EP0563787B1 - Monitoring circuit for computer controlled safety devices - Google Patents

Monitoring circuit for computer controlled safety devices Download PDF

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Publication number
EP0563787B1
EP0563787B1 EP93104908A EP93104908A EP0563787B1 EP 0563787 B1 EP0563787 B1 EP 0563787B1 EP 93104908 A EP93104908 A EP 93104908A EP 93104908 A EP93104908 A EP 93104908A EP 0563787 B1 EP0563787 B1 EP 0563787B1
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EP
European Patent Office
Prior art keywords
monitoring circuit
relay
switch
holding capacitor
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP93104908A
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German (de)
French (fr)
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EP0563787A1 (en
Inventor
Karl Jun. Dungs
Rudolf Haug
Alfred Sinner
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Karl Dungs GmbH and Co KG
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Karl Dungs GmbH and Co KG
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Publication of EP0563787A1 publication Critical patent/EP0563787A1/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H47/00Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
    • H01H47/02Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay
    • H01H47/04Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay for holding armature in attracted position, e.g. when initial energising circuit is interrupted; for maintaining armature in attracted position, e.g. with reduced energising current
    • H01H47/043Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay for holding armature in attracted position, e.g. when initial energising circuit is interrupted; for maintaining armature in attracted position, e.g. with reduced energising current making use of an energy accumulator
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H47/00Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
    • H01H47/002Monitoring or fail-safe circuits

Definitions

  • the invention relates to a monitoring circuit for computer-controlled safety devices with a switchover element that can be brought into an operating position by a first control signal from the computer, a holding capacitor being connected in parallel with the control branch of the switchover element, and the holding capacitor being able to be charged via the charging circuit in the rest position of the switchover element.
  • Such a monitoring circuit is known from GB-A-2 207 307.
  • the known monitoring circuit compares an analog sensor signal with an analog reference signal, the two signals being digitized alternately in the same AD converter. The results of the comparison are continuously evaluated dynamically and a safety control contact is activated accordingly.
  • Safety devices are gas valves, ignition devices and the like in gas installations. ⁇ .
  • Such monitoring circuits have a special need for a simple and intrinsically safe circuit arrangement.
  • the above object is achieved according to the invention in a generic monitoring circuit in that that the resistance of the charging circuit of the holding capacitor is chosen so high that it is not possible for the switching element is to attract directly via the resistor that a voltage divider is switched on in the charging circuit of the holding capacitor, at least one safety-technical device being connected to one end of the voltage divider via a switching element, and the current flowing through the device from the voltage divider when the switching element is switched on Charging the holding capacitor prevents a drive circuit from being provided, through which the drive path of the switching element can become high-resistance or low-resistance, and that the switching element is held in its operating position after the charging of the holding capacitor and simultaneous application of the first drive signal, in which the charging circuit is switched off is.
  • a monitoring circuit for automatic gas burner controls One requirement for such a monitoring circuit for automatic gas burner controls is that the latter remain switched off when an impermissible operating state occurs and that a fault lock must be implemented.
  • the power supply line to each safety-relevant consumer is routed via a changeover contact of the said changeover element, wherein at least one switching element is again provided in the power supply lines to the safety-relevant consumers, the open state of which is also detected.
  • the switching element is connected in parallel with the safety capacitor in the rest position of the switching element together with the safety-relevant consumer, a voltage divider being switched on in the charging circuit of the holding capacitor after the switch of the switching element, with one end of which has at least one safety-related device via one of the said Switching elements is connected and which is closed by the safety-relevant device Switching element current flowing from the voltage divider prevents charging of the holding capacitor.
  • a changeover relay is preferably used as the changeover element.
  • Unlocking must be done manually and must not be caused by a power failure and recurring power.
  • the monitoring circuit according to the invention is designed so that the switchover element remains in its rest position in the event of a power failure and return of the power supply.
  • the fault lock can be stored in an EEPROM, a battery-backed RAM or an additional remanence relay.
  • Such an emergency power supply can, however, be dispensed with if a remanence relay is connected in parallel with the changeover relay as a fault locking element or if the changeover element is a remanence relay.
  • the remanence relay is preferably set and ejected by control pulses from the computer. Under no circumstances may the computer delete the lock.
  • a remanence relay with one or more windings can be used.
  • the remanence relay can also be coupled with an NTC resistor in order to release the remanence relay with a delay.
  • a circuit containing a remanence relay and controlling the actual switching element can also be provided.
  • Such retentive relays have the advantage that the fault is stored for as long as required, even if the mains voltage fails.
  • Remote fault unlocking by means of electrical pulses can only be provided if the fault unlocking device is in the visible range of the burner.
  • the controlling microprocessor can monitor the monitoring circuit itself, the latter has a first output connection which emits a first output signal indicating the position of the switching element, which is led to the microprocessor. Furthermore, the monitoring circuit advantageously has a second output connection via which the microprocessor assists the correct functioning of the monitoring circuit Can query concerns of the first control signal generated by him.
  • the monitoring circuit Since it is preferable for the monitoring circuit to be electrically isolated from the microprocessor, in the preferred embodiment of the monitoring circuit, a potential isolation stage is provided between the latter and the first and the second output connection.
  • the monitoring circuit has a logic antivalence circuit which links the first control signal generated by the microprocessor with a second control signal generated at regular time intervals in such a way that the changeover relay can only be brought into its operating position when both control signals are not present at the same time.
  • a program-controlled synchronization of the first control signal with the second control signal which is also applied to the microprocessor must be carried out in the microprocessor.
  • the antivalence circuit is preferably electrically isolated from the monitoring circuit by a further potential isolating stage.
  • FIG. 1 shows a changeover relay K with a changeover contact K 1, the center contact COM of which is connected to a supply voltage input connection L1.
  • the changeover contact K1 In the idle state, the changeover contact K1 is in the position labeled N c .
  • Parallel to the drive path of the change-over relay K is a holding capacitor C1, which in the rest position N c of the changeover switch K1 via the resistor R1 and the diode is charged V1.
  • the charging of the holding capacitor C1 can only take place if the control circuit of the changeover relay K is high-resistance, ie if the circuit 40 is high-resistance.
  • a storage member z. B. a remanence relay for fault locking is not shown in Fig. 1 and the other figures.
  • the resistor R1 is chosen to be so high that it is not possible for the relay K to pull in directly via R1.
  • the holding capacitor C1 must now be charged until its charge is sufficient to attract the relay and to bring the changeover contact K1 safely into the position labeled No.
  • the monitoring circuit 10 On the right side of the monitoring circuit 10 are shown two output connections A1 and A2 leading to the microprocessor and two input connections E1 and E2, the input connection E1 receiving a signal 101 from the microprocessor and the input connection E2 receiving a signal from a square wave generator or a signal derived from the mains frequency which will be described in more detail later.
  • the circuit 20 arranged between the contact point Nc of the changeover switch K1 and the first output connection A1, the circuit 30 generating the signal 104 at the second output connection A2 and the two input signals 101 and 102 from the input connections E1 and E2 receiving control circuit 40 described in more variants.
  • 2 shows three variants 20a, 20b and 20c of the circuit 20.
  • the variant 20a shown at the top has a rectifier which rectifies the input voltage at the contact point Nc and consists of a resistor 201, a capacitive series resistor 202, a full-wave rectifier 203 and one Electrolytic capacitor 204 exists.
  • the rectifier circuit At its output, the rectifier circuit outputs a voltage which is matched to the input voltage of the microprocessor and is coupled as a signal 103 to the first output terminal A1 via a potential isolating stage, an optocoupler 206 controlled via a resistor 205.
  • the circuit variant 20b shown in the middle assumes that DC voltage is already present at the contact point Mc, so that the rectifier and also the potential isolation stage are unnecessary.
  • the circuit 20b consists of a voltage divider composed of resistance elements 210 and 211 and an inverting operational amplifier 212 which generates the DC voltage signal 103 at the first output terminal A1 with a level adapted to the input voltage of the microprocessor.
  • the circuit variant 20c shown below in FIG. 2 has a similar function to the circuit variant 20a described first and has a potential isolating stage consisting of an isolating transformer 220 and a rectifier stage consisting of a full-wave rectifier 221 and an electrolytic capacitor 222, as well as an output decoupling stage comprising a resistance element 223 and a transistor 224.
  • the circuit 20c also supplies the level-adjusted output signal 103 at the first output terminal A1.
  • the function of the circuit 20 or of the circuit variants 20a, 20b and 20c is that the microprocessor can query the position of the changeover contact K1 at the first output connection A1 on the basis of the logic level of the signal 103. With such a query, the microprocessor z. B. recognize a sticking of the contacts of the switch K1. Furthermore, the microprocessor can use the signal 103 to detect the sticking of one or more of the switches X2 to Xn, since in this case the holding capacitor C1 does not receive its full charging voltage and thus the relay K does not pick up even after the circuit 40 has been activated.
  • the two circuits 30 and 40 are each shown together in two alternative circuit variants 30a, 40a and 30b, 40b.
  • the circuit variant shown in the upper part has an antivalence element 404 in the control circuit 40a, which is connected on the input side to the input connections E1 and E2.
  • the antivalence circuit 404 combines a square-wave signal applied by the microprocessor at the first input terminal E1 with a second input signal 102 at the second input terminal E2, which is generated by a square-wave generator or is derived from the mains frequency.
  • the mains frequency or the signal E2 can also be fed to the microprocessor for synchronization.
  • the antivalence circuit 404 only generates an output signal if the two signals 101 and 102 are not present at the first and second input terminals E1 and E2 at the same time. So that the holding capacitor C1 can be charged, the microprocessor must generate the first input signal 101 at the first input terminal E1 in synchronism with the second input signal 102 at the second input terminal E2, the output signal of the antivalence circuit 404 remaining low, the transistor 401 blocked and thus the drive path of the relay K remains high-impedance.
  • the transistor 401 is connected in the usual way as a switching transistor at its base via a voltage divider consisting of resistance elements 402 and 403 to the output of the antivalence circuit 404.
  • the output circuit 30a simply consists of a diode 301 which is connected to the collector of the transistor 401, so that the microcomputer at the second output terminal A2 can interrogate a signal 104 which indicates whether the switching transistor 401 has switched through or not, ie whether the control path for relay K is low-resistance or high-resistance.
  • the microprocessor To attract and hold relay K, the microprocessor must control input E1 in push-pull to input E2, so that the two input signals 101 and 102 are not present at the same time.
  • a field effect transistor 414 is used in conjunction with a 10 series diode 415.
  • the gate of the field effect transistor 414 is connected to a voltage divider, which is formed by the zener diode 415 and a resistor 413, which in turn lies at its other end at a connection point of a rectifier diode 420 and a capacitor 421.
  • the diode 420 is connected to the center contact COM of the switch K1 and forms a one-way rectifier with the capacitor 421, so that the gate bias voltage generated by this one-way rectifier through the voltage divider 413 and 415 keeps the field effect transistor 414 open, ie high-impedance, until the optocoupler transistor 416 becomes conductive .
  • the driving conditions for the antivalence element 418 by the input signals 101 and 102 at the two input connections E1 and E2 are the same as were explained above for the circuit variant 40a.
  • FIG. 4 shows a preferred circuit arrangement of the monitoring circuit according to the invention, which is composed of the basic circuit according to FIG. 1 and the circuit variants 20a, 30b and 40b according to FIGS. 2 and 3.
  • the switching elements as well as signals and lines which correspond to the corresponding switching elements of FIGS. 1 to 3 are designated in FIG. 4 with the same reference numbers.
  • FIG. 5 shows a function-time diagram, based on which the function of the preferred embodiment of the monitoring circuit according to the invention shown in FIG. 4 is explained below.
  • the input signals 101 and 102 which are present at the first and second input terminals E1 and E2 and with which the antivalence element 418 is applied, are shown.
  • the two output signals 103 and 104 are shown, which occur at the output connections A1 and A2 and can be queried by the microcomputer.
  • the supply voltage supplied to the switches X 2 to X n via the changeover contact N 0 is shown.
  • the time diagram is divided into the charging time period T L and the operating time period T W of the monitoring circuit according to FIG. 4.
  • the microprocessor In order to charge the holding capacitor C1, ie to block the field effect transistor 414, the microprocessor generates the signal 101 in synchronism with the signal 102.
  • the charging process of the Holding capacitor C1 begins at time t 0 , the resistance values of the resistance elements R1 and R2 and the capacitance value of the holding capacitor C1 being chosen such that the charging process lasts at least 50 cycles of the signals E1 and E2.
  • the first output signal 103 shown in the third line in FIG. 5 indicates during the charging period T L , the changeover relay K is in the idle state during this time and Changeover contact K 1 has the position Nc.
  • the second output signal 104 which can be queried by the microcomputer, at the second output terminal A2 (see the fourth line in FIG.
  • the changeover relay K switches the changeover contact K1 to the position N 0 , which the microcomputer recognizes by querying the signal 103 at the first output terminal A1 and then generates the signal E1 in push-pull to the signal E2 (time t 2 ).
  • the field effect transistor 414 becomes conductive on the basis of the output signal of the antivalence circuit 418, which state can be queried at the low level of the output signal 104 at the output terminal A2.
  • the value of the resistor R2 is to be dimensioned such that only a multiple of the network periods, or the periods of the square-wave signal E2, is sufficient to charge the holding capacitor C1 to the level necessary to attract the changeover relay K.
  • the value of R2 must be selected so that it, in conjunction with the value of R3, is sufficient to hold the changeover relay and in Combination with the holding capacitor C1 can bridge a power failure of up to 20 ms.
  • the start-up security of the monitoring circuit according to the invention is ensured in that a consumer connected to the switches X 2 to X n with a resistance 10 10 kOhm prevents the holding capacitor C 1 from being charged to a voltage sufficient for the relay to pull when the switch is closed.
  • the output signals 103 and 104 that can be queried by the microprocessor enable the microprocessor to test the monitoring circuit according to the invention.
  • it can be switched on during operation, e.g. H. when the changeover relay K is activated, are briefly blocked and immediately switched on again (signals 101 'and 104' in FIG. 5).
  • the microprocessor can query whether the transistor 414 can be blocked or not.
  • the monitoring circuit described here is an arrangement which, by means of a safety relay K, initially keeps safety-relevant consumers switched off until a self-test of the controlling computer has been completed while maintaining the required time conditions.
  • a holding capacitor C 1 is connected in parallel to the control branch of the safety relay K, which holding capacitor C 1 can be charged in the rest position N c of the safety relay K via a charging circuit R 1 , V 1 and the relay K after charging with the simultaneous application of a control signal from the microprocessor to the Brings operating position only if specified connection conditions of the safety-relevant consumers are fulfilled.
  • the monitoring circuit according to the invention uses the difference between the pull-in and the drop-out voltage of the safety relay.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electronic Switches (AREA)
  • Safety Devices In Control Systems (AREA)
  • Relay Circuits (AREA)

Abstract

The invention relates to a monitoring circuit for computer-controlled safety devices. The monitoring circuit described here is an arrangement which initially holds safety-relevant loads switched off by means of a safety relay (K) until a self-test of the controlling computer has been completed within required time conditions. A holding capacitor (C1) is connected in parallel with the drive path of the safety relay (K), which holding capacitor (C1) can be charged via a charging circuit (R1, V1) when the safety relay (K) is in the quiescent position (Nc), and, after charging has been completed, moves the relay into the operating position, subject to simultaneous application of a drive signal from the microprocessor, only when specified connection conditions for the safety-relevant loads are met. A remanence relay can be used as the safety relay (K) for defect locking. The monitoring circuit according to the invention uses the difference between the pull-in voltage and the tripping voltage of the safety relay (K). <IMAGE>

Description

Die Erfindung betrifft eine Überwachungsschaltung für computergesteuerte Sicherheitsgeräte mit einem durch ein erstes Ansteuersignal vom Computer in eine Betriebsstellung bringbaren Umschaltglied, wobei ein Haltekondensator parallel zum Ansteuerzweig des Umschaltglieds geschaltet ist, und wobei der Haltekondensator in der Ruhestellung des Umschaltglieds über einen Ladestromkreis aufladbar ist.The invention relates to a monitoring circuit for computer-controlled safety devices with a switchover element that can be brought into an operating position by a first control signal from the computer, a holding capacitor being connected in parallel with the control branch of the switchover element, and the holding capacitor being able to be charged via the charging circuit in the rest position of the switchover element.

Eine derartige Überwachungsschaltung ist aus GB-A-2 207 307 bekannt. Die bekannte Überwachungsschaltung vergleicht ein analoges Sensorsignal mit einem analogen Referenzsignal, wobei die beiden Signale abwechselnd in demselben AD-Wandler digitalisiert werden. Die Ergebnisse des Vergleichs werden ständig dynamisch ausgewertet und entsprechend ein Sicherheitskontrollkontakt betätigt.Such a monitoring circuit is known from GB-A-2 207 307. The known monitoring circuit compares an analog sensor signal with an analog reference signal, the two signals being digitized alternately in the same AD converter. The results of the comparison are continuously evaluated dynamically and a safety control contact is activated accordingly.

Computergesteuerte bzw. mikroprozessorgesteuerte Sicherheitsgeräte bedürfen über normale Sicherungsfunktionen hinaus besonderer Überwachungsmaßnahmen, die auch im Fehlerfall des steuernden Computers die Sicherheit gewährleisten.In addition to normal security functions, computer-controlled or microprocessor-controlled safety devices require special monitoring measures, which also ensure safety in the event of a fault in the controlling computer.

Unter Sicherheitsgeräten versteht man bei Gasinstallationen Gasventile, Zündeinrichtungen u. ä.Safety devices are gas valves, ignition devices and the like in gas installations. Ä.

Dagegen gibt es auch nichtsicherheitsrelevante Verbraucher, wie Gebläsemotoren, Umwälzpumpen, Dreiwegeventile usw.On the other hand, there are also non-safety-related consumers, such as blower motors, circulation pumps, three-way valves, etc.

Für die von den Sicherheitsgeräten zu erfüllenden Sicherheitsklassen gibt es einschlägige Normen und Vorschriften. Dabei werden in der Gasbrenner-Sicherheitstechnik im wesentlichen zwei Betriebsarten unterschieden. Diese sind "intermittierender Betrieb" unter 24 Stunden Dauer und "Dauerbetrieb". Für den intermittierenden Betrieb ist insbesondere eine "Anlaufüberwachung" wichtig, d. h., daß die für die Sicherheit wichtigen Funktionen oder Schaltungskomponenten vor Gasfreigabe geprüft werden müssen. Bei Folgesteuerungen muß ein Fehler im Verlauf einer Schaltfolge erkannt und die Gasfreigabe zweifelsfrei verhindert werden.There are relevant standards and regulations for the safety classes to be fulfilled by the safety devices. There are two main operating modes in gas burner safety technology. These are "intermittent operation" under 24 hours and "continuous operation". For intermittent operation, "start-up monitoring" is particularly important, ie the functions or circuit components important for safety must be checked before the gas is released. In the case of sequential controls, an error must be recognized in the course of a switching sequence and the gas release must be prevented without a doubt.

Beim Dauerbetrieb müssen die Fehler ständig, d.h. kontinuierlich oder quasi kontinuierlich erkannt werden, und die Abschaltung muß innerhalb einer gewissen Zeit erfolgen. Bei einer Mikroprozessorsteuerung solcher Gasbrenner kann es vorkommen, daß der steuernde Mikroprozessor im Fehlerfall ein Steuerprogramm nicht mehr ausführt oder durch Störungen (EMV) unverhergesehene Programmsprünge oder Zustandsänderungen auftreten.During continuous operation, the errors must be constant, i.e. be recognized continuously or quasi continuously, and the shutdown must take place within a certain time. In the case of a microprocessor control of such gas burners, it can happen that the controlling microprocessor no longer executes a control program in the event of a fault or unexpected program jumps or changes in state occur due to faults (EMC).

Gattungsgemäße Überwachungsschaltungen, die mittels eines vom Mikroprozessor durch Ansteuerimpulse beaufschlagten Relais eine sogenannte "Watchdog"-Funktion erfüllen, sind im Stand der Technik bekannt. Das Sicherheitsrelais hält die sicherheitsrelevanten Geräte zunächst abgeschaltet, bis der Mikroprozessor unter Einhaltung geforderter Zeitbedingungen seine Selbsttestroutine erfolgreich abgeschlossen hat. Weiterhin verlangt die Überwachungsschaltung, daß der Mikroprozessor nach Durchführung des Selbsttests ständig weitere Ausgabebefehle erzeugen muß, die das Sicherheitsrelais in seiner Betriebsstellung halten.Generic monitoring circuits, which perform a so-called "watchdog" function by means of a relay acted upon by the microprocessor with control pulses, are known in the prior art. The safety relay initially keeps the safety-relevant devices switched off until the microprocessor has successfully completed its self-test routine in compliance with the required time conditions. Furthermore, the monitoring circuit requires that the microprocessor must continuously generate further output commands after the self-test has been carried out, which keep the safety relay in its operating position.

Bei solchen Überwachungsschaltungen besteht ein besonderes Bedürfnis einer einfachen und möglichst eigensicheren Schaltungsanordnung.Such monitoring circuits have a special need for a simple and intrinsically safe circuit arrangement.

Es ist deshalb Aufgabe der Erfindung eine gattungsgemäße Überwachungsanordnung so zu ermöglichen, daß eine besonders einfache Schaltungsanordnung mit hoher Eigensicherheit realisiert werden kann.It is therefore an object of the invention to enable a generic monitoring arrangement such that a particularly simple circuit arrangement with high intrinsic safety can be implemented.

Die obige Aufgabe wird bei einer gattungsgemäßen Überwachungsschaltung erfindungsgemäß dadurch gelöst,
daß der Widerstand des Ladestromkreises des Haltekondensators so hochohmig gewählt ist, daß es dem Umschaltglied nicht möglich ist, direkt über den Widerstand anzuziehen, daß im Ladestromkreis des Haltekondensators ein Spannungsteiler eingeschaltet ist, wobei mit dem einen Ende des Spannungsteilers mindestens ein sicherheits-technisches Gerät über ein Schaltelement verbunden ist und wobei der durch das Gerät bei durchgeschaltetem Schaltelement vom Spannungsteiler fließende Strom ein Aufladen des Haltekondensators verhindert, daß eine Ansteuerschaltung vorgesehen ist, durch die der Ansteuerweg des Umschaltgliedes hochohmig bzw. niederohmig werden kann, und daß das Umschaltglied nach erfolgter Ladung des Haltekondensators und gleichzeitigem Anliegen des ersten Ansteuersignals in seiner Betriebsstellung gehalten wird, bei der der Ladestromkreis abgeschaltet ist.
The above object is achieved according to the invention in a generic monitoring circuit in that
that the resistance of the charging circuit of the holding capacitor is chosen so high that it is not possible for the switching element is to attract directly via the resistor that a voltage divider is switched on in the charging circuit of the holding capacitor, at least one safety-technical device being connected to one end of the voltage divider via a switching element, and the current flowing through the device from the voltage divider when the switching element is switched on Charging the holding capacitor prevents a drive circuit from being provided, through which the drive path of the switching element can become high-resistance or low-resistance, and that the switching element is held in its operating position after the charging of the holding capacitor and simultaneous application of the first drive signal, in which the charging circuit is switched off is.

Eine Forderung für eine solche Überwachungsschaltung für Gasfeuerungsautomaten besteht darin, daß letztere bei Auftreten eines unzulässigen Betriebszustandes abgeschaltet bleiben und eine Störverriegelung erfolgen muß. Die Stromversorgungsleitung zu jedem sicherheitsrelevanten Verbraucher ist über einen Umschaltkontakt des genannten Umschaltglieds geführt, wobei in den Stromspeiseleitungen zu den sicherheitsrelevanten Verbrauchern nochmals jeweils mindestens ein Schaltelement vorgesehen ist, dessen geöffneter Zustand miterfaßt wird. Dies geschieht dadurch, daß das Schaltelement in der Ruhestellung des Umschaltglieds zusammen mit dem sicherheitsrelevanten Verbraucher dem Haltekondensator parallel geschaltet ist, wobei im Ladestromkreis des Haltekondensators nach dem Umschalter des Umschaltglieds ein Spannungsteiler eingeschaltet ist, mit dessen einem Ende mindestens ein sicherheitstechnisches Gerät über eines der besagten Schaltelemente verbunden ist und wobei der durch das sicherheitsrelevante Gerät bei geschlossenem Schaltelement vom Spannungsteiler her fließende Strom eine Aufladung des Haltekondensators verhindert.One requirement for such a monitoring circuit for automatic gas burner controls is that the latter remain switched off when an impermissible operating state occurs and that a fault lock must be implemented. The power supply line to each safety-relevant consumer is routed via a changeover contact of the said changeover element, wherein at least one switching element is again provided in the power supply lines to the safety-relevant consumers, the open state of which is also detected. This is done in that the switching element is connected in parallel with the safety capacitor in the rest position of the switching element together with the safety-relevant consumer, a voltage divider being switched on in the charging circuit of the holding capacitor after the switch of the switching element, with one end of which has at least one safety-related device via one of the said Switching elements is connected and which is closed by the safety-relevant device Switching element current flowing from the voltage divider prevents charging of the holding capacitor.

Bevorzugt ist als Umschaltglied ein Umschaltrelais eingesetzt.A changeover relay is preferably used as the changeover element.

Die Entriegelung muß von Hand und darf nicht durch Netzspannungsausfall und wiederkehrender Netzspannung erfolgen.Unlocking must be done manually and must not be caused by a power failure and recurring power.

Gemäß einer vorteilhaften Ausbildung ist die erfindungsgemäße Überwachungsschaltung so ausgelegt, daß das Umschaltglied bei Netzausfall und Wiederkehr der Netzspannung in seiner Ruhestellung bleibt.According to an advantageous embodiment, the monitoring circuit according to the invention is designed so that the switchover element remains in its rest position in the event of a power failure and return of the power supply.

Da eine zeitliche Forderung besteht, daß die Störungsverriegelung für mindestens 10 Stunden gespeichert sein muß, kann man für den Fall, daß das Umschaltglied ein Umschaltrelais ist eine über diesen Zeitraum funktionsfähig bleibende Batterie-Notstromversorgung vorsehen. Die Störverriegelung kann in einem EEPROM, einem batteriegepufferten RAM oder einem zusätzlichen Remanenzrelais gespeichert werden.Since there is a time requirement that the fault lock must be stored for at least 10 hours, in the event that the switching element is a switching relay, a battery emergency power supply that remains functional over this period can be provided. The fault lock can be stored in an EEPROM, a battery-backed RAM or an additional remanence relay.

Auf eine solche Notstromversorgung kann jedoch verzichtet werden, wenn als Störverriegelungselement ein Remanenzrelais parallel zum Umschaltrelais geschaltet wird oder das Umschaltglied ein Remanenzrelais ist.Such an emergency power supply can, however, be dispensed with if a remanence relay is connected in parallel with the changeover relay as a fault locking element or if the changeover element is a remanence relay.

Das Remanenzrelais wird bevorzugt durch Ansteuerimpulse vom Computer gesetzt und abgeworfen. Auf keinen Fall darf der Computer die Störverriegelung selbst löschen.The remanence relay is preferably set and ejected by control pulses from the computer. Under no circumstances may the computer delete the lock.

Dabei kann ein Remanenzrelais mit einer oder auch mehreren Wicklungen eingesetzt werden.A remanence relay with one or more windings can be used.

Das Remanenzrelais kann auch mit einem NTC-Widerstand gekoppelt werden, um das Remanenzrelais verzögert abzuwerfen.The remanence relay can also be coupled with an NTC resistor in order to release the remanence relay with a delay.

Selbstverständlich kann auch eine ein Remanenzrelais enthaltende, das eigentliche Umschaltglied ansteuernde Schaltung vorgesehen werden. Solche Remanenzrelais haben den Vorteil, daß die Störung auch bei Ausfall der Netzspannung beliebig lange gespeichert wird. Eine Fern-Störentriegelung mittels elektrischen Impulsen kann nur vorgesehen werden, wenn die Störentriegelungseinrichtung im Sichtbereich des Brenners liegt.Of course, a circuit containing a remanence relay and controlling the actual switching element can also be provided. Such retentive relays have the advantage that the fault is stored for as long as required, even if the mains voltage fails. Remote fault unlocking by means of electrical pulses can only be provided if the fault unlocking device is in the visible range of the burner.

Damit der steuernde Mikroprozessor die Überwachungsschaltung selbst überwachen kann, weist letztere einen ersten Ausgangsanschluß auf, der ein die Stellung des Umschaltglieds angebendes erstes Ausgangssignal abgibt, welches zum Mikroprozessor geführt ist. Weiterhin weist die Überwachungsschaltung vorteilhafterweise einen zweiten Ausgangsanschluß auf, über den der Mikroprozessor die korrekte Funktion der Überwachungsschaltung bei Anliegen des vom ihm erzeugten ersten Ansteuersignals abfragen kann.So that the controlling microprocessor can monitor the monitoring circuit itself, the latter has a first output connection which emits a first output signal indicating the position of the switching element, which is led to the microprocessor. Furthermore, the monitoring circuit advantageously has a second output connection via which the microprocessor assists the correct functioning of the monitoring circuit Can query concerns of the first control signal generated by him.

Da es vorzuziehen ist, daß die Überwachungsschaltung potentialmäßig von dem Mikroprozessor getrennt ist, sind bei der bevorzugten Ausführungsart der Überwachungsschaltung zwischen dieser und dem ersten sowie dem zweiten Ausgangsanschluß jeweils eine Potentialtrennstufe vorgesehen.Since it is preferable for the monitoring circuit to be electrically isolated from the microprocessor, in the preferred embodiment of the monitoring circuit, a potential isolation stage is provided between the latter and the first and the second output connection.

In der bevorzugten Ausführungsform weist die Überwachungsschaltung eine logische Antivalenzschaltung auf, die das vom Mikroprozessor erzeugte erste Ansteuersignal mit einem zweiten, in regelmäßigen Zeitintervallen erzeugten Ansteuersignal so verknüpft, daß das Umschaltrelais nur dann in seine Betriebsstellung bringbar ist, wenn beide Ansteuersignale nicht gleichzeitig anliegen. Dazu muß im Mikroprozessor eine programmgesteuerte Synchronisation des ersten Ansteuersignals mit dem dem Mikroprozessor gleichfalls anliegenden zweiten Ansteuersignal vorgenommen werden.In the preferred embodiment, the monitoring circuit has a logic antivalence circuit which links the first control signal generated by the microprocessor with a second control signal generated at regular time intervals in such a way that the changeover relay can only be brought into its operating position when both control signals are not present at the same time. For this purpose, a program-controlled synchronization of the first control signal with the second control signal which is also applied to the microprocessor must be carried out in the microprocessor.

Vorzugsweise ist die Antivalenzschaltung durch eine weitere Potentialtrennstufe potentialmäßig von der Überwachungsschaltung getrennt.The antivalence circuit is preferably electrically isolated from the monitoring circuit by a further potential isolating stage.

Weitere vorteilhafte Eigenschaften der erfindungsgemäßen Überwachungsschaltung werden im folgenden anhand der Zeichnung näher beschrieben, die mehrere Ausführungsalternativen und eine bevorzugte Ausführungsform der Erfindung darstellt. Es zeigen:

Fig. 1
in Blockform eine prinzipielle Schaltungsanordnung der erfindungsgemäßen Überwachungsschaltung;
Fig. 2
drei alternative Ausführungsformen einer Schaltung zur Erzeugung des am ersten Ausgangsanschluß anliegenden ersten Ausgangssignals;
Fig. 3
zwei alternative Schaltungsvarianten einer Ansteuerschaltung;
Fig. 4
ein Schaltdiagramm einer bevorzugten Ausführungsform der erfindungsgemäßen Überwachungsschaltung; und
Fig. 5
ein Funktions-Zeitdiagramm zur Erläuterung der Funktionen der erfindungsgemäßen Überwachungsschaltung.
Further advantageous properties of the monitoring circuit according to the invention are described in more detail below with reference to the drawing, which represents several alternative embodiments and a preferred embodiment of the invention. Show it:
Fig. 1
in block form a basic circuit arrangement of the monitoring circuit according to the invention;
Fig. 2
three alternative embodiments of a circuit for generating the first output signal present at the first output terminal;
Fig. 3
two alternative circuit variants of a control circuit;
Fig. 4
a circuit diagram of a preferred embodiment of the monitoring circuit according to the invention; and
Fig. 5
a functional timing diagram to explain the functions of the monitoring circuit according to the invention.

Zunächst wird eine prinzipielle und dann alternative Ausführungsformen der erfindungsgemäßen Überwachungsschaltung sowie deren Funktion beschrieben.First, a basic and then alternative embodiments of the monitoring circuit according to the invention and its function are described.

Fig. 1 zeigt ein Umschaltrelais K mit einem Umschaltkontakt K 1, dessen Mittelkontakt COM an einem Speisespannungseingangsanschluß L1 liegt. Im Ruhezustand liegt der Umschaltkontakt K1 in der mit Nc bezeichneten Stellung. Parallel zum Ansteuerpfad des Umschaltrelais K liegt ein Haltekondensator C1, der in der Ruhestellung Nc des Umschaltkontakts K1 über den Widerstand R1 und die Diode V1 aufgeladen wird. Die Aufladung des Haltekondensators C1 kann jedoch nur dann vonstatten gehen, wenn der Ansteuerkreis des Umschaltrelais K hochohmig, d. h. wenn die Schaltung 40 hochohmig ist.1 shows a changeover relay K with a changeover contact K 1, the center contact COM of which is connected to a supply voltage input connection L1. In the idle state, the changeover contact K1 is in the position labeled N c . Parallel to the drive path of the change-over relay K is a holding capacitor C1, which in the rest position N c of the changeover switch K1 via the resistor R1 and the diode is charged V1. However, the charging of the holding capacitor C1 can only take place if the control circuit of the changeover relay K is high-resistance, ie if the circuit 40 is high-resistance.

Ein Speicherglied z. B. ein Remanenzrelais zur Störungsverriegelung ist in Fig. 1 und den weiteren Figuren nicht dargestellt.A storage member z. B. a remanence relay for fault locking is not shown in Fig. 1 and the other figures.

Auf die Funktion der Schaltung 40 wird weiter unten eingegangen. Der Widerstand R1 ist so hochohmig gewählt, daß es dem Relais K nicht möglich ist, direkt über R1 anzuziehen.The function of the circuit 40 is discussed further below. The resistor R1 is chosen to be so high that it is not possible for the relay K to pull in directly via R1.

Der Haltekondensator C1 muß jetzt so lange aufgeladen werden, bis seine Ladung ausreicht, das Relais anzuziehen und den Umschaltkontakt K1 sicher in die mit No bezeichnete Stellung zu bringen.The holding capacitor C1 must now be charged until its charge is sufficient to attract the relay and to bring the changeover contact K1 safely into the position labeled No.

Zum Verständnis der Funktionsweise der beschriebenen Überwachungsschaltung ist es wichtig, daß der erwähnte Widerstand R1 mit einem weiteren Widerstand R2 einen Spannungsteiler bildet, das andere Ende des Widerstandes R2 am Kontaktpunkt N0 des Umschaltkontakts K1 liegt und daß in den mit dem Kontaktpunkt No verbundenen Ausgangsleitungen S1 bis Sn zu den sicherheitsrelevanten Verbrauchern einzeln oder in Gruppen schaltbare Schalter X2 bis Xn angeordnet sind, deren Schaltzustand miterfaßt wird. Dies geschieht dadurch, daß ein nicht abgeschalteter, sicherheitsrelevanter Verbraucher einen Widerstand zwischen dem jeweiligen Ausgang S1 bis Sn und einer Rückleitung N bildet und damit der über den relativ hochohmigen Widerstand R1 fließende Ladestrom für den Haltekondensator C1 über R2 und den eingeschalteten Verbraucher fließt. Dadurch kann der Haltekondensator C1 nicht geladen werden, wenn ein oder mehrere Schalter X2 bis Xn geschlossen sind. Der Widerstand R2 ist so ausgelegt, daß es dem Umschaltrelais K reicht, sich damit auf der No-Seite zu halten. Dabei liegt die Spannung am Relais K zwischen der Abfall- und der Anzugsspannung. Um das Relais K sicher anzuziehen, muß der aus dem Widerstand R3, dem Umschaltrelais K, der Schaltung 30 und der Schaltung 40 bestehende Ansteuerweg niederohmig werden. Um das Umschaltrelais von der Ruhestellung in die Betriebsstellung zu bringen, müssen folgende Bedingungen erfüllt werden:

  • Der Haltekondensator C1 muß über die Ladeschaltung mit der Energiemenge geladen werden, die benötigt wird um das Umschaltrelais K in die Betriebsstellung zu bringen.
  • Diese Energiemenge aus dem Haltekondensator C1 wird über den Widerstand R3 und die Ansteuerschaltung 40 als Anzugsenergie auf die Spule des Umschaltrelais K geschaltet. Reicht diese Energiemenge nicht aus, um das Umschaltrelais K in die Betriebsstellung zu bringen und damit den Haltestromkreis zu schließen, fällt das Umschaltrelais K in seine Ruhestellung zurück.
  • Die Energiemenge des Haltekondensators ist die Ladungsmenge Q, die dem Produkt aus Spannung und Kapazität entspricht.
  • Kapazitätsverlust des Haltekondensators C1 reduziert die Ladungsmenge und damit bleibt das Umschaltrelais K in seiner Ruhestellung.
  • Durch die Wahl eines Haltekondensators C1 mit entsprechender Kapazität kann z. B. erreicht werden, daß die Kondensatorspannung zum Anziehen des Umschaltrelais doppelt so hoch sein muß wie die Anzugsspannung des Umschaltrelais K.
  • Mit einem Haltekondensator sehr hoher Kapazität muß die Kondensatorspannung nur größer oder gleich der Anzugsspannung sein.
  • Durch die Dimensionierung der Ladeschaltung, die Wahl der Kapazität des Kondensators C1 und die Auswahl des Relais kann die Schaltung in weiten Bereichen an die Erfordernisse der Funktion und Anlaufsicherheit angepaßt werden.
  • Die Schaltung ist für Gleich- und Wechselspannung geeignet.
In order to understand the functioning of the monitoring circuit described, it is important that the resistor R 1 mentioned forms a voltage divider with a further resistor R 2 , the other end of the resistor R 2 is at the contact point N 0 of the changeover contact K1, and that the contact point N o connected output lines S 1 to S n to the safety-relevant consumers, switches or switches X 2 to X n which can be switched individually or in groups are arranged, the switching state of which is also detected. This is done in that an unswitched, safety-relevant consumer forms a resistance between the respective output S 1 to S n and a return line N and thus the charging current flowing through the relatively high-resistance resistor R1 flows for the holding capacitor C1 via R2 and the switched-on consumer. As a result, the holding capacitor C1 cannot be charged if one or more switches X 2 to X n are closed. The resistor R2 is designed so that it is enough for the changeover relay K to keep on the N o side. The voltage at relay K is between the drop and the pull-in voltage. In order to reliably attract the relay K, the drive path consisting of the resistor R3, the changeover relay K, the circuit 30 and the circuit 40 must become low-resistance. In order to switch the relay from To bring the rest position into the operating position, the following conditions must be met:
  • The holding capacitor C1 must be charged via the charging circuit with the amount of energy required to bring the changeover relay K into the operating position.
  • This amount of energy from the holding capacitor C1 is connected via the resistor R3 and the control circuit 40 as pulling energy to the coil of the changeover relay K. If this amount of energy is not sufficient to bring the changeover relay K into the operating position and thus to close the holding circuit, the changeover relay K falls back into its rest position.
  • The amount of energy of the holding capacitor is the amount of charge Q, which corresponds to the product of voltage and capacitance.
  • Loss of capacity of the holding capacitor C1 reduces the amount of charge and the changeover relay K remains in its rest position.
  • By choosing a holding capacitor C1 with appropriate capacitance z. B. can be achieved that the capacitor voltage to attract the switching relay must be twice as high as the starting voltage of the switching relay K.
  • With a holding capacitor of very high capacitance, the capacitor voltage only has to be greater than or equal to the starting voltage.
  • Through the dimensioning of the charging circuit, the choice of the capacitance of the capacitor C1 and the selection of the relay, the circuit can be adapted in a wide range to the requirements of the function and start-up reliability.
  • The circuit is suitable for direct and alternating voltage.

An der rechten Seite der Überwachungsschaltung 10 sind zwei zum Mikroprozessor führende Ausgangsanschlüsse A1 und A2 und zwei Eingangsanschlüsse E1 und E2 dargestellt, wobei der Eingangsanschluß E1 ein Signal 101 vom Mikroprozessor und der Eingangsanschluß E2 ein Signal von einem Rechteckgenerator oder ein von der Netzfrequenz abgeleitetes Signal erhalten, die später genauer beschrieben werden.On the right side of the monitoring circuit 10 are shown two output connections A1 and A2 leading to the microprocessor and two input connections E1 and E2, the input connection E1 receiving a signal 101 from the microprocessor and the input connection E2 receiving a signal from a square wave generator or a signal derived from the mains frequency which will be described in more detail later.

Nachstehend werden anhand der Fig. 2 und 3 jeweils die zwischen den Kontaktpunkt Nc des Umschalters K1 und dem ersten Ausgangsanschluß A1 angeordnete Schaltung 20, die das Signal 104 am zweiten Ausgangsanschluß A2 erzeugende Schaltung 30 und die die beiden Eingangssignale 101 und 102 jeweils von den Eingangsanschlüssen E1 und E2 empfangende Ansteuerschaltung 40 in mehrereren Varianten näher beschrieben. Die Fig. 2 stellt drei Varianten 20a, 20b und 20c der Schaltung 20 dar. Die zuoberst dargestellte Variante 20a weist einen die am Kontaktpunkt Nc liegende Eingangsspannung gleichrichtenden Gleichrichter dar, der aus einem Widerstand 201, einem kapazitiven Vorwiderstand 202, einem Vollweggleichrichter 203 und einem Elektrolytkondensator 204 besteht. Die Gleichrichterschaltung gibt an ihrem Ausgang eine an die Eingangsspannung des Mikroprozessors angepaßte Spannung ab, die über eine Potentialtrennstufe, einen über einen Widerstand 205 angesteuerten Optokoppler 206 als Signal 103 zum ersten Ausgangsanschluß A1 gekoppelt wird.2 and 3, the circuit 20 arranged between the contact point Nc of the changeover switch K1 and the first output connection A1, the circuit 30 generating the signal 104 at the second output connection A2 and the two input signals 101 and 102 from the input connections E1 and E2 receiving control circuit 40 described in more variants. 2 shows three variants 20a, 20b and 20c of the circuit 20. The variant 20a shown at the top has a rectifier which rectifies the input voltage at the contact point Nc and consists of a resistor 201, a capacitive series resistor 202, a full-wave rectifier 203 and one Electrolytic capacitor 204 exists. At its output, the rectifier circuit outputs a voltage which is matched to the input voltage of the microprocessor and is coupled as a signal 103 to the first output terminal A1 via a potential isolating stage, an optocoupler 206 controlled via a resistor 205.

Die in der Mitte dargestellte Schaltungsvariante 20b geht davon aus, daß am Kontaktpunkt Mc bereits Gleichspannung liegt, sodaß der Gleichrichter und auch die Potentialtrennstufe entbehrlich sind. Die Schaltung 20b besteht aus einem Spannungsteiler aus Widerstandsgliedern 210 und 211 und einem invertierenden Operationsverstärker 212, der am ersten Ausgangsanschluß A1 das Gleichspannungssignal 103 mit einem an die Eingangsspannung des Mikroprozessors angepaßten Pegel erzeugt.The circuit variant 20b shown in the middle assumes that DC voltage is already present at the contact point Mc, so that the rectifier and also the potential isolation stage are unnecessary. The circuit 20b consists of a voltage divider composed of resistance elements 210 and 211 and an inverting operational amplifier 212 which generates the DC voltage signal 103 at the first output terminal A1 with a level adapted to the input voltage of the microprocessor.

Die in Fig. 2 unten dargestellte Schaltungsvariante 20c hat eine ähnliche Funktion wie die zuerst beschriebene Schaltungsvariante 20a und weist eine aus einem Trenntransformator 220 bestehende Potentialtrennstufe und eine aus einem Vollweggleichrichter 221 und einem Elektrolytkondensator 222 bestehende Gleichrichterstufe sowie eine Ausgangsentkoppelstufe auf die aus einem Widerstandselement 223 und einem Transistor 224 besteht. Auch die Schaltung 20c liefert das pegelmäßig angepaßte Ausgangssignal 103 am ersten Ausgangsanschluß A1.The circuit variant 20c shown below in FIG. 2 has a similar function to the circuit variant 20a described first and has a potential isolating stage consisting of an isolating transformer 220 and a rectifier stage consisting of a full-wave rectifier 221 and an electrolytic capacitor 222, as well as an output decoupling stage comprising a resistance element 223 and a transistor 224. The circuit 20c also supplies the level-adjusted output signal 103 at the first output terminal A1.

Die Funktion der Schaltung 20 bzw. der Schaltungsvarianten 20a, 20b und 20c besteht darin, daß der Mikroprozessor die Stellung des Umschaltkontakts K1 am ersten Ausgangsanschluß A1 anhand des logischen Pegels des Signals 103 abfragen kann. Mit einer solchen Abfrage kann der Mikroprozessor z. B. ein Kleben der Kontakte des Umschalters K1 erkennen. Weiterhin kann der Mikroprozessor mittels des Signals 103 ein Kleben eines oder mehrerer der Schalter X2 bis Xn erkennen, da in diesem Fall der Haltekondensator C1 nicht seine volle Ladespannung erhält und somit das Relais K auch nach Durchsteuern der Schaltung 40 nicht anzieht.The function of the circuit 20 or of the circuit variants 20a, 20b and 20c is that the microprocessor can query the position of the changeover contact K1 at the first output connection A1 on the basis of the logic level of the signal 103. With such a query, the microprocessor z. B. recognize a sticking of the contacts of the switch K1. Furthermore, the microprocessor can use the signal 103 to detect the sticking of one or more of the switches X2 to Xn, since in this case the holding capacitor C1 does not receive its full charging voltage and thus the relay K does not pick up even after the circuit 40 has been activated.

In Fig. 3 sind die beiden Schaltungen 30 und 40 jeweils zusammen in zwei alternativen Schaltungsvarianten 30a, 40a und 30b, 40b dargestellt. Die im oberen Teil dargestellte Schaltungsvariante weist in der Ansteuerschaltung 40a ein Antivalenzglied 404 auf, welches mit den Eingangsanschlüssen E1 und E2 eingangsseitig verbunden ist. Die Antivalenzschaltung 404 verknüpft ein am ersten Eingangsanschluß E1 vom Mikroprozessor angelegtes Rechtecksignal mit einem zweiten Eingangssignal 102 am zweiten Eingangsanschluß E2, das von einem Rechteckgenerator erzeugt wird, oder von der Netzfrequenz abgeleitet ist. Die Netzfrequenz oder das Signal E2 kann auch dem Mikroprozessor zur Synchronisation zugeführt werden. Die Antivalenzschaltung 404 erzeugt nur dann ein Ausgangssignal, wenn die beiden Signale 101 und 102 an dem ersten und zweiten Eingangsanschluß E1 und E2 nicht gleichzeitig anliegen. Damit der Haltekondensator C1 aufgeladen werden kann, muß der Mikroprozessor das erste Eingangssignal 101 am ersten Eingangsanschluß E1 im Gleichtakt zum zweiten Eingangssignal 102 am zweiten Eingangsanschluß E2 erzeugen, wobei das Ausgangssignal der Antivalenzschaltung 404 tief bleibt, der Transistor 401 gesperrt und somit der Ansteuerweg des Relais K hochohmig bleibt. Der Transistor 401 ist in üblicher Weise als Schalttransistor an seiner Basis über einen aus Widerstandselementen 402 und 403 bestehenden Spannungsteiler mit dem Ausgang der Antivalenzschaltung 404 verbunden. Die Ausgangsschaltung 30a besteht in einfacher Weise aus einer Diode 301, die mit dem Kollektor des Transistors 401 verbunden ist, so daß der Mikrocomputer am zweiten Ausgangsanschluß A2 ein Signal 104 abfragen kann, das angibt, ob der Schalttransistor 401 durchgeschaltet hat, oder nicht, d. h. ob der Ansteuerweg für das Relais K niederohmig oder hochohmig ist. Zum Anziehen und zum Halten des Relais K muß der Mikroprozessor den Eingang E1 im Gegentakt zum Eingang E2 ansteuern, so daß die beiden Eingangssignale 101 und 102 nicht gleichzeitig anliegen. Die im unteren Teil der Fig. 3 dargestellten Schaltungsvarianten 30b und 40b unterscheiden sich von den oben beschriebenen Schaltungsvarianten in erster Linie darin, daß das Ausgangssignal der Antivalenzschaltung 418 in der Ansteuerschaltung 40b durch einen Optokoppler 416 potentialmäßig von der Überwachungsschaltung getrennt ist und daß auch das Ausgangssignal A2 der Schaltung 30b potentialmäßig durch einen Optokoppler 302 von der Überwachungsschaltung getrennt ist. Ferner wird statt des bipolaren Schalttransistors 401 der Schaltungsvariante 40a ein Feldeffekttransistor 414 in Verbindung mit einer 10er-Diode 415 eingesetzt. Das Gate des Feldeffekttransistors 414 liegt an einem Spannungsteiler, der durch die Zenerdiode 415 und einen Widerstand 413 gebildet ist, der seinerseits mit seinem anderen Ende an einem Verbindungspunkt einer Gleichrichterdiode 420 und einem Kondensator 421 liegt. Die Diode 420 ist mit dem Mittelkontakt COM des Umschalters K1 verbunden und bildet mit dem Kondensator 421 einen Einweggleichrichter, so daß die von diesem Einweggleichrichter erzeugte Gatevorspannung durch den Spannungsteiler 413 und 415 den Feldeffekttransistor 414 offen, d. h. hochohmig hält, bis der Optokopplertransistor 416 leitend wird. Die Ansteuerbedingungen für das Antivalenzglied 418 durch die Eingangssignale 101 und 102 an den beiden Eingangsanschlüssen E1 und E2 sind dieselben, wie sie oben für die Schaltungsvariante 40a erläutert wurden.In Fig. 3, the two circuits 30 and 40 are each shown together in two alternative circuit variants 30a, 40a and 30b, 40b. The circuit variant shown in the upper part has an antivalence element 404 in the control circuit 40a, which is connected on the input side to the input connections E1 and E2. The antivalence circuit 404 combines a square-wave signal applied by the microprocessor at the first input terminal E1 with a second input signal 102 at the second input terminal E2, which is generated by a square-wave generator or is derived from the mains frequency. The mains frequency or the signal E2 can also be fed to the microprocessor for synchronization. The antivalence circuit 404 only generates an output signal if the two signals 101 and 102 are not present at the first and second input terminals E1 and E2 at the same time. So that the holding capacitor C1 can be charged, the microprocessor must generate the first input signal 101 at the first input terminal E1 in synchronism with the second input signal 102 at the second input terminal E2, the output signal of the antivalence circuit 404 remaining low, the transistor 401 blocked and thus the drive path of the relay K remains high-impedance. The transistor 401 is connected in the usual way as a switching transistor at its base via a voltage divider consisting of resistance elements 402 and 403 to the output of the antivalence circuit 404. The output circuit 30a simply consists of a diode 301 which is connected to the collector of the transistor 401, so that the microcomputer at the second output terminal A2 can interrogate a signal 104 which indicates whether the switching transistor 401 has switched through or not, ie whether the control path for relay K is low-resistance or high-resistance. To attract and hold relay K, the microprocessor must control input E1 in push-pull to input E2, so that the two input signals 101 and 102 are not present at the same time. The circuit variants 30b and 40b shown in the lower part of FIG. 3 differ from the circuit variants described above primarily in that the output signal of the antivalence circuit 418 in the control circuit 40b is electrically isolated from the monitoring circuit by an optocoupler 416 and that the output signal is also isolated A2 of circuit 30b is electrically isolated from the monitoring circuit by an optocoupler 302. In addition, instead of the bipolar switching transistor 401 of the circuit variant 40a, a field effect transistor 414 is used in conjunction with a 10 series diode 415. The gate of the field effect transistor 414 is connected to a voltage divider, which is formed by the zener diode 415 and a resistor 413, which in turn lies at its other end at a connection point of a rectifier diode 420 and a capacitor 421. The diode 420 is connected to the center contact COM of the switch K1 and forms a one-way rectifier with the capacitor 421, so that the gate bias voltage generated by this one-way rectifier through the voltage divider 413 and 415 keeps the field effect transistor 414 open, ie high-impedance, until the optocoupler transistor 416 becomes conductive . The driving conditions for the antivalence element 418 by the input signals 101 and 102 at the two input connections E1 and E2 are the same as were explained above for the circuit variant 40a.

Insgesamt weisen die oben anhand der Fig. 1 bis 3 beschriebenen Schaltungen folgende Merkmale und vorteilhafte Funktionen auf:

  • Ansteuerfehler, die durch einen eventuellen Ausfall oder fehlerhafte Programmsprünge des Mikroprozessors verursacht sein können, werden während des Ladevorgangs dadurch erkannt, daß der Haltekondensator C1 immer wieder entladen wird, so daß dieser die erforderliche Anzugsladespannung nicht erreicht;
  • Ansteuerfehler, wenn das Umschaltrelais K angezogen hat führen zu einem Abfall des Relais K in die NC-Stellung. Ein sofortiges Wiederanziehen ist nicht möglich, da der Haltekondensator C1 nur auf Haltespannung aufgeladen ist. Die Voraussetzung dafür ist, daß das Widerstandselement R1 so dimensioniert ist, daß die Ladung des Haltekondensators C1 erst nach mehreren Zyklen des zweiten Eingangssignals 102 am zweiten Eingangsanschluß zum Anzug des Relais K ausreicht;
  • wenn vom Mikroprozessor das Signal 101 am ersten Eingangsanschluß E1 nicht oder nicht zeitrichtig erzeugt wird, bleibt die erfindungsgemäße Überwachungsschaltung im Ruhezustand, da das zweite Eingangssignal 102 am zweiten Eingangsanschluß E2 verhindert, daß der Haltekondensator C1 auf die Haltespannung aufgeladen wird;
  • der Ausfall eines Bauteils wird erkannt oder führt zu einer Blockierung der Überwachungsschaltung;
  • die Schalter X2 bis Xn stellen einen zweiten Abschaltweg dar;
  • die Überwachungsschaltung kann nicht freischalten, wenn eines der Schalter X2 bis Xn mit angeschlossener Last geschlossen ist. Eine zweckmäßige Dimensionierung der den Ladespannungsteiler bildenden Widerstandselemente R1 und R2 ist R1 ≈ 10 . R2;
Overall, the circuits described above with reference to FIGS. 1 to 3 have the following features and advantageous functions:
  • Control errors, which can be caused by a possible failure or incorrect program jumps of the microprocessor, are recognized during the loading process, that the holding capacitor C1 is discharged again and again so that it does not reach the required starting charge voltage;
  • Activation errors when the changeover relay K has picked up lead to a drop in the relay K to the NC position. Immediate re-tightening is not possible since the holding capacitor C 1 is only charged to the holding voltage. The prerequisite for this is that the resistance element R1 is dimensioned such that the charge of the holding capacitor C1 is sufficient to attract the relay K only after several cycles of the second input signal 102 at the second input terminal;
  • if the microprocessor does not generate the signal 101 at the first input terminal E1 or does not generate it in the correct time, the monitoring circuit according to the invention remains in the idle state since the second input signal 102 at the second input terminal E2 prevents the holding capacitor C1 from being charged to the holding voltage;
  • the failure of a component is recognized or leads to a blocking of the monitoring circuit;
  • switches X 2 to X n represent a second switch-off path;
  • the monitoring circuit cannot activate if one of the switches X 2 to X n is closed with a connected load. An expedient dimensioning of the resistance elements R1 and R2 forming the charge voltage divider is R1 ≈ 10. R2;

Fig. 4 zeigt eine bevorzugte Schaltungsanordnung der erfindungsgemäßen Überwachungsschaltung, die sich aus der Prinzipschaltung gemäß Fig. 1 und den Schaltungsvarianten 20a, 30b und 40b gemäß den Fig. 2 und 3 zusammensetzt. Die mit den entsprechenden Schaltelementen der Fig. 1 bis 3 übereinstimmenden Schaltelemente sowie Signale und Leitungen sind in Fig. 4 mit denselben Bezugsziffern bezeichnet.FIG. 4 shows a preferred circuit arrangement of the monitoring circuit according to the invention, which is composed of the basic circuit according to FIG. 1 and the circuit variants 20a, 30b and 40b according to FIGS. 2 and 3. The switching elements as well as signals and lines which correspond to the corresponding switching elements of FIGS. 1 to 3 are designated in FIG. 4 with the same reference numbers.

In Fig. 5 ist ein Funktions-Zeitdiagramm dargestellt, anhand dessen nachstehend die Funktion der in Fig. 4 gezeigten bevorzugten Ausführungsform der erfindungsgemäßen Überwachungsschaltung erläutert wird. Im oberen Teil der Fig. 5 sind die Eingangssignale 101 und 102, die am ersten und zweiten Eingangsanschluß E1 und E2 anliegen und mit denen das Antivalenzglied 418 beaufschlagt ist, dargestellt. Im mittleren Teil sind die beiden Ausgangssignale 103 und 104 dargestellt, die an den Ausgangsanschlüssen A1 und A2 auftreten und vom Mikrocomputer abfragbar sind. Im unteren Teil von Fig. 5 ist die den Schaltern X2 bis Xn über den Umschaltkontakt N0 zugeführte Speisespannung dargestellt. Das Zeitdiagramm teilt sich in die Ladezeitdauer TL und die Betriebszeitdauer TW der Überwachungsschaltung gemäß Fig. 4. Um den Haltekondensator C1 zu laden, d. h. den Feldeffekttransistor 414 zu sperren, erzeugt der Mikroprozessor das Signal 101 im Gleichtakt zum Signal 102. Der Ladevorgang des Haltekondensators C1 beginnt zum Zeitpunkt t0, wobei die Widerstandswerte der Widerstandsglieder R1 und R2 und der Kapazitätswert des Haltekondensators C1 so gewählt sind, daß der Ladevorgang mindestens 50 Zyklen der Signale E1 und E2 dauert. Wie das in der dritten Zeile in Fig. 5 dargestellte erste Ausgangssignal 103 während der Ladezeitdauer TL angibt, ist das Umschaltrelais K während dieser Zeit im Ruhezustand und der Umschaltkontakt K1 hat die Stellung Nc. Das vom Mikrocomputer abfragbare zweite Ausgangssignal 104 am zweiten Ausgangsanschluß A2 (siehe die vierte Zeile in Fig. 5) gibt während der Ladezeitdauer TL ab dem Zeitpunkt t1 an, daß der Feldeffekttransistor 414 nicht leitend ist. Nach Ablauf der Ladezeitdauer TL schaltet das Umschaltrelais K den Umschaltkontakt K1 in die Stellung N0, was der Mikrocomputer durch Abfrage des Signals 103 am ersten Ausgangsanschluß A1 erkennt und daraufhin das Signal E1 im Gegentakt zum Signal E2 erzeugt (Zeitpunkt t2). Dadurch wird der Feldeffekttransistor 414 aufgrund des Ausgangssignals der Antivalenzschaltung 418 leitend, welcher Zustand am tiefen Pegel des Ausgangssignals 104 am Ausgangsanschluß A2 abfragbar ist.FIG. 5 shows a function-time diagram, based on which the function of the preferred embodiment of the monitoring circuit according to the invention shown in FIG. 4 is explained below. In the upper part of FIG. 5, the input signals 101 and 102, which are present at the first and second input terminals E1 and E2 and with which the antivalence element 418 is applied, are shown. In the middle part the two output signals 103 and 104 are shown, which occur at the output connections A1 and A2 and can be queried by the microcomputer. In the lower part of FIG. 5, the supply voltage supplied to the switches X 2 to X n via the changeover contact N 0 is shown. The time diagram is divided into the charging time period T L and the operating time period T W of the monitoring circuit according to FIG. 4. In order to charge the holding capacitor C1, ie to block the field effect transistor 414, the microprocessor generates the signal 101 in synchronism with the signal 102. The charging process of the Holding capacitor C1 begins at time t 0 , the resistance values of the resistance elements R1 and R2 and the capacitance value of the holding capacitor C1 being chosen such that the charging process lasts at least 50 cycles of the signals E1 and E2. As the first output signal 103 shown in the third line in FIG. 5 indicates during the charging period T L , the changeover relay K is in the idle state during this time and Changeover contact K 1 has the position Nc. The second output signal 104, which can be queried by the microcomputer, at the second output terminal A2 (see the fourth line in FIG. 5) indicates during the charging period T L from the time t 1 that the field effect transistor 414 is not conductive. After the charging time T L has elapsed, the changeover relay K switches the changeover contact K1 to the position N 0 , which the microcomputer recognizes by querying the signal 103 at the first output terminal A1 and then generates the signal E1 in push-pull to the signal E2 (time t 2 ). As a result, the field effect transistor 414 becomes conductive on the basis of the output signal of the antivalence circuit 418, which state can be queried at the low level of the output signal 104 at the output terminal A2.

Um die Gleich- bzw. Gegentaktansteuerung durchzuführen, muß sich der Mikroprozessor auf das am Eingang E1 liegende Rechtecksignal bzw. das von der Netzfrequenz abgeleitete Signal synchronisieren, da sonst das Anziehen bzw. das Halten des Relais nicht möglich ist. Dies bedeutet Sicherheit durch

  • Anzugsverzögerung; und
  • Abwurf des Umschaltrelais K sofort nach Sperrung des Feldeffekttransistors 414 mit einer Abwurfzeit ≤ 5 ms.
In order to carry out the common-mode or push-pull control, the microprocessor must synchronize with the square-wave signal at input E1 or the signal derived from the mains frequency, since otherwise the relay cannot be picked up or held. This means security through
  • Delayed onset; and
  • Release of the changeover relay K immediately after blocking the field effect transistor 414 with a release time ≤ 5 ms.

Der Wert des Widerstandes R2 ist so zu bemessen, daß nur ein Vielfaches der Netzperioden, bzw. der Perioden des Rechtecksignals E2 ausreicht, um den Haltekondensator C1 auf das zum Anziehen des Umschaltrelais K notwenige Niveau zu laden. Der Wert von R2 ist so zu wählen, daß er in Verbindung mit dem Wert von R3 ausreicht, um das Umschaltrelais zu halten und in Kombination mit dem Haltekondensator C1 einen Netzausfall von bis zu 20 ms überbrücken kann.The value of the resistor R2 is to be dimensioned such that only a multiple of the network periods, or the periods of the square-wave signal E2, is sufficient to charge the holding capacitor C1 to the level necessary to attract the changeover relay K. The value of R2 must be selected so that it, in conjunction with the value of R3, is sufficient to hold the changeover relay and in Combination with the holding capacitor C1 can bridge a power failure of up to 20 ms.

Die Anlaufsicherheit der erfindungsgemäßen Überwachungsschaltung ist dadurch sichergestellt, daß ein an den Schaltern X2 bis Xn liegender Verbraucher mit einem Widerstand ≤ 10 kOhm bei geschlossenem Schalter eine Aufladung des Haltekondensators C1 auf eine für den Anzug des Relais ausreichende Spannung verhindert.The start-up security of the monitoring circuit according to the invention is ensured in that a consumer connected to the switches X 2 to X n with a resistance 10 10 kOhm prevents the holding capacitor C 1 from being charged to a voltage sufficient for the relay to pull when the switch is closed.

Durch die vom Mikroprozessor abfragbaren Ausgangssignale 103 und 104 ist eine Prüfung der erfindungsgemäßen Überwachungsschaltung seitens des Mikroprozessors ermöglicht. Um sicherzustellen, daß der Feldeffekttransistor 414 sich schalten läßt, kann er während des Betriebs, d. h. bei angezogenem Umschaltrelais K kurzzeitig gesperrt und gleich danach wieder durchgeschaltet werden (Signale 101' und 104' in Fig. 5). Anhand des Signals 104' am Ausgangsanschluß A2 kann der Mikroprozessor abfragen, ob sich der Transistor 414 sperren läßt oder nicht.The output signals 103 and 104 that can be queried by the microprocessor enable the microprocessor to test the monitoring circuit according to the invention. To ensure that the field effect transistor 414 can be switched, it can be switched on during operation, e.g. H. when the changeover relay K is activated, are briefly blocked and immediately switched on again (signals 101 'and 104' in FIG. 5). Using the signal 104 'at the output terminal A2, the microprocessor can query whether the transistor 414 can be blocked or not.

Die hier beschriebene Überwachungsschaltung ist eine Anordnung, die mittels eines Sicherheitsrelais K sicherheitsrelevante Verbraucher zunächst abgeschaltet hält, bis ein Selbsttest des steuernden Computers unter Einhaltung geforderter Zeitbedingungen abgeschlossen ist. Ein Haltekondensator C1 liegt parallel zum Ansteuerzweig des Sicherheitsrelais K, welcher Haltekondensator C1 in der Ruhestellung Nc des Sicherheitsrelais K über einen Ladestromkreis R1, V1 aufladbar ist und das Relais K nach erfolgter Ladung unter gleichzeitigem Anliegen eines Ansteuersignals vom Mikroprozessor in die Betriebsstellung nur dann bringt, wenn vorgegebene Anschaltbedingungen der sicherheitsrelevanten Verbraucher erfüllt sind. Die erfindungsgemäße Überwachungsschaltung nutzt die Differenz zwischen der Anzugs- und der Abfallspannung des Sicherheitsrelais aus.The monitoring circuit described here is an arrangement which, by means of a safety relay K, initially keeps safety-relevant consumers switched off until a self-test of the controlling computer has been completed while maintaining the required time conditions. A holding capacitor C 1 is connected in parallel to the control branch of the safety relay K, which holding capacitor C 1 can be charged in the rest position N c of the safety relay K via a charging circuit R 1 , V 1 and the relay K after charging with the simultaneous application of a control signal from the microprocessor to the Brings operating position only if specified connection conditions of the safety-relevant consumers are fulfilled. The monitoring circuit according to the invention uses the difference between the pull-in and the drop-out voltage of the safety relay.

Claims (9)

  1. Monitoring circuit for computer-controlled safety devices having a switch-over member (K) which can be brought into an operating position (N0) via a first control signal (E1) of a computer, wherein a holding capacitor (C1) is in parallel with the control path of the switch-over member (K) and the holding capacitor (C1) can be charged-up via a charging current circuit (R1; V1) in the non-operative position (Nc) of the switch-over member (K),
    characterized in that
    the resistance (R1) of the charging circuit current (R1; V1) of the holding capacitor (C1) is chosen to be sufficiently high ohmic that it is not possible to pull-up the switch-over relay (K) directly via the resistance (R1),
    and a voltage divider (R1, R2) is located within the charging current circuit of the holding capacitor (C1) with at least one safety relevant device being connected to one end of the voltage divider (R1, R2) via a switching element (X2, ... Xn) and wherein the current flowing through the device from the voltage divider (R1, R2) when the switching element (X2, ..., Xn) has been switched-on prevents a charging-up of the holding capacitor (C1),
    and a control circuit (40) is provided for by means of which the control path of the switch-over member (K) can be caused to become high ohmic or low ohmic,
    and the switch-over member (K) is held in its operating condition, in which the charging current circuit (R1, V1) is switched-off, after charge-up of the holding capacitor (C1) and simultaneous presence of the first control signal (E1).
  2. Monitoring circuit according to claim 1, characterized in that the switch-over member is a monostable switch-over relay (K).
  3. Monitoring circuit according to claim 1 or 2, characterized in that the monitoring circuit is configured in such a fashion that the switch-over member (K) remains in its non-operative position in the event of a power failure and subsequent return of mains voltage.
  4. Monitoring circuit according to one of the claims 1 or 2, characterized in that a remanence relay is utilized for malfunction storage in addition to the switch-over member (K).
  5. Monitoring circuit according to at least one of the preceding claims, characterized in that the monitoring circuit (10) has a first output terminal (A1) which issues a first output signal (103) indicating the position of the switch-over relay (K).
  6. Monitoring circuit according to at least one of the preceding claims, characterized in that the monitoring circuit (10) has a second output terminal (A2) which issues a second output signal (104) indicating the presence of the first control signal (E1).
  7. Monitoring circuit according to claim 5 or 6, characterized in that a potential separation stage (206; 302) is provided for between the monitoring circuit (10) and both the first (A1) and/or the second output terminal (A2).
  8. Monitoring circuit according to at least one of the preceding claims characterized in that the computer is a microprocessor which carries out a program-controlled internal test routine at regular intervals and which only issues the first control signal (E1) when recognition is made cf proper functioning of the microprocessor.
  9. Monitoring circuit according to claim 8, characterized in that the monitoring circuit has a logical exclusive "OR" circuit (418) which combines the first control signal (E1) issued by the microcomputer with a second control signal (E2) produced in regular time intervals in such a fashion that the switch-over member (K) can only be brought into its operating position when both control signals (E1, E2) are not simultaneously present.
EP93104908A 1992-03-28 1993-03-25 Monitoring circuit for computer controlled safety devices Expired - Lifetime EP0563787B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4210216 1992-03-28
DE4210216A DE4210216C3 (en) 1992-03-28 1992-03-28 Monitoring circuit for computer controlled safety devices

Publications (2)

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EP0563787A1 EP0563787A1 (en) 1993-10-06
EP0563787B1 true EP0563787B1 (en) 1996-11-06

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EP (1) EP0563787B1 (en)
AT (1) ATE145087T1 (en)
DE (1) DE4210216C3 (en)

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US8905063B2 (en) 2011-12-15 2014-12-09 Honeywell International Inc. Gas valve with fuel rate monitor
US8947242B2 (en) 2011-12-15 2015-02-03 Honeywell International Inc. Gas valve with valve leakage test
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US8899264B2 (en) 2011-12-15 2014-12-02 Honeywell International Inc. Gas valve with electronic proof of closure system
US8905063B2 (en) 2011-12-15 2014-12-09 Honeywell International Inc. Gas valve with fuel rate monitor
US8947242B2 (en) 2011-12-15 2015-02-03 Honeywell International Inc. Gas valve with valve leakage test
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US9557059B2 (en) 2011-12-15 2017-01-31 Honeywell International Inc Gas valve with communication link
US9234661B2 (en) 2012-09-15 2016-01-12 Honeywell International Inc. Burner control system
US20160123584A1 (en) * 2012-09-15 2016-05-05 Honeywell International Inc. Burner control system
US9657946B2 (en) * 2012-09-15 2017-05-23 Honeywell International Inc. Burner control system

Also Published As

Publication number Publication date
DE4210216C2 (en) 1994-08-25
EP0563787A1 (en) 1993-10-06
DE4210216A1 (en) 1993-09-30
ATE145087T1 (en) 1996-11-15
DE4210216C3 (en) 1997-04-03

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