PLC with AD and DA functions

Abstract

The utility model discloses a PLC with AD and DA functions, which relates to the technical field of PLCs and comprises an input unit and an output unit, the input unit comprises an AD converter and a plurality of analog quantity input subunits adaptively connected with the AD converter, analog input signals are transmitted to the AD converter through the analog quantity input subunits, and the AD converter is connected with the output unit through the analog quantity input subunits. The AD converter converts the signal into a digital output signal; the analog quantity input subunit comprises an input circuit, a first filtering protection circuit and a first voltage following circuit which are adaptively connected; the output unit comprises a DA converter and a plurality of voltage signal output subunits and / or a plurality of current signal output subunits which are adaptively connected with the DA converter, digital input signals are converted into analog output signals by the DA converter, and the analog output signals are output through the voltage signal output subunits and / or the current signal output subunits. The PLC can reduce the use cost and save the arrangement space of the conversion module.

Description

Technical Field

[0001] The utility model relates to the technical field of PLC, in particular to a PLC with AD and DA functions. Background Art

[0002] In the late 1990s, people gradually realized that traditional PLCs had some limitations and shortcomings, which became factors that restricted their development. Specifically, the shortcomings of traditional PLCs include: (1) It is difficult to build an open hardware architecture, which means that traditional PLCs lack flexibility in hardware design and are difficult to adapt to changing market demands and technological advances. (2) It requires long-term professional training to use. The programming method of traditional PLCs is relatively complex. Workers must undergo a long period of professional training to master the programming method of a certain product, which limits its ease of use and popularity. (3) The price-performance ratio is growing slowly. Due to the monopoly of PLC production by several manufacturers, there is insufficient market competition, and the price-performance ratio is growing slowly, which cannot meet users' pursuit of cost-effectiveness.

[0003] To address these issues, software PLC technology emerged. Software PLCs aim to overcome the shortcomings of traditional PLCs by providing a more flexible and open architecture, as well as easy-to-use programming methods. In particular, analog conversion is a key application of PLCs in automated control systems. It allows the PLC to receive and process analog signals from sensors, such as temperature, pressure, and flow, thereby enabling monitoring and control of production processes. This functionality relies on analog input modules, which convert analog signals into digital signals for easier processing, and analog output modules, which convert digital signals back into analog signals to control external devices. However, existing PLCs often implement analog-to-digital conversion functions through the use of dedicated modules, which increases costs and consumes considerable space. Utility Model Content

[0004] In response to the above problems and technical requirements, the inventors have proposed a PLC with AD and DA functions.

[0005] The technical solution of the utility model is as follows:

[0006] A PLC with AD and DA functions, comprising an input unit and an output unit, wherein the input unit comprises an AD converter and a plurality of analog input subunits adapted to be connected to the AD converter, wherein analog input signals are transmitted to the AD converter via the analog input subunits and converted into digital output signals by the AD converter; the analog input subunits comprise an adapted input circuit, a first filtering protection circuit, and a first voltage follower circuit;

[0007] The output unit includes a DA converter and several voltage signal output subunits and / or several current signal output subunits adapted to be connected to the DA converter. The digital input signal is converted into an analog output signal by the DA converter and output through the voltage signal output subunit and / or the current signal output subunit.

[0008] A further technical solution is that the input circuit includes a common mode choke L4 and a resistor R102, wherein:

[0009] The first output end of the common-mode choke L4 is connected to the first filter protection circuit, and one end of the resistor R102 is connected to the second output end of the common-mode choke L4 and the first filter protection circuit;

[0010] The other end of the resistor R102 forms a current input terminal, the first input terminal of the common mode choke coil L4 forms a voltage input terminal, and the second input terminal of the common mode choke coil L4 forms a common input terminal.

[0011] A further technical solution is that the first filtering protection circuit includes a capacitor C18, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C127, a capacitor C133, a resistor R20 and a resistor R24, wherein:

[0012] One end of the capacitor C34 is connected to the first output end of the common-mode choke L4 and one end of the capacitor C127, the other end of the capacitor C34 is connected to one end of the capacitor C18 and grounded, and the other end of the capacitor C18 is connected to one end of the resistor R102, the other end of the capacitor C127, and the second output end of the common-mode choke L4;

[0013] The capacitor C133 is connected in parallel with the capacitor C127, one end of the resistor R24 is connected to one end of the capacitor C133, and the other end of the resistor R24 is grounded through the capacitor C36, one end of the resistor R20 is connected to the other end of the capacitor C133, and the other end of the resistor R20 is grounded through the capacitor C35.

[0014] A further technical solution is that the first filtering protection circuit further includes a transient voltage suppressor D5, a transient voltage suppressor D6, a resistor R15 and a resistor R16, wherein:

[0015] A first end of the transient voltage suppressor D5 is connected to one end of the capacitor C36 and one end of the resistor R16, and a second end of the transient voltage suppressor D5 and the other end of the resistor R16 are both grounded; a first end of the transient voltage suppressor D6 is connected to one end of the capacitor C35 and one end of the resistor R15, and a second end of the transient voltage suppressor D6 and the other end of the resistor R15 are both grounded.

[0016] A further technical solution is that the first voltage follower circuit includes an operational amplifier U8, an operational amplifier U9, a resistor R1, a resistor R8, a capacitor C26, a capacitor C27, a magnetic bead B7 and a magnetic bead B8, wherein:

[0017] The non-inverting input terminal of the operational amplifier U8 is connected to one end of the resistor R16, and the inverting input terminal of the operational amplifier U8 is connected to the output terminal of the operational amplifier U8 through the resistor R1;

[0018] The positive power supply terminal of the operational amplifier U8 is grounded through the capacitor C27 and connected to the first power supply voltage through the magnetic bead B8; the negative power supply terminal of the operational amplifier U8 is grounded through the capacitor C26 and connected to the second power supply voltage through the magnetic bead B7;

[0019] The non-inverting input terminal of the operational amplifier U9 is connected to one end of the resistor R15, the inverting input terminal of the operational amplifier U9 is connected to the output terminal of the operational amplifier U9 through the resistor R8, and the output terminal of the operational amplifier U8 and the output terminal of the operational amplifier U9 are both connected to the AD converter.

[0020] Its further technical solution is that the voltage signal output subunit includes a second filtering protection circuit and a second voltage follower circuit, and the second voltage follower circuit includes an operational amplifier U4, a resistor R26, a capacitor C55, a capacitor C56, a capacitor C57, a magnetic bead B18 and a magnetic bead B19, wherein,

[0021] The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the operational amplifier U4 through the resistor R26, the capacitor C55 is connected in parallel with the resistor R26, and the negative power supply terminal of the operational amplifier U4 is grounded through the capacitor C56 and connected to the second power supply voltage through the magnetic bead B18;

[0022] The non-inverting input terminal of the operational amplifier U4 is connected to the output terminal of the DA converter, and the positive power supply terminal of the operational amplifier U4 is grounded through the capacitor C57 and connected to the second power supply voltage through the magnetic bead B19.

[0023] Its further technical solution is that the second filtering protection circuit includes capacitor C18, capacitor C19, capacitor C22, capacitor C54, capacitor C60, resistor R27, resistor R81, magnetic bead B20, magnetic bead B21 and transient voltage suppressor D13, wherein,

[0024] One end of the resistor R81 is connected to one end of the capacitor C18, one end of the capacitor C19, the non-inverting input end of the operational amplifier U4, and the output end of the DA converter, and the other ends of the resistor R81, the capacitor C18, and the capacitor C19 are all grounded;

[0025] One end of the capacitor C60 is connected to one end of the capacitor C54 and the output end of the operational amplifier U4 through a magnetic bead B21, and the other end of the capacitor C60 is connected to the other end of the capacitor C54 through a magnetic bead B20. The capacitor C22 is connected in parallel with the capacitor C54.

[0026] One end of the resistor R27 is connected to the output end of the operational amplifier U4, one end of the capacitor C22 and the second end of the transient voltage suppressor D13, and the other end of the resistor R27 and the first end of the transient voltage suppressor D13 are grounded.

[0027] A further technical solution is that the current signal output subunit includes a disconnection detection circuit and a third filtering protection circuit, and the disconnection detection circuit includes an operational amplifier U3, a resistor R4, a resistor R34, a resistor R35, a resistor R36, a resistor R37 and a switch device, wherein,

[0028] The non-inverting input terminal of the operational amplifier U3 is connected to one end of the resistor R36 and one end of the resistor R37, the other end of the resistor R36 is connected to the first power supply voltage, the other end of the resistor R37 is grounded, and the inverting input terminal of the operational amplifier U3 is connected to the first power supply voltage through the resistor R35;

[0029] The output end of the operational amplifier U3 is connected to one end of the resistor R4 and a first end of the switch device, the other end of the resistor R4 is connected to the first power supply voltage, the second end of the switch device is connected to one end of the resistor R34 and the MCU, and the third end of the switch device is grounded.

[0030] A further technical solution is that the switching device includes a MOSFET device.

[0031] A further technical solution is that the third filtering protection circuit includes a switching diode D4, a transient voltage suppressor D6, a resistor R38, a diode D16, a capacitor C8, a capacitor C9, a magnetic bead B3 and a magnetic bead B4, wherein:

[0032] One end of the capacitor C8 is connected to one end of the capacitor C9, the second end of the transient voltage suppressor D6, and the inverting input end of the operational amplifier U3 through a magnetic bead B3. The other end of the capacitor C8 is connected to the other end of the capacitor C9 through a magnetic bead B4. The other end of the capacitor C9 and the first end of the transient voltage suppressor D6 are grounded.

[0033] The anode of the diode D16 is connected to the third terminal of the switching diode D4 and the output terminal of the DA converter through the resistor R38, and the cathode of the diode D16 is connected to the inverting input terminal of the operational amplifier U3.

[0034] The beneficial technical effects of the utility model are:

[0035] This utility model provides a PLC with AD and DA functions, integrating analog-to-digital conversion functions within the PLC main unit, eliminating the need for a dedicated conversion module for digital-to-analog conversion. The provided input and output units have simple circuit structures and low production costs, reducing operational costs and conserving space for the conversion modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of an embodiment of the input unit provided by the present utility model.

[0037] Figure 2 This is a circuit principle diagram of an embodiment of the analog input subunit provided by the utility model.

[0038] Figure 3 It is a schematic diagram of an embodiment of the output unit provided by the utility model.

[0039] Figure 4 This is a circuit principle diagram of an embodiment of a voltage signal output subunit provided by the utility model.

[0040] Figure 5 This is a circuit principle diagram of an embodiment of the current signal output subunit provided by the utility model.

[0041] Figure 6 It is a schematic diagram of a PLC with AD and DA functions provided by the present invention. DETAILED DESCRIPTION

[0042] The specific implementation of the present utility model will be further described below with reference to the accompanying drawings.

[0043] The utility model provides a PLC with AD (Analog to Digital) and DA (Digital to Analog) functions, comprising an input unit and an output unit, wherein the input unit comprises an AD converter and a plurality of analog input subunits adapted to be connected to the AD converter, wherein an analog input signal is transmitted to the AD converter via the analog input subunit and converted into a digital output signal by the AD converter; the analog input subunit comprises an input circuit adapted to be connected, a first filtering protection circuit, and a first voltage follower circuit;

[0044] The output unit includes a DA converter and several voltage signal output subunits and / or several current signal output subunits adapted to be connected to the DA converter. The digital input signal is converted into an analog output signal by the DA converter and output through the voltage signal output subunit and / or the current signal output subunit.

[0045] Specifically, the analog input signal is an analog signal received by the PLC (Programmable Logic Controller) from the outside, such as temperature, pressure, flow, etc. detected by a sensor. The analog input signal is transmitted to the AD converter via the analog input subunit. The analog input signal can be a voltage input signal and / or a current input signal. The AD converter converts the analog input signal into a digital output signal. The digital output signal is processed by the processing unit inside the PLC to generate a control signal. The control signal is the digital input signal input to the output unit. The digital input signal is converted again by the DA converter into an analog output signal. The analog output signal includes a voltage output signal and / or a current output signal. The voltage output signal is output to an external device via the voltage signal output subunit, and the current output signal is output to an external device via the current signal output subunit. The specific form and connection method of the input circuit, the first filtering protection circuit, and the first voltage follower circuit in the analog input subunit can be referred to the following description. The form of the AD converter and the DA converter can be consistent with the existing technology.

[0046] In this embodiment, the input unit is provided with four analog input sub-units, and the AD converter is correspondingly provided with four input channels, such as Figure 1 As shown, the analog input subunits are connected one-to-one with the input channels of the AD converter. The analog input signal input by each analog input subunit is input into the AD converter through the corresponding input channel in differential input mode via the analog input subunit. Even if the analog input signal of a certain input channel changes during operation, the digital conversion values of adjacent channels will not affect each other, thereby reducing interference between input channels.

[0047] At the same time, the output unit in this embodiment is provided with two voltage signal output subunits and two current signal output subunits, and correspondingly the DA converter is provided with four output channels, such as Figure 3 As shown, to reduce interference between output channels, two voltage signal output subunits are connected one-to-one with two of the DA converter's output channels, and two current signal output subunits are connected one-to-one with the other two DA converter's output channels. Even if the digital value of one output channel changes, the analog output signals of adjacent channels will not affect each other. Both the AD converter and the DA converter utilize dedicated voltage regulators as their power supply. The specific forms of the voltage and current signal output subunits are described below.

[0048] Furthermore, the input circuit includes a common mode choke L4 and a resistor R102, wherein:

[0049] The first output end of the common-mode choke L4 is connected to the first filter protection circuit, and one end of the resistor R102 is connected to the second output end of the common-mode choke L4 and the first filter protection circuit;

[0050] The other end of the resistor R102 forms a current input terminal, the first input terminal of the common mode choke coil L4 forms a voltage input terminal, and the second input terminal of the common mode choke coil L4 forms a common input terminal.

[0051] Specifically, Figure 2 The circuit diagram of an embodiment of the analog input subunit is shown. The voltage input terminal is Figure 3 The V0+ terminal shown, the current input terminal is Figure 3 The I0+ terminal shown, the common input terminal is Figure 3 COM0 terminal shown. When the analog input signal is a voltage input signal, the analog input signal is differentially input from the V0+ terminal and the COM0 terminal and applied to the first voltage follower circuit. When the analog input signal is a current input signal, the analog input signal is differentially input from the I0+ terminal and the COM0 terminal. Resistor R102 acts as a sampling resistor to sample the current input signal, generate a sampled voltage, and apply it to the first voltage follower circuit. The common-mode choke L4 is used to improve the EMI capability of the input unit and can attenuate differential-mode noise.

[0052] Furthermore, the first filtering protection circuit includes a capacitor C18, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C127, a capacitor C133, a resistor R20, and a resistor R24, wherein:

[0053] One end of the capacitor C34 is connected to the first output end of the common-mode choke L4 and one end of the capacitor C127, the other end of the capacitor C34 is connected to one end of the capacitor C18 and grounded, and the other end of the capacitor C18 is connected to one end of the resistor R102, the other end of the capacitor C127, and the second output end of the common-mode choke L4;

[0054] The capacitor C133 is connected in parallel with the capacitor C127, one end of the resistor R24 is connected to one end of the capacitor C133, and the other end of the resistor R24 is grounded through the capacitor C36, one end of the resistor R20 is connected to the other end of the capacitor C133, and the other end of the resistor R20 is grounded through the capacitor C35.

[0055] The first filtering protection circuit further includes a transient voltage suppressor D5, a transient voltage suppressor D6, a resistor R15 and a resistor R16, wherein:

[0056] A first end of the transient voltage suppressor D5 is connected to one end of the capacitor C36 and one end of the resistor R16, and a second end of the transient voltage suppressor D5 and the other end of the resistor R16 are both grounded; a first end of the transient voltage suppressor D6 is connected to one end of the capacitor C35 and one end of the resistor R15, and a second end of the transient voltage suppressor D6 and the other end of the resistor R15 are both grounded.

[0057] Specifically, the transient voltage suppressor (TVS) described in this embodiment may be a PG12GAS23 model. It can quickly suppress overvoltages, protecting electronic components from damage. Capacitors C18, C34, C35, C36, C127, C133, and resistors R20 and R24 form a filter to filter out signal noise.

[0058] Furthermore, the first voltage follower circuit includes an operational amplifier U8, an operational amplifier U9, a resistor R1, a resistor R8, a capacitor C26, a capacitor C27, a magnetic bead B7 and a magnetic bead B8, wherein:

[0059] The non-inverting input terminal of the operational amplifier U8 is connected to one end of the resistor R16, and the inverting input terminal of the operational amplifier U8 is connected to the output terminal of the operational amplifier U8 through the resistor R1;

[0060] The positive power supply terminal of the operational amplifier U8 is grounded through the capacitor C27 and connected to the first power supply voltage through the magnetic bead B8; the negative power supply terminal of the operational amplifier U8 is grounded through the capacitor C26 and connected to the second power supply voltage through the magnetic bead B7;

[0061] The non-inverting input terminal of the operational amplifier U9 is connected to one end of the resistor R15, the inverting input terminal of the operational amplifier U9 is connected to the output terminal of the operational amplifier U9 through the resistor R8, and the output terminal of the operational amplifier U8 and the output terminal of the operational amplifier U9 are both connected to the AD converter.

[0062] In this embodiment, the first power supply voltage is +18V, and the second power supply voltage is -12V. The power supply for the operational amplifier U9 is not shown in the figure. In a specific implementation, the power supply for the operational amplifier U9 can be the same as that for the operational amplifier U8. The operational amplifier U8 and resistor R1 form a voltage follower, and the operational amplifier U9 and resistor R8 also form a voltage follower, providing isolation and buffering. That is, the output voltage at the output of the operational amplifier U8 is equal to the input voltage at the non-inverting input, and the output voltage at the output of the operational amplifier U9 is also equal to the input voltage at the non-inverting input.

[0063] Furthermore, the voltage signal output subunit includes a second filtering protection circuit and a second voltage follower circuit, and the second voltage follower circuit includes an operational amplifier U4, a resistor R26, a capacitor C55, a capacitor C56, a capacitor C57, a magnetic bead B18 and a magnetic bead B19, wherein,

[0064] The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the operational amplifier U4 through the resistor R26, the capacitor C55 is connected in parallel with the resistor R26, and the negative power supply terminal of the operational amplifier U4 is grounded through the capacitor C56 and connected to the second power supply voltage through the magnetic bead B18;

[0065] The non-inverting input terminal of the operational amplifier U4 is connected to the output terminal of the DA converter, and the positive power supply terminal of the operational amplifier U4 is grounded through the capacitor C57 and connected to the second power supply voltage through the magnetic bead B19.

[0066] The second filtering protection circuit includes a capacitor C18, a capacitor C19, a capacitor C22, a capacitor C54, a capacitor C60, a resistor R27, a resistor R81, a magnetic bead B20, a magnetic bead B21 and a transient voltage suppressor D13, wherein one end of the resistor R81 is connected to one end of the capacitor C18, one end of the capacitor C19, the non-inverting input end of the operational amplifier U4 and the output end of the DA converter, and the other ends of the resistor R81, the capacitor C18 and the capacitor C19 are all grounded;

[0067] One end of the capacitor C60 is connected to one end of the capacitor C54 and the output end of the operational amplifier U4 through a magnetic bead B21, and the other end of the capacitor C60 is connected to the other end of the capacitor C54 through a magnetic bead B20. The capacitor C22 is connected in parallel with the capacitor C54.

[0068] One end of the resistor R27 is connected to the output end of the operational amplifier U4, one end of the capacitor C22 and the second end of the transient voltage suppressor D13, and the other end of the resistor R27 and the first end of the transient voltage suppressor D13 are grounded.

[0069] Figure 4 The circuit schematic diagram of an embodiment of the voltage signal output subunit is shown. As shown in the figure, the operational amplifier U4, the resistor R26 and the capacitor C55 form a voltage follower. The voltage output signal output by the DA converter is input to the non-inverting input terminal of the operational amplifier U. One end of the capacitor C60 is connected to one end of the magnetic bead B21 to form a first voltage output terminal, that is, Figure 4 The V0_EXCH0(+) terminal shown in FIG. 1 is connected to the other end of the capacitor C60 and one end of the magnetic bead B20 to form a second voltage output terminal, that is, Figure 4The V0_EXCH0(-) terminal, the magnetic beads B21 and B20 are both used to eliminate signal noise. The first and second voltage output terminals are connected to external devices, outputting voltage output signals to control the external devices. The model and function of the transient voltage suppressor are consistent with those described above and are not further described here.

[0070] Furthermore, the current signal output subunit includes a disconnection detection circuit and a third filtering protection circuit. The disconnection detection circuit includes an operational amplifier U3, a resistor R4, a resistor R34, a resistor R35, a resistor R36, a resistor R37 and a switch device, wherein:

[0071] The non-inverting input terminal of the operational amplifier U3 is connected to one end of the resistor R36 and one end of the resistor R37, the other end of the resistor R36 is connected to the first power supply voltage, the other end of the resistor R37 is grounded, and the inverting input terminal of the operational amplifier U3 is connected to the first power supply voltage through the resistor R35;

[0072] The output end of the operational amplifier U3 is connected to one end of the resistor R4 and a first end of the switch device, the other end of the resistor R4 is connected to the first power supply voltage, the second end of the switch device is connected to one end of the resistor R34 and the MCU, and the third end of the switch device is grounded.

[0073] The third filtering protection circuit includes a switching diode D4, a transient voltage suppressor D6, a resistor R38, a diode D16, a capacitor C8, a capacitor C9, a magnetic bead B3 and a magnetic bead B4, wherein:

[0074] One end of the capacitor C8 is connected to one end of the capacitor C9, the second end of the transient voltage suppressor D6, and the inverting input end of the operational amplifier U3 through a magnetic bead B3. The other end of the capacitor C8 is connected to the other end of the capacitor C9 through a magnetic bead B4. The other end of the capacitor C9 and the first end of the transient voltage suppressor D6 are grounded.

[0075] The anode of the diode D16 is connected to the third terminal of the switching diode D4 and the output terminal of the DA converter through the resistor R38, and the cathode of the diode D16 is connected to the inverting input terminal of the operational amplifier U3.

[0076] The switching diode D4 in this invention is model KDS226. Its first terminal is connected to a first power supply voltage, and its second terminal is connected to a second power supply voltage. It is used to limit the output of the DA converter. The current output signal from the DA converter is input to the current signal output subunit via resistor R38 and diode D16. Figure 5The circuit schematic diagram of an embodiment of the current signal output subunit is shown. As shown in the figure, one end of the capacitor C8 is connected to one end of the magnetic bead B3 to form a first current output end, that is, Figure 5 The other end of the capacitor C8 is connected to one end of the magnetic bead B4 to form a second current output end, that is, Figure 4 The I1_EXCH1(-) terminal, the magnetic beads B3 and B4 are used to eliminate signal noise. The first current output terminal and the second current output terminal are connected to an external device to output the current output signal to control the external device.

[0077] The disconnection detection circuit detects the connection status of the external device. Optionally, the switching device in the disconnection detection circuit can be a MOSFET device. For a MOSFET device, the first terminal of the switching device is the gate terminal, the second terminal is the source terminal, and the third terminal is the drain terminal. In this embodiment, the switching device is a PMOS device. The source terminal of the PMOS device is connected to one end of resistor R34 and forms a warning signal output terminal connected to the MCU. The source terminal of the PMOS device is connected to a 5V analog voltage through resistor R34. The drain terminal of the PMOS device is grounded. The gate terminal of the PMOS device is connected to the output terminal of the operational amplifier. The conduction state of the PMOS device is controlled by the operational amplifier U3, and the output state of the warning signal output terminal is controlled by the conduction state of the PMOS device, thereby outputting a warning signal to the MCU when the external device is disconnected. Specifically, when the external device is disconnected, the operational amplifier U3 outputs a high level, turning off the switching device, and the warning signal output terminal outputs a high level to the MCU. The positive power supply terminal of the operational amplifier U3 is connected to the first power supply voltage, and the negative power supply terminal of the operational amplifier U3 is connected to the second power supply voltage. The input unit and output unit provided by the present invention can be integrated into the XBC-U series PLC. The PLC with integrated input unit and output unit is as follows: Figure 6 shown.

[0078] The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiment. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

Claims

1. A PLC with AD and DA functions, characterized in that: The device comprises an input unit and an output unit, wherein the input unit comprises an AD converter and a plurality of analog input subunits adapted to be connected to the AD converter. The analog input signal is transmitted to the AD converter via the analog input subunit and converted into a digital output signal by the AD converter. The analog input subunit comprises an adapted input circuit, a first filtering protection circuit, and a first voltage follower circuit. The output unit includes a DA converter and several voltage signal output subunits and / or several current signal output subunits adapted to be connected to the DA converter. The digital input signal is converted into an analog output signal by the DA converter and output through the voltage signal output subunit and / or the current signal output subunit.

2. The PLC with AD and DA functions according to claim 1, characterized in that: The input circuit includes a common mode choke L4 and a resistor R102, wherein: The first output end of the common-mode choke L4 is connected to the first filter protection circuit, and one end of the resistor R102 is connected to the second output end of the common-mode choke L4 and the first filter protection circuit; The other end of the resistor R102 forms a current input terminal, the first input terminal of the common mode choke coil L4 forms a voltage input terminal, and the second input terminal of the common mode choke coil L4 forms a common input terminal.

3. The PLC with AD and DA functions according to claim 2, characterized in that: The first filtering protection circuit includes a capacitor C18, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C127, a capacitor C133, a resistor R20, and a resistor R24, wherein: One end of the capacitor C34 is connected to the first output end of the common-mode choke L4 and one end of the capacitor C127, the other end of the capacitor C34 is connected to one end of the capacitor C18 and grounded, and the other end of the capacitor C18 is connected to one end of the resistor R102, the other end of the capacitor C127, and the second output end of the common-mode choke L4; The capacitor C133 is connected in parallel with the capacitor C127, one end of the resistor R24 is connected to one end of the capacitor C133, and the other end of the resistor R24 is grounded through the capacitor C36, one end of the resistor R20 is connected to the other end of the capacitor C133, and the other end of the resistor R20 is grounded through the capacitor C35.

4. The PLC with AD and DA functions according to claim 3, characterized in that: The first filtering protection circuit further includes a transient voltage suppressor D5, a transient voltage suppressor D6, a resistor R15 and a resistor R16, wherein: A first end of the transient voltage suppressor D5 is connected to one end of the capacitor C36 and one end of the resistor R16, and a second end of the transient voltage suppressor D5 and the other end of the resistor R16 are both grounded; a first end of the transient voltage suppressor D6 is connected to one end of the capacitor C35 and one end of the resistor R15, and a second end of the transient voltage suppressor D6 and the other end of the resistor R15 are both grounded.

5. The PLC with AD and DA functions according to claim 4, characterized in that: The first voltage follower circuit includes an operational amplifier U8, an operational amplifier U9, a resistor R1, a resistor R8, a capacitor C26, a capacitor C27, a magnetic bead B7 and a magnetic bead B8, wherein: The non-inverting input terminal of the operational amplifier U8 is connected to one end of the resistor R16, and the inverting input terminal of the operational amplifier U8 is connected to the output terminal of the operational amplifier U8 through the resistor R1; The positive power supply terminal of the operational amplifier U8 is grounded through the capacitor C27 and connected to the first power supply voltage through the magnetic bead B8; the negative power supply terminal of the operational amplifier U8 is grounded through the capacitor C26 and connected to the second power supply voltage through the magnetic bead B7; The non-inverting input terminal of the operational amplifier U9 is connected to one end of the resistor R15, the inverting input terminal of the operational amplifier U9 is connected to the output terminal of the operational amplifier U9 through the resistor R8, and the output terminal of the operational amplifier U8 and the output terminal of the operational amplifier U9 are both connected to the AD converter.

6. The PLC with AD and DA functions according to claim 1, characterized in that: The voltage signal output subunit includes a second filtering protection circuit and a second voltage follower circuit, and the second voltage follower circuit includes an operational amplifier U4, a resistor R26, a capacitor C55, a capacitor C56, a capacitor C57, a magnetic bead B18 and a magnetic bead B19, wherein: The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the operational amplifier U4 through the resistor R26, the capacitor C55 is connected in parallel with the resistor R26, and the negative power supply terminal of the operational amplifier U4 is grounded through the capacitor C56 and connected to the second power supply voltage through the magnetic bead B18; The non-inverting input terminal of the operational amplifier U4 is connected to the output terminal of the DA converter, and the positive power supply terminal of the operational amplifier U4 is grounded through the capacitor C57 and connected to the second power supply voltage through the magnetic bead B19.

7. The PLC with AD and DA functions according to claim 6, characterized in that: The second filtering protection circuit includes capacitor C18, capacitor C19, capacitor C22, capacitor C54, capacitor C60, resistor R27, resistor R81, magnetic beads B20, magnetic beads B21 and transient voltage suppressor D13, wherein: One end of the resistor R81 is connected to one end of the capacitor C18, one end of the capacitor C19, the non-inverting input end of the operational amplifier U4, and the output end of the DA converter, and the other ends of the resistor R81, the capacitor C18, and the capacitor C19 are all grounded; One end of the capacitor C60 is connected to one end of the capacitor C54 and the output end of the operational amplifier U4 through a magnetic bead B21, and the other end of the capacitor C60 is connected to the other end of the capacitor C54 through a magnetic bead B20. The capacitor C22 is connected in parallel with the capacitor C54. One end of the resistor R27 is connected to the output end of the operational amplifier U4, one end of the capacitor C22 and the second end of the transient voltage suppressor D13, and the other end of the resistor R27 and the first end of the transient voltage suppressor D13 are grounded.

8. The PLC with AD and DA functions according to claim 1, characterized in that: The current signal output subunit includes a disconnection detection circuit and a third filtering protection circuit. The disconnection detection circuit includes an operational amplifier U3, a resistor R4, a resistor R34, a resistor R35, a resistor R36, a resistor R37 and a switch device, wherein: The non-inverting input terminal of the operational amplifier U3 is connected to one end of the resistor R36 and one end of the resistor R37, the other end of the resistor R36 is connected to the first power supply voltage, the other end of the resistor R37 is grounded, and the inverting input terminal of the operational amplifier U3 is connected to the first power supply voltage through the resistor R35; The output end of the operational amplifier U3 is connected to one end of the resistor R4 and a first end of the switch device, the other end of the resistor R4 is connected to the first power supply voltage, the second end of the switch device is connected to one end of the resistor R34 and the MCU, and the third end of the switch device is grounded.

9. The PLC with AD and DA functions according to claim 8, characterized in that: The switching device includes a MOSFET device.

10. The PLC with AD and DA functions according to claim 8, characterized in that: The third filtering protection circuit includes a switching diode D4, a transient voltage suppressor D6, a resistor R38, a diode D16, a capacitor C8, a capacitor C9, a magnetic bead B3 and a magnetic bead B4, wherein: One end of the capacitor C8 is connected to one end of the capacitor C9, the second end of the transient voltage suppressor D6, and the inverting input end of the operational amplifier U3 through a magnetic bead B3. The other end of the capacitor C8 is connected to the other end of the capacitor C9 through a magnetic bead B4. The other end of the capacitor C9 and the first end of the transient voltage suppressor D6 are grounded. The anode of the diode D16 is connected to the third terminal of the switching diode D4 and the output terminal of the DA converter through the resistor R38, and the cathode of the diode D16 is connected to the inverting input terminal of the operational amplifier U3.

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