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(11) | EP 3 738 856 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | TRAFFIC SIGNALLING DEVICE AND PROCESS FOR CONTROLLING TRAFFIC SIGNALING DEVICE |
| (57) The present invention relates to a LED-based traffic signalling device (10) and a
process for controlling traffic signalling. The LED-based traffic signalling device
(10) includes a light emitting signal area (12). The light emitting signal area (12)
comprises a plurality of LEDs arranged in at least two separately controllable sets
of LEDs (20, 22), wherein a visual output from the light emitting signal area (12)
having a first set of the LEDs (20) activated corresponds to a visual output from
the light emitting signal area (12) having a second set of the LEDs (22) activated,
a LED operation detector (38) connected to the first set of LEDs (20) being configured
to detect that the LEDs of the first set of LEDs (20) is failing in emitting required
luminance and including a status output configured to indicate failure of the first
set of LEDs if failure of the first set of LEDs is detected, and a switch (36) controlled
by the output from the LED operation detector (38) and configured to activate the
second set of LEDs (22) in response to the output of the LED operation detector (38)
indicating failure of the first set of LEDs (20).
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Technical field of the invention
[0001] The present invention relates to a LED-based traffic signalling device and more specific to a LED-based light emitting traffic signalling device.
Background of the invention
[0002] Traffic signalling devices and in particular to traffic lights for warning, aiding, and/or informing of dangers, specific traffic situations, and/or obstacles. Such traffic signalling devices have been supporting drivers of various vehicles for a long time. Various transport systems, such as roads, railway, and even shipping and air traffic relies on the reliable operation of such visual signalling systems. In particular road traffic and railway traffic are dependent on these signalling lights to convey important information, e.g. warning for a train approaching a railway crossing may be of vital importance for pedestrians, car drivers, truck drivers, etc. Therefore, it is important that these traffic lights always are operational.
Summary of the invention
[0003] One object of the present invention is to provide improved traffic lights and in particular improved LED based traffic lights.
[0004] According to one aspect the object may be achieved by a LED-based traffic signalling device including a light emitting signal area. The light emitting signal area comprises a plurality of LEDs arranged in at least two separately controllable sets of LEDs, wherein a visual output from the light emitting signal area having a first set of the LEDs activated corresponds to a visual output from the light emitting signal area having a second set of the LEDs activated; a LED operation detector connected to the first set of LEDs being configured to detect that the LEDs of the first set of LEDs is failing in emitting required luminance and including a status output configured to indicate failure of the first set of LEDs if failure of the first set of LEDs is detected; and a switch controlled by the output from the LED operation detector and configured to activate the second set of LEDs in response to the output of the LED operation detector indicating failure of the first set of LEDs. One advantage of the above traffic signalling device is that the reliability of possibly critical visual signals is increased by the traffic signalling device continuing emitting the required signal even if a primary light source fails. Moreover, the resulting visual output corresponding for the emitted light from the first set of LEDs and for the emitted light from the second set of LEDs is advantageous in that the signalling will be at the required standard and as easy to observe for a person as if the original light source was operational. Hence, the safety for drivers of vehicles or other persons affected by the signalling from the traffic signalling device is increased, because the traffic signalling device continues to deliver all traffic signals even if a light source has failed.
[0005] In some embodiments an alert signal terminal is configured to be in a non-alert state when first set of LEDs is operational and to be set in an alert state when second set of LEDs is activated. An advantage of this feature is that uninterrupted operation of the traffic signal device is possible, because maintenance of the traffic signal device may be performed without the traffic signalling device fails to provide traffic signals. Further, the maintenance may be facilitated in that the traffic signalling device does not need to be checked upon until the alert signal is received by a management function.
[0006] In other embodiments the LEDs of the first set of LEDs and the LEDs of the second set of LEDs are equally distributed over the light emitting signal area. One advantage of this feature is that the traffic signalling device may generate light signals according to requirements even if the primary light source, e.g. the first set of LEDs, is failing. Further, the characteristics of the light emitted from the traffic signalling device may be essentially the same before and after a failure of the primary light source.
[0007] In yet some embodiments the LEDs of the first and second sets of LEDs are arranged in a grid and wherein a LED having neighbouring LEDs in all nine neighbouring positions in the grid have at least four of the neighbouring positions occupied by LEDs from the other set of LEDs. This is one way to achieve the feature of equally distributing LEDs from the two sets over the light emitting signalling area and the advantages are thus the same.
[0008] According to some embodiments the LED operation detector is a current sensor configured to detect the current through the first set of LEDs and outputting a signal indicating the current through the first set of LEDs.
[0009] In further embodiments the traffic signalling device may include a first LED driver configured to drive the first set of LEDs and a second LED driver configured to drive the second set of LEDs, wherein the switch controlled by the output from the LED operation detector is included in the second LED driver.
[0010] According to a further aspect of the invention any of the above embodiments of LED-based traffic signalling devices may be used in a traffic signalling system. The advantages for the features are described above.
[0011] According to yet a further aspect a process for controlling a traffic signalling device, comprises receiving a light control signal indicating whether to emit light or not; continuously checking if a first set of LEDs is emitting required luminance; setting a fail signal if the first set of LEDs does not emit required luminance; driving a first set of LEDs to emit light in accordance with the control signal if the fail-signal is not set; and driving a second set of LEDs to emit light in accordance with the control signal if the fail-signal is set. One advantage of the above traffic signalling process is that the reliability of possibly critical visual signals is increased by the traffic signalling device continuing emitting the required signal even if a primary light source fails.
[0012] In some embodiments the driving of the first set of LEDs to emit light generate a visual output and wherein the driving of the second set of LEDs to emit light generate a corresponding visual output. The resulting visual output corresponding for the emitted light from the first set of LEDs and for the emitted light from the second set of LEDs is advantageous in that the signalling will be at the required standard and as easy to observe for a person as if the original light source was operational. Hence, the safety for drivers of vehicles or other persons affected by the signalling from the traffic signalling device is increased, because the traffic signalling device continues to deliver all traffic signals even if a light source has failed.
[0013] A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description. Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a sensor" or "the sensor" may include several sensors, and the like. Furthermore, the word "comprising" or "including" does not exclude other elements or steps.
Brief description of the drawings
[0014] Other features and advantages of the present invention will become apparent from the following detailed description of a presently preferred embodiment, with reference to the accompanying drawings, in which
Fig 1 depicts an example traffic light that may implement some embodiments of the invention,
Fig. 2 is a schematic diagram of a light source according to some embodiments of the invention,
Fig. 3 is a schematic circuit diagram of the control and the powering of some embodiments of the invention,
Fig. 4 is a flowchart of a process for controlling a traffic signalling device according to some embodiments of the invention.
[0015] Further, in the figures like reference characters designate like or corresponding parts throughout the several figures.
Detailed description of embodiments
[0016] The present invention relates to LED-based traffic signalling devices. An example of a traffic signalling device is a railroad crossing signalling device as the one showed in Fig. 1. According to some embodiments, the traffic signalling device 10 includes a light emitting signal area 12 and electronics for controlling the light emission from the light emitting signal area 12. A traffic signalling device 10 may include one or a plurality of light emitting signal areas 12 depending on the function of the particular traffic signalling device. There may be provided separate electronics controlling the light emission for each light emitting signal area alternatively a circuitry common to all light emitting signal areas 12 may be provided. In yet other alternative embodiments including a plurality of light emitting signal areas 12 some areas may have common control circuitry and some may have control circuitry for a single light emitting signal area 12.
[0017] Now referring to Fig 2, a light emitting signal area 12 includes LEDs 20, 22, operating as a light source for the traffic signalling device 10. According to some embodiments the light emitting signal area 12 includes two sets of LEDs, a first set of LEDs 20 and a second set of LEDs 22. Each set of LEDs is separately driven and may be activated individually at different points in time or simultaneously. The two sets of LEDs 20, 22, are arranged in the light emitting signal area 12 so that the visual output from the light emitting signal area 12 with only the first set of LEDs 20 activated corresponds to the visual output from the light emitting signal area 12 with only the second set of LEDs 22 activated. Corresponding visual output in the context of the present description may be interpreted as the luminance of the output from each of the two sets of LEDs 20,22, being substantially equal and the impression of the shape of the output from each of the two sets of LEDs 20, 22 being substantially equal.
[0018] According to some embodiments corresponding visual output from the first set of LEDs and from the second set of LEDs respectively, is achieved by arranging the LEDs in a grid and having every second LED in a row belonging to the first set of LEDs and the LEDs in-between the LEDs of the first set of LEDs belonging to the second set of LEDs, as shown in Fig. 2. Moreover, the two LEDs referred to using numeral 20 and numeral 22 respectively and drawn outside the light emitting signal area 12 is not supposed to be LEDs positioned outside the light emitting area, but are included in the figure in order to indicate that the circles marked as white are LEDs belonging to the first set of LEDs 20 and the circles having hatching are LEDs belonging to the second set of LEDs 22.
[0019] The skilled person would readily appreciate that there are other ways to combine LEDs of two different sets and still achieve corresponding visual appearance when one or the other set of LEDs is activated. Now referring to Fig. 3, according to some embodiments the electronics controlling the operation of the light emitting signal area 12 include a power input 30, a light control terminal 32, a LED driver 34 driving the first set of LEDs 20, a LED driver 36 driving the second set of LEDs 22, a LED operation detector 38, and an alert output terminal 40.
[0020] The power input 30 is providing the power to the circuitry. The light control terminal 32 is a terminal that is arranged to receive control signals from a traffic light controller or traffic light managing system determining if the light emitting signal area 12 is to be activated, i.e. emit light, or not. The light control terminal is connected to each of the two LED drivers 34, 36, in order to convey the control signal to each of the LED drivers. A first one of the LED drivers 34 is driving the first set of LEDs 20 in response to the control signal from the light control terminal 32.
[0021] Further, the circuit from the first LED driver 34 to the LEDs of the first set of LEDs is monitored by a LED operation detector 38. The LED operation detector 38 is configured to indicate if the first set of LEDs is failing in emitting the required luminance when the light control terminal 32 is signalling that the light emitting signal area 12 is to emit light. The LED operation detector 38 may monitor if the first set of LEDs 20 is emitting the required luminance by, for example, monitoring the current from the driver to the first set or LEDs 20 or by measuring a forward voltage over one or a plurality of LEDs in the first set of LEDs 20.
[0022] A second one of the LED drivers 36 is driving the LEDs of the second set of LEDs 22 also in response to the control signal from the light control terminal 32. However, the second LED driver 36 driving the second set of LEDs 22 is blocked from activation if not the LED operation detector 38 indicates that the first set of LEDs 20 is failing. Hence, the second LED driver 36 has the function of a switch responsive to the signal from the LED operation detector 38 and switching between blocked, i.e. not driving the second set of LEDs to emit light at all, and active, i.e. driving the second set of LEDs to emit light in response to the control signal. On the other hand, if the LED operation detector 38 indicates that the first set of LEDs 20 is failing then the second LED driver 36 drives the second set of LEDs 22 in accordance with the control signal from the light control terminal 32.
[0023] The LED operation detector also provides a signal to the alert output terminal 40, indicating that one set of LEDs is failing and that it may time for maintenance. This terminal may be monitored by the traffic light controller or traffic light managing system and its status or its indication that the first set of LEDs 20 are failing may be communicated to a central maintenance function.
[0024] The process of emitting light by the traffic signalling device in accordance with some embodiments of the invention is depicted in the flowchart of Fig. 4. Initially the first set of LEDs 20 is emitting light in accordance with the control signal on the control terminal 32, step S402, and the second set of LEDs 22 is dark, step S404, until the first set of LEDs 20 fails, step S406. When the first set of LEDs 20 is detected to be failing, the second LED driver is activated and the second set of LEDs 22 is emitting light in accordance with the control signal, step S408, instead of the first set of LEDs 20 emitting light. Hence, the first set of LEDs 20 is not active any more, step S410. The fact that the first set of LEDs is failing is indicated for the light control system via the alert output terminal 40, step S412.
1. LED-based traffic signalling device (10) including a light emitting signal area (12),
the light emitting signal area (12) comprising:
a plurality of LEDs arranged in at least two separately controllable sets of LEDs (20, 22), wherein a visual output from the light emitting signal area (12) having a first set of the LEDs (20) activated corresponds to a visual output from the light emitting signal area (12) having a second set of the LEDs (22) activated;
a LED operation detector (38) connected to the first set of LEDs (20) being configured to detect that the LEDs of the first set of LEDs (20) is failing in emitting required luminance and including a status output configured to indicate failure of the first set of LEDs if failure of the first set of LEDs is detected; and
a switch (36) controlled by the output from the LED operation detector (38) and configured to activate the second set of LEDs (22) in response to the output of the LED operation detector (38) indicating failure of the first set of LEDs (20).
2. The device according to claim 1, further comprising an alert signal terminal (40)
configured to be in a non-alert state when first set of LEDs (20) is operational and
to be set in an alert state when second set of LEDs (22) is activated.
3. The device according to any one of claims 1 to 2, wherein the LEDs of the first set
of LEDs (20) and the LEDs of the second set of LEDs (22) are equally distributed over
the light emitting signal area (12).
4. The device according to claim 3, wherein the LEDs of the first and second sets (20,
22) of LEDs are arranged in a grid and wherein a LED having neighbouring LEDs in all
nine neighbouring positions in the grid have at least four of the neighbouring positions
occupied by LEDs from the other set of LEDs.
5. The device according to any one of claims 1 to 4, wherein the LED operation detector
(38) is a current sensor configured to detect the current through the first set of
LEDs (20) and outputting a signal indicating the current through the first set of
LEDs (20).
6. The device according to any one of claims 1 to 5, further including a first LED driver
(34) configured to drive the first set of LEDs (20) and a second LED driver (36) configured
to drive the second set of LEDs (22), wherein the switch controlled by the output
from the LED operation detector is included in the second LED driver.
7. Use of a LED-based traffic signalling device according to any one of claims 1-6 in
a traffic signalling system.
8. Process for controlling a traffic signalling device, the process comprising:
receiving a light control signal indicating whether to emit light or not;
continuously checking if a first set of LEDs (20) is emitting required luminance;
setting a fail signal if the first set of LEDs (20) does not emit required luminance;
driving a first set of LEDs (20) to emit light in accordance with the control signal if the fail-signal is not set; and
driving a second set of LEDs (22) to emit light in accordance with the control signal if the fail-signal is set;
9. The process according to claim 8, wherein the driving of the first set of LEDs (20)
to emit light generate a visual output and wherein the driving of the second set of
LEDs (22) to emit light generate a corresponding visual output.