of the power MOS tube adopts the chip IR2110, and the control gate of the power MOS tube of the full-bridge inverter circuit is connected with the output terminal of the chip IR2110. The power switch circuit 3 can also adopt a full-bridge inverter circuit, a half-bridge inverter circuit, a forward circuit, a dual-tube forward circuit, a push-pull circuit, a flyback circuit or a resonant inverter circuit composed of other power devices.

Fig. 4 is a circuit example of a specific communication module. Here, the rectification and voltage stabilization circuit 6 is a full-wave rectification and voltage stabilization circuit composed of diodes D1, D2, D3, D4, capacitors C1, C2 and voltage stabilization chip U3. , a rectifying voltage stabilizing circuit or a half-wave rectifying voltage stabilizing circuit can also be used. The rectifying and stabilizing circuit 6 supplies power to the data transmitting circuit 7 , the data receiving circuit 8 and the communication control circuit 9 . The data sending circuit 7 is composed of triodes T5, T6, T7, T8 and a driving circuit U4, the output end of the driving circuit U4 is connected to the bases of the triodes T5, T6, T7, T8, here the triodes T5, T6, T7 , T8 can be replaced by MOSFET. Data receiving circuit 8 is a single-ended comparator circuit composed of voltage dividing resistors R1, R2, comparator U5 and reference voltage source Vref. The output of reference voltage source Vref is connected to the negative terminal of comparator U5. After voltage dividing by resistors R1 and R2 The output is connected to the positive end of the comparator U5; the data receiving circuit 8 may also use a differential comparison circuit. In this example, the communication control circuit 9 is implemented by programming a microprocessor MCU, or it can also be implemented by a CPLD/FPGA chip or other hardware circuits.

Figure 5 is a timing diagram for transmitting one bit of data on the bus. Its transmission process includes 4 stages: positive power supply stage T1, negative power supply stage T2, magnetic reset stage T3 and data communication stage T4.

When the system is working, after the external DC power is input to the power switch circuit 3 of the power module 1, the output waveform is shown in Figure 5 through the adjustment of the switch control circuit 4. In the time period T1, the power switch circuit 3 of the power module 1 outputs a positive voltage to supply power to all communication modules 2 . In the time period T2, the power switch circuit 3 of the power module 1 generates a negative voltage. The purpose of generating the negative voltage is to make the average voltage of the bus in the time period T1 and T2 close to zero, and prevent the isolation transformer 5 in the communication module 2 from generating DC magnetization. As a result, the power switch circuit 3 can also supply power to the communication module 2 during the time period T2. During time periods T3 and T4, the power switch circuit 3 of the power module 1 does not output power. The magnetizing current of the isolation transformer 5 is completely reset during the time period T3. In the time period T4, one bit of data transmission is performed between N communication modules 2, and the transmission principle is as follows: the data receiving circuit 8 converts the output voltage of the isolation transformer 5 into a logic level signal that can be recognized by the digital circuit, and inputs it to the communication module 2. control circuit 9. The communication control circuit 9 can determine whether the bus state is "logic 0" or "logic 1" according to the level status of the data receiving end within the time period T4. When the communication module 2 sends data 0, the data sending circuit 7 is controlled to feed power to the bus through the isolation transformer 5 within the T4 time period, so that the bus is in a "logic 0" state, thereby realizing the process of sending data.

Claims (3)

1. An isolated bus-powered communication system is characterized in that it comprises a power supply module (1) and N communication modules (2) connected to the power supply/communication bus, and N is at least 2, wherein: The power module (1) includes a power switch circuit (3) and a switch control circuit (4), the input terminal of the power switch circuit (3) is connected to the power supply, the output terminal is connected to the power supply/communication bus, and the switch control circuit (4) is connected to the power switch The circuit (3) is connected; The communication module (2) includes an isolation transformer (5), a rectification and voltage stabilization circuit (6), a data transmission circuit (7), a data reception circuit (8) and a communication control circuit (9), and the primary side winding of the isolation transformer (5) Connected to the power supply/communication bus, the secondary winding of the isolation transformer (5) is respectively connected to the input end of the rectification and voltage stabilization circuit (6), the input end of the data receiving circuit (8) and the output end of the data sending circuit (7), The input end of the data sending circuit (7) is connected with the data sending end of the communication control circuit (9), the output end of the data receiving circuit (8) is connected with the data receiving end of the communication control circuit (9), and the rectification and voltage stabilization circuit (6 ) provides power to the data sending circuit (7), data receiving circuit (8) and communication control circuit (9); the transmission of each data bit on the power supply/communication bus of the communication module (2) includes 4 Stages: positive power supply stage, negative power supply stage, magnetic reset stage and data communication stage; in the positive power supply stage, the power switch circuit (3) of the power supply module (1) outputs a positive voltage to supply power to all communication modules (2); In the negative power supply stage, the power switch circuit (3) of the power supply module (1) generates a negative voltage, so that the average voltage of the bus in the positive power supply stage and the negative power supply stage is close to zero, preventing the isolation transformer (5) in the communication module (2) from Generate a DC magnetization effect; in the magnetic reset phase and the data communication phase, the power switch circuit (3) of the power supply module (1) does not output power, and the magnetizing current of the isolation transformer (5) is completely reset in the magnetic reset phase, and in the data communication phase , performing one-bit data transmission among the N communication modules (2). 2. The isolated bus-powered communication system according to claim 1, characterized in that the power switch circuit (3) of the power supply module (1) is a full-bridge inverter circuit, a half-bridge inverter circuit, a forward circuit, a push-pull circuit, flyback circuit or resonant inverter circuit. 3. The isolated bus-powered communication system according to claim 1, characterized in that the rectifying and stabilizing circuit (6) of the communication module (2) is a full-wave rectifying and stabilizing circuit or a half-wave rectifying and stabilizing circuit.

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