EP1051882B1 - Circuit for operating an led luminous signal - Google Patents
Circuit for operating an led luminous signal Download PDFInfo
- Publication number
- EP1051882B1 EP1051882B1 EP99907277A EP99907277A EP1051882B1 EP 1051882 B1 EP1051882 B1 EP 1051882B1 EP 99907277 A EP99907277 A EP 99907277A EP 99907277 A EP99907277 A EP 99907277A EP 1051882 B1 EP1051882 B1 EP 1051882B1
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- EP
- European Patent Office
- Prior art keywords
- light
- emitting diodes
- voltage
- series
- emitting diode
- 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.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
- B61L5/00—Local operating mechanisms for points or track-mounted scotch-blocks; Visible or audible signals; Local operating mechanisms for visible or audible signals
- B61L5/12—Visible signals
- B61L5/18—Light signals; Mechanisms associated therewith, e.g. blinders
- B61L5/1809—Daylight signals
- B61L5/1881—Wiring diagrams for power supply, control or testing
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
- B61L2207/00—Features of light signals
- B61L2207/02—Features of light signals using light-emitting diodes (LEDs)
Definitions
- the invention relates to a circuit according to the preamble of claim 1.
- Such a circuit is known from WO 95/12512.
- a light signal for traffic control is reported there, in which light-emitting diodes are used instead of the signal lamps usually used for lighting.
- Several light-emitting diodes are connected in series to form a function block, which takes over the supply and monitoring of the relevant light-emitting diodes.
- Each light signal has a plurality of such function blocks, which can be switched on and off individually or together from a control point.
- the operating state of the light-emitting diodes within the individual function blocks is monitored in a manner known per se by evaluating the feed current flowing through the light-emitting diodes.
- the current indicator detects the lack of a sufficiently high supply current and transmits an OFF status message to the control station.
- the operating status messages only give the control center a status picture that corresponds to the facts if the assumed relationships between the supply current and the radiation emitted by the light-emitting diodes correspond to reality.
- the load resistance of the light emitting diodes combined in a functional block is in its blocking state by orders of magnitude higher than the load resistance that arises, if the light-emitting diodes are operated in the range of the forward voltage (the LEDs are then in the conductive state), so that an unambiguous current evaluation of the light-emitting diode operating state is possible; in the transition area between the conductive and the blocked state of the light-emitting diodes, however, there is an area in which the light-emitting diodes are already lit but still have a relatively high load resistance; Accordingly, the light-emitting diodes draw only a very small current, which is assessed as an OFF state by the monitoring current indicator.
- the current evaluation alone is not a suitable means of monitoring the function of the light-emitting diodes.
- a suitable supply voltage it can be ensured that either no or a sufficiently high supply voltage is supplied to the LEDs of the individual function blocks from the control point;
- inductive and capacitive coupling of energy to the often very long supply lines from a control point to a light signal cannot be ruled out.
- Such voltages coupled to the supply lines to the light signals can, in the worst case, light up the light-emitting diodes without this being caused by the control point and reliably recognized by a current evaluation. This means that a malfunction of light signals operated with light-emitting diodes that cannot be recognized by the control point cannot be reliably ruled out.
- the object of the present invention is to develop the known circuit according to the preamble of patent claim 1 in such a way that reliable condition monitoring of the light-emitting diodes of a light sign is possible by means of current evaluation.
- the invention solves this problem by applying the characterizing features of claim 1. Thereafter, the light-emitting diodes are short-circuited in the switched-off state, so that any voltages coupled into the leads to the light-emitting symbol cannot lead to the light-emitting diodes lighting up. Only when a sufficiently high supply current flows, which can be assumed to come from the control point, is the short-circuiting of the light-emitting diodes released, so that the light-emitting diodes can emit light; the control unit is informed of the light emitting diodes by evaluating the supply current.
- a low-loss alternating current supply of the illuminated signs over long distances should be possible, with conversion of alternating voltage into direct voltage only taking place at the illuminated sign itself.
- the function blocks are to be switched so that one half works with a positive half wave and the other half with a negative half wave; this reduces the flickering of the light-emitting diodes due to the AC voltage supply.
- the electronic switch should be designed as a self-conducting field-effect transistor, which can be controlled by a current-dependent voltage drop across the series resistor of the light-emitting diodes.
- a field effect transistor advantageously realizes the switching function of an electronic switch provided according to the teaching of claim 1 with almost no loss.
- the dimensioning rule provided according to the teaching of claim 4 makes it possible to determine the voltage at which the light-emitting diodes of the individual function blocks start to light up, regardless of the supply voltage.
- Figure 1 shows schematically and in a fragmentary representation the light emitting diodes LD for operating a light sign.
- This light sign is preferably a light signal for traffic control.
- the light-emitting diodes are arranged distributed over the visible surface of the light signal and are set up to display a certain signal term, in particular a stop or a travel signal term, or another traffic sign when switched on.
- the light-emitting diodes either light up in the color of the signal term to be displayed or they illuminate a color filter for signal display.
- the light-emitting diodes are part of function blocks FB1-FBn, which are preferably configured identically, individually or in a plurality connected in series.
- the light-emitting diodes LD are connected in series with series resistors R, which limit the supply current flowing through the light-emitting diodes in the switched-on state to a predetermined value.
- This DC voltage source can be represented, for example, by a rectifier arrangement which is operated from an AC voltage supplied to the light signal by a remote control point.
- Monitoring devices not shown, monitor the feed current flowing via the light-emitting diode or the light-emitting diodes of the individual function blocks and transmit corresponding operating status messages or a sum message derived therefrom to the control point.
- the case may arise that the light-emitting diodes light up at least temporarily due to interference voltages coupled into the feed lines for the light signal without a correspondingly high supply current flowing, which makes the light-emitting diodes recognizable for the control point.
- the invention ensures that such light-emitting diodes will not light up in the future.
- the low-impedance switching path of an electronic switch T is connected in parallel to the light-emitting diodes LD;
- This electronic switch short-circuits the light-emitting diode assigned to it when the light signal is switched off during operation and thus reliably prevents it from lighting up in the presence of interference voltages.
- the electronic switches for short-circuiting the light-emitting diodes as required can be implemented using any technology.
- the use of self-conducting field-effect transistors whose drain-source paths D-S are connected in parallel with the light-emitting diodes has proven to be particularly advantageous.
- the gate G of the field effect transistors is connected to the distal end of the resistor adjoining the light-emitting diode on the cathode side.
- Figure 2 of the drawing shows a special embodiment of a functional block with a light-emitting diode LD and a field-effect transistor T for short-circuiting this light-emitting diode as required.
- the gate G of the field effect transistor is connected to the tap of a voltage divider consisting of the resistors R1 and R2.
- the voltage at which the light-emitting diode LD begins to light can be set via this voltage divider. Only a fraction of the voltage drop across the resistors R1 and R2 is then available for controlling the field effect transistor.
- This measure ensures that the lighting of a light-emitting diode or a series connection of light-emitting diodes consisting of several light-emitting diodes is independent of the supply voltage; the control voltage is adapted to the supply voltage by specifying a corresponding voltage divider tap.
- the DC supply voltage across the self-conducting field-effect transistor and the resistors R1 and R2 is referred to as U LG , the forward voltage of the light-emitting diode or the series-connected LEDs with U F and the gate-source threshold voltage of the transistor with U S , the relationship follows from this
- the respective voltage divider tap is the only variable in the equation and determines the ignition voltage of the light-emitting diode or light-emitting diodes.
- FIG. 3 shows an embodiment of the circuit according to the invention in which an alternating voltage U x is supplied to the function blocks FB1 * to FBn * from the control point.
- the function blocks contain rectifier diodes D1 to Dn for rectifying the operating AC voltage.
- the individual light-emitting diodes are connected to the two feed lines L1, L2 via the rectifier in such a way that adjacent light-emitting diodes of different function blocks light up during different half-waves of the supply voltage. So shine z. B.
Abstract
Description
Die Erfindung bezieht sich auf eine Schaltung nach dem Oberbegriff des Patentanspruches 1.The invention relates to a circuit according to the preamble of claim 1.
Eine solche Schaltung ist aus der WO 95/12512 bekannt. Dort wird über ein Lichtsignal für die Verkehrssteuerung berichtet, bei dem anstelle der üblicherweise für die Beleuchtung verwendeten Signallampen Leuchtdioden zur Anwendung kommen. Jeweils mehrere Leuchtdioden sind zu einem Funktionsblock in Reihe geschaltet, der die Speisung und Überwachung der betreffenden Leuchtdioden übernimmt. Jedes Lichtsignal weist eine Mehrzahl solcher Funktionsblöcke auf, die von einer Steuerstelle aus einzeln oder gemeinsam an- und abschaltbar sind. Die Überwachung des Betriebszustandes der Leuchtdioden innerhalb der einzelnen Funktionsblöcke geschieht in an sich bekannter Weise durch Bewerten des über die Leuchtdioden fließenden Speisestromes. Bei angeschaltetem Lichtsignal und intakten Leuchtdioden fließt über den bewertenden Stromindikator ein bestimmter Speisestrom, der zu einer Betriebszustandsmeldung EIN an die Steuerstelle führt. Bei unterbrochenem Speisekreis für die Leuchtdioden, sei es störungsbedingt oder nicht, detektiert der Stromindikatior das Fehlen eines ausreichend hohen Speisestromes und gibt eine Zustandsmeldung AUS an die Steuerstelle weiter.Such a circuit is known from WO 95/12512. A light signal for traffic control is reported there, in which light-emitting diodes are used instead of the signal lamps usually used for lighting. Several light-emitting diodes are connected in series to form a function block, which takes over the supply and monitoring of the relevant light-emitting diodes. Each light signal has a plurality of such function blocks, which can be switched on and off individually or together from a control point. The operating state of the light-emitting diodes within the individual function blocks is monitored in a manner known per se by evaluating the feed current flowing through the light-emitting diodes. When the light signal is switched on and the LEDs are intact, a certain supply current flows via the evaluating current indicator, which leads to an operating status message ON to the control point. If the supply circuit for the light-emitting diodes is interrupted, be it due to a fault or not, the current indicator detects the lack of a sufficiently high supply current and transmits an OFF status message to the control station.
Die Betriebszustandsmeldungen vermitteln der Steuerstelle nur dann ein den Tatsachen entsprechendes Zustandsbild, wenn die angenommenen Zusammenhänge zwischen Speisestrom und von den Leuchtdioden emittierter Strahlung der Wirklichkeit entsprechen. Zwar liegt der Lastwiderstand der in einem Funktionsblock zusammengefaßten Leuchtdioden in ihrem Sperrzustand um Größenordnungen über dem Lastwiderstand, der sich einstellt, wenn die Leuchtdioden im Bereich der Flußspannung betrieben werden (die LED's befinden sich dann im leitfähigen Zustand), so daß an sich eine eindeutige Strombewertung des Leuchtdioden-Betriebszustandes möglich ist; im Übergangsbereich zwischen leitfähigem und gesperrtem Zustand der Leuchtdioden gibt es jedoch einen Bereich, bei dem die Leuchtdioden bereits leuchten, aber noch einen verhältnismäßig hohen Lastwiderstand besitzen; dementsprechend ziehen die Leuchtdioden auch nur einen sehr geringen Strom, was von dem überwachenden Stromindikator als AUS-Zustand bewertet wird. Wenn damit zu rechnen ist, daß die Leuchtdioden in diesem Übergangsbereich betrieben werden können, ist die Strombewertung allein also kein geeignetes Mittel zur Funktionsüberwachung der Leuchtdioden. Durch Vorgabe einer geeigneten Speisespannung läßt sich zwar sicherstellen, daß den Leuchtdioden der einzelnen Funktionsblöcke von der Steuerstelle her entweder keine oder eine für den Leuchtbetrieb ausreichend hohe Speisespannung zugeführt wird; nicht ausschließen läßt sich aber das induktive wie auch das kapazitive Einkoppeln von Energie auf die oft sehr langen Zuleitungen von einer Steuerstelle zu einem Lichtsignal. Solche auf die Zuleitungen zu den Lichtsignalen eingekoppelten Spannungen können die Leuchtdioden im ungünstigen Fall zum Leuchten bringen, ohne daß dies von der Steuerstelle aus veranlaßt ist und durch eine Strombewertung zuverlässig erkannt wird. Damit ist ein für die Steuerstelle nicht erkennbares Fehlverhalten von mit Leuchtdioden betriebenen Lichtsignalen nicht zuverlässig auszuschließen.The operating status messages only give the control center a status picture that corresponds to the facts if the assumed relationships between the supply current and the radiation emitted by the light-emitting diodes correspond to reality. The load resistance of the light emitting diodes combined in a functional block is in its blocking state by orders of magnitude higher than the load resistance that arises, if the light-emitting diodes are operated in the range of the forward voltage (the LEDs are then in the conductive state), so that an unambiguous current evaluation of the light-emitting diode operating state is possible; in the transition area between the conductive and the blocked state of the light-emitting diodes, however, there is an area in which the light-emitting diodes are already lit but still have a relatively high load resistance; Accordingly, the light-emitting diodes draw only a very small current, which is assessed as an OFF state by the monitoring current indicator. If it is to be expected that the light-emitting diodes can be operated in this transition area, then the current evaluation alone is not a suitable means of monitoring the function of the light-emitting diodes. By specifying a suitable supply voltage, it can be ensured that either no or a sufficiently high supply voltage is supplied to the LEDs of the individual function blocks from the control point; However, inductive and capacitive coupling of energy to the often very long supply lines from a control point to a light signal cannot be ruled out. Such voltages coupled to the supply lines to the light signals can, in the worst case, light up the light-emitting diodes without this being caused by the control point and reliably recognized by a current evaluation. This means that a malfunction of light signals operated with light-emitting diodes that cannot be recognized by the control point cannot be reliably ruled out.
Aufgabe der vorliegenden Erfindung ist es, die bekannte Schaltung nach dem Oberbegriff des Patentanspruches 1 so weiterzubilden, daß eine zuverlässige Zustandsüberwachung der Leuchtdioden eines Leuchtzeichens durch Strombewertung möglich ist.The object of the present invention is to develop the known circuit according to the preamble of patent claim 1 in such a way that reliable condition monitoring of the light-emitting diodes of a light sign is possible by means of current evaluation.
Die Erfindung löst diese Aufgabe durch die Anwendung der kennzeichnenden Merkmale des Patentanspruches 1. Danach werden die Leuchtdioden in abgeschaltetem Zustand kurzgeschlossen, so daß etwaige in die Zuleitungen zum Leuchtzeichen eingekoppelte Spannungen nicht zum Aufleuchten der Leuchtdioden führen können. Erst beim Fließen eines ausreichend hohen Speisestromes, von dem anzunehmen ist, daß er aus der Steuerstelle stammt, wird der Kurzschluß der Leuchtdioden aufgehoben, so daß die Leuchtdioden Licht emittieren können; durch die Bewertung des Speisetromes wird die Steuerstelle vom Leuchten der Leuchtdioden unterrichtet.The invention solves this problem by applying the characterizing features of claim 1. Thereafter, the light-emitting diodes are short-circuited in the switched-off state, so that any voltages coupled into the leads to the light-emitting symbol cannot lead to the light-emitting diodes lighting up. Only when a sufficiently high supply current flows, which can be assumed to come from the control point, is the short-circuiting of the light-emitting diodes released, so that the light-emitting diodes can emit light; the control unit is informed of the light emitting diodes by evaluating the supply current.
Vorteilhafte Aus- und Weiterbildungen der erfindungsgemäßen Schaltung sind in den Unteransprüchen angegeben.Advantageous developments and refinements of the circuit according to the invention are specified in the subclaims.
So soll nach der Lehre des Anspruches 2 eine verlustarme Wechselstromspeisung der Leuchtzeichen über weite Entfernungen möglich sein, wobei erst am Leuchtzeichen selbst eine Umsetzung von Wechselspannung in Gleichspannung erfolgt. In besonders vorteilhafter Weise sollen dabei die Funktionsblöcke so geschaltet werden, daß die eine Hälfte bei positiver und die andere Hälfte bei negativer Halbwelle arbeitet; dadurch verringert sich das aufgrund der Wechselspannungsspeisung entstehende Flackern der Leuchtdioden.Thus, according to the teaching of claim 2, a low-loss alternating current supply of the illuminated signs over long distances should be possible, with conversion of alternating voltage into direct voltage only taking place at the illuminated sign itself. In a particularly advantageous manner, the function blocks are to be switched so that one half works with a positive half wave and the other half with a negative half wave; this reduces the flickering of the light-emitting diodes due to the AC voltage supply.
Gemäß Anspruch 3 soll der elektronische Schalter als selbstleitender Feldeffekt-Transistor ausgebildet sein, der von einem stromabhängigen Spannungsabfall am Vorwiderstand der Leuchtdioden steuerbar ist. Ein solcher Feldeffekt-Transistor realisiert in vorteilhafter Weise nahezu verlustfrei die nach der Lehre des Anspruches 1 vorgesehene Schaltfunktion eines elektronischen Schalters.According to claim 3, the electronic switch should be designed as a self-conducting field-effect transistor, which can be controlled by a current-dependent voltage drop across the series resistor of the light-emitting diodes. Such a field effect transistor advantageously realizes the switching function of an electronic switch provided according to the teaching of claim 1 with almost no loss.
Die nach der Lehre des Anspruches 4 vorgesehene Bemessungsregel macht es möglich, die Spannung, bei welcher die Leuchtdioden der einzelnen Funktionsblöcke zu leuchten beginnen, unabhängig von der Versorgungsspannung frei zu wählen.The dimensioning rule provided according to the teaching of claim 4 makes it possible to determine the voltage at which the light-emitting diodes of the individual function blocks start to light up, regardless of the supply voltage.
Die Erfindung ist nachstehend anhand von in der Zeichnung dargestellten Ausführungsbeispielen näher erläutert.The invention is explained in more detail below with reference to exemplary embodiments shown in the drawing.
Die Zeichnung zeigt in
- Figur 1
- das Prinzip eines LED-Signals mit Störspannungsunterdrückung für Gleichspannugsspeisung, in
- Figur 2
- einen Schaltungsausschnitt, an dem sich die Bemessungsregel des Anspruches 4 ableiten läßt und in
- Figur 3
- ein LED-Signal für Wechselspannungsspeisung.
- Figure 1
- the principle of an LED signal with interference suppression for DC voltage supply, in
- Figure 2
- a circuit section on which the design rule of claim 4 can be derived and in
- Figure 3
- an LED signal for AC voltage supply.
Figur 1 zeigt schematisch und in ausschnittsweiser Darstellung die Leuchtdioden LD zum Betreiben eines Leuchtzeichens. Bei diesem Leuchtzeichen handelt es sich vorzugsweise um ein Lichtsignal zur Verkehrssteuerung. Dabei sind die Leuchtdioden über die Sichtfläche des Lichtsignales verteilt angeordnet und dazu eingerichtet, in angeschaltetem Zustand einen bestimmten Signalbegriff, insbesondere einen Halt- oder einen Fahrtsignalbegriff, oder ein sonstiges Verkehrszeichen anzuzeigen. Hierzu leuchten die Leuchtdioden entweder in der Farbe des jeweils darzustellenden Signalbegriffes oder aber sie beleuchten ein Farbfilter zur Signaldarstellung. Die Leuchtdioden sind wie im dargestellten Ausführungsbeispiel einzeln oder zu mehreren in Reihe geschaltet Bestandteil von Funktionsblöcken FB1 - FBn, die vorzugsweise identisch ausgeführt sind. Dabei ist es auch möglich, mehrere solcher Reihenschaltungen von Leuchtdioden einander parallel zu schalten, um so größere Teilflächen des Leuchtzeichens auszuleuchten. In bekannter Weise sind die Leuchtdioden LD mit Vorwiderständen R in Reihe geschaltet, die den in angeschaltetem Zustand über die Leuchtdioden fließenden Speisestrom auf einen vorgegebenen Wert begrenzen. Die Speisung der Leuchtdioden erfolgt über Zuleitungen L1, L2 aus einer Gleichspannungsquelle U =.Figure 1 shows schematically and in a fragmentary representation the light emitting diodes LD for operating a light sign. This light sign is preferably a light signal for traffic control. The light-emitting diodes are arranged distributed over the visible surface of the light signal and are set up to display a certain signal term, in particular a stop or a travel signal term, or another traffic sign when switched on. For this purpose, the light-emitting diodes either light up in the color of the signal term to be displayed or they illuminate a color filter for signal display. As in the exemplary embodiment shown, the light-emitting diodes are part of function blocks FB1-FBn, which are preferably configured identically, individually or in a plurality connected in series. It is also possible to connect several such series connections of light-emitting diodes in parallel in order to illuminate larger areas of the illuminated sign. In a known manner, the light-emitting diodes LD are connected in series with series resistors R, which limit the supply current flowing through the light-emitting diodes in the switched-on state to a predetermined value. The LEDs are supplied via leads L1, L2 from a direct voltage source U =.
Diese Gleichspannungsquelle kann beispielsweise durch eine Gleichrichteranordnung dargestellt sein, die aus einer von einer fernen Steuerstelle dem Lichtsignal zugeführten Wechselspannung betrieben wird. Nicht dargestellte Überwachungseinrichtungen überwachen den über die Leuchtdiode bzw. die Leuchtdioden der einzelnen Funktionsblöcke fließenden Speisestrom und übermitteln entsprechende Betriebszustandsmeldungen oder eine daraus abgeleitete Summenmeldung an die Steuerstelle. Wie bereits in der Beschreibungseinleitung ausgeführt, kann dabei der Fall eintreten, daß durch in die Zuleitungen zum Lichtsignal eingekoppelte Störspannungen die Leuchtdioden mindestens vorübergehend aufleuchten ohne daß ein entsprechend hoher Speisestrom fließt, der für die Steuerstelle das Leuchten der Leuchtdioden erkennbar macht. Die Erfindung stellt sicher, daß ein solches störspannungsbedingtes Aufleuchten von Leuchtdioden zukünftig unterbleibt. Zu diesem Zweck ist den Leuchtdioden LD die niederohmige Schaltstrecke eines elektronischen Schalters T parallel geschaltet; dieser elektronische Schalter schließt die ihm zugeordnete Leuchtdiode bei betriebsmäßig abgeschaltetem Lichtsignal kurz und verhindert damit zuverlässig deren Aufleuchten beim Vorhandensein von Störspannungen. Bei Verwendung mehrerer in Reihe geschalteter Leuchtdioden kann entweder eine entsprechende Anzahl von elektronischen Schaltern zum Kurzschließen der einzelnen Leuchtdioden vorhanden sein oder aber es gibt eine oder mehrerer solcher Schalter, die in Summe alle in Reihe geschalteten Leuchtdioden kurzschließen. Sind die Zuleitungen zum Lichtsignal fremdspannungsbeeinflußt, so treiben diese Fremdspannungen in ihrer Amplitude begrenzte Störströme über die elektronischen Schalter und die mit ihnen in Reihe liegenden Vorwiderstände der Leuchtdioden. Annahmegemäß soll dabei die Potentialdifferenz an den Vorwiderständen so gering sein, daß die Schaltstrecken der elektronischen Schalter weiterhin leitend sind. Erst beim Aufschalten der Versorgungsspannung auf die Zuleitungen zum Lichtsignal steigt die Spannung an den mit den kurzgeschlossenen Leuchtdioden in Reihe liegenden Vorwiderständen auf einen Wert an, der ausreicht, die zugehörigen elektronischen Schalter in den Sperrzustand zu steuern. Dabei wird der Kurzschluß für die Leuchtdioden aufgehoben und die Leuchtdioden leuchten auf.This DC voltage source can be represented, for example, by a rectifier arrangement which is operated from an AC voltage supplied to the light signal by a remote control point. Monitoring devices, not shown, monitor the feed current flowing via the light-emitting diode or the light-emitting diodes of the individual function blocks and transmit corresponding operating status messages or a sum message derived therefrom to the control point. As already explained in the introduction to the description, the case may arise that the light-emitting diodes light up at least temporarily due to interference voltages coupled into the feed lines for the light signal without a correspondingly high supply current flowing, which makes the light-emitting diodes recognizable for the control point. The invention ensures that such light-emitting diodes will not light up in the future. For this purpose, the low-impedance switching path of an electronic switch T is connected in parallel to the light-emitting diodes LD; This electronic switch short-circuits the light-emitting diode assigned to it when the light signal is switched off during operation and thus reliably prevents it from lighting up in the presence of interference voltages. When using a plurality of light-emitting diodes connected in series, there can either be a corresponding number of electronic switches for short-circuiting the individual light-emitting diodes, or there are one or more such switches which, in total, short-circuit all light-emitting diodes connected in series. If the supply lines to the light signal are influenced by external voltage, then these external voltages drive interference currents with limited amplitude via the electronic switches and the series resistors of the light-emitting diodes which are in series with them. According to the assumption, the potential difference across the series resistors should be so small that the switching paths of the electronic switches are still conductive. The voltage only increases when the supply voltage is switched on to the light signal lines on the series resistors in series with the short-circuited light-emitting diodes to a value which is sufficient to control the associated electronic switches in the blocking state. The short circuit for the LEDs is canceled and the LEDs light up.
Die elektronischen Schalter zum bedarfsweisen Kurzschließen der Leuchtdioden können prinzipiell in jeder beliebigen Technik ausgeführt sein. Als besonders vorteilhaft hat sich die Verwendung von selbstleitenden Feldeffekt-Transistoren erwiesen, deren Drain-Source-Strecken D-S den Leuchtdioden parallel geschaltet sind. Das Gate G der Feldeffekt-Transistoren ist an dem entfernten Ende des katodenseitig an die Leuchtdiode angrenzenden Widerstandes angeschlossen.In principle, the electronic switches for short-circuiting the light-emitting diodes as required can be implemented using any technology. The use of self-conducting field-effect transistors whose drain-source paths D-S are connected in parallel with the light-emitting diodes has proven to be particularly advantageous. The gate G of the field effect transistors is connected to the distal end of the resistor adjoining the light-emitting diode on the cathode side.
Figur 2 der Zeichnung zeigt eine spezielle Ausgestaltung eines Funktionsblockes mit einer Leuchtdiode LD und einem Feldeffekt-Transistor T zum bedarfsweisen Kurzschließen dieser Leuchtdiode. Das Gate G des Feldeffekt-Transistors ist an den Abgriff eines aus den Widerständen R1 und R2 bestehenden Spannungsteilers angeschlossen. Über diesen Spannungsteiler kann die Spannung eingestellt werden, bei der die Leuchtdiode LD zu leuchten beginnt. Für die Steuerung des Feldeffekt-Transistors steht dann nur ein Bruchteil der an den Widerständen R1 und R2 abfallenden Spannung zur Verfügung. Durch diese Maßnahme wird erreicht, daß das Aufleuchten einer Leuchtdiode oder einer aus mehreren Leuchtdioden bestehenden Reihenschaltung von Leuchtdioden unabhängig ist von der Versorgungsspannung; die Anpassung der Steuerspannung an die Versorgungsspannung geschieht durch Vorgabe eines entsprechenden Spannungsteilerabgriffes.Figure 2 of the drawing shows a special embodiment of a functional block with a light-emitting diode LD and a field-effect transistor T for short-circuiting this light-emitting diode as required. The gate G of the field effect transistor is connected to the tap of a voltage divider consisting of the resistors R1 and R2. The voltage at which the light-emitting diode LD begins to light can be set via this voltage divider. Only a fraction of the voltage drop across the resistors R1 and R2 is then available for controlling the field effect transistor. This measure ensures that the lighting of a light-emitting diode or a series connection of light-emitting diodes consisting of several light-emitting diodes is independent of the supply voltage; the control voltage is adapted to the supply voltage by specifying a corresponding voltage divider tap.
Bezeichnet man die über den selbstleitenden Feldeffekt-Transistor und die Widerstände R1 und R2 anliegende Versorgungsgleichspannung mit ULG, die Flußspannung der Leuchtdiode bzw. der in Reihe geschalteten Leuchtdioden mit UF und die Gate-Source-Schwellppannung des Transistors mit US, so folgt hieraus die Beziehung
Figur 3 zeigt eine Ausführungsform der erfindungsgemäßen Schaltung, bei der den Funktionsblöcken FB1* bis FBn* von der Steuerstelle her eine Wechselspannung Ux zugeführt wird. Die Funktionsblöcke beinhalten Gleichrichterdioden D1 bis Dn zum Gleichrichten der Betriebswechselspannung. Die einzelnen Leuchtdioden sind über die Gleichrichter so an die beiden Zuleitungen L1,L2 angeschlossen, daß im Leuchtzeichen benachbarte Leuchtdioden unterschiedlicher Funktionsblöcke während unterschiedlicher Halbwellen der Versorgungsspannung leuchten. So leuchten z. B. die Leuchtdioden LD1 und LD(n-1) während der einen Halbwelle der Versorgungswechselspannung auf, wobei die Leuchtdioden LD2 und LDn dunkel bleiben, während in der folgenden Halbwelle die beiden letztgenannten Leuchtdioden aufleuchten und die Leuchtdioden LD1 und LDn-1 verlöschen. Durch diese Art der Schaltung verringert sich das ansonsten bei Wechselspannungsansteuerung entstehende Flackern der Leuchtzeichen erheblich.
Auch bei dieser Konstellation der Funktionsblöcke können wiederum eine Vielzahl von Leuchtdioden in Reihe geschaltet und dieser Reihenschaltung gegebenenfalls noch eine oder mehrere weitere Reihenschaltungen von Leuchtdioden parallel geschaltet sein. Es ist dafür zu sorgen, daß bei einem betriebsmäßig abgeschalteten Lichtsignal sämtliche Leuchtdioden der zugehörigen Funktionsblöcke über die zugehörigen elektronischen Schalter kurzgeschlossen sind, so daß ein störbedingtes Aufleuchten in Folge eingekoppelter Störspannungen zuverlässig vermieden wird.FIG. 3 shows an embodiment of the circuit according to the invention in which an alternating voltage U x is supplied to the function blocks FB1 * to FBn * from the control point. The function blocks contain rectifier diodes D1 to Dn for rectifying the operating AC voltage. The individual light-emitting diodes are connected to the two feed lines L1, L2 via the rectifier in such a way that adjacent light-emitting diodes of different function blocks light up during different half-waves of the supply voltage. So shine z. B. the light emitting diodes LD1 and LD (n-1) during one half-wave of the AC supply voltage, the light-emitting diodes LD2 and LDn remaining dark, while in the following half-wave the latter two light-emitting diodes light up and the light-emitting diodes LD1 and LDn-1 go out. This type of circuit significantly reduces the flickering of the illuminated signs that otherwise occurs when AC voltage is controlled.
In this constellation of the function blocks, too, a large number of light-emitting diodes can in turn be connected in series, and this series connection may also be connected in parallel with one or more further series connections of light-emitting diodes. Care must be taken to ensure that when the light signal is switched off during operation, all the light-emitting diodes of the associated function blocks are short-circuited via the associated electronic switches, so that interference-induced lighting up as a result of coupled-in interference voltages is reliably avoided.
Claims (4)
- Circuit for operating a light sign, in particular the light sign of a light signal, the luminous element of which is represented by a plurality of light-emitting diodes, individual light-emitting diodes or a plurality of series-connected light-emitting diodes forming function blocks which can in each case be jointly connected and disconnected by a control station via associated series resistors and the operating status of which can be established by current evaluation, characterised in that connected in parallel with the light-emitting diodes (LD) of each function block (FB1 to FBn) is the low-resistance break (D-S) of at least one electronic switch (T), the control electrode (G) of which is at a voltage (U=) which can be picked off at the series resistor (R) or at a pick-off of the series resistor (R1, R2) for the light-emitting diodes of the respective function block and controls the electronic switch in the high-resistance switching state as soon as the voltage drop at the series resistor or the pick-off of the series resistor exceeds a predetermined value.
- Circuit according to claim 1, characterised in that the light-emitting diodes (LD1, LD2) of the light sign and with them the electronic switches (T) are, via one-way rectifiers (D1, D2), at an alternating voltage (U≈) which can be switched or adjusted by the control station, the rectifiers (D1, D2) assigned to the light-emitting diodes of spatially adjacent function blocks (FB1*, FB2*) and also the associated light-emitting diodes being connected with different polarisation to the supply lines (L1, L2) to the light sign that carry the alternating voltage.
- Circuit according to one of claims 1 or 2,
characterised in that the electronic switch (T) is constructed as a self-conductive field-effect transistor having a drain-source section (D-S) which is connected in parallel with at least one light-emitting diode (LD) of the associated function block (FB1) and having a gate (G) which is connected to the pick-off (R1, R2) or to the remote end of a series resistor (R) connected to the cathode side of the at least one light-emitting diode of the function block. - Circuit according to claim 3, characterised in that the voltage (ULG) at which the at least one light-emitting diode (LD) of a function block begins to give light is adjustable by way of a voltage-divider pick-off at the series resistor (R1 + R2) of the light-emitting diode arrangement according to the following relation:
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19802895 | 1998-01-21 | ||
| DE19802895A DE19802895A1 (en) | 1998-01-21 | 1998-01-21 | Circuit for operating LED light display e.g. for traffic control lighting |
| PCT/DE1999/000180 WO1999038361A1 (en) | 1998-01-21 | 1999-01-15 | Circuit for operating an led luminous signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1051882A1 EP1051882A1 (en) | 2000-11-15 |
| EP1051882B1 true EP1051882B1 (en) | 2001-09-19 |
Family
ID=7855707
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP99907277A Expired - Lifetime EP1051882B1 (en) | 1998-01-21 | 1999-01-15 | Circuit for operating an led luminous signal |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1051882B1 (en) |
| AT (1) | ATE205997T1 (en) |
| DE (2) | DE19802895A1 (en) |
| NO (1) | NO325779B1 (en) |
| WO (1) | WO1999038361A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19846753A1 (en) * | 1998-10-07 | 2000-04-13 | Siemens Ag | Circuit arrangement for operating a light sign |
| NL1014865C2 (en) * | 2000-04-07 | 2001-10-09 | Nma Railway Signalling B V | Signal comprises light-emitting unit in housing with number of light sources, which by means of conduits are connected to external feed source and also incorporates a light source activator |
| DE10164561B4 (en) * | 2001-12-14 | 2004-03-04 | Siemens Ag | Circuit arrangement for operating an LED signal |
| DE102004033070B3 (en) * | 2004-07-08 | 2006-01-12 | Theben Ag | Circuit arrangement for half-wave detection of a 230 V AC voltage |
| DE102014101421B3 (en) * | 2014-02-05 | 2015-07-02 | Gira Giersiepen Gmbh & Co. Kg | Electrical circuit for the building system technology to avoid caused by capacitive coupling currents |
| DE102014203007A1 (en) * | 2014-02-19 | 2015-08-20 | Zumtobel Lighting Gmbh | Circuitry and method for monitoring current flow through LEDs |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS556687A (en) * | 1978-06-29 | 1980-01-18 | Handotai Kenkyu Shinkokai | Traffic use display |
| NL8300449A (en) * | 1983-02-07 | 1984-09-03 | Philips Nv | OPTICAL INDICATOR. |
| GB8512424D0 (en) * | 1985-05-16 | 1985-06-19 | Dewhurst & Partner Plc | Operation & control of light emitting diodes |
| FR2724749A1 (en) * | 1994-09-15 | 1996-03-22 | Sofrela Sa | LED lamps with integral controller for road traffic control signals |
| DE19533116A1 (en) * | 1995-09-07 | 1997-03-13 | Siemens Ag | Driver circuit for a light emitting diode |
| DE19627475C2 (en) * | 1996-07-08 | 2000-12-07 | Siemens Ag | Circuit arrangement for signaling devices in road traffic systems |
-
1998
- 1998-01-21 DE DE19802895A patent/DE19802895A1/en not_active Withdrawn
-
1999
- 1999-01-15 AT AT99907277T patent/ATE205997T1/en active
- 1999-01-15 EP EP99907277A patent/EP1051882B1/en not_active Expired - Lifetime
- 1999-01-15 WO PCT/DE1999/000180 patent/WO1999038361A1/en active IP Right Grant
- 1999-01-15 DE DE59900274T patent/DE59900274D1/en not_active Expired - Lifetime
-
2000
- 2000-07-21 NO NO20003778A patent/NO325779B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE19802895A1 (en) | 1999-07-22 |
| DE59900274D1 (en) | 2001-10-25 |
| WO1999038361A1 (en) | 1999-07-29 |
| NO20003778D0 (en) | 2000-07-21 |
| ATE205997T1 (en) | 2001-10-15 |
| NO20003778L (en) | 2000-09-20 |
| EP1051882A1 (en) | 2000-11-15 |
| NO325779B1 (en) | 2008-07-14 |
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