CN108733122B - Digital output circuit and industrial control equipment - Google Patents
Digital output circuit and industrial control equipment Download PDFInfo
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- CN108733122B CN108733122B CN201810315648.6A CN201810315648A CN108733122B CN 108733122 B CN108733122 B CN 108733122B CN 201810315648 A CN201810315648 A CN 201810315648A CN 108733122 B CN108733122 B CN 108733122B
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- 238000001514 detection method Methods 0.000 claims abstract description 14
- 238000010586 diagram Methods 0.000 description 7
- 230000000670 limiting effect Effects 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 230000005669 field effect Effects 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/569—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection
- G05F1/573—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection with overcurrent detector
- G05F1/5735—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection with overcurrent detector with foldback current limiting
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/05—Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
- G05B19/054—Input/output
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/468—Regulating voltage or current wherein the variable actually regulated by the final control device is dc characterised by reference voltage circuitry, e.g. soft start, remote shutdown
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/10—Plc systems
- G05B2219/11—Plc I-O input output
- G05B2219/1158—Control of output current
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Electromagnetism (AREA)
- Radar, Positioning & Navigation (AREA)
- Electronic Switches (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
The invention provides a digital output circuit and industrial control equipment, wherein the digital output circuit comprises an optocoupler, a first switching tube, a digital output port, a second resistor and an overcurrent protection unit, and the overcurrent protection unit comprises a detection subunit and a voltage clamping subunit; two ends of the detection subunit are respectively connected with the digital output port and the control end of the voltage clamping subunit; the second resistor is connected in series between the first power supply and the first resistor, and the voltage clamping subunit clamps the voltage of the connecting point of the first resistor and the second resistor to a third preset value when the voltage of the connecting point of the first resistor and the second resistor is larger than or equal to a first preset value and the voltage of the control end of the voltage clamping subunit is larger than a second preset value. The digital output port voltage of the digital output circuit is detected to clamp the optocoupler output voltage, so that the digital output circuit is effectively prevented from being damaged due to short circuit and overcurrent while the function of the digital output circuit is not affected.
Description
Technical Field
The present invention relates to the field of electronic devices, and more particularly, to a digital output circuit and an industrial control device.
Background
In the industrial control device, the digital output circuit (Digital Output Circle, simply referred to as DO circuit) is the most widely used circuit, and can be used for transmitting high-low level state information, pulse information and the like to a host computer (for example, a PLC, i.e., a programmable logic controller) by using a frequency converter or a servo motor controller. Generally, the DO circuit is connected to a digital input circuit (Digital Input Circle, abbreviated as DI circuit) of the host computer, as shown in fig. 1.
Since the connection between the DO circuit 11 and the DI circuit 12 is generally manually wired, there is a problem of unclear wiring or miswiring, for example, a case (which may be referred to as a short circuit) in which the DO port is erroneously connected to the power supply VCC (e.g., 24V) of the DI circuit 12. If the DO port of the DO circuit 11 is shorted and the output transistor Q is in a conducting state, the current flowing into the collector of the output transistor Q will be inevitably excessive (this situation may be referred to as overcurrent), and the voltage of the power supply VCC will be directly applied between the collector and the emitter of the output transistor Q at this time, which approximates to the short circuit of the power supply VCC to ground through the output transistor Q, resulting in the output transistor Q power far exceeding its rated power, the output transistor Q will be damaged instantaneously, and such damage is unrecoverable, thereby causing the digital output circuit to fail.
For the above, a recoverable fuse F1 is currently added mainly before the DO port, as shown in FIG. 1. However, when the recoverable fuse F1 is added before the DO port, since the recoverable fuse F1 is broken due to heat generated after overcurrent, the breaking process may last as short as several tens of milliseconds and as long as a delay time of several seconds. In this period, the output transistor Q must generate heat more seriously, and the on-off switching state is repeated all the time due to the restorable characteristic of the restorable fuse F1, so that the temperature of the output transistor Q does not drop significantly. Although this approach does not damage the output transistor Q for a short period of time, it must nevertheless greatly reduce the life of the output transistor Q and the recoverable fuse F1 and ultimately also lead to failure of the digital output circuit.
Disclosure of Invention
The invention aims to solve the technical problem that the service lives of a first switch tube and a recoverable fuse are affected due to wiring errors in the digital output circuit, and provides a novel digital output circuit and industrial control equipment.
The technical scheme of the invention for solving the technical problems is that the digital output circuit comprises an optical coupler, a first switching tube and a digital output port, wherein a collector electrode of the output end of the optical coupler is connected to a first power supply through a first resistor, an emitter electrode of the output end of the optical coupler is connected to a control end of the first switching tube, the digital output circuit also comprises a second resistor and an overcurrent protection unit, and the overcurrent protection unit comprises a detection subunit and a voltage clamping subunit; two ends of the detection subunit are respectively connected with the digital output port and the control end of the voltage clamping subunit; the second resistor is connected in series between the first power supply and the first resistor, and the voltage clamping subunit clamps the voltage of the connection point of the first resistor and the second resistor to a third preset value when the voltage of the connection point of the first resistor and the second resistor is larger than or equal to a first preset value and the voltage of the control end of the voltage clamping subunit is larger than a second preset value.
In the digital output circuit of the present invention, the detection subunit includes a diode, and an anode of the diode is connected to the control terminal of the voltage clamping subunit, and a cathode of the diode is connected to the digital output port.
In the digital output circuit of the present invention, the voltage clamping subunit includes a third resistor and a power supply reference chip, and the control end of the voltage clamping subunit is formed by a reference electrode of the power supply reference chip; the anode of the power supply reference chip is connected with the reference ground, the cathode of the power supply reference chip is connected with the connection point of the first resistor and the second resistor, the reference electrode of the power supply reference chip is connected with the anode of the diode, and two ends of the third resistor are respectively connected with the cathode of the power supply reference chip and the reference electrode of the power supply reference chip.
In the digital output circuit of the present invention, the voltage clamping subunit includes a fourth resistor, a second switching tube, and a diode group; the first end of the second switch tube is connected with the connection point of the first resistor and the second resistor, the second end of the second switch tube is connected with the reference ground through the diode group, the control end of the second switch tube is connected with the anode of the diode, and the two ends of the fourth resistor are respectively connected with the first end and the control end of the second switch tube.
In the digital output circuit of the present invention, the second switching tube is a triode, and the collector of the second switching tube is connected to the connection point of the first resistor and the second resistor, the emitter is connected to the reference ground via the diode group, and the base is connected to the anode of the diode.
In the digital output circuit of the present invention, the voltage clamping subunit includes a fifth resistor, a third switching tube and a comparator; the positive phase input end of the comparator is connected with the anode of the diode, the negative phase input end of the comparator is connected with the reference voltage, and the output end of the comparator is connected with the control end of the third switching tube; the first end of the third switching tube is connected with a connection point of the first resistor and the second resistor, and the second end of the third switching tube is connected with a reference ground; and two ends of the fifth resistor are respectively connected with the connection point of the first resistor and the second resistor and the non-inverting input end of the comparator.
In the digital output circuit of the present invention, the voltage clamping subunit includes a sixth resistor and a seventh resistor, and the sixth resistor and the seventh resistor are connected in series between the second power supply and the reference ground, and the reference voltage is output to the inverting input terminal of the comparator by the connection point of the sixth resistor and the seventh resistor.
In the digital output circuit of the present invention, the third switching tube is a triode, and the collector of the third switching tube is connected to the connection point of the first resistor and the second resistor, the emitter is connected to the reference ground, and the base is connected to the output end of the comparator.
In the digital output circuit of the present invention, the third switching tube is an N-channel metal oxide semiconductor field effect tube, and a drain electrode of the N-channel metal oxide semiconductor field effect tube is connected to a connection point of the first resistor and the second resistor, a source electrode is connected to a reference ground, and a gate electrode is connected to an output end of the comparator.
The invention also provides an industrial control device comprising a digital output circuit as described above.
According to the digital output circuit and the industrial control equipment, the overcurrent protection unit detects the digital output port voltage of the digital output circuit to clamp the optocoupler output voltage, so that the digital output circuit is prevented from being damaged due to short circuit and overcurrent while the function of the digital output circuit is not affected. The invention has the advantages of simple structure and lower cost.
Drawings
FIG. 1 is a schematic diagram of a digital output circuit and a digital input circuit in a prior art industrial control device;
FIG. 2 is a schematic diagram of an embodiment of a digital output circuit of the present invention;
FIG. 3 is a schematic diagram of an over-current protection unit in the digital output circuit of the present invention;
FIG. 4 is a schematic diagram of a first embodiment of an over-current protection unit in a digital output circuit according to the present invention;
FIG. 5 is a schematic diagram of a second embodiment of an over-current protection unit in the digital output circuit according to the present invention;
fig. 6 is a schematic diagram of a third embodiment of an over-current protection unit in the digital output circuit according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Fig. 2 and 3 are schematic diagrams of an embodiment of a digital output circuit according to the present invention, which can be applied to an industrial control device (such as a frequency converter or a servo motor controller, etc.), and can transmit high-low level state information, pulse information, etc. to an upper computer (such as a PLC, i.e. a programmable logic controller). The digital output circuit in this embodiment includes an optocoupler U1, a first resistor R1, a first switching tube Q1 (specifically, a triode or the like may be used), a digital output port DO, a second resistor R2, and an overcurrent protection unit 2, where a collector of an output end of the optocoupler U1 is connected to a first power supply (+24v) via the first resistor R1 and the second resistor R2 connected in series, and an emitter is connected to a control end of the first switching tube Q1 (the first switching tube Q1 is connected between the digital output port DO and a reference ground COM). The overcurrent protection unit 2 includes three pairs of external ports, and a first pair of external ports 21 is connected to a connection point of the first resistor R1 and the second resistor R2, a second pair of external ports 22 is connected to the digital output port DO, and a third pair of external ports 23 is grounded.
The overcurrent protection unit 2 may specifically include a detection subunit 24 and a voltage clamping subunit 25. The two ends of the detection subunit 24 are respectively connected with the control ends of the second pair of external ports 22 (namely the digital output port DO) and the voltage clamping subunit 25; the voltage clamping subunit 25 clamps the voltage of the first pair of external ports 21 to a third preset value when the voltage of the first pair of external ports 21 (i.e., the connection point of the first resistor R1 and the second resistor R2) is greater than or equal to a first preset value and the voltage of the control terminal of the voltage clamping subunit 25 is greater than a second preset value, and does not clamp the voltage of the first pair of external ports 21 when in other states (i.e., the voltage of the first pair of external ports 21 is less than the first preset value or the voltage of the control terminal of the voltage clamping subunit 25 is less than or equal to the second preset value). The first preset value, the second preset value, and the third preset value may be specifically set according to the resistance values of the first resistor R1 and the second resistor R2 and other element parameters.
The second external port 22 of the over-current protection unit 2 is used for monitoring and outputting an over-current/short-circuit condition, when no over-current/short-circuit condition occurs, the impedance between the first external port 21 and the third external port 23 approaches infinity, no current flows into the over-current protection unit 2, and no influence is caused on the normal function of the whole digital output circuit; when the overcurrent/short circuit condition occurs and the optocoupler U1 is in the on state, the impedance between the first pair of external ports 21 and the third pair of external ports 23 of the overcurrent protection unit 2 becomes smaller or a clamping effect occurs, so that the potential of the connection point of the first resistor R1 and the second resistor R2 to the reference ground COM is greatly reduced, and due to the current limiting effect of the first resistor R1 and the current limiting resistor R11, the base current of the first switching tube Q1 is greatly reduced, so that the power consumption of the first switching tube Q1 can be reduced to an acceptable range, and the purpose of protecting the first switching tube Q1 can be achieved.
Specifically, as shown in fig. 4, the detecting subunit 24 may include a diode D1, and an anode of the diode D1 is connected to the control terminal of the voltage clamping subunit 25, and a cathode is connected to the second external port 22 (i.e. the digital output port DO). The voltage clamping subunit 25 includes a third resistor R3 and a power reference chip U2 (e.g., TL431/TL432 chip by mei texas instruments), wherein the power reference chip U2 includes three pins: the reference electrode (R), the anode (A) and the cathode (K), wherein the anode of the power supply reference chip U2 is connected with the third external port 23, the cathode is connected with the first external port 21, the reference electrode is connected with the anode of the diode D1, and two ends of the third resistor R3 are respectively connected with the anode and the reference electrode of the power supply reference chip U2.
Taking TL431/TL432 as an example, the reference voltage is 2.5V, which determines whether the anode and the cathode can be reversely conducted according to the magnitude relation between the reference electrode and the voltage of 2.5V, when the reference electrode voltage is greater than or equal to 2.5V, the voltage between the cathode and the anode can be reduced to 2.5V at the lowest, and when the reference electrode voltage is less than 2.5V, there is almost no current between the cathode and the anode, and the anode is in a cut-off state.
When the optocoupler U1 is turned on and the digital output port DO is not over-current/short-circuited, the first switching tube Q1 is turned on, and the collector-emitter voltage drop of the first switching tube Q1 is about 0.2V, at this time, the digital output port DO is output as a low level. If the conduction voltage drop of the diode D1 is 0.7V at this time, the voltage of the reference electrode input terminal of the power reference chip U2 is about 0.9V, the power reference chip U2 is not turned on, and the output of the digital output port DO of the digital output circuit is not affected.
When the optocoupler U1 is not turned on and the digital output port DO is not over-current/short-circuited, the base electrode of the first switching tube Q1 is not turned on if there is no voltage, so that the collector voltage of the first switching tube Q1 is the voltage of the first power supply, for example, 24V, that is, the cathode voltage of the diode D1 is 24V, which is necessarily higher than the anode voltage of the diode D1, and the diode D1 is turned off, and because the reference electrode input of the power reference chip U2 is high-resistance, there is almost no voltage difference across the third resistor R3. Therefore, the reference electrode of the power reference chip U2 is necessarily higher than the reference voltage of 2.5V, the power reference chip U2 is conducted, and finally the cathode of the power reference chip U2 is stabilized at 2.5V. The current flowing through the power reference chip U2 is about (24V-2.5V)/R2, and the resistance value of the second resistor R2 can be adjusted to meet the recommended application current range of the power reference chip U2.
When the optocoupler U1 is turned on and the digital output port DO is over-current/short-circuited (the general application condition is that a 24V power source is directly connected to the digital output port DO), if the over-current protection unit 2 does not operate, the first switching tube Q1 will necessarily be turned on, and at this time, the cathode voltage of the diode D1 is about the voltage of the digital output port DO, for example, 24V, the diode D1 will necessarily be turned off, and the reference voltage of the power reference chip U2 will be greater than 2.5V, so that the power reference chip U2 operates to clamp the electric potential at the cathode of the power reference chip U2 to 2.5V. In this case, the resistance values of the resistor first resistor R1 and the current limiting resistor R11 may be adjusted to limit the maximum value of the base current of the first switching transistor Q1. If the first switching tube Q1 is in an on state, the base current of the first switching tube Q1 is:
Ib＝(2.5V-U U2-CE -U Q1-BE )/R1-U Q1-BE /R11 (1)
wherein U is U1-CE For the output conduction voltage drop of the optocoupler U1, U Q1-BE Is the voltage drop between the base and emitter of the first switching tube Q1. By adjusting the resistance values of the first resistor R1 and the current limiting resistor R11, the base current Ib of the first switching tube Q1 can be made to be as small as possible, so that the current Ic flowing into the collector electrode of the first switching tube Q1 is greatly reduced, the power of the first switching tube Q1 is also greatly reduced, and the first switching tube Q1 is not damaged.
When the optocoupler U1 is not conductive and the digital output port DO is over-current/short-circuited, the state is consistent with the state in the case when the optocoupler U1 is not conductive and the digital output port DO is not over-current/short-circuited.
As shown in fig. 5, the voltage clamping subunit 25 may also be implemented by: the circuit comprises a fourth resistor R4, a second switching tube Q2 and a diode group (the diode group can be composed of a plurality of diodes D2, D3, … and Dn which are connected in series, and the specific number of the diodes can be adjusted according to the requirement); the first end of the second switching tube Q2 is connected to the first pair of external ports 21, the second end is connected to the reference ground via a diode group, the control end is connected to the anode of the diode D1, and the two ends of the fourth resistor R4 are respectively connected to the first end and the control end of the second switching tube Q2.
For the convenience of analysis, it is assumed that n-1 diodes (n is an integer greater than or equal to 2) are connected in series in the diode group, and the conduction voltage drop of all the diodes D2, D3, …, dn connected in series is V F The on-state voltage drop of diode D1 is also V F The second switching transistor Q2 adopts a second triode. The voltage at the digital output port DO is higher than (n-2) x V F +V BE When the second transistor is turned on, the first pair of external ports 21 of the overcurrent protection unit 2 can be clamped to the potential: (n-1) XV F +V CE Wherein V is BE And V CE The base-emitter conduction voltage drop and the collector-emitter conduction voltage drop of the second triode respectively. This protects the digital output circuit from the first switching tube Q1 in the event of a short circuit/overcurrent.
As shown in fig. 6, the voltage clamping subunit 25 may also be implemented by: the circuit comprises a fifth resistor R5, a third switching tube Q3 and a comparator U3; the positive input end of the comparator U3 is connected with the anode of the diode D1, and the negative input end is connected with the reference voltage V REF The output end is connected with the control end of the third switching tube Q3; the first end of the third switching tube Q3 is connected with the first pair of external ports 21 through a resistor R0, and the second end of the third switching tube Q3 is connected with the third pair of external ports 23; both ends of the fifth resistor R5 are connected to the first pair of external ports 21 and the non-inverting input terminal of the comparator U3, respectively.
In particular, the reference voltage may be implemented by a sixth resistor R6 and a seventh resistor R7 connected in series between the second power supply +v1 and the reference ground, and the reference voltage is output from the connection point of the sixth resistor R6 and the seventh resistor R7 to the inverting input terminal of the comparator U3.
In the present embodiment, if the on-voltage drop of the diode D1 is V F The voltage at the digital output port DO is higher than V REF -V F When the voltage at the non-inverting input terminal of the comparator U3 is higher than the voltage at the inverting input terminal, the comparator U3 outputs a high level, and the third switching tube Q3 is turned on. By setting the proportional relation among the resistor R0, the first resistor R1 and the second resistor R2, the first external port 21 of the overcurrent protection unit 2 can be clamped to a desired voltage, and if the clamped voltage is larger than V REF The voltage at the non-inverting input of the comparator U3 is always greater than the voltage at the inverting input as long as the digital output DO is in a short/overcurrent condition, thereby protecting the output transistor Q1.
The third switching transistor Q3 may be a second transistor, and a collector of the second transistor is connected to the first pair of external ports 21 via a resistor R0, an emitter is connected to the ground reference, and a base is connected to an output terminal of the comparator U3. Of course, the third switching tube Q3 may also be an nmos fet, and the drain of the nmos fet is connected to the first pair of external ports 21 via the series resistor R0, the source is connected to the ground, and the gate is connected to the output terminal of the comparator U3.
The invention also provides an industrial control device which can be a frequency converter, a servo motor controller and the like, comprises the digital output circuit, and transmits high-low level state information, pulse information and the like to an upper computer (such as a programmable logic controller) through the digital output circuit.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present invention should be covered by the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims (8)
1. The digital output circuit comprises an optocoupler, a first switching tube and a digital output port, wherein a collector electrode of the output end of the optocoupler is connected to a first power supply through a first resistor, and an emitter electrode of the output end of the optocoupler is connected to a control end of the first switching tube; two ends of the detection subunit are respectively connected with the digital output port and the control end of the voltage clamping subunit; the second resistor is connected in series between the first power supply and the first resistor, and the voltage clamping subunit clamps the voltage of the connection point of the first resistor and the second resistor to a third preset value when the voltage of the connection point of the first resistor and the second resistor is larger than or equal to a first preset value and the voltage of the control end of the voltage clamping subunit is larger than a second preset value;
the voltage clamping subunit comprises a third resistor and a power supply reference chip, and the control end of the voltage clamping subunit is formed by a reference electrode of the power supply reference chip; the anode of the power supply reference chip is connected with a reference ground, the cathode of the power supply reference chip is connected with a connecting point of the first resistor and the second resistor, the reference electrode is connected with the detection subunit, and two ends of the third resistor are respectively connected with the cathode of the power supply reference chip and the reference electrode.
2. The digital output circuit comprises an optocoupler, a first switching tube and a digital output port, wherein a collector electrode of the output end of the optocoupler is connected to a first power supply through a first resistor, and an emitter electrode of the output end of the optocoupler is connected to a control end of the first switching tube; two ends of the detection subunit are respectively connected with the digital output port and the control end of the voltage clamping subunit; the second resistor is connected in series between the first power supply and the first resistor, and the voltage clamping subunit clamps the voltage of the connection point of the first resistor and the second resistor to a third preset value when the voltage of the connection point of the first resistor and the second resistor is larger than or equal to a first preset value and the voltage of the control end of the voltage clamping subunit is larger than a second preset value;
the voltage clamping subunit comprises a fourth resistor, a second switching tube and a diode group; the first end of the second switch tube is connected with the connection point of the first resistor and the second resistor, the second end of the second switch tube is connected with the reference ground through the diode group, the control end of the second switch tube is connected with the detection subunit, and the two ends of the fourth resistor are respectively connected with the first end and the control end of the second switch tube.
3. The digital output circuit of claim 2, wherein the second switching tube is a triode, and wherein a collector of the second switching tube is connected to a connection point of the first resistor and the second resistor, an emitter is connected to a reference ground via the diode group, and a base is connected to the detection subunit.
4. The digital output circuit comprises an optocoupler, a first switching tube and a digital output port, wherein a collector electrode of the output end of the optocoupler is connected to a first power supply through a first resistor, and an emitter electrode of the output end of the optocoupler is connected to a control end of the first switching tube; two ends of the detection subunit are respectively connected with the digital output port and the control end of the voltage clamping subunit; the second resistor is connected in series between the first power supply and the first resistor, and the voltage clamping subunit clamps the voltage of the connection point of the first resistor and the second resistor to a third preset value when the voltage of the connection point of the first resistor and the second resistor is larger than or equal to a first preset value and the voltage of the control end of the voltage clamping subunit is larger than a second preset value;
the voltage clamping subunit comprises a fifth resistor, a third switching tube and a comparator; the non-inverting input end of the comparator is connected with the detection subunit, the inverting input end of the comparator is connected with the reference voltage, and the output end of the comparator is connected with the control end of the third switching tube; the first end of the third switching tube is connected with a connection point of the first resistor and the second resistor, and the second end of the third switching tube is connected with a reference ground; and two ends of the fifth resistor are respectively connected with the connection point of the first resistor and the second resistor and the non-inverting input end of the comparator.
5. The digital output circuit of claim 4, wherein the voltage clamping subunit comprises a sixth resistor and a seventh resistor, and the sixth resistor and the seventh resistor are connected in series between a second power supply and a reference ground, and the reference voltage is output to the inverting input terminal of the comparator from the connection point of the sixth resistor and the seventh resistor.
6. The digital output circuit of claim 4, wherein the third switching tube is a triode, and wherein a collector of the third switching tube is connected to a connection point of the first resistor and the second resistor, an emitter of the third switching tube is connected to a reference ground, and a base of the third switching tube is connected to an output end of the comparator.
7. The digital output circuit of claim 4, wherein the third switching tube is an nmos fet, and a drain of the nmos fet is connected to a connection point of the first resistor and the second resistor, a source is connected to a reference ground, and a gate is connected to an output of the comparator.
8. An industrial control device comprising a digital output circuit as claimed in any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810315648.6A CN108733122B (en) | 2018-04-10 | 2018-04-10 | Digital output circuit and industrial control equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810315648.6A CN108733122B (en) | 2018-04-10 | 2018-04-10 | Digital output circuit and industrial control equipment |
Publications (2)
| Publication Number | Publication Date |
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| CN108733122A CN108733122A (en) | 2018-11-02 |
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| CN108733122A (en) | 2018-11-02 |
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