A digital quantity input circuit and device

Abstract

The present invention provides a digital quantity input circuit and device, the digital quantity input circuit includes a first port and a second port as input ends; an anti-reverse voltage divider module connected between the first port and the second port, the anti-reverse voltage divider module includes a first voltage divider circuit and a second voltage divider circuit connected in parallel; a rectifier module, having a first pin and a third pin as its input, and a second pin and a fourth pin as its output; the first pin of the rectifier module is connected to the output end of the first voltage divider circuit and the second voltage divider circuit, and the third pin is connected to the second port; an isolated output module, the two input ends of which are connected between the second pin and the fourth pin of the rectifier module, and the electrical signal output by the rectifier module is isolated and processed and then output through its two output ends. The present invention is designed by using low-cost devices, can be compatible with a variety of signal sources, and has a protection function.

Description

Technical Field

[0001] The present invention relates to the technical field of digital quantity input and output, and in particular to a digital quantity input circuit and equipment. Background Art

[0002] Currently in the field of electronic circuit technology, commonly used digital input circuits usually can only support PNP-type input wiring or NPN-type input wiring. The wiring method is single. If compatibility with both wiring methods is required, the design cost will increase.

[0003] like Figure 1 The digital input circuit shown in the figure is designed with two comparators and multiple resistors. The circuit uses a 24V power supply voltage Vcc and adds a 3.3V pull-up voltage VL to the output terminal OUTPUT. The working principle of the circuit is: when the input terminal INPUT is suspended and no level signal is input, the voltage VIN input to the reverse input terminal of the comparator U1A and the positive input terminal of the comparator U1B = Vcc*R4 / (R4+R5), and the output terminal OUTPUT outputs a high level with a logic value of "1"; when a low level (0V) signal is input to the input terminal INPUT, the voltage VIN input to the reverse input terminal of the comparator U1A and the positive input terminal of the comparator U1B are both 0V, the comparator U1A is turned off, and the comparator U1B is turned on. When the output is turned on, 0V is output, the output level of the output terminal OUTPUT is low, and the logic value is "0"; when a high level (24V) signal is input to the input terminal INPUT, the voltage VIN input to the reverse input terminal of the comparator U1A and the positive input terminal of the comparator U1B are both 24V, and the comparator U1B is turned off. The comparator U1A is turned on and outputs 0V, and the output level of the output terminal OUTPUT is still low, and the logic value is "0". Therefore, according to the level of the output terminal OUTPUT, it can be judged whether there is a digital signal input. Although this circuit is compatible with the input wiring of NPN sensors and PNP sensors, it uses two comparators, which is costly and has high requirements for the voltage of the comparator. The circuit does not have a protection function, and adding EMC devices alone further increases the design cost.

[0004] like Figure 2Another digital input circuit shown in FIG. 1 is designed with 4 MOS tubes, 2 photocouplers and multiple resistors. The working principle of the circuit is: when the sensor side connected to the circuit is not connected to the signal, the photocouplers U1 and U2 are both turned off, and the output terminal D outputs a low level; when the sensor side connected to the circuit is connected to an NPN sensor, the A terminal is at a high level and the B terminal is at a low level, the photocoupler U1 is turned on, and the photocoupler U2 is turned off. At this time, the gates of the PMOS tube Q1 and the NMOS tube Q3 are both at a high level, and the gates of the PMOS tube Q2 and the NMOS tube Q4 are both at a low level. According to the characteristics of the MOS tube, the PMOS tube Q1 and the NMOS tube Q4 are turned off, and the PMOS tube Q2 and the NMOS tube Q3 are turned on. The voltage 5V applied to the photocoupler U2 passes through the turned-on PMOS tube Q2, and then outputs a high level from the output terminal D; when a PNP sensor is connected to the sensor side of the access circuit, the B terminal is high level and the A terminal is low level, the photocoupler U2 is turned on, and the photocoupler U1 is turned off. At this time, the gates of the PMOS tube Q1 and the NMOS tube Q3 are both low level, and the gates of the PMOS tube Q2 and the NMOS tube Q4 are both high level. According to the characteristics of the MOS tube, the PMOS tube Q2 and the NMOS tube Q3 are turned off, and the PMOS tube Q1 and the NMOS tube Q4 are turned on. The voltage 5V applied to the photocoupler U1 passes through the turned-on PMOS tube Q1, the resistor R6 and the NMOS tube Q4, and then outputs a high level from the output terminal D. Therefore, according to the level of the output of the output terminal OUTPUT, it can be judged whether there is a digital signal input. Although this circuit is compatible with the input wiring of NPN sensors and PNP sensors, it requires 4 MOS tubes and 2 photocouplers, which are relatively expensive and do not have protection functions. Adding EMC devices separately further increases the design cost. Summary of the invention

[0005] In view of this, the main purpose of the embodiments of the present invention is to provide a digital quantity input circuit and device, which are designed with low-cost devices, are compatible with multiple signal sources, and have protection functions.

[0006] The technical solution adopted by the present invention is a digital quantity input circuit, comprising a first port and a second port as input ends;

[0007] an anti-reverse voltage-dividing module, connected between the first port and the second port, the anti-reverse voltage-dividing module comprising a first voltage-dividing circuit and a second voltage-dividing circuit connected in parallel, the first voltage-dividing circuit allows the electrical signal to flow unidirectionally from the first port to the second port, the second voltage-dividing circuit allows the electrical signal to flow unidirectionally from the second port to the first port, and the first voltage-dividing circuit and the second voltage-dividing circuit respectively have output ends;

[0008] A rectifier module having a first pin and a third pin as inputs thereof, and a second pin and a fourth pin as outputs thereof; the first pin of the rectifier module is connected to the output ends of the first voltage divider circuit and the second voltage divider circuit, and the third pin is connected to the second port;

[0009] The isolated output module has two input ends connected between the second pin and the fourth pin of the rectifier module, and isolates and processes the electrical signal output by the rectifier module and then outputs it through its two output ends.

[0010] From the above, the digital quantity input circuit provided by the present invention can realize the forward input and reverse input of the signal by designing the first voltage divider circuit and the second voltage divider circuit that only allow the unidirectional input of the electrical signal, and output the unidirectional signal after rectification by the rectifier module. An isolated output circuit is also provided to realize the isolated output of the signal. The present invention is compatible with a variety of signal sources and has a protection function.

[0011] Optionally, it further includes a protection module connected between the first port and the second port, and the protection module includes a voltage-stabilizing diode and a capacitor connected in parallel.

[0012] From the above, by using parallel voltage stabilizing diodes and capacitors, voltage stabilization and filtering at the input end are achieved, and surge and spike protection of the circuit is also provided.

[0013] Optionally, the first voltage divider circuit comprises a first forward diode, a first resistor, a second resistor, and a second forward diode connected in series in sequence, and a common end of the first resistor and the second resistor is an output end of the first voltage divider circuit;

[0014] The second voltage divider circuit includes a first reverse diode, a third resistor, a fourth resistor and a second reverse diode which are connected in series in sequence, and a common end of the three resistors and the fourth resistor is an output end of the second voltage divider circuit.

[0015] Optionally, also include:

[0016] a first capacitor connected in parallel with the second resistor;

[0017] A second capacitor is connected in parallel with the fourth resistor.

[0018] From the above, by using anti-reverse diodes, voltage-dividing resistors and filter capacitors to design the voltage-dividing circuit of this solution, a very wide voltage input range can be achieved, while having the functions of unidirectional input and filtering.

[0019] Optionally, the rectifier module includes a full-bridge rectifier circuit, and the full-bridge rectifier circuit includes:

[0020] A third forward diode, a third reverse diode, a fourth reverse diode and a fourth forward diode connected in series in a ring shape;

[0021] The common end of the third forward diode and the fourth forward diode is the first pin, the common end of the third forward diode and the third reverse diode is the second pin, the common end of the third reverse diode and the fourth reverse diode is the third pin, and the common end of the fourth reverse diode and the fourth forward diode is the fourth pin.

[0022] From the above, the full-bridge rectifier circuit can be used to rectify the bidirectional signal and output a unidirectional signal to the back-end circuit.

[0023] Optionally, the isolated output module includes a photocoupler.

[0024] From the above, the use of optocoupler devices can be used to optically isolate the circuit and provide protection for the subsequent circuit.

[0025] An embodiment of the present invention further provides a digital quantity input device, comprising the above-mentioned digital quantity input circuit and a signal source, wherein the first port and the second port of the digital quantity input circuit are correspondingly connected to the signal source.

[0026] Optionally, a voltage source module is also included, which is used to provide voltage for the digital input circuit and the connected signal source. The voltage source module includes a voltage source and a unidirectional diode and a current limiting resistor connected in series.

[0027] From the above, the above-mentioned digital input circuit is used as the basic input circuit of the device of the present invention, and is supplemented by a voltage source module. When in use, corresponding wiring is performed according to the model of the signal source. The device can realize digital input connection of multiple signal sources and has isolation protection function.

[0028] Optionally, the signal source is one of the following signal sources: a PNP signal source, an NPN signal source, a dry contact signal source, and a wet contact signal source.

[0029] When the signal source is a PNP type signal source, the output end of the voltage source module is connected to the input end of the PNP type signal source, the output end of the PNP type signal source is connected to the first port of the digital quantity input circuit, and the ground end of the PNP type signal source and the second port of the digital quantity input circuit are grounded together;

[0030] When the signal source is an NPN type signal source, the output end of the voltage source module is connected to the second port of the digital input circuit, the first port of the digital input circuit is connected to the input end of the NPN type signal source, and the output end of the NPN type signal source is grounded;

[0031] When the signal source is a dry contact signal source, the output end of the voltage source module is connected to the input end of the dry contact signal source, the output end of the dry contact signal source is connected to the first port of the digital quantity input circuit, and the second port of the digital quantity input circuit is grounded;

[0032] When the signal source is a wet contact signal source, the positive output terminal of the wet contact signal source is connected to the first port of the digital input circuit, and the negative output terminal of the wet contact signal source and the second port of the digital input circuit are grounded together.

[0033] From the above, through the wiring methods listed above for different types of signal sources, this device can achieve compatibility with multiple signal sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a circuit diagram of a digital quantity input circuit in the prior art;

[0035] Figure 2 It is a circuit diagram of another digital quantity input circuit in the prior art;

[0036] Figure 3 It is a module principle diagram of the digital quantity input circuit of the present invention;

[0037] Figure 4 A circuit diagram of a digital quantity input circuit of the present invention;

[0038] Figure 5 A circuit diagram of connecting a digital quantity input device of the present invention to a PNP type signal source;

[0039] Figure 6 A circuit diagram of connecting a digital quantity input device of the present invention to an NPN type signal source;

[0040] Figure 7 A circuit diagram of connecting a digital quantity input device of the present invention to a dry contact signal source;

[0041] Figure 8 A circuit diagram of connecting a digital quantity input device of the present invention to a wet contact signal source. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] In order to solve the problems of single wiring method and high cost of digital input circuits in the prior art, an embodiment of the present invention provides a digital input circuit, which adopts a low-cost device design and is compatible with various wiring methods of signal sources, such as PNP type, NPN type, wet contact, dry contact, etc., and has a wide range of applications. At the same time, the present invention has functions such as circuit protection and circuit isolation, which can realize protection of the entire circuit.

[0044] To achieve the above object, an embodiment of the present invention provides a digital quantity input circuit comprising: a first port and a second port as input terminals;

[0045] An anti-reverse voltage-dividing module is connected between the first port and the second port, and the anti-reverse voltage-dividing module includes a first voltage-dividing circuit and a second voltage-dividing circuit connected in parallel, the first voltage-dividing circuit allows the electrical signal to flow unidirectionally from the first port to the second port, the first voltage-dividing circuit includes a first forward diode, a first resistor, a second resistor, and a second forward diode connected in series in sequence, and the common end of the first resistor and the second resistor is the output end of the first voltage-dividing circuit; the second voltage-dividing circuit allows the electrical signal to flow unidirectionally from the second port to the first port, the second voltage-dividing circuit includes a first reverse diode, a third resistor, a fourth resistor, and a second reverse diode connected in series in sequence, and the common end of the three resistors and the fourth resistor is the output end of the second voltage-dividing circuit;

[0046] A rectifier module, comprising a full-bridge rectifier circuit, the full-bridge rectifier circuit comprising: a third forward diode, a third reverse diode, a fourth reverse diode and a fourth forward diode connected in series in a ring; the common end of the third forward diode and the fourth forward diode is the first pin, the common end of the third forward diode and the third reverse diode is the second pin, the common end of the third reverse diode and the fourth reverse diode is the third pin, and the common end of the fourth reverse diode and the fourth forward diode is the fourth pin; the first pin and the third pin serve as inputs of the full-bridge rectifier circuit, and the second pin and the fourth pin serve as outputs of the full-bridge rectifier circuit; the first pin is connected to the output ends of the first voltage divider circuit and the second voltage divider circuit, and the third pin is connected to the second port;

[0047] An isolated output module, comprising a photocoupler, wherein two input ends of the photocoupler are connected between the second pin and the fourth pin of the rectifier module, and the electrical signal output by the rectifier module is isolated and processed and then output through the two output ends of the photocoupler;

[0048] Also included is a protection module connected between the first port and the second port, the protection module including a voltage stabilizing diode and a capacitor connected in parallel;

[0049] It also includes a first capacitor connected in parallel with the second resistor and a second capacitor connected in parallel with the fourth resistor.

[0050] Refer to the following Figure 3 As shown, a digital quantity input circuit provided by a specific embodiment of the present invention is described in detail. The digital quantity input circuit includes a port 1 and a port 2 for connecting a signal source as an input terminal. The port 1 and the port 2 can support the input of a bidirectional signal, and also includes:

[0051] An anti-reverse voltage-dividing module 100 is connected between the port 1 and the port 2. The anti-reverse voltage-dividing module 100 includes a first voltage-dividing circuit and a second voltage-dividing circuit connected in parallel. The first voltage-dividing circuit allows the electrical signal to flow unidirectionally from the port 1 to the port 2. The second voltage-dividing circuit allows the electrical signal to flow unidirectionally from the port 2 to the port 1. The first voltage-dividing circuit and the second voltage-dividing circuit each have an output end.

[0052] The rectifier module 200 has a first pin and a third pin as inputs thereof, and a second pin and a fourth pin as outputs thereof, wherein the first pin of the rectifier module 200 is connected to the output ends of the first voltage divider circuit and the second voltage divider circuit, and the third pin is connected to the port 2;

[0053] An isolated output module 300, whose two input terminals are connected between the second pin and the fourth pin of the rectifier module 200, isolates the electrical signal output by the rectifier module 200 and outputs it through its two output terminals;

[0054] It also includes a protection module 400 connected between the port 1 and the port 2. The protection module 400 can be implemented by using a parallel voltage stabilizing diode and a capacitor to achieve voltage stabilization and filtering of the input signal, and also provides circuit surge and spike protection.

[0055] The following is combined with Figure 4 The circuit diagram of the digital quantity input circuit of the present invention is shown, and the circuit connection mode and technical principle of the present invention are explained in detail. The digital quantity input circuit of the present invention includes a CHx terminal and a COM terminal as input terminals, and the CHx terminal and the COM terminal can realize bidirectional input of signals, that is, when the CHx terminal is a positive input terminal, the COM terminal is a negative input terminal, or when the COM terminal is a positive input terminal, the CHx terminal is a negative input terminal;

[0056] The CHx terminal and the COM terminal are connected in parallel with a protection circuit consisting of a voltage stabilizing diode TVS and a capacitor C3, which can realize voltage stabilization and filtering of the input signal, and also provide circuit surge and spike protection;

[0057] A first voltage divider circuit and a second voltage divider circuit are connected in parallel between the CHx terminal and the COM terminal, wherein the first voltage divider circuit comprises a forward diode D2, a resistor R2, a resistor R4, and a forward diode D8 connected in series in sequence, wherein the positive electrode of the forward diode D2 is connected to the CHx terminal, and the negative electrode of the forward diode D8 is connected to the COM terminal, and the first voltage divider circuit realizes a unidirectional passage of the input signal from the CHx terminal to the COM terminal; the second voltage divider circuit comprises a reverse diode D1, a resistor R1, a resistor R3, and a reverse diode D7 connected in series in sequence, wherein the negative electrode of the reverse diode D1 is connected to the CHx terminal, and the positive electrode of the reverse diode D7 is connected to the COM terminal, and the second voltage divider circuit realizes a unidirectional passage of the input signal from the COM terminal to the CHx terminal; capacitors C1 and C2 are connected in parallel at both ends of the resistor R1 and the resistor R4, respectively, for filtering interference signals, wherein the resistor R1=R4, R2=R3, the capacitor C1=C2, and the diodes D1, D2, D7, and D8 are identical devices;

[0058] The rear ends of the first voltage divider circuit and the second voltage divider circuit are also connected to a full-bridge rectifier circuit, which includes a forward diode D3, a reverse diode D4, a reverse diode D6, and a forward diode D5 connected in series in a ring. The ring series connection of the diodes D3, D4, D5, and D6 is such that the cathode of the diode D3 is connected to the cathode of the diode D4, the anode of the diode D4 is connected to the cathode of the diode D6, the anode of the diode D6 is connected to the anode of the diode D5, and the cathode of the diode D5 is connected to the anode of the diode D3. The common pins of the forward diode D3 and the forward diode D5 are respectively connected to the common ends of the resistors R1 and R3 and the common ends of the resistors R2 and R4, and the common pins of the reverse diode D4 and the reverse diode D6 are connected to the COM end.

[0059] The rear end of the full-bridge rectifier circuit is also connected to an isolated output circuit, which includes a photocoupler U1, wherein the two input ends of the photocoupler U1 are respectively connected to the common pins of the forward diode D3 and the reverse diode D4 and the common pins of the reverse diode D6 and the forward diode D5.

[0060] According to the above connection mode, the working principle of the digital quantity input circuit of the present invention is:

[0061] When the CHx terminal is the positive input terminal and the COM terminal is the negative input terminal, the first voltage divider circuit is turned on, and the input signal enters from the CHx terminal, passes through the diode D2 and the resistor R2, and enters the common pin of the diode D3 and the diode D5 in the full-bridge rectifier circuit from the common terminal of the resistors R2 and R4, and is input to the positive input terminal of the photocoupler U1 after passing through the diode D3, and then returns from the negative input terminal of the photocoupler U1. The returned signal enters the common pin of the diode D6 and the diode D5 in the full-bridge rectifier circuit, and is derived from the common pin of the diode D6 and the diode D4 after passing through the diode D6, and is output from the COM terminal;

[0062] When the above-mentioned COM terminal is the positive input terminal and the CHx terminal is the negative input terminal, the second voltage divider circuit is turned on, and the input signal enters from the COM terminal, enters the common pin of the diode D6 and the diode D4 in the full-bridge rectifier circuit, passes through the diode D4, is input to the positive input terminal of the photocoupler U1, and then returns from the negative input terminal of the photocoupler U1. The returned signal enters the common pin of the diode D6 and the diode D5 in the full-bridge rectifier circuit, passes through the diode D5, enters the common terminal of the resistors R1 and R3, and is output from the CHx terminal after passing through the resistor R1 and the diode D1.

[0063] According to the above circuit diagram and working principle, it can be concluded that:

[0064] R2=R3=(VCC-UD2-UD3-UD6-U1) / I1, where VCC is the total input voltage of the circuit of the present invention, I1 is the maximum current limiting current through the diode in the photocoupler U1, and the resistance values ​​of R2 and R3 can be adjusted according to the actual needs of the circuit to ensure that I1 does not exceed the maximum current limiting current;

[0065] R1=R4=(UD2+UD3+UD6+U1-UD8) / I2, where I2 is the current passing through resistor R4;

[0066] IIN=I1+I2, where IIN is the total input current of the circuit of the present invention.

[0067] In another embodiment of the present invention, a device including the above-mentioned digital quantity input circuit is provided, which is compatible with multiple types of signal sources. The device is equipped with a unidirectional output stable voltage source module, which includes a voltage source and a unidirectional diode and a current limiting resistor connected in series, and can provide a unidirectional stable 24V voltage when performing digital quantity input. Figure 5-Figure 8 As shown, the implementation method of the device of the present invention for connecting the digital quantity input of the PNP type signal source, the NPN type signal source, the dry contact signal source, and the wet contact signal source is described in detail. It should be noted that according to Figure 4It can be seen from the circuit that when the CHx terminal and the COM terminal are conducting, one of the first and second voltage divider circuits is conducting, and the other is not conducting due to the reverse diode, that is, only two resistors are connected to the circuit. Therefore, for ease of viewing, Figure 5-Figure 8 In FIG. 1 , only two resistors that are turned on are shown.

[0068] like Figure 5 As shown, when the signal source is a PNP type signal source, the output end of the above-mentioned voltage source module is connected to the input end of the PNP type signal source, the output end of the PNP type signal source is connected to the CHx end of the above-mentioned digital input circuit, and the ground end of the PNP type signal source and the COM end of the above-mentioned digital input circuit are commonly grounded CH_GND.

[0069] At this time, the CHx terminal is the positive input terminal, and the COM terminal is the negative input terminal. According to the above principle, the direction of the electrical signal in the connection circuit is:

[0070] Voltage source module-PNP tube-CHx-D2-R2-D3-U1-D6-COM-CH_GND.

[0071] like Figure 6 As shown, when the signal source is an NPN type signal source, the output end of the above-mentioned voltage source module is connected to the COM end of the above-mentioned digital input circuit, the CHx end of the digital input circuit is connected to the input end of the NPN type signal source, and the output end of the NPN type signal source is grounded CH_GND.

[0072] At this time, the COM terminal is the positive input terminal, and the CHx terminal is the negative input terminal. According to the above principle, the direction of the electrical signal in the connection circuit is:

[0073] Voltage source module-COM-D4-U1-D5-R1-D1-CHx-NPN tube-CH_GND.

[0074] like Figure 7 As shown, when the signal source is a dry contact signal source (such as a passive switch), the output end of the above-mentioned voltage source module is connected to the input end of the dry contact signal source, the output end of the dry contact signal source is connected to the CHx end of the above-mentioned digital input circuit, and the COM end of the digital input circuit is grounded CH_GND.

[0075] At this time, the CHx terminal is the positive input terminal, and the COM terminal is the negative input terminal. According to the above principle, the direction of the electrical signal in the connection circuit is:

[0076] Voltage Source Module-Dry Contact-CHx-D2-R2-D3-U1-D6-COM-CH_GND.

[0077] like Figure 8As shown, when the signal source is a wet contact signal source (such as an active switch or an active circuit), the positive output terminal of the wet contact signal source is connected to the CHx terminal of the above-mentioned digital input circuit, and the negative output terminal of the wet contact signal source and the COM terminal of the above-mentioned digital input circuit are commonly grounded CH_GND.

[0078] At this time, the CHx terminal is the positive input terminal, and the COM terminal is the negative input terminal. According to the above principle, the direction of the electrical signal in the connection circuit is:

[0079] Wet contact positive - CHx - D2 - R2 - D3 - U1 - D6 - COM - CH_GND - Wet contact negative.

[0080] In the connection circuits between the above four signal sources and the devices of the digital quantity input circuit, it is possible to check whether there is input of the digital quantity signal by checking whether the optocoupler U1 outputs an optical signal.

[0081] In summary, the digital input circuit and device provided by the present invention are designed with low-cost devices, are compatible with multiple signal sources, and have protection functions, solving the problems of single wiring method and high cost of digital input circuits in the prior art. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A digital quantity input circuit, characterized in that: including a first port and a second port as input ports; an anti-reverse voltage-dividing module, connected between the first port and the second port, the anti-reverse voltage-dividing module comprising a first voltage-dividing circuit and a second voltage-dividing circuit connected in parallel, the first voltage-dividing circuit enables the electrical signal to flow unidirectionally from the first port to the second port, and the second voltage-dividing circuit enables the electrical signal to flow unidirectionally from the second port to the first port, the first voltage-dividing circuit comprises a first forward diode, a first resistor, a second resistor, and a second forward diode connected in series in sequence, and a common end of the first resistor and the second resistor is an output end of the first voltage-dividing circuit; the second voltage-dividing circuit comprises a first reverse diode, a third resistor, a fourth resistor, and a second reverse diode connected in series in sequence, and a common end of the three resistors and the fourth resistor is an output end of the second voltage-dividing circuit; A rectifier module having a first pin and a third pin as inputs thereof, and a second pin and a fourth pin as outputs thereof; the first pin of the rectifier module is connected to the output ends of the first voltage divider circuit and the second voltage divider circuit, and the third pin is connected to the second port; The isolated output module has two input ends connected between the second pin and the fourth pin of the rectifier module, and isolates and processes the electrical signal output by the rectifier module and then outputs it through its two output ends.

2. The digital quantity input circuit according to claim 1, characterized in that: It also includes a protection module connected between the first port and the second port, and the protection module includes a voltage-stabilizing diode and a capacitor connected in parallel.

3. The digital quantity input circuit according to claim 1, characterized in that: Also includes: a first capacitor connected in parallel with the second resistor; A second capacitor is connected in parallel with the fourth resistor.

4. The digital quantity input circuit according to claim 1, characterized in that: The rectifier module includes a full-bridge rectifier circuit, and the full-bridge rectifier circuit includes: A third forward diode, a third reverse diode, a fourth reverse diode and a fourth forward diode connected in series in a ring shape; The common end of the third forward diode and the fourth forward diode is the first pin, the common end of the third forward diode and the third reverse diode is the second pin, the common end of the third reverse diode and the fourth reverse diode is the third pin, and the common end of the fourth reverse diode and the fourth forward diode is the fourth pin.

5. The digital quantity input circuit according to claim 1, characterized in that: The isolated output module includes a photoelectric coupler.

6. A digital quantity input device, characterized in that: include: The digital input circuit according to any one of claims 1 to 5, and a signal source; The first port and the second port of the digital quantity input circuit are connected to the signal source accordingly.

7. The digital quantity input device according to claim 6, characterized in that: It also includes a voltage source module for providing voltage to the digital quantity input circuit and the connected signal source. The voltage source module includes a voltage source and a unidirectional diode and a current limiting resistor connected in series.

8. The digital quantity input device according to claim 7, characterized in that: The signal source is one of the following signal sources: a PNP type signal source, an NPN type signal source, a dry contact signal source and a wet contact signal source.

9. The digital quantity input device according to claim 8, characterized in that: When the signal source is a PNP type signal source, the output end of the voltage source module is connected to the input end of the PNP type signal source, the output end of the PNP type signal source is connected to the first port of the digital quantity input circuit, and the ground end of the PNP type signal source and the second port of the digital quantity input circuit are grounded together; When the signal source is an NPN type signal source, the output end of the voltage source module is connected to the second port of the digital input circuit, the first port of the digital input circuit is connected to the input end of the NPN type signal source, and the output end of the NPN type signal source is grounded; When the signal source is a dry contact signal source, the output end of the voltage source module is connected to the input end of the dry contact signal source, the output end of the dry contact signal source is connected to the first port of the digital quantity input circuit, and the second port of the digital quantity input circuit is grounded; When the signal source is a wet contact signal source, the positive output terminal of the wet contact signal source is connected to the first port of the digital input circuit, and the negative output terminal of the wet contact signal source and the second port of the digital input circuit are grounded together.

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