WO2008141384A1 - Determining proportion of faulty leds in a traffic light display - Google Patents

Determining proportion of faulty leds in a traffic light display Download PDF

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Publication number
WO2008141384A1
WO2008141384A1 PCT/AU2008/000712 AU2008000712W WO2008141384A1 WO 2008141384 A1 WO2008141384 A1 WO 2008141384A1 AU 2008000712 W AU2008000712 W AU 2008000712W WO 2008141384 A1 WO2008141384 A1 WO 2008141384A1
Authority
WO
WIPO (PCT)
Prior art keywords
leds
proportion
light display
traffic light
faulty
Prior art date
Application number
PCT/AU2008/000712
Other languages
French (fr)
Other versions
WO2008141384A9 (en
Inventor
Malcolm Young
Original Assignee
Aldridge Traffic Systems Pty Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from AU2007902743A external-priority patent/AU2007902743A0/en
Application filed by Aldridge Traffic Systems Pty Limited filed Critical Aldridge Traffic Systems Pty Limited
Priority to CN200880022706A priority Critical patent/CN101796556A/en
Priority to EP08747980A priority patent/EP2149130A1/en
Priority to AU2008253601A priority patent/AU2008253601B2/en
Publication of WO2008141384A1 publication Critical patent/WO2008141384A1/en
Publication of WO2008141384A9 publication Critical patent/WO2008141384A9/en

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Classifications

    • 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
    • H05B45/54—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits in a series array 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to a method and apparatus for determining a proportion of faulty light emitting diodes (hereinafter referred to as "LEDs") in a traffic light display or lantern.
  • LEDs faulty light emitting diodes
  • Knowledge that more than an allowable proportion of the LEDs in a display are faulty may enable traffic control equipment to turn off the faulty display, and for subsequent servicing of the traffic light display to occur.
  • an apparatus for determining a proportion of faulty LEDs i n a traffic light display havi ng a pl urality of LEDs comprising:-
  • (c) means for processing the signal indicative of the one or more faulty LEDs to determi ne the proportion of faulty LEDs in the traffic light display.
  • the processing means includes a threshold device that is activated when the proportion of faulty LEDs is more than an allowable proportion.
  • the apparatus further includes means for informing traffic control equipment of the activation of the threshold device.
  • the traffic light display may be turned off by the traffic control equipment when the threshold device is activated.
  • the processi ng means includes a differential amplifier which connects to both the common sensi ng point and to a voltage divider ci rcuit i n series with the common sensing point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of faulty LEDs in the traffic light display, the potential difference being converted to a signal that is indicative of the proportion of faulty LEDs in the traffic light display.
  • an assembly for controlling the operating status of a traffic lig ht display having a pl urality of LEDs comprising:-
  • (c) means for informing the traffic control equipment of the proportion of faulty LEDs in the traffic l ight display so that, when the proportion of faulty LEDs is more than an allowable proportion , the threshold device is activated to turn off the traffic light display.
  • a method for determining a proportion of LEDs with open circuit failures in an array of LEDs in a traffic light display the array of LEDs being arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprisi ng the steps of>
  • (c) providi ng a differential amplifier which connects to both the common sensing poi nt and to a voltage divider circuit in series with the common sensi ng point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of LEDs i n the array having open ci rcuit failures, the potential difference being converted to a signal for determining the proportion of LEDs with open circuit failures by the differential amplifier.
  • the proportion of LEDs with open circuit failures to be determined is more than an allowable proportion, and the method includes the further steps of: -
  • a method for controlling the operating status of a traffic light display having an array of LEDs arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprising the steps of:-
  • each LED section 12, 14, 16 consists of two LEDs and optionally a current limiting resistor in series.
  • a multiplicity of fault sensing resistors 18, 20, 22 is used to connect the centre point of each LED section to a common sensing point A.
  • a sensing signal that can conveniently be a 1 kHz square wave with a peak value corresponding to the total voltage applied to the LED sections is fed to point A through a resistor B.
  • a differential amplifier C is connected to point A and to a voltage divider circuit at D so arranged that, when all LEDs are operating correctly, the potential difference between A and D is small.
  • This is a bridge circuit.
  • a characteristic of a bridge circuit is that, when balanced, the output is at a minimum (about zero) and if the bridge is unbalanced then the output at E increases.
  • the degree on unbalance of the bridge is proportional to the number of LED sections that have an open circuit LED.
  • the output of the amplifier C will be a 1 kHz square wave whose amplitude is proportional to the number of LED sections with a faulty open circuit LED.
  • the square wave from C is fed to rectifier F and filter G and then to threshold device H which will be activated only when more than a chosen proportion of the LED sections are faulty.
  • the output from H may also be used to turn off the faulty lantern.

Landscapes

  • Traffic Control Systems (AREA)
  • Train Traffic Observation, Control, And Security (AREA)

Abstract

A method for determining a proportion of LEDs with open circuit failures in an array of LEDs in a traffic light display, the array of LEDs being arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprising the steps of:- (a) providing a fault sensing resistor which connects between each pair of LEDs in series and a common sensing point, (b) feeding a sensing signal of a predetermined frequency to the common sensing point, (c) providing a differential amplifier which connects to both the common sensing point and to a voltage divider circuit in series with the common sensing point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of LEDs in the array having open circuit failures, the potential difference being converted to a signal for determining the proportion of LEDs with open circuit failures by the differential amplifier.

Description

DETERMINING PROPORTION OF FAULTY LEDS IN A TRAFFIC LIGHT DISPLAY
TECHNICAL FIELD The present invention relates to a method and apparatus for determining a proportion of faulty light emitting diodes (hereinafter referred to as "LEDs") in a traffic light display or lantern. BACKGROUND ART
In the use of LEDs in traffic light displays, it is considered useful to know if more than a specified proportion of the LEDs in a display are faulty.
Experience has shown that open circuit failures are the most common type of failure of an LED.
Knowledge that more than an allowable proportion of the LEDs in a display are faulty may enable traffic control equipment to turn off the faulty display, and for subsequent servicing of the traffic light display to occur.
Although a preferred embodiment of the invention will be described later in the specification with reference to its application to determining a proportion of LEDs with open circuit failures in an array of LEDs arranged as a plurality of sections in parallel and in which each section contains two LEDs in series, it will be apparent to persons skilled in the art that the invention is not limited thereto but has wider application to other types of failures and to other arrays of
LEDs.
SUMMARY OF INVENTION
Accordingly, it is an object of the present invention to provide a simple and reliable way of determining a proportion of faulty LEDs in a traffic light display having a plurality of LEDs and, in particular, of determining a proportion of LEDs with open circuit failures i n an array of LEDs i n a traffic light display connected to traffic control equipment.
It is another object of the present i nvention to provide a simple and reliable way of control ling the operating status of a traffic light display having a pl urality of LEDs.
According to one aspect of the present invention, there is provided an apparatus for determining a proportion of faulty LEDs i n a traffic light display havi ng a pl urality of LEDs, the apparatus comprising:-
(a) means for communicati ng the presence of one or more faulty LEDs to a common sensing point,
(b) means for feeding a signal to the common sensing point for sensi ng the one or more faulty LEDs, and
(c) means for processing the signal indicative of the one or more faulty LEDs to determi ne the proportion of faulty LEDs in the traffic light display.
Preferably, the processing means includes a threshold device that is activated when the proportion of faulty LEDs is more than an allowable proportion.
It is preferred that the apparatus further includes means for informing traffic control equipment of the activation of the threshold device.
The traffic light display may be turned off by the traffic control equipment when the threshold device is activated.
I n a preferred form, the processi ng means includes a differential amplifier which connects to both the common sensi ng point and to a voltage divider ci rcuit i n series with the common sensing point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of faulty LEDs in the traffic light display, the potential difference being converted to a signal that is indicative of the proportion of faulty LEDs in the traffic light display.
According to another aspect of the present i nvention, there is provided an assembly for controlling the operating status of a traffic lig ht display having a pl urality of LEDs, the assembly comprising:-
(a) a traffic light display that includes the above described apparatus,
(b) traffic control equipment,
(c) means for informing the traffic control equipment of the proportion of faulty LEDs in the traffic l ight display so that, when the proportion of faulty LEDs is more than an allowable proportion , the threshold device is activated to turn off the traffic light display. According to a further aspect the present invention , there is provided a method for determining a proportion of LEDs with open circuit failures in an array of LEDs in a traffic light display, the array of LEDs being arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprisi ng the steps of>
(a) providing a fault sensing resistor which connects between each pair of LEDs in series and a common sensi ng point,
(b) feeding a sensing signal of a predetermined frequency to the common sensing point,
(c) providi ng a differential amplifier which connects to both the common sensing poi nt and to a voltage divider circuit in series with the common sensi ng point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of LEDs i n the array having open ci rcuit failures, the potential difference being converted to a signal for determining the proportion of LEDs with open circuit failures by the differential amplifier.
Preferably, the proportion of LEDs with open circuit failures to be determined is more than an allowable proportion, and the method includes the further steps of: -
(d) feeding the signal from the differential amplifier to a rectifier and filter,
(e) providing a threshold device to which the rectified and filtered signal is fed , the threshold device being activated when more than an allowable proportion of LEDs in the array have open circuit failures, and
(f) providing traffic control equipment which is informed of the activation of the threshold device.
According to a still further aspect of the present invention, there is provided a method for controlling the operating status of a traffic light display having an array of LEDs arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprising the steps of:-
(a) determining a proportion of LEDs with open circuit failures in the array of LEDs in the traffic light display according to steps (a) to
(c) of the above described method ,
(b) feeding the signal indicative of the proportion to a rectifier and filter,
(c) providing a threshold device to which the rectified and filtered signal is fed, the threshold device being activated when more than an allowable proportion of LEDs in the array have open circuit failures, and (d) providing traffic control equipment which is informed of the activation of the threshold device, and which turns off the traffic light display.
BRI EF DESCRIPTION QF THE DRAWI NG In order that the invention may be readily understood and put into practical effect, reference will now be made to the accompanying drawing of Figure 1 which is a block circuit diagram representing a method and apparatus according to a preferred embodiment of the present invention. MODES FOR CARRYING OUT THE INVENTION As shown in Fig 1 , each LED section 12, 14, 16 consists of two LEDs and optionally a current limiting resistor in series. A multiplicity of fault sensing resistors 18, 20, 22 is used to connect the centre point of each LED section to a common sensing point A. A sensing signal that can conveniently be a 1 kHz square wave with a peak value corresponding to the total voltage applied to the LED sections is fed to point A through a resistor B. A differential amplifier C is connected to point A and to a voltage divider circuit at D so arranged that, when all LEDs are operating correctly, the potential difference between A and D is small. This is a bridge circuit. A characteristic of a bridge circuit is that, when balanced, the output is at a minimum (about zero) and if the bridge is unbalanced then the output at E increases.
In the arrangement shown in Fig 1 , the degree on unbalance of the bridge is proportional to the number of LED sections that have an open circuit LED. The output of the amplifier C will be a 1 kHz square wave whose amplitude is proportional to the number of LED sections with a faulty open circuit LED. The square wave from C is fed to rectifier F and filter G and then to threshold device H which will be activated only when more than a chosen proportion of the LED sections are faulty. The output of the threshold device H
is used to inform traffic control equipment that the lantern being monitored may be faulty. The output from H may also be used to turn off the faulty lantern.
Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognised that departures can be made within the scope of the invention, which is not limited to the details described herein but is to be accorded the full scope of the appended claims so as to embrace any and all equivalent devices and apparatus.

Claims

CLAIMS:
1 . An apparatus for determining a proportion of faulty LEDs in a traffic light display having a plurality of LEDs, the apparatus comprising:-
(a) means for communicating the presence of one or more faulty LEDs to a common sensing point,
(b) means for feeding a signal to the common sensing point for sensing the one or more faulty LEDs, and
(c) means for processing the signal indicative of the one or more faulty LEDs to determine the proportion of faulty LEDs in the traffic light display.
2. The apparatus of claim 1 wherein the processing means includes a threshold device that is activated when the proportion of faulty LEDs is more than an allowable proportion.
3. The apparatus of claim 2 further including means for informing traffic control equipment of the activation of the threshold device.
4. The apparatus of claim 3 wherein the traffic light display is turned off by the traffic control equipment when the threshold device is activated.
5. The apparatus of claim 1 wherein the processing means includes a differential amplifier which connects to both the common sensing point and to a voltage divider circuit in series with the common sensing point, and wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of faulty LEDs in the traffic light display, the potential difference being converted to a signal that is indicative of the proportion of faulty LEDs in the traffic light display.
6. An assembly for controlling the operating status of a traffic light display having a plurality of LEDs, the assembly comprising:-
(a) a traffic light display that includes the apparatus of claim 2,
(b) traffic control equipment, and
(c) means for informing the traffic control equipment of the proportion of faulty LEDs in the traffic light display so that, when the proportion of faulty LEDs is more than an allowable proportion, the threshold device is activated to turn off the traffic light display.
7. A method for determining a proportion of LEDs with open circuit failures in an array of LEDs in a traffic light display, the array of LEDs being arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprising the steps of:-
(a) providing a fault sensing resistor which connects between each pair of LEDs in series and a common sensing point,
(b) feeding a sensing signal of a predetermined frequency to the common sensing point, and
(c) providing a differential amplifier which connects to both the common sensing point and to a voltage divider circuit in series with the common sensing point, wherein the potential difference between the common sensing point and the voltage divider circuit is dependent on the proportion of LEDs in the array having open circuit failures, the potential difference being converted to a signal for determining the proportion of LEDs with open circuit failures by the differential amplifier.
8. The method of claim 7 wherein the proportion of LEDs with open circuit failures to be determined is more than an allowable proportion, and the method includes the further steps of:-
(d) feeding the signal from the differential amplifier to a rectifier and filter,
(e) providing a threshold device to which the rectified and filtered signal is fed , the threshold device being activated when more than an allowable proportion of LEDs in the array have open circuit failures, and
(f) providing traffic control equipment which is informed of the activation of the threshold device.
9. A method for controlling the operating status of a traffic light display having an array of LEDs arranged as a plurality of sections in parallel and in which each section includes a pair of LEDs in series, the method comprising the steps of:-
(a) determining a proportion of LEDs with open circuit failures in the array of LEDs in the traffic light display according to steps (a) to (c) of the method of claim 7,
(b) feeding the signal indicative of the proportion to a rectifier and filter,
(c) providing a threshold device to which the rectified and filtered signal is fed, the threshold device being activated when more 1 O
than an allowable proportion of LEDs in the array have open circuit failures, and (d) providing traffic control equipment which is informed of the activation of the threshold device, and which turns off the traffic light display.
PCT/AU2008/000712 2007-05-22 2008-05-22 Determining proportion of faulty leds in a traffic light display WO2008141384A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN200880022706A CN101796556A (en) 2007-05-22 2008-05-22 Determining proportion of faulty leds in a traffic light display
EP08747980A EP2149130A1 (en) 2007-05-22 2008-05-22 Determining proportion of faulty leds in a traffic light display
AU2008253601A AU2008253601B2 (en) 2007-05-22 2008-05-22 Determining proportion of faulty LEDs in a traffic light display

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2007902743 2007-05-22
AU2007902743A AU2007902743A0 (en) 2007-05-22 Method and apparatus for determining the proportion of faulty light emitting diodes in a traffic light display

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WO2008141384A1 true WO2008141384A1 (en) 2008-11-27
WO2008141384A9 WO2008141384A9 (en) 2010-11-25

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EP (1) EP2149130A1 (en)
CN (1) CN101796556A (en)
AU (1) AU2008253601B2 (en)
NZ (1) NZ617222A (en)
WO (1) WO2008141384A1 (en)
ZA (1) ZA200906703B (en)

Cited By (7)

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Publication number Priority date Publication date Assignee Title
CN101894512A (en) * 2010-07-30 2010-11-24 深圳市中庆微科技开发有限公司 Fault early warning system for LED display screen
EP2487998A1 (en) * 2011-02-09 2012-08-15 National Semiconductor Corporation Technique for identifying at least one faulty light emitting diode in a string of light emitting diodes
CN103620755A (en) * 2011-06-30 2014-03-05 应用材料公司 Lamp failure detector
DE102014100738A1 (en) 2013-01-29 2014-07-31 Varroc Automotive Systems s.r.o. Error detection circuit for one LED string
CN108417073A (en) * 2018-05-18 2018-08-17 上海会为智能技术有限公司 A kind of signal lamp running-state displaying method, device, equipment and medium
GB2566485A (en) * 2017-09-14 2019-03-20 Unipart Rail Ltd Rail signal arrangement for a rail signalling system
DE102021203550A1 (en) 2021-04-09 2022-10-13 Siemens Aktiengesellschaft Lighting device, emergency stop button and operating procedures

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CN101944276B (en) * 2010-08-19 2016-01-20 深圳市中庆微科技开发有限公司 A kind of LED screen bad point monitoring and pre-alarming method and system
CN101964166A (en) * 2010-09-13 2011-02-02 南京通用电器有限公司 Circuit for detecting dead pixel of LED display screen and method thereof

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FR2724749A1 (en) * 1994-09-15 1996-03-22 Sofrela Sa LED lamps with integral controller for road traffic control signals
WO1998049872A1 (en) * 1997-04-30 1998-11-05 Signal House Limited Traffic signals
US6570505B1 (en) * 1997-12-30 2003-05-27 Gelcore Llc LED lamp with a fault-indicating impedance-changing circuit
DE29807002U1 (en) * 1998-04-17 1998-07-02 Garufo Gmbh Signaling system
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Cited By (14)

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Publication number Priority date Publication date Assignee Title
CN101894512A (en) * 2010-07-30 2010-11-24 深圳市中庆微科技开发有限公司 Fault early warning system for LED display screen
CN101894512B (en) * 2010-07-30 2015-09-16 深圳市中庆微科技开发有限公司 A kind of LED display fault early warning system
EP2487998A1 (en) * 2011-02-09 2012-08-15 National Semiconductor Corporation Technique for identifying at least one faulty light emitting diode in a string of light emitting diodes
CN103620755A (en) * 2011-06-30 2014-03-05 应用材料公司 Lamp failure detector
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US9341664B2 (en) 2013-01-29 2016-05-17 Varroc Lighting Systems, s.r.o. LED failure detection
CZ305640B6 (en) * 2013-01-29 2016-01-20 Varroc Lighting Systems, s.r.o. Fault detector circuit in a string of light emitting diodes
DE102014100738A1 (en) 2013-01-29 2014-07-31 Varroc Automotive Systems s.r.o. Error detection circuit for one LED string
DE102014100738B4 (en) 2013-01-29 2019-08-08 Varroc Automotive Systems s.r.o. Error detection circuit for one LED string
GB2566485A (en) * 2017-09-14 2019-03-20 Unipart Rail Ltd Rail signal arrangement for a rail signalling system
GB2566485B (en) * 2017-09-14 2020-04-29 Unipart Rail Ltd Rail signal arrangement for a rail signalling system
US11383743B2 (en) 2017-09-14 2022-07-12 Unipart Rail Limited Rail signal arrangement for a rail signaling system
CN108417073A (en) * 2018-05-18 2018-08-17 上海会为智能技术有限公司 A kind of signal lamp running-state displaying method, device, equipment and medium
DE102021203550A1 (en) 2021-04-09 2022-10-13 Siemens Aktiengesellschaft Lighting device, emergency stop button and operating procedures

Also Published As

Publication number Publication date
EP2149130A1 (en) 2010-02-03
ZA200906703B (en) 2010-06-30
WO2008141384A9 (en) 2010-11-25
CN101796556A (en) 2010-08-04
AU2008253601A1 (en) 2008-11-27
AU2008253601B2 (en) 2013-11-28
NZ617222A (en) 2014-07-25

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