Device for communication between a controller and a field device

Abstract

A device, preferably a plug-in module, for communication between a controller and a field device. The device includes contacts, wherein a first subset of the contacts is electrically conductively connected or connectable to the controller and a second subset of the contacts is electrically conductively connected or connectable to the field device. The apparatus further includes a circuit having an input electrically conductively connected to the first subset of the contacts and an output electrically conductively connected to the second subset of the contacts. The circuit includes a voltage-limiting unit adapted to limit a voltage at the output, and a current-limiting unit adapted to limit a current between the input and the output and to interrupt the current when the voltage-limiting unit responds.

Claims

1. A device for communication between a controller and a field device, comprising: contacts, wherein a first subset of the contacts is electrically connected or connectable to the controller, and a second subset of the contacts is electrically connected or connectable to the field device; and a circuit, an input of which is electrically conductively connected to the first subset of the contacts and an output of which is electrically conductively connected to the second subset of the contacts, the circuit comprising a voltage-limiting unit configured to limit a voltage at the output, and a current-limiting unit configured to limit a current between the input and the output and to interrupt the current upon response of the voltage-limiting unit, wherein the current-limiting unit further comprises a measuring resistor and a detecting resistor, wherein an input of a switching element is electrically conductively connected to the input of the current-limiting unit, an output of the switching element is electrically conductively connected to the output of the current-limiting unit via the measuring resistor, and a signal input of the switching element for detecting the current is electrically conductively connected to the output of the current-limiting unit via the detecting resistor.

2. The device according to claim 1, wherein the voltage-limiting unit is configured to limit the voltage at the output to a voltage limit value.

3. The device of claim 2, wherein the voltage-limiting unit includes a Z-diode or a varistor.

4. The device according to claim 1, wherein the current-limiting unit is configured to limit the current to a current limit value.

5. The device according to claim 4, wherein the current-limiting unit is the switching element.

6. The device according to claim 1, wherein the current-limiting unit comprises the switching element, wherein the switching element comprises an input, an output and a signal input, wherein the switching element is configured to electrically conductively connect the input of the switching element and the output of the switching element in a conducting switching state and electrically disconnect the input of the switching element and the output of the switching element in a current-interrupting switching state, the current-limiting unit being further configured to detect the current at the signal input and to control the switching state as a function of the detected current.

7. The device according to claim 1, wherein the voltage-limiting unit and the current-limiting unit are connected in series, or the current-limiting unit is connected between the input and the output, or wherein the voltage-limiting unit is connected in parallel with the output for limiting the voltage at the output.

8. The device according to claim 1, wherein the voltage-limiting unit for limiting the voltage at the output is configured to short-circuit the output upon response, and wherein the current-limiting unit is configured to interrupt the current in response to the short-circuiting of the output.

9. The device according to claim 8, wherein the contacts are configured for pluggable electrically conductive connection to a base module, wherein the first subset of the contacts are electrically conductively connected or connectable to the controller via the base module and the second subset of the contacts are electrically conductively connected or connectable to the field device via the base module.

10. The device according to claim 1, wherein the device comprises a circuit board on which the circuit is disposed, and wherein conductive traces on the circuit board electrically conductively connect the circuit to the contacts.

11. The device according to claim 1, further comprising a further voltage-limiting unit configured to limit a voltage at the input, optionally wherein the further voltage-limiting unit is configured to limit the voltage at the input to a further voltage limit value.

12. The device according to claim 11, wherein the voltage-limiting unit is a Z-diode or a varistor.

13. The device according to claim 1, wherein the input or the first subset of the contacts comprises at least two input poles and the output or the second subset of the contacts comprises at least two output poles, wherein one of the input poles, is selectively electrically conductively connected to one of the output poles by means of the current-limiting unit or wherein one of the input poles, is permanently electrically conductively connected to an output pole.

14. The device according to claim 1, wherein the input or the first subset of the contacts comprises at least two input poles and one of the input poles, is electrically conductively connected to another one of the input poles, by means of the further voltage-limiting unit upon the response, or wherein the output or the second subset of the contacts comprises at least two output poles and one of the output poles, is electrically conductively connected to another one of the output poles, by means of the voltage-limiting unit upon the response.

15. The device according to claim 1, wherein an output of the current-limiting unit is electrically conductively connected to the voltage-limiting unit or wherein an input of the current-limiting unit is electrically conductively connected to the further voltage-limiting unit.

16. A device for communication between a controller and a field device, comprising: contacts, wherein a first subset of the contacts is electrically connected or connectable to the controller, and a second subset of the contacts is electrically connected or connectable to the field device; and a circuit, an input of which is electrically conductively connected to the first subset of the contacts and an output of which is electrically conductively connected to the second subset of the contacts, the circuit comprising a voltage-limiting unit configured to limit a voltage at the output, and a current-limiting unit configured to limit a current between the input and the output and to interrupt the current upon response of the voltage-limiting unit wherein a switching element is clocked between a current-conducting switching state and a current-interrupting switching state.

17. The device according to claim 16, wherein the clocking is achieved via pulse width modulation.

18. The device according to claim 17, wherein a duty cycle of the pulse width modulation is a monotonically decreasing function of the current, or wherein the duty cycle is zero when a voltage threshold is reached or exceeded.

19. A device for communication between a controller and a field device, comprising: contacts, wherein a first subset of the contacts is electrically connected or connectable to the controller, and a second subset of the contacts is electrically connected or connectable to the field device; and a circuit, an input of which is electrically conductively connected to the first subset of the contacts and an output of which is electrically conductively connected to the second subset of the contacts, the circuit comprising a voltage-limiting unit configured to limit a voltage at the output, and a current-limiting unit configured to limit a current between the input and the output and to interrupt the current upon response of the voltage-limiting unit, and a capacitance connected in parallel with the current-limiting unit.

20. The device of claim 19, wherein the capacitance is adapted to transmit a fieldbus signal from the input to the output independently of a switching state of the current-limiting unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the disclosure is explained in more detail with reference to the drawings by means of preferred embodiments.

(2) It is shown:

(3) FIG. 1 a schematic representation of a device for communication between a controller and a field device according to a first embodiment;

(4) FIG. 2 a schematic representation of the device for communication between a controller and a field device according to a second embodiment;

(5) FIG. 3 a schematic representation of the device for communication between a controller and a field device according to a third embodiment;

(6) FIG. 4 a schematic current-voltage diagram for the output of the circuit of the device; and

(7) FIG. 5 a schematic current-voltage diagram for the switching element of the circuit of the device.

DETAILED DESCRIPTION

(8) FIG. 1 shows a schematic representation of an embodiment of a device, generally designated by reference numeral 100, for communication between a controller 300 and a field device 400. The device 100 may be in the form of a plug-in module 100 for electrical and mechanical connection to a base module 200.

(9) The device 100 includes contacts 102, a first subset 102A of the contacts 102 being electrically conductively connected or connectable to the controller 300. A second subset 1026 of the contacts 102 is electrically conductively connected or connectable to the field device 400.

(10) For example, the contacts 102 may be implemented by means of a connector half 103. The device 100 further comprises a circuit 104. An input 104A of the circuit 104 is electrically conductively connected to the first subset 102A of the contacts 102. An output 1046 of the circuit 104 is electrically conductively connected to the second subset of the contacts 102. The circuit 104 includes a voltage-limiting unit 106B configured to limit a voltage at the output 104B, and a current-limiting unit 108 configured to limit a current between the input 104A and the output 104B and to interrupt the current when the voltage-limiting unit 106A or 106B responds.

(11) While the first embodiment of the device 100 shown in FIG. 1 is connectable to the controller 300 and the field device 400 via a pluggable connection 103 and 203, in a variant of each embodiment, the controller 300 and the field device 400 may be directly connectable to the device 100 (for example, by means of corresponding connections 204 and 206 of the device 100, respectively).

(12) The base module 200 is configured for pluggably receiving the device 100 (for example, the plug-in module 100). The base module 200 comprises complementary contacts 202 for pluggable electrically conductive connection to the contacts 102 of the device 100. For example, the contacts 202 may be implemented by means of a connector half 203 complementary to the connector half 103 (for example, a slot matching the contacts).

(13) For example, the electrical and mechanical coupling between the plug-in module 100 and the base module 200 is provided by an existing connector half 103 in the base of the plug-in module 100. This connector half 103, together with the counterpart 203, i.e. the complementary connector half 203, forms an interface 103, 203 to the base module 200.

(14) A first subset 202A of the complementary contacts 202 may respectively contact the first subset 102A of the contacts of the received device 100. A second subset 202B of the complementary contacts 202 may respectively contact the second subset 1026 of the contacts 102 of the received device 100. The base module 200 includes a control side terminal 204 electrically connected to the first subset 202A of the complementary contacts 202. The base module 200 further comprises a field-side terminal 206 electrically conductively connected to the second subset 202B of the complementary contacts 202.

(15) Any embodiment described herein may be designed or configured to comply with the European Union (EU) Directive on Explosion Protection (French: ATmosphères Explosibles, or ATEX for short). The ATEX comprises two directives, namely the ATEX Product Directive 2014/34/EU and the ATEX Operational Directive 1999/92/EC. Alternatively or additionally, any embodiment described herein may be designed or configured to comply with provisions of IECEx. IECEx is a non-governmental system under the auspices of the International Electrotechnical Commission (IEC).

(16) Any embodiment of the device 100 described herein may be realizable as a non-ignitable (technically referred to as “non-incendive”) plug-in module, for example, in accordance with ATEX and/or IECEx in Europe and/or in accordance with a so-called “non-incendive” ignition protection type in the United States. Non-ignition capability or non-incendivity is a frequent requirement in the process industry.

(17) The non-ignition capability or non-incendivity may be satisfied due to current and voltage limiting without using resistive current and voltage limiting. As a result, embodiments of the device 100 may avoid exposing components thereof to high power dissipation at maximum load. In particular, a fire of a transfer element in control cabinets may be avoided.

(18) The circuit 104 may further be configured to process signals. For example, the circuit 104 may comprise a signal processing circuit (SPC for short). A range of functions for signal processing the signal received at the input 104A from the controller 300 to the field side output at the output 1046 (or the reverse signal direction) may include any variety. Without limitation as to further signal processing functions, the present description addresses functions for non-firing use cases.

(19) Embodiments of the device 100 offer the possibility of bringing the power dissipation of previous non-ignitable circuits, in particular previous resistive circuits, to as low a level as possible, thus ensuring the necessary ignition protection type.

(20) For this purpose, the aforementioned SPC 104 of the plug-in module 100 comprises a circuit 106A, 1066 and 108 that maintains the current of the field device 400 as a load and the voltage at the required protection level. For example, this circuit 104 may be designed or configured to control a solenoid valve, optionally supplemented by a galvanic isolation between input 104A and output 104B.

(21) The aim of the following circuit is to minimize the current problems of other products available on the market. Currently, said circuits for “non-incendive” products are mainly built on a resistive basis. This always implies the problem that in the event of a fault (or high continuous load) a power dissipation of, for example, 5 W can emitted at a resistor. This adds up in a system according to the required channels (for example the control 300). In individual cases, this power loss can lead to burnt-out circuits in control cabinets.

(22) The circuit 104 in embodiments of the device 100 may be configured to allow currents less than the current limit value of, for example, 170 mA to flow to the field device 400 as a load. Any currents greater than the current limit value are limited to the current limit value. A significantly lower power dissipation is established at the components based on the voltage drop across the current-limiting unit 108 (for example, as electronic control).

(23) This lower power dissipation makes it possible to design the device 100 in a more compact way and in accordance with the conditions, which, for example, fits well in a housing 101 of the plug-in module 100. The narrow design is compact and modular (for example, interchangeable). Embodiments may be compatible with programmable logic controllers (PLCs), a process control system, or a distributed control system (DCS for short) as a controller 300. Furthermore, embodiments may be compatible with Universal Input/Output Systems (in technical terms, “Universal I/O System”) in which input 104A is connected or connectable to a program-based configurable interface of the controller 300.

(24) FIG. 2 shows a schematic diagram of the device 100 for communication between the controller 300 and the field device 400 according to a second embodiment. The second embodiment example may be realizable by itself or as a further development of the first embodiment example.

(25) The current-limiting unit 108 comprises a switching element 120. The switching element 120 comprises an input 126, an output 128, and a signal input 130. The switching element 120 is configured to electrically conductively connect the input 126 of the switching element 120 and the output 128 of the switching element 120 in a conducting switching state, and to electrically disconnect the input 126 of the switching element 120 and the output 128 of the switching element 120 in a current-interrupting switching state. The current-limiting unit 108 may be further configured to detect or sense the current as a voltage signal at the signal input 130, and to control the switching state depending on the sensed or detected current.

(26) The current-limiting unit 108 further comprises a measuring resistor 122 and a detecting resistor 124. The input 126 of the switching element 120 is electrically conductively connected to the input 116A of the current-limiting unit 108. The output 128 of the switching element 120 is electrically conductively connected to the output 116B of the current-limiting unit 108 via the measuring resistor 122. The signal input 130 of the switching element 120 for detecting the current is electrically conductively connected to the output 1166 of the current-limiting unit 108 via the detecting resistor 124. Since the resistors 122 and 124 are connected in parallel with respect to the output 116B, and no significant voltage is dropped across the detecting resistor 124 (due to the low current flow through the detecting resistor 124), the current-dependent voltage drop across the measuring resistor 122 is present at the signal input 130.

(27) Each embodiment of the device 100 may be configured to include either the voltage-limiting unit 106B or the further voltage-limiting unit 106A, or both.

(28) The further voltage-limiting unit 106A and the voltage-limiting unit 106B may include a first Z-diode D.sub.1 and a second Z-diode D.sub.2, which set the current (for example, the output current I.sub.A) to zero at an input voltage U.sub.E and an output voltage U.sub.A, respectively, greater than the voltage limit value U.sub.WP (for example, 28 V). Optionally, the voltage-limiting units 106A and 106B may each have different voltage limit values.

(29) The circuit 104 (which may also be referred to as an ignition protection circuit) includes, as a current-limiting unit 108, an integrated circuit (IC.sub.1) having an electronic control that limits the current (for example, the output current I.sub.A) to I.sub.WP (for example, 170 mA or 5 W/U.sub.WP) at an output voltage U.sub.A that is less than the voltage limit U.sub.WP.

(30) The current-limiting unit 108 includes a measuring resistor 122 (also: output resistor) R.sub.2 through which the IC.sub.1 108 outputs the limited current I.sub.A. The IC.sub.1 108 detects the voltage drop across the output resistor R.sub.2 as a measure of the output current I.sub.A via a detecting resistor (also tap resistor) R.sub.1.

(31) Optionally, the IC.sub.1 108 includes a TAB attachment point 132 for mounting the raw IC.sub.1 108 directly on the printed circuit board 101 (PCB for short), i.e., for so-called tape-automated bonding (TAB). Heat from the reduced power dissipation of the IC.sub.1 108 may be dissipated to a cooling element on the PCB 101 via the TAB attachment point 132.

(32) Optionally, the circuit 104 includes a capacitor C.sub.1 118, which connects input 104A and output 104B of the ignition protection circuit. Via this, a high frequency component may be passed through the circuit 104 independently of the current-limiting unit 108 acting on the direct current (DC) component.

(33) FIG. 3 shows a schematic diagram of the device 100 for communication between the controller 300 and the field device 400 according to a third embodiment, which may be combinable with the first or second embodiment of the device 100.

(34) In order to minimize the power dissipation in IC.sub.1 108, the switching transistor 134 in IC.sub.1 108 may be switched through at the operating point (U.sub.WP, I.sub.WP). This means that the relationship R.sub.2=(U.sub.E−U.sub.WP)/I.sub.WP may apply or hold between the output resistor R.sub.2, the input voltage U.sub.E, and the voltage limit U.sub.WP.

(35) The current-limiting unit 108 may include a differential amplifier 136 (for example inverted on the output side) that detects (i.e., senses) the current at the input 130 as a voltage drop across the measuring resistor 122 via the detecting resistor 124, and controls the switching state of the switching transistor 134 as a function of the current. This control may further comprise pulse width modulation of the switching state of the switching element 120 (for example, the switching transistor 134).

(36) In FIG. 4, the conventional resistive limiting and electronic limiting of an embodiment of the device 100 are schematically shown graphically in an output characteristic to show the differences between the conventional resistive circuits and the circuit 104.

(37) The dashed line represents the behavior of a resistive circuit. The full line represents the output characteristic of circuit 104 (e.g. an electronic control). Both circuits, are intended to provide the necessary type of ignition protection at the work point (WP for short). For example, the WP corresponds to the current limit value (for example 170 mA) and the voltage limit value (for example 28 V).

(38) The current limit value and the voltage limit value may be defined by the values required by the directive for IECEx and ATEX or an ignition protection type for protection in hazardous areas (for example, so-called Ex products). In principle, any embodiment of the circuit 104 may be formed for any predetermined current limit value and/or voltage limit value. Therefore, the values for current, voltage and power mentioned herein are assumed to be exemplary only.

(39) By clocking the switching element 120 (for example, the switching transistor 134) to limit the current I.sub.A at the output 104B to the current limit value I.sub.WP, the power dissipation P.sub.LOSS=I.sub.A (U.sub.WP−U.sub.A) can be prevented or reduced in the switching element 120 (for example, the switching transistor 134) of the current-limiting unit 108.

(40) FIG. 4 shows the limitation of the voltage U.sub.A at the output 104B to the voltage limit value U.sub.WP (“case 1”) and of the current I.sub.A at the output 104B to the current limit value I.sub.WP achievable by embodiments of the device 100. “Case 2” shows (also for a variant of the embodiments without the further, i.e. input side, voltage-limiting unit 106A, for example without the Z-diode D1) how the current is interrupted in case of an output side overvoltage.

(41) FIG. 5 schematically shows the voltage U.sub.T applied to the switching element 134 (for example, between the source and drain) and the current I.sub.T flowing through the switching element 134. In the exemplary case of an n-channel MOSFET as the switching element 134, the current may be I.sub.DS=I.sub.T and the voltage may be U.sub.DS=U.sub.T at the source “S” and the drain “D”.

(42) By alternating (for example, clocking, for example according to pulse width modulation) between the conductive (i.e., closed) switching state 506 and the current-interrupting switching state 508, the current can be limited and the switching element 134 can always be operated in the switching region 502. A large power dissipation in the dissipative region 504 can thus be avoided.

(43) Although the disclosure has been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various modifications may be made and equivalents may be used as substitutes. Further, many modifications may be made to adapt a particular situation or material to the teachings of the invention. Consequently, the disclosure is not limited to the disclosed embodiments, but encompasses all embodiments falling within the scope of the appended claims.

(44) TABLE-US-00001 List of reference signs Device, for example a plug-in module 100 Device board 101 Contacts of the device, for example plug-in 102 contacts of the plug-in module First subset of contacts  102A Second subset of contacts  102B Connector half 103 Circuit of the device 104 Input of the circuit  104A Output of the circuit  104B Other voltage-limiting unit  106A Voltage-limiting unit  106B Current-limiting unit 108 Conductive traces (or tracks) to the  110A first subset of contacts Conductive traces (or tracks) to the  110B second subset of contacts Input poles  112A Output poles  112B Permanent connection 114 Input of the current-limiting unit  116A Output of the current-limiting unit  116B Capacitance, for example a capacitor 118 Switching element 120 Measuring resistor 122 Detecting resistor 124 Input of the switching element 126 Output of the switching element 128 Signal input of the switching element 130 Attachment point of the Tape-Automated 132 Bonding (TAB) Switching transistor, for example a MOSFET 134 Base module 200 Complementary contacts of the base module 202 Complementary connector half 203 Control-side connection 204 Field-side connection 206 Controller, e.g., controlling unit 300 Switching region 502 Dissipative region 504 Current-conducting switching state 506 of the switching element Current-interrupting switching state 508 of the switching element