EP2229667A1 - An led driver method for traffic lanterns - Google Patents

An led driver method for traffic lanterns

Info

Publication number
EP2229667A1
EP2229667A1 EP08856603A EP08856603A EP2229667A1 EP 2229667 A1 EP2229667 A1 EP 2229667A1 EP 08856603 A EP08856603 A EP 08856603A EP 08856603 A EP08856603 A EP 08856603A EP 2229667 A1 EP2229667 A1 EP 2229667A1
Authority
EP
European Patent Office
Prior art keywords
led
voltage
output
fault
led driver
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08856603A
Other languages
German (de)
French (fr)
Inventor
Malcolm Young
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aldridge Traffic Systems Pty Ltd
Original Assignee
Aldridge Traffic Systems Pty Ltd
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 AU2007906653A external-priority patent/AU2007906653A0/en
Application filed by Aldridge Traffic Systems Pty Ltd filed Critical Aldridge Traffic Systems Pty Ltd
Publication of EP2229667A1 publication Critical patent/EP2229667A1/en
Withdrawn legal-status Critical Current

Links

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
    • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/20—Responsive to malfunctions or to light source life; for protection
    • H05B47/24—Circuit arrangements for protecting against overvoltage

Definitions

  • the present i nvention relates to a light emitting diode (LED) driver method and apparatus for traffic lanterns.
  • LED light emitting diode
  • LEDs light emitting diodes
  • This invention addresses the need to control the current in the LEDs and to discover the failed proportion.
  • an LED driver for a traffic lantern comprisi ng a current mi rror adapted to control the current through an LED of the lantern , a fault detector arrangement connected to an output of the current mirror and the LED and adapted to indicate a fault condition if the voltage measured is outside a pred etermi ned range, and a voltage sensor arrangement adapted to provide an output voltage proportional to the average voltage of other LED drivers for the lantern which are not connected to faulty LEDs.
  • the fault detector monitors the output voltage of the current mirror and produces first and second outputs, the first output being fed to a fault circuit in which the first output is combined with the first outputs from a plurality of other LED d rivers and then compared , and the second output bei ng fed to the voltage sensor arrangement, and wherein the voltage sensor arrangement is also fed an output voltage of the LED.
  • the output voltage of the voltage sensor arrangement i s equal to the LED output voltage when a fault is absent and is equal to an open circuit when a fault is present.
  • the output voltage of the voltage sensor arrangement is fed to a voltage controller comprising a combi ni ng circuit and thence an LED power supply.
  • the LED driver consists of a current mirror to control the current through the LED, a fault detector arrangement and a driver voltage sensor arrangement.
  • the current mirror can usefully have a current ratio of about 20 , meaning that a current into the control terminal of say 1 mA wi ll result i n a current i n the output of 2OmA.
  • the fault detector arrangement is connected to the output of the current mirror and the driven LED or LEDs and indicates a fault condition if the voltage measured is too low (indicating an open circuit LED) or too high (indicating a short circuit LED).
  • the voltage sensor arrangement provides an output voltage (or current) proportional to the average voltage of those LED drivers which are not connected to faulty LEDs. In excluding the LEDs with faults, the output of the fault detectors may be used .
  • the driver voltage sensor arrangement is used to adjust or control the voltage applied to the LEDs so that enough voltage is present to operate the LEDs and the other systems but no excess voltage is used as this would cause excessive power loss in the current mirrors.
  • the fault detector arrangement is used to either report the proportion of faulty LEDs via some communications devices or to disconnect the traffic lantern , thus causing a measurable change in consumed power.
  • the LED driver apparatus and method are now descri bed in greater detai l by reference to Fig.1 .
  • the LED current control i nput at 12 is fed to current mirror 14, the output 1 6 of which feeds power to LED 1 8.
  • the fault detector 20 monitors the output voltage as described above and produces two outputs.
  • the output at 22 is fed to a fault circuit comprising a combining circuit and thence a fault level comparator (not shown).
  • the combini ng circuit combines the outputs from a plurality of similar LED drivers. It is to be understood that Fig. 1 shows only one of many si milar LED drivers that are used together.
  • the fault detector output at 24 is fed to voltage sensor (or monitor) 26.
  • the voltage sensor 26 also monitors the LED voltage via connection 28.
  • the voltage sensor output at 30 is a simple function of the LED voltage while the fault d etector 20 indicates correct operation of the LED and is some other useful value at other times.
  • the output of the voltage sensor 26 could be equal to the LED voltage when a fault is absent and an open circuit when a fault is present. This allows the output of the voltage sensor 26 to be indicative of only the correctly functioni ng LEDs.
  • the output 30 is fed to a voltage controller comprisi ng a combining circuit and thence the LED power supply (not shown).
  • the LED power supply uses the combined voltage sensors to set its own voltage to work efficiently.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Traffic Control Systems (AREA)

Abstract

An LED driver for a traffic lantern has a current mirror (14) adapted to control the current through an LED (18) of the lantern, and a fault detector (20) connected to an output (16) of the current mirror (14) and the LED (1 8). The fault detector (20) is adapted to indicate a fault condition if the voltage measured is outside a predetermined range. The LED driver also has a voltage sensor (26) adapted to provide an output voltage (30) proportional to the average voltage of other LED drivers for the lantern which are not connected to faulty LEDs.

Description

AN LED DRIVER METHOD FOR TRAFFI C LANTERNS
TECHNICAL FI ELD
The present i nvention relates to a light emitting diode (LED) driver method and apparatus for traffic lanterns. BACKG ROU N D ART
In the use of light emitting diodes (LEDs) in traffic lanterns, it is useful to know what proportion of the LEDs are faulty and to signal to the traffic control equipment when more than a chosen proportion of the LEDS have failed. DISCLOSURE OF INVENTION
This invention addresses the need to control the current in the LEDs and to discover the failed proportion.
Accord i ng to the invention, there is provided an LED driver for a traffic lantern comprisi ng a current mi rror adapted to control the current through an LED of the lantern , a fault detector arrangement connected to an output of the current mirror and the LED and adapted to indicate a fault condition if the voltage measured is outside a pred etermi ned range, and a voltage sensor arrangement adapted to provide an output voltage proportional to the average voltage of other LED drivers for the lantern which are not connected to faulty LEDs.
Preferably, the fault detector monitors the output voltage of the current mirror and produces first and second outputs, the first output being fed to a fault circuit in which the first output is combined with the first outputs from a plurality of other LED d rivers and then compared , and the second output bei ng fed to the voltage sensor arrangement, and wherein the voltage sensor arrangement is also fed an output voltage of the LED.
It is preferred that the output voltage of the voltage sensor arrangement i s equal to the LED output voltage when a fault is absent and is equal to an open circuit when a fault is present. In a preferred form, the output voltage of the voltage sensor arrangement is fed to a voltage controller comprising a combi ni ng circuit and thence an LED power supply.
B RI EF DESCRI PTION OF THE DRAWING I n order that the invention may be more readily understood and put i nto practical effect, reference will now be made to the following block schematic diagram (Fig. 1 ) of an LED driver according to a preferred embodiment of the invention.
MODES FOR CARRYI NG OUT THE I NVENTI ON I n general terms, the LED driver consists of a current mirror to control the current through the LED, a fault detector arrangement and a driver voltage sensor arrangement.
The current mirror can usefully have a current ratio of about 20 , meaning that a current into the control terminal of say 1 mA wi ll result i n a current i n the output of 2OmA.
The fault detector arrangement is connected to the output of the current mirror and the driven LED or LEDs and indicates a fault condition if the voltage measured is too low (indicating an open circuit LED) or too high (indicating a short circuit LED). The voltage sensor arrangement provides an output voltage (or current) proportional to the average voltage of those LED drivers which are not connected to faulty LEDs. In excluding the LEDs with faults, the output of the fault detectors may be used .
In operation with other subsystems, the present invention may be applied as follows. The driver voltage sensor arrangement is used to adjust or control the voltage applied to the LEDs so that enough voltage is present to operate the LEDs and the other systems but no excess voltage is used as this would cause excessive power loss in the current mirrors. The fault detector arrangement is used to either report the proportion of faulty LEDs via some communications devices or to disconnect the traffic lantern , thus causing a measurable change in consumed power.
The LED driver apparatus and method are now descri bed in greater detai l by reference to Fig.1 . The LED current control i nput at 12 is fed to current mirror 14, the output 1 6 of which feeds power to LED 1 8. The fault detector 20 monitors the output voltage as described above and produces two outputs. The output at 22 is fed to a fault circuit comprising a combining circuit and thence a fault level comparator (not shown). The combini ng circuit combines the outputs from a plurality of similar LED drivers. It is to be understood that Fig. 1 shows only one of many si milar LED drivers that are used together. The fault detector output at 24 is fed to voltage sensor (or monitor) 26. The voltage sensor 26 also monitors the LED voltage via connection 28. The voltage sensor output at 30 is a simple function of the LED voltage while the fault d etector 20 indicates correct operation of the LED and is some other useful value at other times. Typically, the output of the voltage sensor 26 could be equal to the LED voltage when a fault is absent and an open circuit when a fault is present. This allows the output of the voltage sensor 26 to be indicative of only the correctly functioni ng LEDs. The output 30 is fed to a voltage controller comprisi ng a combining circuit and thence the LED power supply (not shown). The LED power supply uses the combined voltage sensors to set its own voltage to work efficiently.
Various mod ifications may be made in details of design and construction without departing from the scope and ambit of the i nvention.

Claims

CLAIMS:
1 . An LED driver for a traffic lantern comprising a current mirror adapted to control the current through an LED of the lantern, a fault detector arrangement connected to an output of the current mirror and the LED and adapted to indicate a fault condition if the voltage measured is outside a predetermined range, and a voltage sensor arrangement adapted to provide an output voltage proportional to the average voltage of other LED drivers for the lantern which are not connected to faulty LEDs.
2. The LED driver of claim 1 wherein the fault detector monitors the output voltage of the current mirror and produces first and second outputs, the first output being fed to a fault circuit in which the first output is combined with the first outputs from a plurality of other LED drivers and then compared, and the second output being fed to the voltage sensor arrangement, and wherein the voltage sensor arrangement is also fed an output voltage of the LED.
3. The LED driver of claim 2 wherein the output voltage of the voltage sensor arrangement is equal to the LED output voltage when a fault is absent and is equal to an open circuit when a fault is present.
4. The LED driver of claim 3 wherein the output voltage of the voltage sensor arrangement is fed to a voltage controller comprising a combining circuit and thence an LED power supply.
5. The LED driver of claim 1 wherein the current mirror has a current ratio of about 20.
EP08856603A 2007-12-03 2008-12-03 An led driver method for traffic lanterns Withdrawn EP2229667A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2007906653A AU2007906653A0 (en) 2007-12-03 An LED driver method for traffic lanterns
PCT/AU2008/001778 WO2009070828A1 (en) 2007-12-03 2008-12-03 An led driver method for traffic lanterns

Publications (1)

Publication Number Publication Date
EP2229667A1 true EP2229667A1 (en) 2010-09-22

Family

ID=40717186

Family Applications (1)

Application Number Title Priority Date Filing Date
EP08856603A Withdrawn EP2229667A1 (en) 2007-12-03 2008-12-03 An led driver method for traffic lanterns

Country Status (6)

Country Link
EP (1) EP2229667A1 (en)
CN (1) CN101896951A (en)
AU (1) AU2008331420B2 (en)
NZ (1) NZ586130A (en)
WO (1) WO2009070828A1 (en)
ZA (1) ZA201004263B (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102024340B (en) * 2010-12-30 2013-06-26 广东大榕树信息科技有限公司 Traffic light monitoring device and monitoring method thereof
US9524641B2 (en) * 2011-03-22 2016-12-20 GE Lighting Solutions, LLC LED traffic signal fault logging system and method
CN102956110B (en) * 2011-08-19 2014-12-10 中国长城计算机深圳股份有限公司 LED traffic signal lamp and drive circuit thereof
CN106304462A (en) * 2016-07-26 2017-01-04 合肥联信电源有限公司 A kind of emergency lighting lamp fault protection circuit
CN107633696A (en) * 2017-09-18 2018-01-26 南昌金科交通科技股份有限公司 A kind of system of Contrast tuned imaging traffic lights
CN112085957A (en) * 2019-05-27 2020-12-15 云南金隆伟业电子有限公司 Multifunctional traffic signal lamp

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2724749A1 (en) * 1994-09-15 1996-03-22 Sofrela Sa LED lamps with integral controller for road traffic control signals
GB9708861D0 (en) * 1997-04-30 1997-06-25 Signal House Limited Traffic signals
US6583731B2 (en) * 2001-04-19 2003-06-24 Singapore Technologies Electronics Ltd. Fault detection for traffic light systems using electronic lighting elements

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2009070828A1 *

Also Published As

Publication number Publication date
WO2009070828A1 (en) 2009-06-11
WO2009070828A9 (en) 2010-11-25
CN101896951A (en) 2010-11-24
ZA201004263B (en) 2011-04-28
AU2008331420B2 (en) 2013-10-24
NZ586130A (en) 2013-10-25
AU2008331420A1 (en) 2009-06-11

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