Isolated serial communication circuit based on transformer

Abstract

The utility model discloses an isolated serial port communication circuit based on a transformer, and relates to the technical field of isolated serial port communication. The device specifically comprises a power supply module, a main control circuit, a drive circuit of an isolation transformer, the isolation transformer, an electromagnetic transmission antenna, a signal receiving and amplifying circuit, a signal envelope detection and amplifying circuit, a signal amplitude comparison circuit, a serial port receiving circuit and an RS485 communication circuit. The isolation transformer driving circuit is driven through I / O push-pull output of the MCU module of the main control circuit, excitation signals are generated in the primary stage of the transformer, then the electromagnetic antenna is directly driven through the secondary coil of the transformer to transmit the signals, and meanwhile, the circuit can receive signals transmitted by other peripheral equipment with the same circuit. Not only can isolation communication requirements be met, but also a plurality of external instruments can be externally hung through a commonly used serial port, so that the device can be applied to more use scenes.

Description

Technical Field

[0001] The utility model relates to the technical field of isolated serial port communication, in particular to an isolated serial port communication circuit based on a transformer. Background Art

[0002] Serial port technology is an important data transmission technology. It can be used to transmit data bit by bit through data lines between different peripherals, between computer systems, or between peripherals and computer systems. At first, it was only used for data transmission between computers and external devices. With the development of technology, serial port technology has also been continuously developed. It has become an important data transmission technology and is widely used in data transmission between different peripherals, between computer systems, or between peripherals and computer systems. The development of serial port technology is mainly driven by the development of computer technology. With the development of computer technology, serial port technology has also been continuously developed, so that serial port technology can meet different application requirements and support different data transmission rates.

[0003] However, in some special application fields, such as the field of petroleum instrument communication, serial communication between different instruments cannot be carried out through direct data line connection, but requires signal isolation and transmission communication. Common serial port isolation methods mostly use optical couplers for front-end and back-end isolation communication, or special isolation chips for isolation communication, but most of them cannot meet the communication requirements of industries with special requirements, such as the oil field, especially the use requirements of harsh environments such as high temperature and high pressure. Utility Model Content

[0004] The utility model provides an isolated serial communication circuit based on a transformer, which solves the problem that the common serial isolation methods proposed in the above background technology mostly use optical couplers to perform front-end and rear-end isolation communications, or use special isolation chips and other means to perform isolation communications, and cannot be performed through a direct data line connection, and cannot meet the problems of industry fields with special requirements.

[0005] The utility model provides the following technical solutions: a transformer-based isolated serial communication circuit, comprising a power module, a main control circuit, a driving circuit of an isolation transformer, an isolation transformer, an electromagnetic transmission antenna, a signal receiving amplifier circuit, a signal envelope detection amplifier circuit, a signal amplitude comparison circuit, a serial port receiving circuit and an RS485 communication circuit, wherein the I / O output port of the main control circuit is connected to the driving circuit of the isolation transformer, the serial port receiving I / O of the MCU of the main control circuit is connected to the serial port receiving circuit, and the main control circuit is connected to the RS485 communication circuit; the primary port of the isolation transformer is connected to the driving circuit of the isolation transformer, and the secondary port of the isolation transformer is connected to the electromagnetic transmission antenna; the signal amplitude comparison circuit is connected to the serial port receiving circuit and the signal envelope detection amplifier circuit; the signal receiving amplifier circuit is connected to the primary port of the isolation transformer and the signal envelope detection amplifier circuit;

[0006] The driving circuit of the isolation transformer includes a first circuit connected to one end of the primary port of the isolation transformer and a second circuit connected to the other end of the primary port of the isolation transformer, the first circuit includes a capacitor C15, a resistor R34 and a transistor Q1 connected in sequence, a grounding resistor R35 is provided between the resistor R34 and the transistor Q1, and the second circuit includes a capacitor C19, a resistor R39 and a transistor Q2 connected in sequence, a grounding resistor R37 is provided between the resistor R39 and the transistor Q2;

[0007] The signal receiving amplifier circuit includes a multi-stage operational amplifier with high unity gain bandwidth, high DC voltage gain and high slew rate; the signal envelope detection amplifier circuit includes a capacitor C24, a diode 1N4148, a current limiting resistor R52 and a capacitor C25, and a resistor R54 and a resistor R48 are arranged between the capacitor C24 and the diode 1N4148, the other end of the resistor R54 is grounded, and the other end of the resistor R48 is connected to the power module; the signal amplitude comparison circuit includes a dual-channel standard comparator.

[0008] Preferably, the power input end of the main control circuit, the power input end of the driving circuit of the isolation transformer, the power input end of the signal receiving amplifier circuit, the power input end of the signal envelope detection amplifier circuit, the power input end of the signal amplitude comparison circuit, the power input end of the serial port receiving circuit and the power input end of the RS485 communication circuit are all connected to the power module.

[0009] Preferably, the amplification factors of each stage of the operational amplifier of the signal receiving and amplifying circuit may be different.

[0010] Preferably, the dual-channel standard comparator has high performance characteristics such as low input offset voltage, low input bias current, low input current, etc., and can also output a level compatible with TTL, MOS and CMOS.

[0011] Preferably, the main control circuit includes a processor with a multi-channel serial port communication function.

[0012] Preferably, the capacitor C24 is connected to the second-stage amplification output terminal of the signal receiving amplification circuit, and one end of the capacitor C25 is grounded.

[0013] Preferably, the transistor Q1 and the transistor Q2 are both NPN type.

[0014] Compared with the prior art, the utility model has the following beneficial effects:

[0015] 1. The transformer-based isolated serial communication circuit generates a push-pull signal through the I / O port of the MCU in the main control circuit. The push-pull signal drives the driving circuit of the isolation transformer. The isolation transformer generates an electromagnetic wave signal that can be transmitted wirelessly for data isolation and transmission. The signal receiving amplifier circuit, the signal envelope detection amplifier circuit, and the signal amplitude comparison circuit can amplify, shape, and compare the isolated wireless electromagnetic signals sent by other circuits, so as to convert the transmission signal into a signal feature that conforms to the serial communication protocol. The main control circuit then packages the data as required and sends it to other terminals or host computers. This not only meets the requirements of isolated communication, but also allows a variety of peripheral instruments to be plugged in through the commonly used serial port, so that it can be applied to more usage scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The utility model provides a driving circuit of an isolation transformer for an isolated serial communication circuit based on a transformer and a schematic diagram of the isolation transformer;

[0017] Figure 2 This is a schematic diagram of a signal receiving and amplifying circuit of a transformer-based isolated serial communication circuit proposed by the utility model;

[0018] Figure 3 This is a schematic diagram of a signal envelope detection and amplification circuit of a transformer-based isolated serial communication circuit proposed by the utility model;

[0019] Figure 4 The present invention provides a schematic diagram of a signal amplitude comparison circuit and a serial port receiving circuit of a transformer-based isolated serial port communication circuit;

[0020] Figure 5 The utility model provides a schematic diagram of an RS485 communication circuit of an isolated serial communication circuit based on a transformer;

[0021] Figure 6This is a schematic diagram of a main control circuit of a transformer-based isolated serial communication circuit proposed by the utility model;

[0022] Figure 7 This is a schematic diagram of a power supply circuit of a transformer-based isolated serial communication circuit proposed by the utility model;

[0023] Figure 8 It is a schematic diagram of the connection between the driving circuit of the isolation transformer and the isolation transformer, the signal receiving amplifier circuit and the signal envelope detection amplifier circuit;

[0024] Fig. 9 This is a principle block diagram of a transformer-based isolated serial communication circuit proposed by the utility model. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] Embodiment 1

[0027] A transformer-based isolated serial communication circuit, including a power module, a main control circuit, an isolation transformer drive circuit, an isolation transformer, an electromagnetic transmission antenna, a signal receiving amplifier circuit, a signal envelope detection amplifier circuit, a signal amplitude comparison circuit, a serial receiving circuit, and an RS485 communication circuit. Fig. 9 As shown;

[0028] The power input end of the main control circuit, the power input end of the driving circuit of the isolation transformer, the power input end of the signal receiving amplifier circuit, the power input end of the signal envelope detection amplifier circuit, the power input end of the signal amplitude comparison circuit, the power input end of the serial port receiving circuit and the power input end of the RS485 communication circuit are all connected to the power module, the main control circuit is connected to the driving circuit of the isolation transformer, the serial port receiving circuit and the RS485 communication circuit, the driving circuit of the isolation transformer is connected to the I / O output port of the main control circuit and the primary port of the isolation transformer, the secondary port of the isolation transformer is connected to the electromagnetic transmission antenna and the primary port signal receiving and amplifying circuit, the serial port receiving circuit is connected to the serial port receiving I / O of the MCU of the main control circuit and the signal amplitude comparison circuit, the signal amplitude comparison circuit is connected to the serial port receiving circuit and the signal envelope detection amplifier circuit, the signal envelope detection amplifier circuit is connected to the signal amplitude comparison circuit and the signal receiving amplifier circuit, and the signal receiving amplifier circuit is connected to the primary port of the isolation transformer and the signal envelope detection amplifier circuit;

[0029] The main control circuit transmits the data signal through the isolation transformer drive circuit, isolation transformer and electromagnetic transmission antenna. The main control circuit also organizes and packages the received data signals that meet the serial port protocol according to the requirements through the serial port receiving circuit. The RS485 communication circuit is used to send the processed data to other terminals or host computers for data display. At the same time, this RS485 communication circuit can also receive data transmitted to the main control by other terminals or host computers, and then the main control circuit drives the isolation transformer to transmit the signal.

[0030] The signal receiving and amplifying circuit is used to amplify the received weak isolated transmission signal, the signal envelope detection circuit is used to complete the envelope detection processing of the amplitude modulated signal, and the signal amplitude comparison circuit is used to convert the signal after envelope detection processing into a TTL level that can meet the serial communication protocol.

[0031] like Figure 1 As shown, Figure 1 The invention relates to a driving circuit of an isolation transformer of a signal transmitting circuit and an isolation transformer, and generates an excitation signal source for a primary port of the isolation transformer through the driving circuit of the isolation transformer.

[0032] The driving mode of the isolation transformer driving circuit is that the I / O of the MCU of the main control circuit directly drives the 2-way transistor push-pull circuit to generate the excitation signal source of the primary of the isolation transformer. The isolation transformer transmits the excitation signal generated by the isolation transformer driving circuit to the secondary of the transformer through electromagnetic induction, and then the secondary of the transformer directly drives the electromagnetic transmission antenna for signal isolation transmission.

[0033] The driving circuit of the isolation transformer includes a first circuit connected to one end of the primary port of the isolation transformer and a second circuit connected to the other end of the primary port of the isolation transformer, the first circuit includes a capacitor C15, a resistor R34 and a transistor Q1 connected in sequence, a grounding resistor R35 is provided between the resistor R34 and the transistor Q1, the second circuit includes a capacitor C19, a resistor R39 and a transistor Q2 connected in sequence, a grounding resistor R37 is provided between the resistor R39 and the transistor Q2, and both the transistor Q1 and the transistor Q2 are NPN type.

[0034] like Figure 5 As shown, Figure 5This is the schematic diagram of the RS485 communication circuit. The RS485 communication circuit exchanges data with other terminals or host computers through the RS485 communication bus. The RS485 communication circuit can be used to send processed data to other terminals or host computers for data display. At the same time, this RS485 communication circuit can also receive data transmitted to the main control by other terminals or host computers, and then the main control circuit drives the isolation transformer to transmit the signal for isolated communication.

[0035] like Figure 6 As shown, Figure 6 This is the schematic diagram of the main control circuit. The I / O port of the MCU in the main control circuit generates a push-pull signal of the frequency required for the transmission signal. The push-pull signal drives the drive circuit of the isolation transformer. The isolation transformer generates an electromagnetic wave signal that can be transmitted wirelessly for data isolation and transmission. At the same time, the main control circuit also organizes and packages the serial port signal data transmitted by the receiving circuit.

[0036] like Figure 7 As shown, Figure 7 This is the schematic diagram of the power supply circuit, which provides power to the signal transmitting circuit, signal receiving circuit, CPU and other circuits.

[0037] like Figure 8 As shown, Figure 8 The present invention is a schematic diagram of the connection between the driving circuit of the isolation transformer, the isolation transformer, the signal receiving amplifying circuit and the signal envelope detection amplifying circuit. The isolation transformer transmits the excitation signal generated by the isolation transformer driving circuit to the secondary port of the transformer by electromagnetic induction, and then the secondary port of the isolation transformer directly drives the electromagnetic transmission antenna to perform signal isolation transmission. The signal receiving amplifying circuit amplifies the received weak isolation transmission signal. During the signal amplification process, the signal envelope detection circuit performs envelope detection processing on the amplitude modulated signal.

[0038] like Fig. 9 As shown, Fig. 9 This is a schematic diagram of a transformer-based isolated serial communication circuit proposed in this application.

[0039] The transformer-based isolated serial communication circuit of the utility model is applied to a special use environment where serial communication is required but direct data line connection communication cannot be used.

[0040] Embodiment 2

[0041] See attached Figure 2Based on the first embodiment, the signal receiving amplifier circuit is composed of two stages of NE5532 operational amplifiers with high unity gain bandwidth, high DC voltage gain and high slew rate. The signal receiving amplifier circuit is composed of multiple such operational amplifiers to form multi-stage amplification so as to meet the requirements of the signal amplitude required at each stage. After the sampling signal is amplified by the multi-stage signal amplifier circuit, the signal envelope detection circuit and the signal amplitude comparison circuit convert the signal into a standard TTL signal and transmit it to the serial port receiving I / O of the main control circuit. Figure 2 As shown in the figure, it is a signal receiving and amplifying circuit, which is suitable for amplifying and transmitting small signal amplitudes. According to the requirements of each node for different signal amplitudes, the amplification factor of each operational amplifier is different. The amplification factor of each level can be calculated according to the amplification factor formula of the operational amplifier (common-phase amplification formula: Vout = (1 + Rf / R1) * Vin, reverse-phase amplification formula: Vout = - (Rf / R1) * Vin). After the second-stage amplification output, the useful signal in the amplitude modulated signal is demodulated by the signal envelope detection circuit, and then enters the signal amplitude comparison circuit through the third-stage amplification circuit. The LM193 in the signal amplitude comparison circuit generates a pulse interval level signal that meets the baud rate of the serial communication protocol, and then is converted into a +3.3V TTL level of the serial communication protocol through the serial receiving circuit, and finally transmitted to the serial receiving I / O of the main control circuit for data sorting and packaging processing.

[0042] Embodiment 3

[0043] See attached Figure 3 Based on the first embodiment, the signal envelope detection circuit performs detection processing on the amplified amplitude modulated signal, such as Figure 3As shown, the signal envelope detection amplifier circuit includes a capacitor C24, a diode 1N4148, a current limiting resistor R52 and a capacitor C25. A resistor R54 and a resistor R48 are arranged between the capacitor C24 and the diode 1N4148. The other end of the resistor R54 is grounded, and the other end of the resistor R48 is connected to the power module. The capacitor C24 is connected to the second-stage amplification output end of the signal receiving amplifier circuit. One end of the capacitor C25 is grounded. The main principle is that when the signal is greater than the conduction voltage of the diode 1N4148, the diode 1N4148 is turned on. At this time, the capacitor C is charged through the current limiting resistor R. When the signal amplitude is less than the conduction voltage of the diode 1N4148, the capacitor C is charged through the current limiting resistor R. When the voltage is applied, the capacitor will discharge, but because the signal frequency is greater than the charging and discharging cycle of the capacitor, the charging and discharging time of the capacitor can be calculated by the formula t=RC. The discharge time of the capacitor is much shorter than the charging time. After the charging and discharging process is cyclically repeated, the useful signal is successfully extracted, and then amplified by the third-stage operational amplifier NE5532, and then the LM193 in the signal amplitude comparison circuit generates a pulse interval level signal that meets the baud rate of the serial communication protocol, and then converted into the TTL level of the +3.3V serial communication protocol through the serial port receiving circuit, and finally transmitted to the serial port receiving I / O of the main control circuit for data sorting and packaging processing.

[0044] Embodiment 4

[0045] See attached Figure 4 Based on the first embodiment, the signal amplitude comparison circuit processes the waveform output by the envelope detection circuit again so that the signal can meet the level requirements of the serial communication protocol. Figure 4 As shown in the figure, it is a signal amplitude comparison circuit, which compares two voltages through LM193 and then outputs the required corresponding voltage signal. The voltage threshold setting of the comparator LM193 can be calculated according to the voltage divider formula: V = (Vin*R1) / (R2+R1). After the signal output by the pre-stage envelope detection circuit and the third-stage operational amplifier circuit enters the comparator LM193, it can be seen from the schematic diagram that when the signal amplitude is greater than the voltage threshold set by the comparison circuit, the comparison circuit will output a low-level signal. If the signal amplitude does not exceed the voltage threshold set by the comparison circuit, the comparison circuit will output a high-level signal, which is then converted to the +3.3V TTL level of the serial communication protocol through the serial port receiving circuit, and finally transmitted to the serial port receiving I / O of the main control circuit for data sorting and packaging processing.

[0046] In summary, the utility model transformer-based isolated serial communication circuit drives the isolation transformer driving circuit through the I / O push-pull output of the MCU module of the main control circuit, generates an excitation signal at the primary of the transformer, and then directly drives the electromagnetic antenna to transmit the signal through the secondary coil of the transformer; at the same time, this circuit can receive signals transmitted by other peripheral devices with the same circuit, and transmit the received signal to the signal receiving amplifier circuit, the envelope detection amplifier circuit, and the signal amplitude comparison circuit, and then convert the effective signal into a signal that complies with the serial communication protocol and transmit it to the serial receiving I / O of the MCU of the main control circuit, and finally display the corresponding data according to the user's requirements. This circuit can be widely used in special fields where the front-end and rear-end equipment cannot directly use cables to connect and communicate.

[0047] The above are only preferred specific implementation methods of the utility model, but the protection scope of the utility model is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the utility model, who makes equivalent replacements or changes based on the technical scheme and utility model concept of the utility model, should be covered by the protection scope of the utility model.

Claims

1. A transformer-based isolated serial communication circuit, comprising a power module, a main control circuit, a driving circuit of an isolation transformer, an isolation transformer, an electromagnetic transmission antenna, a signal receiving amplifier circuit, a signal envelope detection amplifier circuit, a signal amplitude comparison circuit, a serial port receiving circuit and an RS485 communication circuit, characterized in that: The I / O output port of the main control circuit is connected to the driving circuit of the isolation transformer, the serial port receiving I / O of the MCU of the main control circuit is connected to the serial port receiving circuit, and the main control circuit is connected to the RS485 communication circuit; the primary port of the isolation transformer is connected to the driving circuit of the isolation transformer, and the secondary port of the isolation transformer is connected to the electromagnetic transmission antenna; the signal amplitude comparison circuit is connected to the serial port receiving circuit and the signal envelope detection amplifier circuit; the signal receiving amplifier circuit is connected to the primary port of the isolation transformer and the signal envelope detection amplifier circuit; The driving circuit of the isolation transformer includes a first circuit connected to one end of the primary port of the isolation transformer and a second circuit connected to the other end of the primary port of the isolation transformer, the first circuit includes a capacitor C15, a resistor R34 and a transistor Q1 connected in sequence, a grounding resistor R35 is provided between the resistor R34 and the transistor Q1, and the second circuit includes a capacitor C19, a resistor R39 and a transistor Q2 connected in sequence, a grounding resistor R37 is provided between the resistor R39 and the transistor Q2; The signal receiving amplifier circuit includes a multi-stage operational amplifier with high unity gain bandwidth, high DC voltage gain and high slew rate; the signal envelope detection amplifier circuit includes a capacitor C24, a diode 1N4148, a current limiting resistor R52 and a capacitor C25, and a resistor R54 and a resistor R48 are arranged between the capacitor C24 and the diode 1N4148, the other end of the resistor R54 is grounded, and the other end of the resistor R48 is connected to the power module; the signal amplitude comparison circuit includes a dual-channel standard comparator.

2. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The power input end of the main control circuit, the power input end of the driving circuit of the isolation transformer, the power input end of the signal receiving amplifier circuit, the power input end of the signal envelope detection amplifier circuit, the power input end of the signal amplitude comparison circuit, the power input end of the serial port receiving circuit and the power input end of the RS485 communication circuit are all connected to the power module.

3. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The amplification factors of each stage of the operational amplifier of the signal receiving and amplifying circuit may be different.

4. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The dual-channel standard comparator has high-performance characteristics such as low input offset voltage, low input bias current, low input current, etc., and can also output a level compatible with TTL, MOS and CMOS.

5. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The main control circuit includes a processor with a multi-channel serial port communication function.

6. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The capacitor C24 is connected to the second stage amplification output terminal of the signal receiving amplification circuit, and one end of the capacitor C25 is grounded.

7. The transformer-based isolated serial communication circuit according to claim 1, characterized in that: The transistor Q1 and the transistor Q2 are both NPN type.

Images