SE1950582A1

SE1950582A1 - Traffic signalling device and process for controlling traffic signaling device

Info

Publication number: SE1950582A1
Application number: SE1950582A
Authority: SE
Inventors: Fredrik Carlberg; Gert Andersson; Rasmus Backman
Original assignee: Ind I Ystad Ab
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2020-11-17
Also published as: EP3738856A1

Abstract

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).

Description

TRAFFIC SIGNALLING DEVICE AND PROCESS FOR CONTROLLINGTRAFFIC SIGNALING DEVICE Technical field of the inventionThe present invention relates to a LED-based traffic signalling deviceand more specific to a LED-based light emitting traffic signalling device.

Background of the invention Traffic signalling devices and in particular to traffic lights for warning,aiding, and/or informing of dangers, specific traffic situations, and/orobstacles. Such traffic signalling devices have been supporting drivers ofvarious vehicles for a long time. Various transport systems, such as roads,railway, and even shipping and air traffic relies on the reliable operation ofsuch visual signalling systems. ln particular road traffic and railway traffic aredependent on these signalling lights to convey important information, e.g.warning for a train approaching a railway crossing may be of vital importancefor pedestrians, car drivers, truck drivers, etc. Therefore, it is important thatthese traffic lights always are operational.

Summary of the invention One object of the present invention is to provide improved traffic lightsand in particular improved LED based traffic lights.

According to one aspect the object may be achieved by a LED-basedtraffic signalling device including a light emitting signal area. The light emittingsignal area comprises a plurality of LEDs arranged in at least two separatelycontrollable sets of LEDs, wherein a visual output from the light emittingsignal area having a first set of the LEDs activated corresponds to a visualoutput from the light emitting signal area having a second set of the LEDsactivated; a LED operation detector connected to the first set of LEDs beingconfigured to detect that the LEDs of the first set of LEDs is failing in emittingrequired luminance and including a status output configured to indicate failureof the first set of LEDs if failure of the first set of LEDs is detected; and aswitch controlled by the output from the LED operation detector andconfigured to activate the second set of LEDs in response to the output of theLED operation detector indicating failure of the first set of LEDs. One 2 advantage of the above traffic signalling device is that the reliability ofpossibly critical visual signals is increased by the traffic signalling devicecontinuing emitting the required signal even ifa primary light source fails.Moreover, the resulting visual output corresponding for the emitted light fromthe first set of LEDs and for the emitted light from the second set of LEDs isadvantageous in that the signalling will be at the required standard and aseasy 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 thesignalling from the traffic signalling device is increased, because the trafficsignalling device continues to deliver all traffic signals even if a light sourcehas failed. ln some embodiments an alert signal terminal is configured to be in anon-alert state when first set of LEDs is operational and to be set in an alertstate when second set of LEDs is activated. An advantage of this feature isthat uninterrupted operation of the traffic signal device is possible, becausemaintenance of the traffic signal device may be performed without the trafficsignalling device fails to provide traffic signals. Further, the maintenance maybe facilitated in that the traffic signalling device does not need to be checkedupon until the alert signal is received by a management function. ln other embodiments the LEDs of the first set of LEDs and the LEDsof the second set of LEDs are equally distributed over the light emitting signalarea. One advantage of this feature is that the traffic signalling device maygenerate light signals according to requirements even if the primary lightsource, e.g. the first set of LEDs, is failing. Further, the characteristics of thelight emitted from the traffic signalling device may be essentially the samebefore and after a failure of the primary light source. ln yet some embodiments the LEDs of the first and second sets ofLEDs are arranged in a grid and wherein a LED having neighbouring LEDs inall nine neighbouring positions in the grid have at least four of theneighbouring positions occupied by LEDs from the other set of LEDs. This isone way to achieve the feature of equally distributing LEDs from the two setsover the light emitting signalling area and the advantages are thus the same.

According to some embodiments the LED operation detector is acurrent sensor configured to detect the current through the first set of LEDsand outputting a signal indicating the current through the first set of LEDs. ln further embodiments the traffic signalling device may include a firstLED driver configured to drive the first set of LEDs and a second LED driver 3 configured to drive the second set of LEDs, wherein the switch controlled bythe output from the LED operation detector is included in the second LEDdriver.

According to a further aspect of the invention any of the aboveembodiments of LED-based traffic signalling devices may be used in a trafficsignalling system. The advantages for the features are described above.

According to yet a further aspect a process for controlling a trafficsignalling device, comprises receiving a light control signal indicating whetherto emit light or not; continuously checking if a first set of LEDs is emittingrequired luminance; setting a fail signal if the first set of LEDs does not emitrequired luminance; driving a first set of LEDs to emit light in accordance withthe control signal if the fail-signal is not set; and driving a second set of LEDsto emit light in accordance with the control signal if the fail-signal is set. Oneadvantage of the above traffic signalling process is that the reliability ofpossibly critical visual signals is increased by the traffic signalling devicecontinuing emitting the required signal even ifa primary light source fails. ln some embodiments the driving of the first set of LEDs to emit lightgenerate a visual output and wherein the driving of the second set of LEDs toemit light generate a corresponding visual output. The resulting visual outputcorresponding for the emitted light from the first set of LEDs and for theemitted light from the second set of LEDs is advantageous in that thesignalling will be at the required standard and as easy to observe for a personas if the original light source was operational. Hence, the safety for drivers ofvehicles or other persons affected by the signalling from the traffic signallingdevice is increased, because the traffic signalling device continues to deliverall traffic signals even if a light source has failed.

A further scope of applicability of the present invention will becomeapparent from the detailed description given below. However, it should beunderstood that the detailed description and specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only, since various changes and modifications within the scope ofthe invention will become apparent to those skilled in the art from this detaileddescription. Hence, it is to be understood that this invention is not limited tothe particular component parts of the device described or steps of themethods described as such device and method may vary. lt is also to beunderstood that the terminology used herein is for purpose of describingparticular embodiments only, and is not intended to be limiting. lt must be 4 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 ofthe elements unless the context clearly dictates otherwise. Thus, for example,reference to "a sensor" or "the sensor" may include several sensors, and thelike. Furthermore, the word "comprising" or "including" does not exclude otherelements or steps.

Brief description of the drawinqs Other features and advantages of the present invention will becomeapparent from the following detailed description of a presently preferredembodiment, with reference to the accompanying drawings, in which Fig 1 depicts an example traffic light that may implement someembodiments of the invention, Fig. 2 is a schematic diagram of a light source according to someembodiments of the invention, Fig. 3 is a schematic circuit diagram of the control and the powering ofsome embodiments of the invention, Fig. 4 is a flowchart of a process for controlling a traffic signallingdevice according to some embodiments of the invention.

Further, in the figures like reference characters designate like orcorresponding parts throughout the several figures.

Detailed description of embodimentsThe present invention relates to LED-based traffic signalling devices.

An example of a traffic signalling device is a railroad crossing signallingdevice as the one showed in Fig. 1. According to some embodiments, thetraffic signalling device 10 includes a light emitting signal area 12 andelectronics for controlling the light emission from the light emitting signal area12. A traffic signalling device 10 may include one or a plurality of light emittingsignal areas 12 depending on the function of the particular traffic signallingdevice. There may be provided separate electronics controlling the lightemission for each light emitting signal area alternatively a circuitry common toall light emitting signal areas 12 may be provided. ln yet other alternativeembodiments including a plurality of light emitting signal areas 12 some areasmay have common control circuitry and some may have control circuitry for asingle light emitting signal area 12.

Now referring to Fig 2, a light emitting signal area 12 includes LEDs20, 22, operating as a light source for the traffic signalling device 10.According to some embodiments the light emitting signal area 12 includes twosets of LEDs, a first set of LEDs 20 and a second set of LEDs 22. Each set ofLEDs is separately driven and may be activated individually at different pointsin time or simultaneously. The two sets of LEDs 20, 22, are arranged in thelight emitting signal area 12 so that the visual output from the light emittingsignal area 12 with only the first set of LEDs 20 activated corresponds to thevisual output from the light emitting signal area 12 with only the second set ofLEDs 22 activated. Corresponding visual output in the context of the presentdescription may be interpreted as the luminance of the output from each ofthe two sets of LEDs 20,22, being substantially equal and the impression ofthe shape of the output from each of the two sets of LEDs 20, 22 beingsubstantially equal.

According to some embodiments corresponding visual output from thefirst set of LEDs and from the second set of LEDs respectively, is achieved byarranging the LEDs in a grid and having every second LED in a row belongingto the first set of LEDs and the LEDs in-between the LEDs of the first set ofLEDs belonging to the second set of LEDs, as shown in Fig. 2. Moreover, thetwo LEDs referred to using numeral 20 and numeral 22 respectively anddrawn outside the light emitting signal area 12 is not supposed to be LEDspositioned outside the light emitting area, but are included in the figure inorder to indicate that the circles marked as white are LEDs belonging to thefirst set of LEDs 20 and the circles having hatching are LEDs belonging to thesecond set of LEDs 22.

The skilled person would readily appreciate that there are other waysto combine LEDs of two different sets and still achieve corresponding visualappearance when one or the other set of LEDs is activated. Now referring toFig. 3, according to some embodiments the electronics controlling theoperation of the light emitting signal area 12 include a power input 30, a lightcontrol terminal 32, a LED driver 34 driving the first set of LEDs 20, a LEDdriver 36 driving the second set of LEDs 22, a LED operation detector 38, andan alert output terminal 40.

The power input 30 is providing the power to the circuitry. The lightcontrol terminal 32 is a terminal that is arranged to receive control signalsfrom a traffic light controller or traffic light managing system determining if thelight emitting signal area 12 is to be activated, i.e. emit light, or not. The light 6 control terminal is connected to each of the two LED drivers 34, 36, in orderto convey the control signal to each of the LED drivers. A first one of the LEDdrivers 34 is driving the first set of LEDs 20 in response to the control signalfrom the light control terminal 32.

Further, the circuit from the first LED driver 34 to the LEDs of the firstset of LEDs is monitored by a LED operation detector 38. The LED operationdetector 38 is configured to indicate if the first set of LEDs is failing in emittingthe required luminance when the light control terminal 32 is signalling that thelight emitting signal area 12 is to emit light. The LED operation detector 38may 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 20or by measuring a forward voltage over one or a plurality of LEDs in the firstset of LEDs 20.

A second one of the LED drivers 36 is driving the LEDs of the secondset of LEDs 22 also in response to the control signal from the light controlterminal 32. However, the second LED driver 36 driving the second set ofLEDs 22 is blocked from activation if not the LED operation detector 38indicates that the first set of LEDs 20 is failing. Hence, the second LED driver36 has the function of a switch responsive to the signal from the LEDoperation detector 38 and switching between blocked, i.e. not driving thesecond set of LEDs to emit light at all, and active, i.e. driving the second setof LEDs to emit light in response to the control signal. On the other hand, ifthe LED operation detector 38 indicates that the first set of LEDs 20 is failingthen the second LED driver 36 drives the second set of LEDs 22 inaccordance with the control signal from the light control terminal 32.

The LED operation detector also provides a signal to the alert outputterminal 40, indicating that one set of LEDs is failing and that it may time formaintenance. This terminal may be monitored by the traffic light controller ortraffic light managing system and its status or its indication that the first set ofLEDs 20 are failing may be communicated to a central maintenance function.

The process of emitting light by the traffic signalling device inaccordance with some embodiments of the invention is depicted in theflowchart of Fig. 4. lnitially the first set of LEDs 20 is emitting light inaccordance with the control signal on the control terminal 32, step S402, andthe second set of LEDs 22 is dark, step S404, until the first set of LEDs 20fails, step S406. When the first set of LEDs 20 is detected to be failing, thesecond LED driver is activated and the second set of LEDs 22 is emitting light 7 in accordance with the control signal, step S408, instead of the first set ofLEDs 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 lightcontrol system via the alert output terminal 40, step S412.

The LED driver may in some embodiments be a TPS92610-Q1Automotive Single-Channel Linear LED Driver including a LED Diagnosticsfunctionality and enabled to generate a failure signal if the LED Diagnosticsindicate that the LED circuitry is failing.

Claims

1. LED-based traffic signalling device (10) including a light emittingsignal area (12), the light emitting signal area (12) comprising: a plurality of LEDs arranged in at least two separately controllable setsof LEDs (20, 22), wherein a visual output from the light emitting signalarea (12) having a first set of the LEDs (20) activated corresponds to a visualoutput from the light emitting signal area (12) having a second set of theLEDs (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 failingin emitting required luminance and including a status output configured toindicate failure of the first set of LEDs if failure of the first set of LEDs isdetected; 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 theoutput of the LED operation detector (38) indicating failure of the first set ofLEDs (20).

2. The device according to claim 1, further comprising an alert signalterminal (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) isactivated.

3. The device according to any one of claims 1 to 2, wherein the LEDsof the first set of LEDs (20) and the LEDs of the second set of LEDs (22) areequally distributed over the light emitting signal area (12).

4. The device according to claim 3, wherein the LEDs of the first andsecond sets (20, 22) of LEDs are arranged in a grid and wherein a LEDhaving neighbouring LEDs in all nine neighbouring positions in the grid haveat least four of the neighbouring positions occupied by LEDs from the otherset of LEDs.

5. The device according to any one of claims 1 to 4, wherein the LEDoperation detector (38) is a current sensor configured to detect the current 9 through the first set of LEDs (20) and outputting a signal indicating the currentthrough the first set of LEDs (20).

6. The device according to any one of claims 1 to 5, further including afirst LED driver (34) configured to drive the first set of LEDs (20) and asecond LED driver (36) configured to drive the second set of LEDs (22),wherein the switch controlled by the output from the LED operation detector isincluded in the second LED driver.

7. Use of a LED-based traffic signalling device according to any one ofclaims 1-6 in a traffic signalling system.

8. Process for controlling a traffic signalling device, the processcomprising: receiving a light control signal indicating whether to emit light or not; continuously checking if a first set of LEDs (20) is emitting requiredluminance; setting a fail signal if the first set of LEDs (20) does not emit requiredluminance; driving a first set of LEDs (20) to emit light in accordance with thecontrol signal if the fail-signal is not set; and driving a second set of LEDs (22) to emit light in accordance with thecontrol signal if the fail-signal is set;

9. The process according to claim 8, wherein the driving of the first setof LEDs (20) to emit light generate a visual output and wherein the driving ofthe second set of LEDs (22) to emit light generate a corresponding visualoutput.