EP2191694A2 - Détection et compensation de défaillances de del dans de longues chaînes de del - Google Patents

Détection et compensation de défaillances de del dans de longues chaînes de del

Info

Publication number
EP2191694A2
EP2191694A2 EP08803688A EP08803688A EP2191694A2 EP 2191694 A2 EP2191694 A2 EP 2191694A2 EP 08803688 A EP08803688 A EP 08803688A EP 08803688 A EP08803688 A EP 08803688A EP 2191694 A2 EP2191694 A2 EP 2191694A2
Authority
EP
European Patent Office
Prior art keywords
led
leds
current
chain
switching elements
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Withdrawn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
EP08803688A
Other languages
German (de)
English (en)
Inventor
Peter Schilling
Michael Schäfer
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.)
Continental Automotive GmbH
Original Assignee
Continental Automotive GmbH
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 Continental Automotive GmbH filed Critical Continental Automotive GmbH
Publication of EP2191694A2 publication Critical patent/EP2191694A2/fr
Withdrawn legal-status Critical Current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]
    • H05B45/40—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
    • 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

Definitions

  • the invention relates to an electrical circuit arrangement according to the preamble of claim 1 and to a method for detecting and compensating for LED failures in LED chains according to the preamble of claim 6.
  • LEDs Light-emitting diodes
  • LEDs are among the optoelectronic semiconductor devices. According to their diode characteristic, they emit light when they are operated in the forward direction by applying a forward voltage, wherein the luminance is proportional to the forward current in wide ranges.
  • LEDs are used in backlit displays. These backlights must be adapted in their luminance to the prevailing environmental conditions and may need to be very bright; For example, the application for driver information systems in the automotive sector may be mentioned here. Therefore, a plurality of LEDs are often connected together to achieve the required brightness.
  • Characteristic parameters for the circuitry arrangement of the LED's are the forward voltage associated with production-related tolerances and their change due to temperature fluctuations. In addition, changes in this parameter during the operating time lead to changes in the brightness of individual LEDs and thus to an inhomogeneous illumination of the displays.
  • the prior art has involved the arrangement of a plurality of LEDs in a series connection, a so-called LED chain. set.
  • the chain length depends on the available input voltage and the maximum forward voltage of the LEDs in the operating range.
  • the LEDs are distributed over several chains connected in parallel. Nevertheless, due to the series connection of the diodes in the event of failure of a single LED, the current flow through the chain in question remains interrupted for a particular chain, and thus the entire chain is dark.
  • the distribution of the LEDs on several chains also has the disadvantage that the current through each LED chain must be controlled separately in order to compensate for the tolerances of the forward voltages and the temperature drift. It must therefore be provided for each chain its own power control.
  • the parallel-connected chains are connected to a common voltage source of constant voltage, whereby the efficiency of the circuit deteriorates because the
  • the invention is therefore based on the object to further develop a circuit arrangement of the type described above and to provide a process executable with the circuit arrangement according to the invention that a homogeneous illumination with minimal power loss can be achieved.
  • This object is solved by the characterizing features in claim 1 and the characterizing features in claim 6.
  • the inventive concept of the solution in the features of the main claim and in the features of the independent subclaim 6 is to realize by additional wiring of the LED chain, a control engineering method with which the failure of one LED or more LED 's can be detected and compensated And so the light emission with the functional LED's continues to be guaranteed.
  • further switching elements in particular parallel to the LED or parallel to a group of LEDs, are provided according to the invention. By bridging the defective LEDs, these switching elements allow the current flow through the chain to be maintained, thereby preventing the failure of the entire chain.
  • the switching elements are preferably controlled by a switch control unit following an algorithm according to the invention.
  • the switch control unit On the input side, the switch control unit is connected via an error signal with an error detection unit.
  • the measured current intensity through the LED chain and a predetermined current setpoint are advantageously used as input signals of the error detection unit.
  • the detected by a measuring element current through the LED chain is supplied to the error detection unit and compared there with a predetermined current setpoint. At a certain deviation of the measured current value from the setpoint, the error detection unit generates an error signal, which is passed on to the switch control unit.
  • the switch control unit is thus activated in the event of a fault.
  • the switch control unit controls now the switching elements such that the faulty LED 's are bridged and in accordance with the invention, the current flow and thus the light emission in the functional LED' s can be maintained.
  • an algorithm for controlling the switching elements is implemented such that in the faulty chain, the switching elements are first closed one after the other until the LED current again corresponds to the desired value. In this way, the failure of a single faulty LED is reliably compensated.
  • the LED current has not reached the setpoint when a switching element is closed, all possible combinations of two switching elements each, then of three, etc. switching elements are switched.
  • the arrangement has the advantage of eliminating the simultaneous failure of multiple LEDs.
  • a controllable voltage source via a control value is connected to an LED control.
  • the LED controller on a setpoint input and a measurement input for the detected via a measuring element current through the LED chain.
  • This arrangement allows the LED controller from the LED current value and the predetermined setpoint determined a control value for controlling the voltage source such that the voltage applied across the chain operating voltage corresponds to the minimum required value.
  • This control of the voltage source reduces the voltage drop across the LEDs, thus reducing the power dissipation of the circuit and increasing the life of the devices.
  • with minimal power loss can be dispensed with further cooling measures, resulting in an advantageous manner, a small volume of construction.
  • Possible circuitry implementations of the method according to the invention provide that the error detection is integrated either in the LED control or that the error Detection unit is designed as a separate unit independent of the LED control and has an independent switch control.
  • the spatial arrangement of the individual LEDs of a chain should be distributed as homogeneously as possible over the surface to be illuminated in order to ensure the optical uniformity of the illumination if one or more LEDs fail.
  • the drawing shows a chain of LED 's Ll - L6 each with parallel switching elements Sl - S6.
  • Ll - L6 groups of diodes d. H. a plurality of diodes in series, are provided, which are then bridged together by the parallel to the respective group switching elements Sl - S6.
  • the switching elements S1-S6 are actuated by a central switch control unit 2.
  • this switch control unit 2 an algorithm is implemented which specifies which of the switching elements S1-S6 are switched in which time sequence.
  • the switch control unit 2 is activated by an error signal 3. If such occurs
  • the switch control unit 2 switches the switching elements Sl - S6 in such a way that first in the Chain in which the measured LED current 8 deviates from the desired value 10, the switching elements Sl - S6 individually one after the other (but not necessarily in a linear order) are closed until the LED current 8 again corresponds to the current setpoint 10. If the LED current 8 has not reached the current setpoint value 10 when a switching element S1-S6 is closed, then all possible combinations of two switching elements S1-S6, then of three, etc. switching elements S1-S6 are switched. This prevents the short circuit of functioning LEDs.
  • the error detection unit 4 is integrated in the LED controller 6, but can also be designed as a separate unit independent of the LED controller 6 with its own switch control.
  • Both the error detection unit 4 and the LED controller 6 use as input signals the LED current 8 through the LED chain and a brightness-specifying current setpoint value 10.
  • the error detection unit 4 generates in the deviation of the LED current 8 from the current setpoint 10th from this the error signal 3 for the switch control unit 2.
  • the LED controller 6 generates a control value 12 in order to regulate the voltage source 15 to the minimum value prescribed by the forward voltage of the LEDs. Excessive voltage potentials that can not be converted into active power (for a given LED current 8), but rather generate power loss and thus heat generation, are avoided.
  • a measuring element 16 is used for detecting the LED current 8.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Abstract

L'invention concerne un circuit comprenant un montage en série de DEL (chaîne de DEL), les DEL (L1 - L6) étant alimentées par une source de courant (14) commandée. L'objectif de l'invention est de concevoir un procédé de régulation qui permette, par l'intermédiaire d'un câblage supplémentaire de la chaîne de DEL, de détecter et de compenser la défaillance d'une ou de plusieurs DEL (L1 - L6) et de continuer ainsi à garantir l'émission de lumière au moyen des DEL opérationnelles. À cet effet, d'autres éléments de commutation (S1 - S6) sont montés en particulier parallèlement à la DEL ou parallèlement à un groupe de DEL. Ces éléments de commutation (S1 - S6) sont commandés à partir d'une unité de détection d'erreurs (4) par l'intermédiaire d'une unité de commande de commutation (6) et permettent de maintenir le flux de courant à travers la chaîne par pontage des DEL défectueuses et d'empêcher ainsi une défaillance de la chaîne entière.
EP08803688A 2007-09-07 2008-09-04 Détection et compensation de défaillances de del dans de longues chaînes de del Withdrawn EP2191694A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007042561A DE102007042561A1 (de) 2007-09-07 2007-09-07 Erkennen und Kompensieren von LED Ausfällen in langen LED-Ketten
PCT/EP2008/061718 WO2009034014A2 (fr) 2007-09-07 2008-09-04 Détection et compensation de défaillances de del dans de longues chaînes de del

Publications (1)

Publication Number Publication Date
EP2191694A2 true EP2191694A2 (fr) 2010-06-02

Family

ID=40339966

Family Applications (1)

Application Number Title Priority Date Filing Date
EP08803688A Withdrawn EP2191694A2 (fr) 2007-09-07 2008-09-04 Détection et compensation de défaillances de del dans de longues chaînes de del

Country Status (3)

Country Link
EP (1) EP2191694A2 (fr)
DE (1) DE102007042561A1 (fr)
WO (1) WO2009034014A2 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010009208B4 (de) * 2010-02-25 2016-12-15 Michael Schweizer Anzeigesystem
US11375594B2 (en) * 2018-09-20 2022-06-28 Signify Holding B.V. Tapped linear driver and driving method
CN112820238B (zh) * 2019-10-30 2022-07-01 群创光电股份有限公司 显示器
US11330689B2 (en) 2019-10-30 2022-05-10 Innolux Corporation Display device

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1006506A1 (fr) * 1998-12-03 2000-06-07 Hewlett-Packard Company Affichage optique pour véhicule
JP4241487B2 (ja) * 2004-04-20 2009-03-18 ソニー株式会社 Ｌｅｄ駆動装置、バックライト光源装置及びカラー液晶表示装置
US7800876B2 (en) * 2006-01-09 2010-09-21 Microsemi Corp. - Analog Mixed Signal Group Ltd. Fault detection mechanism for LED backlighting

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2009034014A2 *

Also Published As

Publication number Publication date
WO2009034014A2 (fr) 2009-03-19
WO2009034014A3 (fr) 2009-05-28
DE102007042561A1 (de) 2009-03-12

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