EP2088833B1 - Procédé destiné au fonctionnement d'un dispositif d'éclairage à Leds de véhicule automobile - Google Patents

Procédé destiné au fonctionnement d'un dispositif d'éclairage à Leds de véhicule automobile Download PDF

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Publication number
EP2088833B1
EP2088833B1 EP09000921A EP09000921A EP2088833B1 EP 2088833 B1 EP2088833 B1 EP 2088833B1 EP 09000921 A EP09000921 A EP 09000921A EP 09000921 A EP09000921 A EP 09000921A EP 2088833 B1 EP2088833 B1 EP 2088833B1
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EP
European Patent Office
Prior art keywords
frequency
led
modulation
lighting device
motor vehicle
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.)
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Application number
EP09000921A
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German (de)
English (en)
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EP2088833A1 (fr
Inventor
Michael Mayer
Gerhard Schneider
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.)
Audi AG
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Audi AG
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Publication date
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Publication of EP2088833A1 publication Critical patent/EP2088833A1/fr
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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]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter 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]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]

Definitions

  • the invention relates to a method for operating a motor vehicle lighting device comprising at least one LED and a pulse width modulated driving the LED control device.
  • WO 2006/015476 A1 For example, a method of dimming an LED device having a plurality of LEDs is known in which all individual LEDs should be dimmable in a range of 0% to 100%. To operate such an LED device is further stated that this can be modulated with a pulse width modulation PWM, a pulse code modulation PCM or a frequency modulation FM. These types of modulation are generally known to the person skilled in the art. The variations described relate either to the amplitude or to the duty cycle in a pulse width modulation and not just to the frequency. With regard to the frequency, it is simply stated that it must be high enough to avoid the stroboscopic effect.
  • US 5,783,909 relates to a method for keeping the light intensity of an LED constant.
  • Factors influencing light intensity are age and temperature.
  • a light sensor and a temperature sensor are to be provided.
  • the average value of the current driving the LED is adjusted by changing either the pulse width, the frequency, or the baseline.
  • the modulation frequency is changed depending on sensor data.
  • LEDs In motor vehicles, lighting devices with one or more LEDs are increasingly being used, be it as interior lighting, be it in the headlights or the taillights.
  • the LED To ensure the longest possible lifetime, it is known not to provide the LED with a constant, temporally constant current, but clocked by pulse width modulation clocked. That is, the current is switched on and off via a pulse width modulation interface via a high frequency pulse generator.
  • the modulation frequency is constant, it is chosen in each case so high that the intermittent switching operation is not perceived by the human eye, so that it does not come to a stroboscopic effect. Usual frequencies are approx. 100 Hz.
  • the brightness is adjusted via the pulse-pause ratio (the so-called duty cycle), which can be changed accordingly.
  • An extension of the relative pulse duration that is to say the switch-on duration, corresponds in the time average to a longer switch-on duration of the LED, thus a greater brightness, while a reduction of the pulse duration or pulse width corresponds to a lower brightness.
  • the emitted luminous flux is approximately proportional to the mean value of the current, which is determined by the pulse-pause ratio.
  • the operating frequency usually selected to avoid the stroboscopic effect is still so high that the use is correspondingly high high quality and therefore more expensive semiconductor devices than LED components is required, which are able to represent the modulation frequency.
  • the invention is therefore based on the problem to provide an operating method for a pulse-width modulated LED drive, which allows a reduction of the modulation frequency while avoiding a stroboscopic effect.
  • the LED is continuously driven with different frequencies over time. This means that there is no constant frequency relative to the set brightness, but the frequency changes continuously, while the pulse-pause ratio and thus the adjusted brightness remains constant. As a result of this constant frequency change, a stroboscopic effect is avoided with particular advantage, since there is no chronologically constant change between the switch-on and switch-off state, which could be perceived by the viewer. This means that there is no time-constant light pattern that can be detected. Rather, according to the invention, a continuously changing switching behavior is realized which counteracts or avoids the stroboscopic effect.
  • the modulation frequency which was chosen in terms of its height solely for avoiding the stroboscopic effect in previously known control methods.
  • the stroboscopic effect is avoided by the frequency variation, but not by the frequency level alone.
  • the frequency or the frequency band within which the modulation frequency varies must be so high that also the varying frequency jumps just can not be perceived, but already frequencies are sufficient that are> 50 Hz.
  • EMC electromagnetic compatibility
  • the modulation frequency may be repetitively increased or decreased in a frequency sweep, starting from a starting frequency, preferably linearly to a target frequency, and jumping back to the starting frequency upon reaching the target frequency.
  • the modulation frequency preferably increases or decreases linearly from a start frequency to a target frequency. After reaching the target frequency, the frequency is automatically changed in a frequency jump back to the starting frequency, after which the frequency increase or decrease takes place again. This pattern is going through continuously.
  • modulation frequency repetitively preferably linearly between a maximum and a minimum frequency changed.
  • the frequency response here also preferably linearly changes, but the linearity is not a mandatory requirement.
  • a third alternative provides for the modulation frequency to be changed in a continuously changing manner within a defined frequency band via a random generator.
  • any control frequencies within the frequency band that have been previously defined are selected via the random number generator, which are then controlled via the control unit. So it comes to continuous frequency jumps, the holding time of a frequency defined by the random generator is again as low as possible, and preferably below one second.
  • control method according to the invention can be used both in lighting devices comprising only one LED, as well as in lighting devices with multiple LEDs combined in an array. In this case, all LEDs are then preferably driven together, that is, the entire array is operated via the frequency-varying method according to the invention.
  • the multiple arrays can all be driven together in the manner according to the invention if all the LEDs are to be operated.
  • the invention further relates to a motor vehicle comprising a lighting device with at least one LED and a pulse width modulated the LED controlling control device, which is designed to carry out the method described.
  • Fig. 1 shows a lighting device 1 according to the invention in the form of an array 2 consisting of several LEDs 3, of which four are shown in the example shown. Shown is also a control device 4, via which the operating current, which is applied to the array 2 or the LEDs 3 via the motor vehicle electrical system, is controlled pulse width modulated.
  • the illumination device can be any illumination device of the motor vehicle, be it a signal or indicator light in the region of the rear of the vehicle, the vehicle side or the vehicle front, be it an LED headlight or a lighting device from the vehicle interior.
  • the brightness is varied by adjusting the pulse-pause ratio, that is, the ratio between the turn-on and turn-off time of the individual LEDs 3.
  • the frequency with which the switch-on and switch-off process is controlled, in the inventive method or the illumination device according to the invention shown is shown.
  • Fig. 2 shows a first embodiment of such a control method.
  • the control frequency f is plotted. Shown is a start frequency f s and a target frequency f z . In the example shown, it is assumed that the starting frequency f s is lower than the target frequency f z .
  • the operating frequency continuously changes over time between the start frequency f s and the target frequency f z , wherein the frequency within each cycle, starting from the start frequency f s in the example shown is linearly increased to the target frequency f z after which the frequency is again reduced directly to the starting frequency f s in a frequency jump, after which it in turn increases linearly to the target frequency f z , etc. It forms over time t in Fig. 2 shown "sawtooth pattern" off. As a result of this continuous frequency variation, after a constant switching frequency does not occur, the stroboscopic effect is advantageously avoided since the viewer's eye is not given a time-constant switching pattern.
  • the resulting average switching frequency is significantly lower than in conventional lighting devices that are operated at a constant high frequency of usually 100 Hz.
  • the start frequency f s could be, for example, 60 Hz and the target frequency f z 90 Hz, this being merely an example, that is, other frequencies can also be selected. It would also be conceivable, starting from a higher starting frequency f s, to lower the frequency to the target frequency f z and then to increase it again to the starting frequency in a frequency jump. Again, a similar sawtooth pattern would result.
  • Fig. 3 shows a further possibility of a frequency response, whereby here again along the abscissa the time t and along the ordinate the frequency f is plotted.
  • the frequency varies continuously between a minimum frequency f min and a maximum frequency f max .
  • a linear frequency increase or frequency reduction is shown by way of example.
  • an average frequency results due to the avoidance of the stroboscopic effect due to the frequency variation is lower than previously usual constant control frequencies.
  • the minimum frequency f min and the maximum frequency f max can be 60 Hz and 90 Hz, and a minimum frequency of 50 Hz and a maximum frequency of 100 Hz or other frequency combinations would also be conceivable.
  • Fig. 4 a third embodiment of a frequency response.
  • the time t is plotted along the abscissa and the frequency f is plotted along the ordinate.
  • a frequency band between the minimum frequency f min and the maximum frequency f max is defined.
  • a random generator which is part of the control device 4
  • a random frequency within the frequency band is then selected, which is then set by the control device 4.
  • Fig. 4 clearly shows arise over time a variety of frequency jumps, that is, the random number generator continuously selects new frequencies within the frequency band, so that the frequency changes continuously leaps and there is no continuous frequency control here.
  • the individual frequency levels are kept very short, the hold time should be ⁇ 1 second, which is also only an exemplary value. Also conceivable would be shorter or longer holding times, wherein the holding time can also depend on how high the actual control frequency chosen by the random generator is. Higher frequencies may be kept slightly longer than lower ones, or vice versa.

Landscapes

  • Lighting Device Outwards From Vehicle And Optical Signal (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Claims (7)

  1. Procédé d'utilisation d'un dispositif d'éclairage pour véhicule automobile, qui comprend au moins une LED ainsi qu'un dispositif de commande qui commande les LED par modulation de la largeur d'impulsions,
    caractérisé en ce que
    la fréquence de modulation est modifiée en continu.
  2. Procédé selon la revendication 1, caractérisé en ce que la fréquence de modulation augmente ou diminue de manière répétée en balayant les fréquences de préférence linéairement depuis une fréquence initiale jusqu'à une fréquence cible et resautant sur la fréquence initiale lorsque la fréquence cible a été atteinte.
  3. Procédé selon la revendication 1, caractérisé en ce que la fréquence de modulation est modifiée de manière répétée, de préférence linéairement, entre une fréquence maximale et une fréquence minimale.
  4. Procédé selon la revendication 1, caractérisé en ce qu'un générateur aléatoire commande en permanence et en alternance la modification de la fréquence de modulation à l'intérieur d'une plage de fréquences définie.
  5. Procédé selon l'une des revendications précédentes, caractérisé en ce que lorsque le dispositif d'éclairage utilise plusieurs LED réunies en une batterie, toutes les LED sont pilotées conjointement.
  6. Procédé selon la revendication 5, caractérisé en ce que lorsque le dispositif d'éclairage utilise plusieurs batteries, toutes les batteries sont pilotées conjointement.
  7. Véhicule automobile comprenant au moins un dispositif d'éclairage (1) comprenant au moins une LED (3) ainsi qu'un dispositif de commande (4) qui commande les LED (3) en modulant la largeur d'impulsions, en vue de l'exécution d'un procédé selon l'une des revendications précédentes.
EP09000921A 2008-02-08 2009-01-23 Procédé destiné au fonctionnement d'un dispositif d'éclairage à Leds de véhicule automobile Active EP2088833B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102008008181A DE102008008181A1 (de) 2008-02-08 2008-02-08 Verfahren zum Betrieb einer Kraftfahrzeugbeleuchtungseinrichtung

Publications (2)

Publication Number Publication Date
EP2088833A1 EP2088833A1 (fr) 2009-08-12
EP2088833B1 true EP2088833B1 (fr) 2011-06-29

Family

ID=40673405

Family Applications (1)

Application Number Title Priority Date Filing Date
EP09000921A Active EP2088833B1 (fr) 2008-02-08 2009-01-23 Procédé destiné au fonctionnement d'un dispositif d'éclairage à Leds de véhicule automobile

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Country Link
EP (1) EP2088833B1 (fr)
DE (1) DE102008008181A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009032404A1 (de) * 2009-07-08 2011-01-13 Claas Selbstfahrende Erntemaschinen Gmbh Mähdrescher
US20120075596A1 (en) 2010-09-24 2012-03-29 Hannah Eric C High efficiency illumination
DE202015102108U1 (de) * 2015-04-28 2016-08-01 Zumtobel Lighting Gmbh Betriebsgerät zum Betreiben mindestens einer LED und Anordnung zur Beleuchtung mit einem Betriebsgerät und mindestens einer LED
DE102019128495A1 (de) 2019-10-22 2021-04-22 HELLA GmbH & Co. KGaA Verfahren zum Ansteuern von Elektromotoren mit einem pulsweitenmodulierten Signal

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4373146A (en) * 1980-10-20 1983-02-08 Gte Products Corporation Method and circuit for operating discharge lamp
US5783909A (en) * 1997-01-10 1998-07-21 Relume Corporation Maintaining LED luminous intensity
FI106770B (fi) * 1999-01-22 2001-03-30 Nokia Mobile Phones Ltd Valaiseva elektroninen laite ja valaisumenetelmä
DE20024002U1 (de) * 2000-03-17 2009-03-26 Tridonicatco Gmbh & Co. Kg Spannungsversorgung von Leuchtdioden (LEDs)
AU2003201751A1 (en) * 2002-02-14 2003-09-04 Koninklijke Philips Electronics N.V. Switching device for driving a led array
JP2006049127A (ja) * 2004-08-05 2006-02-16 Koito Mfg Co Ltd 照明用光源の点灯装置
ES2375204T3 (es) * 2004-08-12 2012-02-27 Koninklijke Philips Electronics N.V. Método y aparato para ajustar a escala la alimentación de corriente promedio a elementos emisores de luz.
US7307391B2 (en) * 2006-02-09 2007-12-11 Led Smart Inc. LED lighting system

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Publication number Publication date
EP2088833A1 (fr) 2009-08-12
DE102008008181A1 (de) 2009-08-13

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