EP0974947B1 - Traffic light apparatus and method to monitor the traffic light apparatus - Google Patents

Abstract

A light signal unit has at least one signal generator (1) whose light-source is designed in the form of a matrix of light-emitting diodes (LEDs) (6). Also included is a monitoring device (2,7,9) for checking the LEDs for their fault-free operating condition. The monitor has a light sensing device (7), as well as an evaluating device (3) connected to the light sensor (7) for comparing a light sensing signal (57) generated by the light sensor with a given desired value, the light sensing device (7) being positioned in the beam-path of the LEDs (6). The given desired value corresponds to a normal operating state of the LEDs.

Description

The invention relates to a light signal system according to the preamble of claim 1 and a method to monitor this traffic light system.

Advances in semiconductor technology have among other things led to ever more light-intensive LEDs that are suitable for a variety of applications. So are also applications of these components as light sources for signal transmitters known. For example, from US-A-4,954 822 known a traffic light, in the very light-intensive Light emitting diodes on a support in a geometric Patterns are arranged that represent a traffic sign, for example for a pedestrian crossing. The light emitting diodes are supplied by an operating voltage, which means a full-wave rectifier from a standard AC line voltage derived and based on the nominal voltage of the components is transformed down. Possibilities are also described an operation with reduced luminous flux, for example by suppressing a half-wave of the AC mains voltage and thus the current drawn from the rectifier is reduced. It remains to be seen whether this makes sense. essential is the advantage described in any case that When properly controlled, LEDs are durable and a signal generator equipped with it a much lower one electrical power requires as a comparable, Conventionally equipped with a light bulb. The known solution does not disclose any specific measures for Monitoring the signal generator for correct operation.

From US-A-5 663 719 a traffic signal generator is also known, in which light-emitting diodes as a light source on a circuit board are arranged in a configuration that matches the pattern a traffic sign. With this known solution is geared towards the possibility, among other things, of conventionally equipped signaling devices the light bulbs with simple Exchange to be replaced by LEDs. You can Disadvantages occur. LEDs are related to deviations from the nominal voltage, i.e. with voltage drops far more sensitive than incandescent lamps. According to the known solution a significant loss of light at a level below the nominal voltage lying operating voltage avoided in that the LEDs in individual, connected in series with each other Chains are arranged, the light emitting diode chains are. It is also provided that the individual chains through To be able to bridge switches. In case of too low Mains voltage is switched off individual LED chains. The consequence of this is that the light-emitting diodes are also switched on with different mains voltages always approximately with yours Nominal voltage, i.e. operated with high luminous efficacy. The number is then reduced in the event of voltage drops of the actually operated LEDs, the one that enters However, light loss is less than if all LEDs, but with a correspondingly lower voltage would be operated. So far is with the known solution a certain monitoring of the signal generator for nominal operation deviating operating conditions are provided, strictly speaking concerns however, this does not yet monitor the signal generator for malfunctions.

FR 2 672 145 A1 describes a device for detection known from lamp errors in tri-color light signal systems, which has three photodetectors each assigned to a lamp, the photodetectors each a part of a Lamp emitted luminous flux received. There will be the output signals of the photodetectors in logic circuits evaluated for lighting errors and alarm signals triggered if necessary. The photo detectors can be on the reflector or on the Version of the lamps may be arranged.

An at least periodic monitoring of signal transmitters by Traffic signal systems, but is at least in many countries mandatory requirement when the traffic lights are in public Area used for traffic regulation. The individual functions of the signal generator are closed consider. So z. B. a falsely glowing "Green light" has a different consequence for the traffic situation than the same malfunction with a "red light". If "green" a road user will automatically assume that the corresponding direction of traffic is released and with far less caution in the intersection area retract as if it were z. B. by a permanent red light is delayed and finally continue to drive should look for. In contrast, the failure of the red light similarly bring about a critical dangerous situation, because the road user automatically accepts that Traffic light system is switched off.

So it is not enough to only shut down traffic lights monitor that the signal generator is sufficiently well recognizable are, d. H. as with the above solution, the light intensity of the Signal generator is readjusted to prevent signs of aging, Compensate for line voltage fluctuations or line losses. Regulation are carried out periodically in many countries Monitoring of the signal generator in order to be as immediate as possible any malfunction, d. H. especially the lack Correspondence of the actual state of each signal generator with its according to a signal program predefined current target state determine and then the traffic light system in reset an emergency operating state.

In the case of signal generators conventionally equipped with incandescent lamps such malfunctions due to current and voltage measurement detected on the light source or its supply lines. The known measures and circuits are with LEDs equipped with signal transmitters are only of limited suitability. As already mentioned, the characteristic of LEDs is from luminous flux to operating voltage much more critical than with a light bulb. On the other hand, the power consumption is a signal generator, equipped with those already available today LEDs, orders of magnitude lower than when used a light bulb. Simple adjustments to known circuit measures to monitor signaling devices are therefore critical, often no longer as strict safety regulations enough to classify. Still, the problem arises To create the conditions for this when replacing the light bulb with as little maintenance as possible instead To be able to use LEDs as light sources. This problem will at least in part of the stand the technology, but with regard to critical Malfunctions not resolved.

The present invention is therefore based on the object a light signal system of the type mentioned with a Monitor to create that on the properties of the light emitting diodes used as the light source are precisely matched and a corresponding method for monitoring the traffic light system.

The first subtask is the light signal system type mentioned in the characterizing part of the claim 1 described features solved. The solution to the others Partial task is characterized by the claim 1 dependent method claim described.

In contrast to those mentioned above, with conventional signal generators monitoring measures successfully used by means of Current and voltage measurements at the light source or the leads of the present invention are different Tread the path. Current and / or voltage measurements appear too imprecise or circuits too critical for it their dimensioning. According to the invention hence the monitoring of the LEDs for their error-free Function implemented by means of a light sensor that detects a relative, however defined part of that of the light emitting diodes total luminous flux emitted. This light sensor outputs a corresponding output signal that with relative easy to prepare so that it is processed based on this Light sensor signals a clear comparison between Actual state and predefined current target state of the Signal transmitter is to be carried out. So every is illegal Determine deviation, so that the traffic light system if necessary in their emergency operating state provided for in the signal program is to be reset.

According to further developments of the Invention, the LEDs with a pulsed operating voltage supplied, the z. B. by full-wave rectification is derived from the AC line voltage. In this Context is particularly advantageous in that also gives a characteristic light sensor signal whose Pulse frequency matches the mains frequency. The amplitude value this light sensor signal is a measure of the current luminous flux emitted by the LED matrix. The Signal frequency is a clear quantity that the Light source is switched on. According to a further training the invention is also the functional state of the Monitor light sensor yourself. This tests the light sensor are carried out during switching breaks of the signal generator. Around thereby producing no perceptible flashes of light these tests not by means of the LEDs, but under Using a test diode, the radiation in the invisible area and their partial radiation is detected by the light sensor. The test signal is also pulse-shaped, but of a pulse rate that is unique deviates from the mains frequency. This is clearly too distinguish whether the light sensor signal by the light emitting diodes or triggered by the test diode. The monitoring device including switching and evaluation device finally integrated into the signal generator, so that it too an easy exchange of the different light sources is possible.

Other developments of the invention and further advantages are defined in subclaims and the description below of exemplary embodiments.

Figur 1 eine Signalanlage mit zwei Signalgebern, deren Lichtquelle als eine Matrix von Leuchtdioden ausgebildet ist und in die jeweils eine Signalgebersteuerung integriert ist sowie eine gemeinsame Schalt- und Auswerteeinrichtung,

Figur 2 in einer schematischen Darstellung den Aufbau der Signalgeber, die insbesondere aufzeigt, daß zur Überwachung der Funktion der eigentlichen Signaldioden neben diesen auch eine Testleuchtdiode sowie ein als eine Fotodiode ausgebildeter Lichtsensor vorgesehen ist,

Figur 3 eine Prinzipschaltung für die Ansteuerung der Signaldioden des Signalgebers,

Figur 4 eine analoge Prinzipschaltung für die Ansteuerung der Testdiode,

Figur 5 eine in der Signalgebersteuerung vorgesehene Schaltungsanordnung zum Ansteuern des Lichtsensors sowie zum Auswerten seiner Ausgangssignale und

Figur 6 bis Figur 9 eine Reihe von Impulsdiagrammen zur Erläuterung der Überwachung signifikanter Betriebszustände des Signalgebers.

Embodiments of the invention are described below with reference to the drawing. It shows:

FIG. 1 shows a signal system with two signal transmitters, the light source of which is designed as a matrix of light-emitting diodes and in each of which a signal transmitter control is integrated, and a common switching and evaluation device,

FIG. 2 shows a schematic illustration of the structure of the signal transmitters, which shows in particular that a test light-emitting diode and a light sensor designed as a photodiode are provided in addition to the function of the actual signal diodes,

FIG. 3 shows a basic circuit for controlling the signal diodes of the signal transmitter,

FIG. 4 shows an analog basic circuit for controlling the test diode,

5 shows a circuit arrangement provided in the signal transmitter control for controlling the light sensor and for evaluating its output signals and

6 to 9 show a series of pulse diagrams to explain the monitoring of significant operating states of the signal generator.

In Figure 1 is a light signal system in the form of a block diagram shown as an example with two signal transmitters 1. Each of these signal transmitters 1 is a signal transmitter control 2 assigned directly in the housing of the signal generator 1 is arranged. Via supply and control lines that each of these signal generators is to be described in detail 1 or its signal generator control 2 with a Switching and evaluation device 3 connected. This is your turn connected to a device controller 4, which in known Way the operating states of the signal generator 1 accordingly controls a predetermined signal schedule.

Figure 2 illustrates the structure of the signal generator 1, its housing is covered on the front by a lens 5. This lens 5 is analogous to known lenses conventional signal generator designed so that here a detailed description is unnecessary. Inside the signal generator 1 is at a predetermined distance from this lens 5 and essentially parallel to it in a two-dimensional one Matrix a plurality of radiation-intensive light-emitting diodes arranged, hereinafter referred to as signal diodes 6 become. These form in their entirety and controlled together an extensive light source for the signal generator 1. This field of signal diodes is controlled together 6 through the already mentioned signal generator control 2, as will be explained.

Signal transmitter of a traffic light system with LEDs as one Equipping switchable light sources is well known per se. However, signaling devices of this type have so far not widely used in the market. This is partly due to the fact that the use of LEDs in this application so far compared to conventionally used incandescent lamp no special advantages offered, also because the luminous efficacy of earlier LEDs was still too limited. Advances in semiconductor technology but now make it possible to use radiation-intensive methods at low cost Manufacture light-emitting diodes in relation to their energy balance more than the conventional incandescent lamp are.

The high safety requirements for signaling devices be placed in traffic signal systems to dangerous Excluding signaling states, however, require also a corresponding one to the properties of light emitting diodes customized monitoring. In the present case, now not the proper functioning of the signal diodes 6 - similar to a conventional light bulb - through a appropriate current and / or voltage measurement carried out, but took a different path.

Instead of indirectly monitoring the function of the Signal generator 1 by means of auxiliary variables, such as the current consumed or voltage applied to the light source, the immediate occurs Monitoring the radiation status of the signal diodes 6 by a light sensor 7, preferably as a photodiode is trained. You could easily use this light sensor 7 facing the signal diodes 6, for example on the inside arrange the lens 5. However, this is not necessary. It is more advantageous with regard to the arrangement and wiring the matrix of the signal diodes 6 and the Light sensor 7 also this as another element in the Arrange the level of the signal diodes 6. With this arrangement of the Light sensor 7 is exploited that part of the signal diodes 6 emitted light on the inside of the Diffuser is reflected and shines on the light sensor 7. A correspondingly amplified and weighted output signal the light sensor 7 is thus a measure of the current Signaling state of the signal generator 1 or its Signal diodes 6. This function of the light sensor is shown in FIG 7 by partial beams reflected on the lens 5 8 indicated schematically.

Now it must not be overlooked that with the strict security requirements, to put on traffic lights are also to monitor the function of the light sensor 7 itself is. This function monitoring of the light sensor 7 would be can be realized, for example, by the signal diodes 6 activated in signal pauses by a short test pulse be with the proper functioning of the light sensor 7 produces a corresponding output signal. Here but LEDs in contrast to a conventional light bulb such tests of the Light sensor 7 lead to flashes of light from human Eye perceived. This undesirable effect leaves avoid themselves if within the matrix of the signal diodes 6 In addition to the light sensor 7, a test diode 9 is also provided becomes. The radiation characteristic of this test diode 9 is chosen such that it is in the invisible range radiates, but their radiation is still in the range of sensitivity of the light sensor 7. Let these boundary conditions in combination with today's usual components of light sensor 7 and test diode 9 also quite possible.

In FIG. 2, this fact is indicated by corresponding, from the test diode 9 and emitted via the lens 5 the light sensor 7 illustrates reflected rays 10.

Corresponding tests of the signal generator 1 are controlled by the switching and evaluation device 3. As schematically in Figure 1 indicated, this first has a switching relay 11, via the signal generator controls 2 mains AC voltage u ~ is fed. So it is possible in one by the Switching and evaluation device 3 found defective and the signaling state, which is a danger to traffic 1 disconnect from the mains. Furthermore, the switching and Evaluation device 3 control signals s6 and s9. It serves the control signal s6 for switching the signal generator on and off 1, more precisely the signal diodes 6 and will be below referred to as signal control signal s6. The other of the Switching and evaluation device 3 the signaling controls 2 supplied control signal is used to switch the Test diode 9 and is therefore subsequently used as a test control signal designated s9. From the signal generator controls 2 receives the Switching and evaluation device 3, on the other hand, a signal, the an output signal preprocessed in the signal generator controls 2 of the corresponding light sensors 7. These signals are now referred to as light sensor signals s7. As shown in FIG. 1, these signals can each individually on separate lines between the switching and Evaluation device 3 and the signal generator controls 2 could be transmitted, alternatively this line multiple replaced by a serial transmission device become. In the signal generators 1 is now the signal generator controls 2 assigned, each a full-wave rectifier 12 provided to which the AC line voltage u ~ is supplied. The full-wave rectifier 12 sets the AC line voltage u ~ into a rectified mains voltage u = with a frequency um, which is twice the mains AC voltage, such as is indicated in Figure 2 by the corresponding pulse shape.

In Figure 3 is now as a detail on the design of the Signal generator controls 2 a block diagram for the control the signal diodes 6 shown. The signal diodes 6 the signal generator 1 are connected in parallel on the one hand via a series resistor R1 on the rectified Mains voltage u = and on the other hand over the switching distance of one Switching transistor T1 to ground, i.e. in the return path to Full-wave rectifier 12. The is activated or deactivated Switching transistor T1 by the signal control signal supplied to its base s6. As long as the switching transistor T1 is activated is, the signal diodes 6 are thus alternating in frequency the rectified mains voltage u = on or off. The temporary switch-off is already at the mains frequency of the signal diodes 6 in the zero crossings of the rectified Mains voltage u = no longer perceptible to the human eye, so that the visual signal function is not affected is.

In Figure 4, the operating circuit for the test diode is now analog 9 shown. Again, the test diode 9 is over a corresponding series resistor R2 on the rectified Mains voltage u = on the one hand and over the switching distance of a another switching transistor T2 on the other hand. At the The basis of this further switching transistor are used for Turning off the test diode 9, the test control signals s9 supplied.

FIG. 5 shows an operating circuit for the light sensor 7 shown. This is via a further series resistor again to the rectified mains voltage u = on the one hand and connected to ground on the other. The light sensor 7 is thus permanently prepared as long as AC mains voltage u ~ is present. That modulated by the radiation received Output signal of the light sensor 7 is via an amplifier stage 13 fed to a high-pass filter 14 and finally via a signal shaping stage 15 as a preprocessed light sensor signal s7 delivered to the switching and evaluation device 3.

Here, in particular, is the function of the high-pass filter 14 to point. The light sensor 7 not only receives from the lens 5 reflected light of the signal diodes or the test diode, but also through the lens 5 incoming light from the environment, in particular one Daylight. Regarding the monitoring function of the Light sensor 7, this scattered light is to be understood as an interference. But it can be assumed that the intensity this stray light from outside in relation to the modulation frequency of the signal diodes 6 as is to be regarded more or less uniformly. This results this interference in a DC component of the output signal of the light sensor 7, which is just over the high-pass filter 14 is eliminated. The dimensioning of this high-pass filter the higher the modulation frequency, the easier it is the signal diodes is 6. Alternatively to one passive high-pass filter would be an active filter stage, e.g. realized by "Sample & Hold" circuits possible if it would be necessary to make very short-term changes to take into account relatively radiation-intensive scattered light.

The monitoring device described above for with Signaling devices equipped with LEDs now make it possible to continuously or the signal transmitters at shorter intervals 1 to check that they are working properly. Tested are the two possible target states of a signal generator 1 in which it should be activated or deactivated.

In FIG. 6 the case is now in the form of a pulse diagram shown, in which the signal generator 1 is to be switched off (Desired state "Off"). The actual state is now based on the Light sensor signal s7 detected. FIG. 6 shows that the light sensor signal s7 in the example shown with a small one determined by its operating parameters Delay the course of the test control signal s9 immediately follows. To also in this case by the interference mentioned To be able to control the incident light well, the Frequency of the test control signal s9 be at least a few Hz. If now, as shown in Figure 6, the light sensor signal s7 the test control signal with a predetermined amplitude reflects s9 immediately, the result is like follows to evaluate. On the one hand, the actual status of the signal generator is correct 1 matches the current target state and on the other hand it is also found that the light sensor 7 is working properly works. The operating state of the monitored Signal generator 1 is therefore error-free.

The opposite is shown in FIG. 7. Again it is Target state of signal generator 1 "Off". Again in this state of the signaling device 1 that is switched off as intended or its signal diodes 6 generates the test control signal s9 and thus the test diode 9 is activated in a pulsed manner. In this The case is the light sensor signal s7 due to a pulse train marked, the short-term, with double network frequency shows successive dips. This pulse form of the Light sensor signal s7 clearly reflects that the signal diodes 6 in the monitored period of the rectified Mains voltage u = nevertheless light up, even though the signal transmitter 1 should be switched off. Target and actual status of the monitored Signal generator 1 therefore do not match, i.e. of the Signal generator 1 is working incorrectly.

In FIG. 8, "on" is now in relation to the other desired state. of the monitored signal generator 1 the normal case shown in match the target and actual status. The test diode 9 is deactivated because the corresponding test control signal s9 is reset is. This is already shown in Figure 7 Light control signal generated with the characteristic pulse shape. In this case the test shows that the signal diodes 6 In accordance with the intended target state work. By comparing the amplitude of the Light sensor signal s7 is with a predetermined target amplitude it can also be determined whether the monitored Signal generator 1 has occurred.

Finally, FIG. 9 illustrates the case in which the not monitored signal generator 1 in a target state "on" is switched on. In this case, they already come back using the pulse shapes described for FIG Test control signal s9 and the light sensor signal s7. That means, the monitored signal generator is switched off. Sollund Actual state do not match. The monitored signal generator 1 works incorrectly.

The above-described embodiments for a Monitoring device of a signal transmitter equipped with light-emitting diodes a traffic light system have shown that With such light signal systems, applicable safety regulations without further ado let fulfill. The examples have further shown that it is useful to the special Properties of the illuminant used in this case to be taken into account and also used to advantage. Conventionally used with auto switches equipped with incandescent lamps Monitoring functions are not simply taken over. This excludes possible sources of error. on the other hand the monitoring device at hand works in its possible configurations to that extent independent of one usual device control, as this is quite conventional can be constructed and for a control of light signal transmitters with LEDs in their basic structure not must be adjusted. For the operator of traffic signal systems this means that it can be easily renovated in existing ones Light signal systems conventionally equipped with light bulbs Signalers to be replaced by those that are now using energy-saving LEDs are equipped.

Claims (12)

1. Light signalling system having at least one signal transmitter (1), which has a light source and a diffuser (5) as a transparent cover, and having a monitoring device (2, 7, 9) for checking the light source for its fault-free operating state, the monitoring device (2, 7, 9) having a light sensor (7), arranged in the beam path of the light source, and an evaluating device (3), connected to said light sensor (7), for the purpose of comparing a light sensor signal (s7) generated by the light sensor with a predetermined desired value which corresponds to a normal operating state of the light source, characterized in that the light source is formed by light-emitting diodes (6) arranged in the form of a matrix, and in that the light sensor (7) is arranged on the plane of the light-emitting diodes (6) and is, like the light-emitting diodes (6), aligned with the diffuser (5), the light sensor (7) receiving partial radiation from the light-emitting diodes (6) which is reflected on the diffuser (5).
2. Light signalling system according to Claim 1, characterized in that the matrix of light-emitting diodes (6) arranged in the signal transmitter (1) is directly associated with a signal transmitter controller (2) which is supplied with, as a pulsed operating voltage (u=) for the light-emitting diodes (6), a mains AC voltage (u~), rectified by means of a rectifier arrangement (12).
3. Light signalling system according to Claim 2, characterized in that a preprocessing unit (13, 14, 15), which is connected to the output of the light sensor (7), is provided in the signal transmitter controller (2) for the purpose of conditioning its output signal, said preprocessing unit (13, 14, 15) outputting the light sensor signal (s7) to the evaluation unit (3) as a conditioned signal.
4. Light signalling system according to Claim 3, characterized in that the preprocessing unit (13, 14, 15) has a preamplifier (13), which is connected to the output of the light sensor (7) and is connected to a high-pass filter (14), to which a signal conditioning stage (15) is connected as the output stage.
5. Light signalling system according to one of Claims 1 to 4, characterized in that arranged on the plane of the light-emitting diodes (6) is a test diode (9), whose emitted radiation lies outside of the visible spectral range, and in that the spectral sensitivity of the light sensor (7) is in this case such that it detects the spectral range of the test diode (9) as well as that of the light-emitting diodes (6) emitting visible light.
6. Light signalling system according to Claim 5, characterized in that the evaluation device (3) is also in the form of a switching device and is connected to the signal transmitter controller (2) via signal lines, by means of which control signals (s6, s9) are transmitted to the signal transmitter controller (2) for the purpose of activating, staggered in time, the light-emitting diodes (6) or the test diode (9).
7. Light signalling system according to Claim 6, characterized in that the evaluation device (3) has means for comparing the two desired states ("off"/"on") of the signal transmitter (1) with its actual state defined by the corresponding state of the light sensor signal (s7).
8. Light signalling system according to Claim 7, characterized in that the evaluation device (3) in this case has means for comparing the amplitude of the light sensor signal (s7) with a predetermined desired value which corresponds to a rated value for the radiation emitted by the light-emitting diodes (6).
9. Light signalling system according to one of claims 1 to 8, characterized in that the evaluation device (3) is connected to a device controller (4), which is conventional per se, for one or more signal transmitters (1), signal programs for the connected signal transmitter(s) (1) being stored in said device controller (4).
10. Method for monitoring a light signalling system according to Claim 1, characterized in that, in the active signal state, the light-emitting diodes (6) are supplied with a pulsed operating voltage (u=) formed from the mains AC voltage (u~), and in that the output signal of the light sensor (7), preamplified and filtered by a high-pass filter, is preprocessed to form a pulsed light sensor signal (s7) which is modulated in the active signal state of the light-emitting diodes (6) corresponding to the pulse frequency of the pulsed operating voltage (u=).
11. Method for monitoring a light signalling system according to Claim 10, characterized in that the pulsed operating voltage (u=) is formed by rectifying the mains AC voltage (u~), and in that, when the light-emitting diodes (6) are activated, the frequency of the pulsed light sensor signal (s7) is modulated corresponding to the frequency of the mains AC voltage (u~).
12. Method for monitoring a light signalling system according to either of Claims 10 or 11, characterized in that the light sensor signal (s7) is evaluated in terms of its frequency and its amplitude by comparing it with predetermined desired values, and corresponding actual states for the switching state of the light-emitting diodes (6) or for their luminous flux currently being output are derived from this comparison, in that, when there is no correspondence between the instantaneous desired and actual state, a fault signal is generated and output to a device controller (4), in which a signal program for the connected signal transmitter(s) (1) is stored, and in that, on this basis, this device controller (4) resets the connected signal transmitter(s) (1) to a defined fault state.

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