EP1583399A2 - Leuchtdiodenfeld - Google Patents

Leuchtdiodenfeld Download PDF

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Publication number
EP1583399A2
EP1583399A2 EP05251845A EP05251845A EP1583399A2 EP 1583399 A2 EP1583399 A2 EP 1583399A2 EP 05251845 A EP05251845 A EP 05251845A EP 05251845 A EP05251845 A EP 05251845A EP 1583399 A2 EP1583399 A2 EP 1583399A2
Authority
EP
European Patent Office
Prior art keywords
leds
string
led
array
switching means
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Withdrawn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
EP05251845A
Other languages
English (en)
French (fr)
Other versions
EP1583399A3 (de
Inventor
Brian Christopher Latham
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.)
Oxley Developments Co Ltd
Original Assignee
Oxley Developments Co 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
Application filed by Oxley Developments Co Ltd filed Critical Oxley Developments Co Ltd
Publication of EP1583399A2 publication Critical patent/EP1583399A2/de
Publication of EP1583399A3 publication Critical patent/EP1583399A3/de
Withdrawn legal-status Critical Current

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    • 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]
    • H05B45/30—Driver circuits
    • H05B45/395—Linear regulators
    • 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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • 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]
    • H05B45/30—Driver circuits
    • H05B45/36—Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
    • 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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • 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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/48—Details of LED load circuits with an active control inside an LED matrix having LEDs organised in strings and incorporating parallel shunting devices

Definitions

  • the present invention relates to LED arrays.
  • LEDs are typically placed side-by-side upon some form of carrier such as a printed circuit board.
  • carrier such as a printed circuit board.
  • the necessary number of LEDs is typically split between a set of series-connected "strings" of LEDs, each string being connected across the supply.
  • the number of LEDs in a string is chosen such that their total forward voltage is slightly lower than the supply voltage.
  • the string length could be chosen to give a 26 V forward voltage across the string, e.g. by using 10 LEDs each with a forward voltage (V f ) of 2.6. This arrangement permits power loss in an associated LED driver/control circuit to be kept low whilst effecting enough control to protect the LEDs from overcurrent and enabling intensity reduction if required.
  • V f LED forward voltage
  • V f increases as temperature reduces.
  • ambient temperature is reduced from 25°C to -40°C the string's forward voltage would increase from 26V to 28.8V, exceeding the supply.
  • This range of operating temperatures is not excessive for military and aeronautical applications. The result could be that at extremely low temperatures so little current would pass that the LEDs would not illuminate at all, and at more moderate low temperatures LED output would be very low.
  • Supply voltage variations can also prevent the LED array from operating correctly given that the minimum voltage of a nominal 28V supply array may be 22V or even less.
  • European patent application 1006506 (Hewlett-Packard Company) concerns an optical vehicle display having a set of LEDs arranged in a matrix. A circuit diagram is shown in which each of the LEDs is provided with a parallel-connected switch by which an LED which fails can be short-circuited enabling the remaining LEDs to continue to function. The LED matrix is driven from a current source. The problems posed by changes in LED forward voltage and supply voltage is not addressed in this document.
  • European patent application EP 1318701 (Audi AG) concerns a method and apparatus for driving a plurality of LEDs.
  • the circuit includes a series-connected set of light emitting diodes, and a current source and switch connected in series with the diodes.
  • a topped bridge across some, but not all, of the diodes contains a second current source and a second switch.
  • US 6320322 (Rohm Co,. Ltd.) discloses an arrangement having red, green and blue LEDs. By adjusting the luminance of the three elements, a range of colours can be created. Driving circuitry for the three LEDs is disclosed, but this does not address the problems associated with changes in LED forward voltage and supply voltage.
  • German Grebrauchsmusterschrift 20101418 (Insta Elektro GmbH & Co. KG) concerns a switching control for multiple lighting units with a microcomputer controller, in which individual LEDs can be bridged by respective switches
  • an array of light emitting diodes comprising at least one string of LEDs within which the LEDs are connected in series with one another, the string being connectable across a potential difference to drive the LEDs, and at least one switching means being provided for selectively reducing the effective length of the string by removing at least one LED from the current path through the string.
  • LEDs light emitting diodes
  • the “array” in question could have just one LED string, in the more typical case it comprises a plurality of strings in parallel with one another.
  • the strings typically all comprise the same number of LEDs.
  • the switching means serves to selectively bridge at least one LED in order to effectively remove it from the string.
  • a further preferred embodiment comprises two or more switching means for selectively removing different LEDs or sets of LEDs from the string, providing three or more possible string lengths.
  • a transistor is the preferred form of switching means and has the advantage of creating no appreciable electromagnetic interference. It can also be used to regulate LED current.
  • the switching means is controlled by an electronic controller responsive to one or more of (I) a measured temperature; (ii) a measured LED current; and (iii) a measured supply voltage.
  • the illustrated array 2 contains a total of fifty LEDs 4 arranged in five series strings 6. Of course the total number of LEDs is chosen according to requirements for optical power output. The total length of each string is chosen with reference to the intended supply voltage and the LEDs' forward voltage. The supply is connected across high rail 8 and ground 10. The strings are connected in parallel with each other.
  • a microprocessor/controller 12 receives, in this particular embodiment, two inputs.
  • the first input is indicative of the supply voltage, and is obtained through a connection 14 to the mid point of a potential divider formed by two resistors R1, R2 which are connected in series across the supply.
  • the second of the two inputs is indicative of the sum of the currents passing through the LED strings 6 and is obtained by detecting the voltage across a resistor R3 through which all of the strings are connected to ground.
  • the controller selects the states of control outputs O1, 02, 03 to respective switching transistors T1, T2, T3. In this way, the controller determines the length of the LED strings.
  • T1 serves, when in its closed circuit or "on” state, to connect the LED 4' at the end of each string to resistor R3 and so to ground. If T1 is on and the other transistors are "off” (open circuit) then all ten of the LEDs in each string are illuminated. If T2 is then switched on and T1 is switched off then the second LED 4" in each string is connected to ground via T2 and R3. End LEDs 4' are effectively disconnected and no longer illuminated. Each LED string 6 is thus shortened to contain nine illuminated LEDs. Switching on T3 and switching off T2 then connects the third LED 4'" in each string via T3 and R3 to ground. Both end LEDs 4' and second LEDs 4" are then disconnected and each string contains only eight illuminated LEDs.
  • the strings' forward voltage is correspondingly adjusted and in this way compensation is effected both for the temperature dependent changes in forward voltage of individual LEDs and for supply voltage variation.
  • shortening of the strings entails reducing the total number of LEDs which are illuminated. In the case where compensation is effected for low temperature, this need not necessarily reduce total light output, since LED efficiency is higher at low temperatures. Where compensation is being made for low supply voltage, LED current is of course increased and even if this is insufficient to maintain light output there will at least be significant intensity, which is acceptable in some programs where LED lights are replacing incandescent bulbs whose output would in any case drop to 40% of normal if supply voltage falls from 28V to 22V.
  • the controller 12 sets the state of transistors T1 - T3, and hence the LED string length, based upon its sensor inputs. In the illustrated example this is done on the basis of supply voltage and LED current. However there are other operating parameters which could be sensed and used in setting string length. For example ambient temperature or LED operating temperature could be measured and taken account of in this regard.
  • a current regulating function is also carried out by whichever transistor is conducting.
  • the microprocessor 12 monitors voltage across resistor R3, which corresponds to total LED current. In response, the microprocessor controls the conductive transistor T1, T2 or T3 and thereby regulates the current.
  • the LED array may of course be incorporated into any form of LED lamp, light or bulb.
  • the low component count makes the present invention particularly suited to use in units designed to substitute directly for incandescent bulbs (e.g. having a conventional bayonet or screw bulb fitting).
  • the fact that no appreciable electromagnetic interference is created also makes the invention suitable for sensitive applications e.g. on aircraft.

Landscapes

  • Led Devices (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
EP05251845A 2004-04-03 2005-03-24 Leuchtdiodenfeld Withdrawn EP1583399A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0407574 2004-04-03
GBGB0407574.3A GB0407574D0 (en) 2004-04-03 2004-04-03 Method and drive circuit for controlling leds

Publications (2)

Publication Number Publication Date
EP1583399A2 true EP1583399A2 (de) 2005-10-05
EP1583399A3 EP1583399A3 (de) 2006-10-04

Family

ID=32247799

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05251845A Withdrawn EP1583399A3 (de) 2004-04-03 2005-03-24 Leuchtdiodenfeld

Country Status (2)

Country Link
EP (1) EP1583399A3 (de)
GB (1) GB0407574D0 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007041131A1 (de) * 2007-08-30 2009-03-05 Osram Gesellschaft mit beschränkter Haftung Anordnung, Verwendung und Verfahren zur Ansteuerung von Licht emittierenden Bauelementen
CN102458004A (zh) * 2010-10-20 2012-05-16 凯杰照明股份有限公司 Led灯具的驱动电路的自调整方法
DE102007006438B4 (de) * 2007-02-05 2014-12-11 Marc ALBRECHT Schaltung zur gleichzeitigen Ansteuerung einer Anordnung gleichartiger Verbraucher
DE102007063879B3 (de) * 2007-08-30 2016-08-18 Osram Gmbh Anordnung, Verwendung und Verfahren zur Ansteuerung von Licht emittierenden Bauelementen
DE102007040152B4 (de) * 2006-08-29 2020-07-09 Avago Technologies International Sales Pte. Ltd. Vorrichtung und Verfahren zum Treiben einer LED

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2758551A1 (de) * 1977-12-23 1979-06-28 Elmeg Schaltungsanordnung zur steuerung von lichtemittierenden dioden (led)
DE3832109A1 (de) * 1988-09-21 1990-03-22 Juergen Munz Leuchte
DE20101418U1 (de) * 2001-01-26 2001-05-17 Insta Elektro Gmbh & Co Kg Schaltungsanordnung zum Betreiben von mehreren Leuchtmitteln
US20010033503A1 (en) * 2000-03-28 2001-10-25 Hamp Charles Henry Low power lighting system with LED illumination
DE10131845A1 (de) * 2001-06-30 2003-01-23 Hella Kg Hueck & Co Schaltungseinrichtung für die Spannungsversorgung von Leuchtdioden in einem Kraftfahrzeug
EP1318701A2 (de) * 2001-12-05 2003-06-11 Audi Ag Anordnung zur Ansteuerung einer Anzahl von lichtemittierenden Dioden im Verfahren zum Betreiben einer derartigen Anordnung
US20030164809A1 (en) * 2002-03-01 2003-09-04 Wa-Hing Leung Solid state lighting array driving circuit

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2758551A1 (de) * 1977-12-23 1979-06-28 Elmeg Schaltungsanordnung zur steuerung von lichtemittierenden dioden (led)
DE3832109A1 (de) * 1988-09-21 1990-03-22 Juergen Munz Leuchte
US20010033503A1 (en) * 2000-03-28 2001-10-25 Hamp Charles Henry Low power lighting system with LED illumination
DE20101418U1 (de) * 2001-01-26 2001-05-17 Insta Elektro Gmbh & Co Kg Schaltungsanordnung zum Betreiben von mehreren Leuchtmitteln
DE10131845A1 (de) * 2001-06-30 2003-01-23 Hella Kg Hueck & Co Schaltungseinrichtung für die Spannungsversorgung von Leuchtdioden in einem Kraftfahrzeug
EP1318701A2 (de) * 2001-12-05 2003-06-11 Audi Ag Anordnung zur Ansteuerung einer Anzahl von lichtemittierenden Dioden im Verfahren zum Betreiben einer derartigen Anordnung
US20030164809A1 (en) * 2002-03-01 2003-09-04 Wa-Hing Leung Solid state lighting array driving circuit

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007040152B4 (de) * 2006-08-29 2020-07-09 Avago Technologies International Sales Pte. Ltd. Vorrichtung und Verfahren zum Treiben einer LED
DE102007006438B4 (de) * 2007-02-05 2014-12-11 Marc ALBRECHT Schaltung zur gleichzeitigen Ansteuerung einer Anordnung gleichartiger Verbraucher
DE102007041131A1 (de) * 2007-08-30 2009-03-05 Osram Gesellschaft mit beschränkter Haftung Anordnung, Verwendung und Verfahren zur Ansteuerung von Licht emittierenden Bauelementen
DE102007041131B4 (de) * 2007-08-30 2015-07-23 Osram Gmbh Anordnung, Verwendung und Verfahren zur Ansteuerung von Licht emittierenden Bauelementen
DE102007063879B3 (de) * 2007-08-30 2016-08-18 Osram Gmbh Anordnung, Verwendung und Verfahren zur Ansteuerung von Licht emittierenden Bauelementen
CN102458004A (zh) * 2010-10-20 2012-05-16 凯杰照明股份有限公司 Led灯具的驱动电路的自调整方法

Also Published As

Publication number Publication date
EP1583399A3 (de) 2006-10-04
GB0407574D0 (en) 2004-05-05

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