Analog quantity output circuit, analog quantity output card and distributed control system

Abstract

The invention provides an analog quantity output circuit, an analog quantity output card and a decentralized control system. The analog quantity output circuit comprises a controller, a digital-to-analog converter, a first signal conversion circuit and a second signal conversion circuit, the input end of the digital-to-analog converter is connected with the output end of the controller, and different output ends of the digital-to-analog converter are respectively connected with the input ends of the first signal conversion circuit and the second signal conversion circuit; the first signal conversion circuit is used for converting a voltage signal output by the digital-to-analog converter into a target current signal, and the second signal conversion circuit is used for converting the voltage signal output by the digital-to-analog converter into a target voltage signal; a voltage signal and a current signal can be output through the circuit, the problem that the analog quantity output mode is single is solved, meanwhile, output of different analog quantities is achieved through different output ends of the digital-to-analog converter, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of DCS control, and in particular to an analog output circuit, an analog output card and a distributed control system. Background Art

[0002] The analog output structure in DCS (Distributed Control System) is: a current output circuit is built using the first operational amplifier, and the current is amplified using the second operational amplifier circuit after filtering, and then driven to drive the field equipment. The analog signal uses FPGA (Field-Programmable Gate Array) with software logic for signal demodulation and modulation.

[0003] At present, most analog output cards use a separate DAC chip and a separate ADC chip for each channel. Such a design circuit is complex, corresponds to a single requirement, and is costly. Summary of the invention

[0004] The technical problem to be solved by the present disclosure is to overcome the defects of single output mode and high cost of analog output cards in the prior art, and to provide an analog output circuit, an analog output card and a distributed control system.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] In a first aspect, an analog output circuit is provided, the analog output circuit comprising a controller, a digital-to-analog converter, a first signal conversion circuit and a second signal conversion circuit;

[0007] The input end of the digital-to-analog converter is connected to the output end of the controller, and different output ends of the digital-to-analog converter are respectively connected to the input ends of the first signal conversion circuit and the second signal conversion circuit;

[0008] The first signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target current signal, and the second signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target voltage signal.

[0009] Optionally, the first signal conversion circuit includes a first voltage follower circuit and a conversion circuit;

[0010] The input end of the first voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the first voltage follower circuit is connected to the input end of the conversion circuit, and the output end of the conversion circuit is used to connect to an external device.

[0011] Optionally, the second signal conversion circuit includes a second voltage follower circuit and a voltage amplifier circuit;

[0012] The input end of the second voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the second voltage follower circuit is connected to the input end of the voltage amplifier circuit, and the output end of the voltage amplifier circuit is used to connect to an external device.

[0013] Optionally, the analog output circuit further includes a selection circuit, an analog-to-digital converter and a plurality of recovery circuits; the selection circuit includes a plurality of switches, and the recovery circuits correspond to the switches one by one;

[0014] One end of each of the multiple switches is connected to the output end of the corresponding recovery circuit, and the other end of each of the multiple switches is connected to the input end of the digital-to-analog converter;

[0015] The sampling circuit is used to collect the voltage signal on the corresponding channel of the digital-to-analog converter;

[0016] The selection circuit is electrically connected to the controller, and the controller is used to switch different switches in sequence according to the sampling period;

[0017] The output end of the analog-to-digital converter is connected to the input end of the controller.

[0018] Optionally, the controller includes an FPGA chip and an MCU chip, and the FPGA chip is connected to the analog-to-digital converter, the digital-to-analog converter and the MCU chip respectively;

[0019] The MCU chip is used to send instructions to the digital-to-analog converter through the FPGA chip, and receive a feedback signal in response to the instruction output by the analog-to-digital converter through the FPGA chip;

[0020] The instruction is used to instruct the voltage signal converted by the digital-to-analog converter to be transmitted to the corresponding output terminal.

[0021] Optionally, the analog output circuit further includes a first protection circuit and a second protection circuit;

[0022] One end of the first protection circuit is connected to the output end of the first signal conversion circuit, and the other end of the protection circuit is used to connect to an external device;

[0023] One end of the second protection circuit is connected to the output end of the second signal conversion circuit, and the other end of the protection circuit is used to connect to the external device.

[0024] Optionally, the analog output circuit further includes a first isolation circuit, which is connected in series between the controller and the analog-to-digital converter.

[0025] Optionally, the analog output circuit further includes a second isolation circuit, and the second isolation circuit is connected in series between the controller and the digital-to-analog converter.

[0026] In a second aspect, an analog output card is provided, wherein the analog output card comprises the analog output circuit as described in the first aspect.

[0027] In a third aspect, a distributed control system is provided, wherein the distributed control system includes the analog output card as described in the second aspect.

[0028] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0029] The positive and progressive effects of the present disclosure are: the output end of the controller is connected through the input end of the digital-to-analog converter, and different output ends of the digital-to-analog converter are respectively connected to the input ends of the first signal conversion circuit and the second signal conversion circuit; the first signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target current signal, and the second signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target voltage signal; the analog output circuit can output voltage signals and current signals at the same time, which solves the problem of a single analog output mode, and at the same time realizes the output of different analog quantities through different output ends of a digital-to-analog converter, reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of an analog output circuit provided in Embodiment 1 of the present disclosure;

[0031] Figure 2 A schematic diagram of another analog output circuit provided in Embodiment 1 of the present disclosure;

[0032] Figure 3 A schematic diagram of another analog output circuit provided in Embodiment 1 of the present disclosure;

[0033] Figure 4 A schematic diagram of another analog output circuit provided in Embodiment 1 of the present disclosure;

[0034] Figure 5 A schematic diagram of another analog output circuit provided in Embodiment 1 of the present disclosure;

[0035] Figure 6 A schematic diagram of another analog output circuit provided in Embodiment 1 of the present disclosure;

[0036] Figure 7A schematic diagram of an analog output circuit provided in Example 2 of the present disclosure. DETAILED DESCRIPTION

[0037] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0038] Prefixes such as "first" and "second" are used in the embodiments of the present disclosure only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present disclosure does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes. In addition, in the description of the present embodiment, unless otherwise specified, the meaning of "plurality" is two or more.

[0039] Example 1

[0040] Figure 1 This is a schematic diagram of an analog output circuit provided in this embodiment. The analog output circuit 100 includes a controller 101 , a digital-to-analog converter 102 , a first signal conversion circuit 103 and a second signal conversion circuit 104 .

[0041] The input end of the digital-to-analog converter 102 is connected to the output end of the controller 101, and different output ends of the digital-to-analog converter 102 are respectively connected to the input ends of the first signal conversion circuit 103 and the second signal conversion circuit 104; the first signal conversion circuit 103 is used to convert the voltage signal output by the digital-to-analog converter 102 into a target current signal, and the second signal conversion circuit 104 is used to convert the voltage signal output by the digital-to-analog converter 102 into a target voltage signal.

[0042] In this embodiment, the analog output circuit can output voltage signals and current signals at the same time, solving the problem of a single analog output mode. At the same time, different analog outputs are achieved through different output ends of a digital-to-analog converter, reducing the complexity of the circuit and reducing the manufacturing cost.

[0043] In a specific example, the digital-to-analog converter can use a power-supply DAC chip, such as the SGM71612R81 chip. The digital-to-analog converter can use SPI (Serial Peripheral Interface, serial peripheral interface) or IIC (Inter-Integrated Circuit, also known as I2C) signals to exchange data with the controller and external devices.

[0044] In an optional embodiment, Figure 2As shown, the first signal conversion circuit 103 includes a first voltage follower circuit 31 and a conversion circuit 32; the input end of the first voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the first voltage follower circuit is connected to the input end of the conversion circuit, and the output end of the conversion circuit is used to connect to an external device.

[0045] In this embodiment, the first voltage follower circuit has a high input impedance and a low output impedance, which enables the voltage signal output by the digital-to-analog converter to closely follow the input voltage without almost changing its amplitude. Such a circuit is usually used to isolate a signal source and a load, preventing the load from affecting the signal source, while allowing the signal to be transmitted between different circuit parts without loss or distortion.

[0046] In this embodiment, the conversion circuit is a voltage-current conversion circuit, which is used to convert an input voltage signal into a target current signal, and the target current signal is usually 4-20 mA.

[0047] In an optional embodiment, Figure 2 As shown, the second signal conversion circuit 104 includes a second voltage follower circuit 41 and a voltage amplifier circuit 42; the input end of the second voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the second voltage follower circuit is connected to the input end of the voltage amplifier circuit, and the output end of the voltage amplifier circuit is used to connect to the external device.

[0048] In this embodiment, the voltage amplifier circuit increases the amplitude of the input voltage signal to a higher level, and the output target voltage signal is usually 0 to 10 V. Among them, the operational amplifier is a common amplification element in the voltage amplifier circuit, and can be configured as a non-inverting amplifier or an inverting amplifier to achieve the required gain.

[0049] In an optional embodiment, Figure 3 As shown, the analog output circuit 100 further includes a selection circuit 106, an analog-to-digital converter 107 and a plurality of recovery circuits 108; the selection circuit includes a plurality of switches, and the recovery circuits correspond to the switches one by one.

[0050] One end of the multiple switches is respectively connected to the output end of the corresponding recovery circuit 108, and the other end of the multiple switches is connected to the input end of the digital-to-analog converter 102; the recovery circuit 108 is used to collect the voltage signal on the corresponding channel of the digital-to-analog converter 102; the selection circuit 106 is electrically connected to the controller 101, and the controller is used to switch different switches in sequence according to the sampling period; the output end of the analog-to-digital converter 107 is connected to the input end of the controller 101.

[0051] In this embodiment, the sampling circuit is used to collect the voltage signal on the corresponding channel of the digital-to-analog converter, and the selection circuit, i.e., the multi-way selection circuit, selects multiple sampling circuits in the form of switches. In a specific example, the input end of the sampling circuit can be connected to the output end of the first voltage follower circuit, or connected to the output end of the second voltage follower circuit. The voltage follower circuit, also known as the buffer circuit, has the main function of faithfully copying the voltage waveform of the input signal to the output end to ensure that the signal will not be attenuated or distorted due to impedance mismatch during transmission.

[0052] In practical applications, the voltage signal output by the digital-to-analog converter is usually divided, that is, the analog output circuit also includes a voltage divider circuit, one end of the first voltage divider circuit is connected to the output end of the digital-to-analog converter, and the other end of the voltage divider circuit is connected to the input end of the first signal conversion circuit or the second signal conversion circuit, and the sampling circuit is used to collect the voltage signal output after passing through the first voltage follower circuit or the second voltage follower circuit.

[0053] In a specific example, the digital-to-analog converter may use an eight-channel DAC chip, the analog-to-digital converter may use an eight-channel ADC chip, and the selection circuit is an eight-in-one switching switch, which may use an SGM4518XTS16G chip. Each channel of the DAC chip may be connected to a first signal conversion circuit or a second signal conversion circuit.

[0054] For example, the first four channels of the DAC chip are respectively connected to a first signal conversion circuit, and the last four channels are respectively connected to a second signal conversion circuit. The controller outputs the digital signal to be output through the specified channel to the corresponding first signal conversion circuit or the second signal conversion circuit through instructions. Specifically, the first signal conversion circuit converts the input voltage signal into a target current signal and transmits it to the target circuit, and the second signal conversion circuit converts the input voltage signal into a target voltage signal and transmits it to the target circuit. At the same time, under the control of the controller, each switch of the eight-in-one switching switch is closed in sequence according to the cycle, so that the voltage signal collected by the corresponding sampling circuit is transmitted to the ADC chip in sequence according to the cycle, and the ADC chip performs analog-to-digital conversion on the received voltage signal and transmits the feedback signal obtained after the conversion to the controller.

[0055] In an optional embodiment, Figure 4 As shown, the controller 101 includes an FPGA chip 11 and an MCU chip 12, and the FPGA chip is connected to the analog-to-digital converter, the digital-to-analog converter and the MCU chip respectively.

[0056] The MCU chip is used to send instructions to the digital-to-analog converter through the FPGA chip, and to receive a feedback signal output by the analog-to-digital converter in response to the instruction through the FPGA chip; wherein the instruction is used to instruct the voltage signal converted by the digital-to-analog converter to be transmitted to the corresponding output terminal.

[0057] In this embodiment, by realizing the function of the analog output circuit to output voltage signal and current signal at the same time, the problem of single analog output mode is solved. At the same time, the MCU chip receives the feedback signal output by the analog-to-digital converter in response to the instruction through the FPGA chip.

[0058] In an optional embodiment, Figure 5 As shown, the analog output circuit further includes a first protection circuit 109 and a second protection circuit 110 .

[0059] One end of the first protection circuit is connected to the output end of the first signal conversion circuit, and the other end of the protection circuit is used to connect to the external device; one end of the second protection circuit is connected to the output end of the second signal conversion circuit, and the other end of the protection circuit is used to connect to the external device.

[0060] In this embodiment, each channel of the digital-to-analog converter corresponds to a protection circuit for realizing protection functions such as electrostatic protection, misconnection protection, surge protection, etc. Among them, the required protection type, such as overvoltage protection, overcurrent protection, electrostatic discharge protection, etc., is determined according to the data sheet of the digital-to-analog converter and the application environment to ensure that the protection circuit can respond quickly under abnormal conditions and limit or eliminate damage to the digital-to-analog converter.

[0061] In an optional embodiment, Figure 6 As shown, the analog output circuit further includes a first isolation circuit 111, which is connected in series between the controller and the analog-to-digital converter.

[0062] In this embodiment, the first isolation circuit may include a photoelectric isolator, which can prevent problems such as power reverse and ground short circuit, thereby improving the safety and reliability of the entire circuit; since the photoelectric isolator uses optical isolation to transmit signals and does not require physical contact, it can also avoid damage to the equipment due to factors such as noise, looseness, and oxidation caused by contact; the photoelectric isolator also has good electrical insulation and anti-interference capabilities, and has strong common-mode suppression capabilities.

[0063] In an optional embodiment, Figure 6As shown, the analog output circuit further includes a second isolation circuit 112, which is connected in series between the controller and the digital-to-analog converter.

[0064] In this embodiment, the second isolation circuit may include a photoelectric isolator. After the analog-to-digital converter converts the collected analog signal into a digital signal, the signal is fed back to the controller through the photoelectric isolator.

[0065] In an optional embodiment, the analog output circuit also includes a power supply, which is used to power each device in the analog output circuit; wherein the power supply also includes a power conversion circuit, which is used to convert the power supply voltage into a voltage that meets the requirements of each device in the circuit to meet the power supply requirements of each device.

[0066] Example 2

[0067] This embodiment provides an analog output card component, and the analog output card component includes the analog output circuit as described in Embodiment 1.

[0068] The analog output card can output voltage signals and current signals at the same time through the analog output circuit, which solves the problem of single analog output mode, and realizes the output of different analog quantities through different output terminals of a digital-to-analog converter, thereby reducing the manufacturing cost. Furthermore, the feedback information in response to the instruction of the controller is transmitted to the controller through an analog-to-digital converter, thereby reducing the cost of the analog output card.

[0069] In this embodiment, in the production process of the analog output card, in order to facilitate production, the analog output card can be manufactured according to the following method: Figure 7 The circuit shown is manufactured, wherein the voltage follower circuit 201 is determined to be the first voltage follower circuit or the second voltage follower circuit by detecting whether the first resistor 202 and the second resistor 203 are installed. Specifically, when it is detected that the first resistor 202 has been installed and the second resistor 203 has not been installed, the voltage follower circuit 201 is connected to the conversion circuit 32 through the first resistor 202, so the circuit is used to output the target current signal; when it is detected that the first resistor 202 has not been installed and the second resistor 203 has been installed, the voltage follower circuit 201 is connected to the voltage amplifier circuit 42 through the second resistor 203, so the circuit is used to output the target voltage signal.

[0070] Example 3

[0071] This embodiment provides a distributed control system, which includes the analog output card as described in Embodiment 2.

[0072] A distributed control system is a computer control system used for industrial process control. It distributes control functions to multiple control nodes instead of concentrating them in a central control room. Distributed control systems connect various control nodes through a communication network to achieve real-time exchange and processing of data. Distributed control systems are widely used in process control in industries such as petroleum, chemical, electric power, water treatment, and food processing. It improves production efficiency, safety, and reliability by providing highly automated and optimized control strategies.

[0073] In an optional embodiment, the distributed control system further includes a host computer. After receiving the feedback information, the controller sends it to the host computer, and the host computer is used to send instructions to the controller. In a specific example, the host computer also provides a graphical user interface, allowing the user to monitor the status of the distributed control system, operate the equipment, and view reports. Specifically, the host computer can monitor the status of the distributed control system, trigger alarms and event responses, such as fault detection and exception handling.

[0074] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. An analog output circuit, characterized in that: The analog output circuit includes a controller, a digital-to-analog converter, a first signal conversion circuit and a second signal conversion circuit; The input end of the digital-to-analog converter is connected to the output end of the controller, and different output ends of the digital-to-analog converter are respectively connected to the input ends of the first signal conversion circuit and the second signal conversion circuit; The first signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target current signal, and the second signal conversion circuit is used to convert the voltage signal output by the digital-to-analog converter into a target voltage signal.

2. The analog output circuit according to claim 1, characterized in that: The first signal conversion circuit includes a first voltage follower circuit and a conversion circuit; The input end of the first voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the first voltage follower circuit is connected to the input end of the conversion circuit, and the output end of the conversion circuit is used to connect to an external device.

3. The analog output circuit according to claim 1, characterized in that: The second signal conversion circuit includes a second voltage follower circuit and a voltage amplifier circuit; The input end of the second voltage follower circuit is connected to the output end of the digital-to-analog converter, the output end of the second voltage follower circuit is connected to the input end of the voltage amplifier circuit, and the output end of the voltage amplifier circuit is used to connect to an external device.

4. The analog output circuit according to claim 1, characterized in that: The analog output circuit further includes a selection circuit, an analog-to-digital converter, and a plurality of recovery circuits; the selection circuit includes a plurality of switches, and the recovery circuits correspond to the switches one by one; One end of each of the multiple switches is connected to the output end of the corresponding recovery circuit, and the other end of each of the multiple switches is connected to the input end of the digital-to-analog converter; The sampling circuit is used to collect the voltage signal on the corresponding channel of the digital-to-analog converter; The selection circuit is electrically connected to the controller, and the controller is used to switch different switches in sequence according to the sampling period; The output end of the analog-to-digital converter is connected to the input end of the controller.

5. The analog output circuit according to claim 4, characterized in that: The controller includes an FPGA chip and an MCU chip, and the FPGA chip is connected to the analog-to-digital converter, the digital-to-analog converter and the MCU chip respectively; The MCU chip is used to send instructions to the digital-to-analog converter through the FPGA chip, and receive a feedback signal in response to the instruction output by the analog-to-digital converter through the FPGA chip; The instruction is used to instruct the voltage signal converted by the digital-to-analog converter to be transmitted to the corresponding output terminal.

6. The analog output circuit according to claim 5, characterized in that: The analog output circuit also includes a first protection circuit and a second protection circuit; One end of the first protection circuit is connected to the output end of the first signal conversion circuit, and the other end of the protection circuit is used to connect to an external device; One end of the second protection circuit is connected to the output end of the second signal conversion circuit, and the other end of the protection circuit is used to connect to the external device.

7. The analog output circuit according to claim 6, characterized in that: The analog output circuit further includes a first isolation circuit, which is connected in series between the controller and the analog-to-digital converter.

8. The analog output circuit according to claim 7, characterized in that: The analog output circuit further includes a second isolation circuit, which is connected in series between the controller and the digital-to-analog converter.

9. An analog output card, characterized in that: The analog output card comprises the analog output circuit as claimed in any one of claims 1 to 8.

10. A distributed control system, characterized in that: The distributed control system comprises the analog output card as claimed in claim 9.

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