EP1417864A1 - Illuminated sign for traffic control and method for functional monitoring of such a sign - Google Patents

Illuminated sign for traffic control and method for functional monitoring of such a sign

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Publication number
EP1417864A1
EP1417864A1 EP02760115A EP02760115A EP1417864A1 EP 1417864 A1 EP1417864 A1 EP 1417864A1 EP 02760115 A EP02760115 A EP 02760115A EP 02760115 A EP02760115 A EP 02760115A EP 1417864 A1 EP1417864 A1 EP 1417864A1
Authority
EP
European Patent Office
Prior art keywords
light
sign
led
current
emitting diodes
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.)
Granted
Application number
EP02760115A
Other languages
German (de)
French (fr)
Other versions
EP1417864B1 (en
Inventor
Bernhard Hering
Rudolf Schierjott
Gerhard Treffer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
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Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1417864A1 publication Critical patent/EP1417864A1/en
Application granted granted Critical
Publication of EP1417864B1 publication Critical patent/EP1417864B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/006—Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs
    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/20—Responsive to malfunctions or to light source life; for protection

Definitions

  • the invention relates to a light sign for traffic control, in particular road traffic, according to the preamble of claim 1 and a method for monitoring the function of such a sign according to the preamble of claim 9.
  • characters of various types and importance are used to control traffic in order to support smooth traffic handling. This applies to ship travel, airplanes, for example at airports, and for all rail traffic, but especially for road traffic. Due to the constantly increasing volume of traffic, more and more traffic and light signals are used to regulate inner-city traffic or to direct long-distance traffic. An increasing proportion of these signs are generated by light sources. Typical examples of this are the alternating light signs of the traffic light systems at road junctions or the alternating traffic signs on so-called motorway cross sections. In the case of the light signals mentioned, today mainly light bulbs serve as light sources. Incandescent lamps can fail due to a short circuit or interruption, causing a character to be generated by them to be garbled, with insufficient light intensity or not displayed at all.
  • a light signal that is not properly displayed does not mislead road users, it must be switched off immediately to avoid the risk of an accident.
  • a safety-relevant sign such as a red traffic light, a speed limit or a warning indicator
  • the monitoring must be active continuously, i.e. even if the corresponding sign is not active, i.e. is not lit.
  • Functional monitoring of the incandescent lamps generating a sign can be carried out via the passage of current through their filaments.
  • the inertia of a filament allows the functionality of the incandescent lamp to be tested by briefly energizing the filament for, for example, 1 ms, without light escaping.
  • a microprocessor gives commands to activate the lamps, the signals from the lamps and sensors are monitored and the driver is informed of a malfunction by a display on the dashboard.
  • a power transistor connects the lighting system to the car battery.
  • a high-resistance voltage divider is connected, the center potential of which serves as a criterion when checking a voltage condition.
  • the microprocessor checks the value of the center potential of the voltage divider every 10 ms. When the light is switched on, the potential is 12 V, when it is off, 0 V.
  • the test In order to obtain a positive display for all possible errors and light operating modes, the test must be expanded, to include the OFF mode when the light is on and the ON mode when the light is off.
  • a switched on lamp is switched off by the system once per second for approx. 100 ms; if it is off, the system switches on periodically every 40 s for 100 ms.
  • the test begins when the engine is started and ends 100 s after it is switched off. This extended operation ensures that lamp failures are also detected during the filament cooling period.
  • the incandescent lamp is increasingly being replaced by the light-emitting diode, hereinafter also abbreviated to LED, which as a low-maintenance and highly available light source for optical signs has many advantages for the economical operation of Offers traffic lights.
  • the problem is that characters that could be generated with LED could previously only be monitored when they were switched on.
  • the LED technology could not be used for safety-relevant signs that must be monitored for functionality even when the device is switched off. Due to the quasi-inertia-free conversion of current into light in LED light sources, a function test analogous to the so-called cold lamp test was not possible without generating disruptive and therefore unacceptable light flashes.
  • the invention is therefore based on the object of providing a light sign and a method for function monitoring of a sign of the type mentioned at the outset, so that the functionability of the sign can be monitored both when the sign is switched on and when it is switched off, with a reasonable technical outlay.
  • a subtask is achieved according to the invention by a light sign of the type mentioned at the outset with the features mentioned in the characterizing part of patent claim 1.
  • the immediately occurring light emission of the LED can be restricted such that it can no longer be perceived by the viewer even in the dark. This avoids flashes of light that disturb road users.
  • the increase in current through the light-emitting diodes is used as a criterion for the functionality.
  • the monitoring device of the light sign comprises switching means for switching off the current supply when a predetermined threshold value for the current intensity is reached.
  • the limitation of the electrical current flowing through the light-emitting diodes is achieved here by specifying a maximum threshold value at which the LED current that builds up is switched off.
  • the switching means are constructed as digital logic circuit with a memory element '.
  • the LED current limitation can thus be implemented, for example, by using a D flip-flop as a memory element and by means of further standard components in semiconductor circuit technology.
  • the monitoring device is also designed to measure the voltage drop across the energized light-emitting diodes. Through this separate additional monitoring of the voltage, a failed light-emitting diode can be determined despite the LED current flow, for example in the event of a short circuit. This increases the reliability of the functional test of a light sign according to the invention.
  • the light sources are arranged as a chain of light-emitting diodes connected in series or as a cluster of light-emitting diodes connected to one another. This is advantageously used when designing light signs with line-shaped symbols or flat structures.
  • Light signs according to the invention with function monitoring in traffic signs are preferred, in particular those Can be used with changing display options for different signs, or with traffic light systems, i.e. the well-known traffic lights.
  • a voltage monitoring signal representing the voltage drop across the energized light-emitting diodes is additionally generated.
  • the voltage monitoring signal is used as an additional criterion when assessing the functionality of a light-emitting diode in order to be able to rule out a short circuit in the event of a positive LED current supply.
  • the current is supplied in an inactive state or periodically in an inactive phase of the light-emitting diode.
  • the function monitoring can thus be carried out both when the light signal is not in operation - even for a longer period of several months - and during operation in which the regular LED current supply is periodically switched off for a short phase, in which case the even shorter test energization takes place.
  • FIG. 1 shows a circuit for current control in a light signal according to the invention
  • FIG. 2 the time segments of an LED control signal
  • FIG. 3 the logic circuit as switching means of the monitoring device
  • a light sign according to the invention for example a variable message sign for the alternate display of different traffic signs, is generated, for example, in an outdoor facility designed as a sign bridge over roadways.
  • the outdoor system has a mains connection for the voltage supply of the LED chains, for which a commercial industrial switching power supply for 48 V DC voltage with an input power of 100 W is used. It is connected to a route station via a CAN bus, which includes a modem and a control and a master module. For example, 32 LED chains, each divided into four groups of eight, can be controlled via a common control module.
  • the control module contains a digital part and an analog part.
  • the digital part has modules for initialization, module detection, read-write logic, a test register, the enable logic for normal and test operation, the LED current setting and the current and voltage monitoring, while the 32 LED current regulators Form analog part.
  • Up to 8 such control modules can be connected to a common control unit. It is controlled by a processor module that executes a stored program for controlling and monitoring the LED chains.
  • a light-emitting diode chain consists, for example, of 11 to 19 LEDs connected in series. 1, each LED chain is driven by a transistor Q3 connected as a current source.
  • the output voltage of a digital-to-analog converter DAC which is applied to the base of transistor Q3 via a transistor Q4, serves as a reference variable for the current strength. If a positive control signal is present at the LED switch-on signal LE, a collector current is set in the transistor Q3 after a circuit-related delay time of approximately 1 ⁇ s, which approximately corresponds to the quotient of the voltage of the converter DAC and the resistor R5.
  • the chain current in turn causes a voltage drop in a resistor R1 connected upstream of the LED chain, which, when the collector-emitter threshold of a transistor Q1 is reached, controls it and generates the current monitoring signal 10.
  • a transistor Q2 is also controlled via resistors R2 and R3 when the voltage drop across the LED chain reaches a value set by the voltage divider ratio R2 to R3, and thus a voltage monitoring signal UO is generated via transistor Q2.
  • Resistors R6 and R7 or R8 and R9 are used for signal conversion to TTL level.
  • the monitoring signals 10 and UO are stored in the control module and reported back to the control unit and processed there.
  • the current monitoring is carried out for all chains with a uniform, fixed threshold:
  • the current sensor output shows "OFF” if the chain current is less than 4 mA and it shows "ON” if it is greater than 7 mA.
  • the voltage monitoring of all LED chains is also carried out with a uniform, fixed threshold.
  • test mode all LED chains are checked cyclically and current errors are found within 10 s.
  • an LED chain will fail if the specified setpoint for the voltage shows "ON” and the measured actual sensor value for the current "OFF".
  • a current fault only leads to a shutdown if a character that is currently required is no longer shown as recognizable can.
  • a sign is no longer representable if the number of faulty LED chains exceeds the supplied limit.
  • the LED control signal with an active light source is constructed periodically with a period T Perloc ie of, for example, 10.0 ms.
  • a period begins with the start point t 0 and is divided into a light-emitting period T Leuch t, so the maximum LED current flow time of 9.0 ms for example, and a test time T interval of, for example 1.0 ms.
  • the lighting time T Vietnameset is composed of the actual conduction time T st rom / the dimming depending on the ambient brightness about 0.1 to 1.0 times the light-emitting time T is Leu CHT.
  • T pause takes place of a maximum of 0.3 microseconds long test pulse T Tes t for monitoring the function of the LED bar.
  • the pulse length ensures that the LED current does not result in the emission of light that disturbs road users.
  • the test pulse T test can of course not only take place in a periodic interruption of the lighting time T LeU cht, but also in a longer inactive state of the light source, so that the availability of the light sign for a safety-relevant application can be checked at any time.
  • the maximum LED lighting time required for the purpose of avoiding visible flashes of light is achieved by supplementing the current regulator circuit - as described in FIG. 1 - with a logic circuit according to FIG.
  • the LED switch-on signal LE is controlled via the output OR_out of an OR gate OR, for example of the 74HC32 type.
  • OR OR gate OR
  • the input OR_inl is 1 and thus the output OR_out is also 1.
  • the LED input OR_inl is 0 and the test input is 1. This is at an input XOR_in2 of an EXODER gate XOR, for example of the type 74HC86. State 0 is present at the other input XOR_inl, so that output XOR_out assumes the value 1 due to the various input states.
  • the exit XOR_out is connected to the second input OR_in2 of the OR gate OR, which thus also assumes the value 1.
  • OR_out is 1, which turns on the LED test power.
  • the input XOR_inl is connected to the output FF_Q_out of a clock state controlled D-flip-flop FF, for example of the type 74HC74, at whose D-input FF_Reset the signal of the test input is applied, i.e. the value 1.
  • the flip-flop FF only reacts to the initial state if the clock variable assumes the value 1 at the C input FF_Clock. This is the case when the current monitor 10 supplies the value 1, that is to say the LED current has exceeded the predetermined threshold value.
  • the Q output FF_Q_out of the flip-flop FF will take the value 1, corresponding to Q the value 0.
  • the input state at XOR_inl will change from 0 to 1, which leads to an output state XOR_out of 0; this switches off the LED current supply via the OR gate.
  • FF_Q_out signals 1 that the LED chain is OK.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Traffic Control Systems (AREA)
  • Road Signs Or Road Markings (AREA)
  • Time Recorders, Dirve Recorders, Access Control (AREA)

Abstract

An illuminated sign for traffic control, in particular for road traffic, which comprises light sources for generation of the sign and a monitoring device for functional monitoring of the light source, whereby the light sources are embodied as light diodes (LED) and the monitoring device is embodied as a device for the limited current loading of the light diodes (LED). The functional monitoring of said sign can be achieved with reasonable technical requirements in both the deactivated and activated state thereof.

Description

Beschreibungdescription
Lichtzeichen zur Verkehrssteuerung und Verfahren zur Funktionsüberwachung eines solchen ZeichensTraffic control light signals and method for monitoring the function of such a sign
Die Erfindung betrifft ein Lichtzeichen zur Verkehrssteuerung, insbesondere des Straßenverkehrs, gemäß dem Oberbegriff des Patentanspruches 1 sowie ein Verfahren zur Funktionsüberwachung eines solchen Zeichens gemäß dem Oberbegriff des Patentanspruches 9.The invention relates to a light sign for traffic control, in particular road traffic, according to the preamble of claim 1 and a method for monitoring the function of such a sign according to the preamble of claim 9.
Im allgemeinen werden zur Unterstützung einer reibungslosen Verkehrsabwicklung Zeichen unterschiedlichster Art und Wichtigkeit zur Steuerung des Verkehrs eingesetzt. Dies gilt für die Schiff-Fahrt, für Flugzeuge, beispielsweise auf Flughäfen, sowie für den gesamten Schienenverkehr, insbesondere jedoch für den Straßenverkehr. Aufgrund des ständig steigenden Verkehrsaufkommens werden immer mehr Verkehrs- und Lichtzeichen zum Regeln des innerstädtischen Verkehrs bzw. zum Leiten des Fernverkehrs eingesetzt. Ein zunehmender Teil dieser Zeichen wird durch Lichtquellen erzeugt. Typische Beispiele hierfür sind die Wechsellichtzeichen der Lichtsignalanlagen an Fahrbahn-Kreuzungen oder die Wechselverkehrszeichen auf sogenannten Autobahn-Querschnitten. Bei den genannten Lichtzeichen dienen heute vorwiegend Glühlampen als Lichtquellen. Glühlampen können durch Kurzschluss oder Unterbrechung ausfallen, wodurch ein durch sie zu erzeugendes Zeichen verstümmelt, mit unzureichender Lichtstärke oder überhaupt nicht angezeigt wird. Damit ein nicht ordnungsgemäß dargestelltes Lichtzeichen die Verkehrsteilnehmer nicht irreführt, muss es zur Vermeidung eines Unfallrisikos sofort abgeschaltet werden. Um die Verfügbarkeit eines sicherheitsrelevanten Zeichens, etwa eine rote Ampel, eine Geschwindigkeitsbegrenzung oder eine Warnanzeige, auch im abgeschalteten Zustand überprüfen zu können, muss die Überwachung ständig, also auch dann wirksam sein, wenn das entsprechende Zeichen nicht aktiv ist, also gerade nicht leuchtet. Eine Funktionsüberwachung der ein Zeichen erzeugenden Glühlampen kann über den Stromdurchgang durch deren Glühfäden erfolgen. Die Trägheit eines Glühfadens erlaubt, dass durch kurzzeitige Bestromung des Glühfadens für beispielsweise 1 ms die Funktionsfähigkeit der Glühlampe getestet werden kann, ohne dass Licht austritt. Als Referenz für einen solchen Kaltlampentest zur automatischen Überprüfung einer Autolichtanlage sei der Artikel "On-board multiplexing system checks car's lights automatically" aus Electronics international, Seiten 68 und 70, genannt. Über einen Mikroprozessor werden dort Befehle zum Aktivieren der Lampen gegeben, die Signale der Lampen und Sensoren überwacht und der Fahrer über eine Fehlfunktion durch eine Anzeige auf dem Armaturenbrett informiert. Ein Leistungstransistor verbindet die Lichtanlage mit der Autobatterie. Parallel dazu ist ein hochohmiger Spannungsteiler geschaltet, dessen Mittenpotential als Kriterium beim Überprüfen eines La penzustandes dient. Im Betrieb überprüft der Mikroprozessor den Wert des Mittenpotentials des Spannungsteilers alle 10 ms. Bei eingeschaltetem Licht beträgt das Potential 12 V, wenn es aus ist, 0 V. Bei einem Kurzschluss im Lampenschaltkreis beträgt es allerdings in beiden Fällen 0 V. Um eine positive Anzeige für alle möglichen Fehler und Lichtbetriebsarten zu erhalten, muss der Test erweitert werden, um den AUS-Modus bei eingeschaltetem Licht und den EIN-Modus bei ausgeschalteten Licht mit einzuschließen. Eine eingeschaltete Lampe wird vom System einmal pro Sekunde für ca. 100 ms ausgeschaltet; wenn sie aus ist, schaltet das System periodisch alle 40 s für 100 ms ein. Der Test beginnt mit dem Anlassen des Motors und endet 100 s nach dem Abstellen. Dieser verlängerte Betrieb stellt sicher, dass Lampenausfälle auch während der Abkühlperiode des Glühfadens detektiert werden.In general, characters of various types and importance are used to control traffic in order to support smooth traffic handling. This applies to ship travel, airplanes, for example at airports, and for all rail traffic, but especially for road traffic. Due to the constantly increasing volume of traffic, more and more traffic and light signals are used to regulate inner-city traffic or to direct long-distance traffic. An increasing proportion of these signs are generated by light sources. Typical examples of this are the alternating light signs of the traffic light systems at road junctions or the alternating traffic signs on so-called motorway cross sections. In the case of the light signals mentioned, today mainly light bulbs serve as light sources. Incandescent lamps can fail due to a short circuit or interruption, causing a character to be generated by them to be garbled, with insufficient light intensity or not displayed at all. So that a light signal that is not properly displayed does not mislead road users, it must be switched off immediately to avoid the risk of an accident. In order to be able to check the availability of a safety-relevant sign, such as a red traffic light, a speed limit or a warning indicator, even when the device is switched off, the monitoring must be active continuously, i.e. even if the corresponding sign is not active, i.e. is not lit. Functional monitoring of the incandescent lamps generating a sign can be carried out via the passage of current through their filaments. The inertia of a filament allows the functionality of the incandescent lamp to be tested by briefly energizing the filament for, for example, 1 ms, without light escaping. The article "On-board multiplexing system checks car's lights automatically" from Electronics international, pages 68 and 70, should be mentioned as a reference for such a cold lamp test for automatically checking a car lighting system. A microprocessor gives commands to activate the lamps, the signals from the lamps and sensors are monitored and the driver is informed of a malfunction by a display on the dashboard. A power transistor connects the lighting system to the car battery. In parallel, a high-resistance voltage divider is connected, the center potential of which serves as a criterion when checking a voltage condition. During operation, the microprocessor checks the value of the center potential of the voltage divider every 10 ms. When the light is switched on, the potential is 12 V, when it is off, 0 V. In the event of a short circuit in the lamp circuit, however, it is 0 V in both cases. In order to obtain a positive display for all possible errors and light operating modes, the test must be expanded, to include the OFF mode when the light is on and the ON mode when the light is off. A switched on lamp is switched off by the system once per second for approx. 100 ms; if it is off, the system switches on periodically every 40 s for 100 ms. The test begins when the engine is started and ends 100 s after it is switched off. This extended operation ensures that lamp failures are also detected during the filament cooling period.
Nun wird die Glühlampe zunehmend durch die Leuchtdiode, im nachfolgenden auch durch LED abgekürzt, verdrängt, die als wartungsarme und hochverfügbare Lichtquelle für optische Zeichen viele Vorteile für den wirtschaftlichen Betrieb von Lichtsignalanlagen bietet. Problematisch ist, dass mit LED erzeugbare Zeichen bisher nur im eingeschalteten Zustand überwacht werden konnten. Damit konnte die LED-Technik für sicherheitsrelevante Zeichen, die auch im abgeschalteten Zustand auf Funktionsfähigkeit überwacht werden müssen, nicht verwendet werden. Aufgrund der quasi-trägheitslosen Umwandlung von Strom in Licht bei LED-Lichtquellen war eine zum sogenannten Kaltlampentest analoge Funktionsprüfung nicht möglich, ohne störende und damit nicht akzeptable Lichtblitze zu erzeugen. Bei völliger Dunkelheit machen sich bei einem LED- Betrieb mit Nennstrom weitgehend unabhängig von der Wiederholrate bereits Impulse ab einer Länge von etwa 0,3 μs sowie Dauerströme ab ca. 5 μA störend bemerkbar. Zeichen mit einer Funktionsüberwachung, welche ausreichend kurze bzw. schwache Stromimpulse erzeugen und sicher überwachen können, ließen sich bisher mit vertretbarem Aufwand nicht realisieren.Now the incandescent lamp is increasingly being replaced by the light-emitting diode, hereinafter also abbreviated to LED, which as a low-maintenance and highly available light source for optical signs has many advantages for the economical operation of Offers traffic lights. The problem is that characters that could be generated with LED could previously only be monitored when they were switched on. As a result, the LED technology could not be used for safety-relevant signs that must be monitored for functionality even when the device is switched off. Due to the quasi-inertia-free conversion of current into light in LED light sources, a function test analogous to the so-called cold lamp test was not possible without generating disruptive and therefore unacceptable light flashes. In complete darkness, with LED operation with nominal current, pulses from a length of about 0.3 μs and continuous currents from approx. 5 μA are noticeably irrespective of the repetition rate. So far, signs with function monitoring, which can generate sufficiently short or weak current pulses and monitor them safely, could not be realized with reasonable effort.
Der Erfindung liegt daher die Aufgabe zugrunde, ein Lichtzeichen sowie ein Verfahren zur Funktionsüberwachung eines Zeichens der eingangs genannten Art bereitzustellen, so dass bei vertretbarem technischen Aufwand die Funktionsfähigkeit des Zeichens sowohl im ein- als auch im ausgeschalteten Zustand überwacht werden kann.The invention is therefore based on the object of providing a light sign and a method for function monitoring of a sign of the type mentioned at the outset, so that the functionability of the sign can be monitored both when the sign is switched on and when it is switched off, with a reasonable technical outlay.
Eine Teilaufgabe wird erfindungsgemäß gelöst durch ein Lichtzeichen der eingangs genannten Art mit den im kennzeichnenden Teil des Patentanspruchs 1 genannten Merkmalen. Durch eine Begrenzung des sich nach dem Einschalten der Lichtquelle aufbauenden Stromes durch die Leuchtdioden nach Zeitdauer oder Stärke kann die unmittelbar eintretende Lichtaussendung der LED derart eingeschränkt werden, dass sie vom Betrachter auch bei Dunkelheit nicht mehr wahrnehmbar ist. Dadurch werden die Verkehrsteilnehmer störende Lichtblitze vermieden. Als Kriterium für die Funktionsfähigkeit wird der Stromanstieg durch die Leuchtdioden verwendet. In einer bevorzugten Ausgestaltung der Erfindung umfasst die Überwachungseinrichtung des Lichtzeichens Schaltmittel zum Abschalten der eingeschalteten Bestromung bei Erreichen eines vorgegebenen Schwellenwertes für die Stromstärke. Die Begrenzung des durch die Leuchtdioden fließenden elektrischen Stromes wird hier durch Vorgabe eines maximalen Schwellenwertes erreicht, bei dem die sich aufbauende LED-Stromstärke abgeschaltet wird. Bei der schaltungstechnischen Umsetzung dieser Stromregelung können in vorteilhafter Weise Teile der bestehenden Stromüberwachungseinrichtung aus der Glühlampentechnik verwendet und somit der Schaltungsaufwand minimiert werden.A subtask is achieved according to the invention by a light sign of the type mentioned at the outset with the features mentioned in the characterizing part of patent claim 1. By limiting the current built up by the light emitting diodes after the light source has been switched on, according to the duration or intensity, the immediately occurring light emission of the LED can be restricted such that it can no longer be perceived by the viewer even in the dark. This avoids flashes of light that disturb road users. The increase in current through the light-emitting diodes is used as a criterion for the functionality. In a preferred embodiment of the invention, the monitoring device of the light sign comprises switching means for switching off the current supply when a predetermined threshold value for the current intensity is reached. The limitation of the electrical current flowing through the light-emitting diodes is achieved here by specifying a maximum threshold value at which the LED current that builds up is switched off. When implementing this current control in terms of circuitry, parts of the existing current monitoring device from incandescent lamp technology can be used in an advantageous manner, and the circuit complexity can thus be minimized.
In einer vorteilhaften Ausführungsform der Erfindung sind die Schaltmittel als digitale Logikschaltung mit einem Speicherelement' ausgebildet . Die Realisierung der LED-Strombegrenzung kann so beispielsweise durch Verwendung eines D-Flip-Flops als Speicherelement sowie mittels weiterer Standard-Bauelemente der Halbleiterschaltungstechnik erfolgen.In an advantageous embodiment of the invention, the switching means are constructed as digital logic circuit with a memory element '. The LED current limitation can thus be implemented, for example, by using a D flip-flop as a memory element and by means of further standard components in semiconductor circuit technology.
In einer bevorzugten Ausführungsform der Erfindung ist die Überwachungseinrichtung ferner zum Messen der an den bestrom- ten Leuchtdioden abfallenden Spannung ausgebildet. Durch diese getrennte Zusatzüberwachung der Spannung kann eine ausgefallene Leuchtdiode trotz LED-Stromflusses, etwa bei einem Kurzschluss, festgestellt werden. Dies erhöht die Zuverlässigkeit der Funktionsprüfung eines erfindungsgemäßen Lichtzeichens .In a preferred embodiment of the invention, the monitoring device is also designed to measure the voltage drop across the energized light-emitting diodes. Through this separate additional monitoring of the voltage, a failed light-emitting diode can be determined despite the LED current flow, for example in the event of a short circuit. This increases the reliability of the functional test of a light sign according to the invention.
In weiteren vorteilhaften Ausbildungen sind die Lichtquellen als eine Kette von in Reihe geschalteten Leuchtdioden oder als ein Cluster von miteinander verbundenen Leuchtdioden angeordnet. Mit Vorteil findet dies Anwendung bei der Gestaltung von Lichtzeichen mit linienförmigen Symbolen oder flächigen Gebilden.In further advantageous configurations, the light sources are arranged as a chain of light-emitting diodes connected in series or as a cluster of light-emitting diodes connected to one another. This is advantageously used when designing light signs with line-shaped symbols or flat structures.
Vorzugsweise sind erfindungsgemäße Lichtzeichen mit Funktionsüberwachung bei Verkehrszeichen, insbesondere bei solchen mit wechselnder Darstellungsmöglichkeit unterschiedlicher Zeichen, oder bei Lichtsignalanlagen, also der allgemein bekannten Verkehrsampel, einsetzbar.Light signs according to the invention with function monitoring in traffic signs are preferred, in particular those Can be used with changing display options for different signs, or with traffic light systems, i.e. the well-known traffic lights.
Die andere Teilaufgabe wird gelöst durch ein Verfahren der eingangs genannten Art mit den im kennzeichnenden Teil des Patentanspruches 9 genannten Merkmalen. In dem die Bestromung der Leuchtdioden zunächst eingeschaltet wird, ein die Stromstärke durch die Leuchtdioden repräsentierendes Stromüberwachungssignal generiert wird, und bei Erreichen eines vorgegebenen Schwellenwertes für das Stromüberwachungssignal die Bestromung wieder ausgeschaltet wird, werden die als Leuchtdioden ausgebildeten Lichtquellen des Lichtzeichens bei der Funktionsüberwachung derart begrenzt bestromt, dass lediglich eine vom Betrachter nicht mehr wahrnehmbare Lichtaussendung erfolgt.The other subtask is achieved by a method of the type mentioned at the outset with the features mentioned in the characterizing part of patent claim 9. In which the energization of the light-emitting diodes is first switched on, a current monitoring signal representing the current intensity through the light-emitting diodes is generated, and when the current supply is switched off again when a predetermined threshold value for the current monitoring signal is reached, the light sources of the light sign designed as light-emitting diodes are energized to a limited extent during function monitoring that only a light emission that is no longer perceptible by the viewer takes place.
In einer bevorzugten Ausführung des erfindungemäßen Verfahrens wird zusätzlich ein die an den bestromten Leuchtdioden abfallende Spannung repräsentierendes Spannungsüberwachungs- signal generiert. Das Spannungsüberwachungssignal wird als Zusatzkriterium bei der Beurteilung der Funktionsfähigkeit einer Leuchtdiode herangezogen, um bei einer positiven LED- Bestromung einen Kurzschluss ausschließen zu können.In a preferred embodiment of the method according to the invention, a voltage monitoring signal representing the voltage drop across the energized light-emitting diodes is additionally generated. The voltage monitoring signal is used as an additional criterion when assessing the functionality of a light-emitting diode in order to be able to rule out a short circuit in the event of a positive LED current supply.
In einer vorteilhaften Ausgestaltung des erfindungsgemäßen Verfahrens erfolgt die Bestromung in einem inaktiven Zustand oder periodisch in einer inaktiven Phase der Leuchtdiode. Damit kann die Funktionsüberwachung sowohl durchgeführt werden, wenn das Lichtzeichen - auch für einen längeren Zeitraum von mehreren Monaten - nicht im Betrieb ist, als auch während des Betriebes, in dem die reguläre LED-Bestromung periodisch für eine kurze Phase ausgeschaltet wird, in welcher dann die noch kürzere Testbestromung stattfindet. Ein Ausführungsbeispiel sowie weitere Vorteile der Erfindung werden im folgenden anhand der Zeichnungen näher erläutert, in derenIn an advantageous embodiment of the method according to the invention, the current is supplied in an inactive state or periodically in an inactive phase of the light-emitting diode. The function monitoring can thus be carried out both when the light signal is not in operation - even for a longer period of several months - and during operation in which the regular LED current supply is periodically switched off for a short phase, in which case the even shorter test energization takes place. An exemplary embodiment and further advantages of the invention are explained in more detail below with reference to the drawings, in which:
FIG 1 eine Schaltung zur Stromregelung in einem erfindungsgemäßen Lichtzeichen, in FIG 2 die Zeitabschnitte eines LED-Ansteuersignals und in FIG 3 die Logikschaltung als Schaltmittel der Überwachungseinrichtung1 shows a circuit for current control in a light signal according to the invention, in FIG. 2 the time segments of an LED control signal and in FIG. 3 the logic circuit as switching means of the monitoring device
schematisch dargestellt sind.are shown schematically.
Ein erfindungsgemäßes Lichtzeichen, etwa ein Wechselverkehrszeichen für die wechselweise Darstellung unterschiedlicher Verkehrszeichen, wird beispielsweise in einer als Schilderbrücke über Fahrbahnen ausgebildeten Außenanlage erzeugt. Die Außenanlage weist einen Netzanschluss zur Spannungsversorgung der LED-Ketten auf, wofür ein handelsübliches Industrie- Schaltnetzteil für 48 V Gleichspannung bei einer Eingangsleistung von 100 W verwendet wird. Sie ist über einen CAN-BUS mit einer Streckenstation verbunden, die ein Modem sowie ein Steuer- und ein Mastermodul umfasst. Über eine gemeinsame Ansteuerbaugruppe sind beispielsweise 32 LED-Ketten, aufgeteilt in je vier Achtergruppen, ansteuerbar. Die Ansteuerbaugruppe enthält einen Digitalteil und einen Analogteil. Der Digitalteil weist Module für die Initialisierung, die Baugruppenerkennung, die Schreib-Lese-Logik, ein Testregister, die Freigabelogik für den Normal- und den Testbetrieb, die LED- Stromeinstellung sowie die Strom- und Spannungsüberwachung auf, während die 32 LED-Stromregler den Analogteil bilden. Bis zu 8 solcher Ansteuerbaugruppen können an eine gemeinsame Steuereinheit angeschlossen werden. Die Steuerung erfolgt über ein Prozessor-Modul, das ein gespeichertes Programm zur Ansteuerung und Überwachung der LED-Ketten ausführt.A light sign according to the invention, for example a variable message sign for the alternate display of different traffic signs, is generated, for example, in an outdoor facility designed as a sign bridge over roadways. The outdoor system has a mains connection for the voltage supply of the LED chains, for which a commercial industrial switching power supply for 48 V DC voltage with an input power of 100 W is used. It is connected to a route station via a CAN bus, which includes a modem and a control and a master module. For example, 32 LED chains, each divided into four groups of eight, can be controlled via a common control module. The control module contains a digital part and an analog part. The digital part has modules for initialization, module detection, read-write logic, a test register, the enable logic for normal and test operation, the LED current setting and the current and voltage monitoring, while the 32 LED current regulators Form analog part. Up to 8 such control modules can be connected to a common control unit. It is controlled by a processor module that executes a stored program for controlling and monitoring the LED chains.
In einem Wechselverkehrszeichen für den Einsatz auf Bundesautobahnen besteht eine Leuchtdioden-Kette z.B. aus 11 bis 19 in Reihe geschalteter Leuchtdioden LED. Jede LED-Kette wird gemäß FIG 1 von einem als Stromquelle geschalteten Transistor Q3 angesteuert. Als Führungsgröße für die Stromstärke dient die Ausgangsspannung eines Digital-Analog-Wandlers DAC, welche über einen Transistor Q4 an die Basis des Transistors Q3 gelegt wird. Liegt am LED-Einschaltsignal LE ein positives Ansteuersignal an, stellt sich nach einer schaltungsbedingten Verzögerungszeit von ca. 1 μs im Transistor Q3 ein Kollektorstrom ein, der näherungsweise dem Quotienten aus der Spannung des Wandlers DAC und dem Widerstand R5 entspricht. Dieser Konstantstrom fließt abzüglich eines geringen durch die Widerstände R2 und R3 fließenden Querstromes als Arbeitsstrom durch die LED-Kette. Der Kettenstrom ruft seinerseits einen Spannungsabfall in einem der LED-Kette vorgeschalteten Widerstand Rl hervor, der bei Erreichen der Kollektor-Emitter- Schwelle eines Transistors Ql diesen durchsteuert und das Stromüberwachungssignal 10 generiert. Über Widerstände R2 und R3 wird außerdem ein Transistor Q2 angesteuert, wenn der Spannungsabfall über der LED-Kette einen durch das Spannungsteilerverhältnis R2 zu R3 eingestellten Wert erreicht, und so über den Transistor Q2 ein Spannungsüberwachungssignal UO generiert wird. Zur Signalwandlung auf TTL-Pegel dienen dabei Widerstände R6 und R7 bzw. R8 und R9. Die Überwachungssignale 10 und UO werden in der Ansteuerbaugruppe gespeichert und an die Steuereinheit zurückgemeldet und dort verarbeitet. Die Stromüberwachung erfolgt für alle Ketten mit einer einheitlichen, fixen Schwelle: Der Stromsensorausgang zeigt "AUS", wenn der Kettenstrom geringer als 4 mA und er zeigt "EIN", wenn er größer als 7 mA ist. Ebenso erfolgt die Spannungsüberwachung aller LED-Ketten mit einer einheitlichen, fixen Schwelle. Im Testbetrieb werden zyklisch alle LED-Ketten geprüft und Stromfehler innerhalb von 10 s gefunden. Im Nor al- und Testbetrieb führt zum Ausfall einer LED-Kette, wenn der Vorgabe-Sollwert für die Spannung "EIN" und gleichzeitig der gemessene Ist-Sensorwert für die Stromstärke "AUS" zeigt. Ein Stromfehler führt nur dann zum Abschalten, wenn ein aktuell benötigtes Zeichen nicht mehr erkennbar dargestellt werden kann. Ein Zeichen gilt als nicht mehr darstellbar, wenn die Zahl der fehlerhaften LED-Ketten das versorgte Limit überschreitet .In a variable message sign for use on federal highways, a light-emitting diode chain consists, for example, of 11 to 19 LEDs connected in series. 1, each LED chain is driven by a transistor Q3 connected as a current source. The output voltage of a digital-to-analog converter DAC, which is applied to the base of transistor Q3 via a transistor Q4, serves as a reference variable for the current strength. If a positive control signal is present at the LED switch-on signal LE, a collector current is set in the transistor Q3 after a circuit-related delay time of approximately 1 μs, which approximately corresponds to the quotient of the voltage of the converter DAC and the resistor R5. This constant current minus a small cross current flowing through the resistors R2 and R3 flows as a working current through the LED chain. The chain current in turn causes a voltage drop in a resistor R1 connected upstream of the LED chain, which, when the collector-emitter threshold of a transistor Q1 is reached, controls it and generates the current monitoring signal 10. A transistor Q2 is also controlled via resistors R2 and R3 when the voltage drop across the LED chain reaches a value set by the voltage divider ratio R2 to R3, and thus a voltage monitoring signal UO is generated via transistor Q2. Resistors R6 and R7 or R8 and R9 are used for signal conversion to TTL level. The monitoring signals 10 and UO are stored in the control module and reported back to the control unit and processed there. The current monitoring is carried out for all chains with a uniform, fixed threshold: The current sensor output shows "OFF" if the chain current is less than 4 mA and it shows "ON" if it is greater than 7 mA. The voltage monitoring of all LED chains is also carried out with a uniform, fixed threshold. In test mode, all LED chains are checked cyclically and current errors are found within 10 s. In normal and test operation, an LED chain will fail if the specified setpoint for the voltage shows "ON" and the measured actual sensor value for the current "OFF". A current fault only leads to a shutdown if a character that is currently required is no longer shown as recognizable can. A sign is no longer representable if the number of faulty LED chains exceeds the supplied limit.
Das LED-Ansteuersignal bei aktiver Lichtquelle ist gemäß FIG 2 periodisch aufgebaut mit einer Periodendauer TPerlocie von beispielsweise 10,0 ms. Eine Periode beginnt mit dem Startpunkt t0 und ist unterteilt in eine Leuchtzeit TLeucht, also der maximalen LED-Bestromungszeit von z.B. 9,0 ms, und eine Testzeit TPause von z.B. 1,0 ms. Die Leuchtzeit Teucht setzt sich zusammen aus der tatsächlichen Bestromungszeit Tstrom/ die zum Dimmen abhängig von der Umgebungshelligkeit etwa das 0,1- bis 1,0-fache der Leuchtzeit TLeUcht beträgt. Während der Testzeit TPause erfolgt der maximal 0,3 μs lange Testpuls TTest zur Funktionsüberwachung der LED-Kette. Dabei ist durch die Impulslänge gewährleistet, dass die LED-Bestromung keine einen Verkehrsteilnehmer störende Lichtaussendung zur Folge hat. Der Testpuls TTest kann natürlich nicht nur in einer periodischen Unterbrechung der Leuchtzeit TLeUcht erfolgen, sondern auch in einem länger andauernden inaktiven Zustand der Lichtquelle, damit die Verfügbarkeit des Lichtzeichens für eine sicherheitsrelevante Anwendung jederzeit überprüfbar ist.According to FIG. 2, the LED control signal with an active light source is constructed periodically with a period T Perloc ie of, for example, 10.0 ms. A period begins with the start point t 0 and is divided into a light-emitting period T Leuch t, so the maximum LED current flow time of 9.0 ms for example, and a test time T interval of, for example 1.0 ms. The lighting time T eucht is composed of the actual conduction time T st rom / the dimming depending on the ambient brightness about 0.1 to 1.0 times the light-emitting time T is Leu CHT. During the test time T pause takes place of a maximum of 0.3 microseconds long test pulse T Tes t for monitoring the function of the LED bar. The pulse length ensures that the LED current does not result in the emission of light that disturbs road users. The test pulse T test can of course not only take place in a periodic interruption of the lighting time T LeU cht, but also in a longer inactive state of the light source, so that the availability of the light sign for a safety-relevant application can be checked at any time.
Die zum Zwecke einer Vermeidung von sichtbaren Lichtblitzen erforderliche maximale LED-Bestromungszeit wird durch Ergänzung der Stromreglerschaltung - wie in FIG 1 beschrieben - mit einer Logikschaltung gemäß FIG 3 erreicht. Das LED-Einschaltsignal LE wird über den Ausgang OR_out eines ODER- Gatters OR, z.B. vom Typ 74HC32, gesteuert. Bei regulärer LED-Bestromung ist der Eingang OR_inl gleich 1 und damit der Ausgang OR_out ebenfalls 1. Im Testbetrieb ist der LED-Input OR_inl gleich 0 und der Test-Input gleich 1. Dieser liegt am einen Eingang XOR_in2 eines EXODER-Gatters XOR, z.B. vom Typ 74HC86, an. Am anderen Eingang XOR_inl liegt zunächst der Zustand 0 an, so dass der Ausgang XOR_out aufgrund der verschiedenen Eingangszustände den Wert 1 annimmt. Der Ausgang XOR_out ist mit dem zweiten Eingang OR_in2 des ODER-Gatters OR verbunden, der damit ebenfalls den Wert 1 annimmt. Folglich ist OR_out gleich 1, wodurch die LED-Testbestromung einschaltet. Der Eingang XOR_inl ist mit dem Ausgang FF_Q_out eines taktzustandgesteuerten D-Flip-Flops FF, z.B. vom Typ 74HC74, verbunden, an dessen D-Eingang FF_Reset das Signal des Test-Inputs anliegt, also der Wert 1. Das Flip-Flop FF reagiert erst auf den Ausgangszustand, wenn am C-Eingang FF_Clock die Taktvariable den Wert 1 annimmt. Dies ist dann der Fall, wenn die Stromüberwachung 10 den Wert 1 liefert, also die LED-Stromstärke den vorgegebenen Schwellenwert überschritten hat. Nun wird der Q-Ausgang FF_Q_out des Flip-Flops FF den Wert 1 annehmen, entsprechend Q den Wert 0. Zum einen wechselt dadurch der Eingangszustand bei XOR_inl von 0 auf 1, was zu einem Ausgangszustand XOR_out von 0 führt; dies schaltet über das OR-Gatter die LED-Bestromung ab. Zum anderen wird über FF_Q_out gleich 1 signalisiert, dass die LED-Kette in Ordnung ist. The maximum LED lighting time required for the purpose of avoiding visible flashes of light is achieved by supplementing the current regulator circuit - as described in FIG. 1 - with a logic circuit according to FIG. The LED switch-on signal LE is controlled via the output OR_out of an OR gate OR, for example of the 74HC32 type. With regular LED current supply, the input OR_inl is 1 and thus the output OR_out is also 1. In test mode, the LED input OR_inl is 0 and the test input is 1. This is at an input XOR_in2 of an EXODER gate XOR, for example of the type 74HC86. State 0 is present at the other input XOR_inl, so that output XOR_out assumes the value 1 due to the various input states. The exit XOR_out is connected to the second input OR_in2 of the OR gate OR, which thus also assumes the value 1. As a result, OR_out is 1, which turns on the LED test power. The input XOR_inl is connected to the output FF_Q_out of a clock state controlled D-flip-flop FF, for example of the type 74HC74, at whose D-input FF_Reset the signal of the test input is applied, i.e. the value 1. The flip-flop FF only reacts to the initial state if the clock variable assumes the value 1 at the C input FF_Clock. This is the case when the current monitor 10 supplies the value 1, that is to say the LED current has exceeded the predetermined threshold value. Now the Q output FF_Q_out of the flip-flop FF will take the value 1, corresponding to Q the value 0. On the one hand, the input state at XOR_inl will change from 0 to 1, which leads to an output state XOR_out of 0; this switches off the LED current supply via the OR gate. On the other hand, FF_Q_out signals 1 that the LED chain is OK.

Claims

Patentansprüche claims
1. Lichtzeichen zur Verkehrssteuerung, insbesondere des Straßenverkehrs, mit Lichtquellen zum Erzeugen des Zeichens und einer Überwachungseinrichtung zur Funktionsüberwachung der Lichtquellen, dadurch gekennzei chnet , dass die Lichtquellen als Leuchtdioden (LED) und die Überwachungseinrichtung zum begrenzten Bestromen der Leuchtdioden (LED) ausgebildet ist.1. Light signs for traffic control, in particular road traffic, with light sources for generating the sign and a monitoring device for function monitoring of the light sources, characterized in that the light sources are designed as light-emitting diodes (LED) and the monitoring device for limited current supply to the light-emitting diodes (LED).
2. Lichtzeichen nach Anspruch 1, dadurch ge kennze ichnet , dass die Überwachungseinrichtung Schaltmittel zum Abschalten der eingeschalteten Bestromung bei Erreichen eines vorgegebenen Schwellenwertes für die Stromstärke umfasst.2. Light sign according to claim 1, characterized in that the monitoring device comprises switching means for switching off the current supply when a predetermined threshold value for the current intensity is reached.
3. Lichtzeichen nach Anspruch 2, dadurch gekennze ichnet , dass die Schaltmittel als digitale Logikschaltung mit einem Speicherelement (FF) ausgebildet sind.3. Light sign according to claim 2, characterized in that the switching means are designed as a digital logic circuit with a memory element (FF).
4. Lichtzeichen nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet , dass die Überwachungseinrichtung ferner zum Messen der an den bestromten Leuchtdioden (LED) abfallenden Spannung ausgebildet ist.4. Light sign according to one of claims 1 to 3, characterized in that the monitoring device is further configured to measure the voltage drop across the energized light-emitting diodes (LED).
5. Lichtzeichen nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet , dass die Lichtquellen als eine Kette von in Reihe geschalteten Leuchtdioden (LED) angeordnet sind.5. Light sign according to one of claims 1 to 4, characterized in that the light sources are arranged as a chain of light-emitting diodes (LED) connected in series.
6. Lichtzeichen nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet , dass die Lichtquellen als ein Cluster von mit einander verbundenen Leuchtdioden (LED) angeordnet sind. 6. Light sign according to one of claims 1 to 4, characterized in that the light sources are arranged as a cluster of interconnected light-emitting diodes (LED).
7. Verkehrszeichen, insbesondere zur wechselnden Darstellung unterschiedlicher Zeichen, mit einem Lichtzeichen nach einem der Ansprüche 1 bis 6.7. Traffic sign, in particular for changing the representation of different signs, with a light sign according to one of claims 1 to 6.
8. Lichtsignalanlage, insbesondere Verkehrsampel, mit einem Lichtzeichen nach einem der Ansprüche 1 bis 6.8. traffic light system, in particular traffic lights, with a light signal according to one of claims 1 to 6.
9. Verfahren zur Funktionsüberwachung eines Lichtzeichens zur Verkehrssteuerung, insbesondere des Straßenverkehrs, mit als Leuchtdioden ausgebildeten Lichtquellen zum Erzeugen des Zeichens, dadurch gekennzeichnet , dass die Bestromung der Leuchtdioden eingeschaltet wird, dass ein die Stromstärke durch die Leuchtdioden repräsentierendes Stromüberwachungssignal generiert wird, und dass bei Erreichen eines vorgegebenen Schwellenwertes für das Stromüberwachungssignal die Bestromung ausgeschaltet wird.9. Method for monitoring the function of a light sign for traffic control, in particular road traffic, with light sources designed as light-emitting diodes for generating the sign, characterized in that the energization of the light-emitting diodes is switched on, that a current monitoring signal representing the current strength through the light-emitting diodes is generated, and that at When a predetermined threshold value for the current monitoring signal is reached, the current supply is switched off.
10. Verfahren nach Anspruch 9, dadurch gekennze i chnet , dass zusätzlich ein die an den bestromten Leuchtdioden abfallende Spannung repräsentierendes Spannungs- überwachungssignal generiert wird.10. The method according to claim 9, characterized in that a voltage monitoring signal representing the voltage drop across the energized LEDs is additionally generated.
11. Verfahren nach Anspruch 9 oder 10, dadurch gekennzeichnet , dass die Bestromung in einem inaktiven Zustand oder periodisch in einer inaktiven Phase der Leuchtdioden erfolgt. 11. The method according to claim 9 or 10, characterized in that the energization takes place in an inactive state or periodically in an inactive phase of the LEDs.
EP02760115A 2001-08-16 2002-08-05 Illuminated sign for traffic control and method for functional monitoring of such a sign Expired - Lifetime EP1417864B1 (en)

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US7129856B2 (en) 2006-10-31
ATE315885T1 (en) 2006-02-15
DE50205600D1 (en) 2006-04-06
DE10140331C2 (en) 2003-11-06
NO20040669L (en) 2004-02-16
CA2457620A1 (en) 2003-02-27
WO2003017728A1 (en) 2003-02-27
EP1417864B1 (en) 2006-01-11
DE10140331A1 (en) 2003-04-03
US20040201496A1 (en) 2004-10-14
HUP0401026A2 (en) 2004-08-30

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