EP2193308A1

EP2193308A1 - Illuminating device with light buffer

Info

Publication number: EP2193308A1
Application number: EP08802568A
Authority: EP
Inventors: Robert Kraus
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2007-09-24
Filing date: 2008-09-24
Publication date: 2010-06-09
Also published as: US8497621B2; WO2009040111A1; DE102007045540A1; WO2009040111A4; CN101809355A; US20100201284A1

Abstract

The illuminating device (1, 11) with at least one light source (2) designed for operation with alternating current and/or PWM, particularly a light emitting diode, comprises at least one light buffer (7, 8, 9) for absorbing light energy from the light source and for the time-delayed emission of the stored light energy.

Description

description

Lighting device with light buffer

Frequently, spurious flicker is observed in AC or PWM driven light sources. This problem is particularly pronounced for light-emitting diodes (LEDs), since the illumination of LEDs as current-controlled components essentially depends on the impressed current and stops virtually immediately with the drop of the current below a certain value (level).

For lamps powered by AC power sources, rectifiers with smoothing capacitors are typically required to suppress flicker. h., An additional electronics, which is associated with additional manufacturing costs. In addition, this increases the probability of failure of the circuit. In order to effectively avoid the current / voltage fluctuation, larger capacitors that take up a lot of space usually have to be taken.

It is therefore an object of the present invention to provide a lighting device which effectively suppresses flicker due to a light source operated by AC and / or pulse width modulation (PWM), and is also easy to manufacture, reliable and robust.

This object is achieved by means of a lighting device according to claim 1 and a method according to claim 20. Advantageous embodiments can be taken in particular from the subclaims.

The lighting device has at least one suitable for operation with alternating current and / or pulse width modulation light source, in particular light emitting diode. The lighting device further comprises at least one light buffer for absorbing light energy from the light source and time-delayed E mission of stored light energy. In other words, the light buffer serves to absorb (pump) the light energy of the light source during the illumination of the light source - in the "Em" phase - in order to continue to illuminate in the so-called "off" phase of the light source (relaxation) and thus reducing the flicker of the lighting device during operation. The associated relaxation time t_relax is defined as the time in which the radiation intensity drops by a factor of e when the primary radiation is switched off. A light buffer may also have several different relaxation times, eg. B. depending on the radiated wavelength.

A light source or lamp operated with alternating current is preferred.

For more effective smoothing of the light emission amplitude over time ("smearing"), the lighting device has at least two light buffers with different relaxation times.

It may be advantageous if at least two light buffers having different relaxation times are sensitive to different wavelengths.

In general, it may be advantageous if those light buffers that are sensitive to a shorter wavelength have a longer relaxation time.

In particular, it is advantageous if the light buffer which is sensitive to the shortest wavelength has the greatest relaxation time.

Generally, the light buffer may be located both in the immediate vicinity of the light source (eg, on the LED chip, in or on the LED package, etc.) and remote from the light source. A lighting device is preferred in which the light buffer which is used for the shortest possible lenlänge is sensitive, which is arranged at least one light source closest.

Furthermore, a lighting device in which at least one light buffer additionally has a wavelength-converting property is preferred. As a result, in addition to a simple and space-saving manner, a color radiation of the lamp can be adjusted.

In general, a light source, in particular LED, can be used for this purpose, which generates a primary radiation with a shorter wavelength than the secondary radiation emitted by the conversion layers. UV LEDs are particularly advantageous for this because the primary radiation is invisible. Therefore, no "color flickering" caused by the primary radiation is visible, and UV LEDs also have a high luminous efficacy.

In particular, a lighting device is preferred in which the light buffer that is sensitive to the shortest wavelength has no or no significant amount of wavelength conversion material.

For particularly simple and safe production and handling, the wavelength conversion material comprises phosphorus.

As light buffer materials and / or conversion materials, one or more suitable phosphorescent or luminescent materials may be used, in particular phosphorus-based. For example, as light buffer materials and / or conversion materials are suitable:

White phosphorus;

Yellow phosphorus (eg yttrium aluminum garnet with Ce activates Y3 (Al, Si) 5012: Ce (YAG: Ce));

Red phosphorus (eg activated by Eu or Sn). Gallophosphates and silicates can be used as white phosphorus (eg based on Zmk gallophosphate with nanopores, Eu-doped silicates, such as Li ₂ SrSiO ₄ : Eu (2+), Ba ₉ Sc ₂ Si ₆ O ₂₄ IEu (2+ ), Ca ₃ Si ₂ O ₇ : Eu (2+), Sr orthosilicates Sr ₂ SiO ₄ [Eu (2+), La (3+)]).

Generally, the light buffer material (s) of the respective light buffer may be the same and the wavelength conversion material (s) (i.e., both

Having a light buffer property as well as a wavelength conversion property), as well as being essentially selected for only one of the properties.

For even more effective smearing, the relaxation time t_relax of at least one light buffer - in particular of the light buffer closest to the light source (s) in the case of several light buffers - is greater than the period T of the AC voltage, ie t_relax> T. If the light buffer contains chemical components or subregions has multiple relaxation times (for example at different wavelengths of the emitted radiation), it is preferred if this condition is fulfilled at least for a relaxation time.

A light-emitting device is preferred in which a light-off time of the light buffer is at least 1 ms, preferably at least 5 ms, more preferably at least 10 ms. Half-life decay times well below 1 ms are less preferred because at very high current frequencies (eg, during high-frequency PWM operation) the eye integrates light differences, and at long dark times (eg very low AC frequencies) half-life decay time then flicker can not effectively depress. Half-value decay time is understood to mean the time-dependent, possibly frequency-dependent, duration of a luminescent material to which a luminous intensity only shuts off after the primary light source has been switched off is still 50% of the output light intensity at the switch-off time.

Particularly preferred is a relaxation time of at least one light buffer, which is greater than about five times the period T of the AC voltage, ie t_relax> 5 -T.

It is even more preferable if the relaxation time is greater than ten times the period T of the AC voltage but less than fifty times the period T of the AC voltage, that is, 10 -t <t_relax <50 -T. Thus, for such a light buffer for a lighting device operated by a mains voltage of 50 Hz, a preferred relaxation time t relax of about 0.2 s to about 1 s results.

For example, the known phosphors have relaxation times of less than 1 μs to hours, so that these times can be easily realized by the choice of the appropriate phosphor (e.g., white phosphorus).

Preference is also given to a lighting device, which has as light source a chain of several antiparallel-connected LEDs, which is directly connected to the power source.

Also preferred is a lighting device which has a driver for driving the at least one light source, which comprises a rectifier with no or with only a small-sized smoothing capacitor.

A lighting device which has a light bulb socket can be preferred.

But may also be preferred, a lighting device which is adapted to be used in a fluorescent lamp socket. These so-called retrofit lamps particularly preferably fit substantially into a standardized contour, eg. B. suitable for E26.

The object is also achieved by means of a lamp which has at least one such lamp.

The object is also achieved by means of a method for illuminating, in which a light source, in particular light-emitting diode, is operated with alternating current and / or in PWM Betπeb, light energy emitted by the light source is absorbed by at least one light buffer and the absorbed light energy for smoothing a Lichtmtensitat Delayed is emitted again.

In the following figures, the invention is schematically illustrated in more detail. Here, where appropriate, the same or equivalent components may be provided in different figures with the same reference numerals.

1 shows a cross-sectional illustration in side view of a retrofit lamp according to the invention to an LED-based light bulb;

FIG 2 shows a cross-sectional view in side view of a erfmdungsgemaße retrofit lamp to a fluorescent tubes on LED basis.

1 shows a lighting device 1 in the form of a so-called. Retrofit lamp to a light bulb with E26 contour based on ultraviolet emitting light-emitting diodes (UV LEDs) 2 as

Light source (s). The UV LEDs 2 are mounted symmetrically in the circumferential direction on a substrate 3, which is designed here as a metal core board. The substrate 3 and a light-transmitting bulb or shell 4 surrounding the substrate 3 and the LEDs 2 are mounted on an Edison socket 5, which has known electrical contacts 6 for supplying power to the LEDs 2. The UV LEDs 2 are connected so that they are arranged in branches of an LED chain, wherein the branches are connected in anti-parallel to each other and the chain is directly connected to the contacts 6 of the base 5. Each LED 2 thus draws current from a half-wave of the applied alternating current of here exemplary 50 Hz and lights up accordingly 50 times per second, when the current or the voltage of the half-wave exceeds a certain threshold.

In this lamp 1, three light buffers are present or the light buffer is divided into three zones. A layered near-zone light buffer 7 is arranged in the immediate vicinity of the light sources 2. A diffusely scattering intermediate-zone light buffer 8 surrounds the near-zone light buffer 7. The intermediate-zone light buffer 8 is in turn surrounded by a remote zone light buffer 9, which is applied in layers to the piston 4.

The intermediate zone light buffer 8 and the remote zone light buffer 9 have phosphorescent additives which serve to produce the desired color spectrum of the lighting device 1.

The near-zone light buffer 7 has a relaxation time t_relax_n, the intermediate-zone light buffer 8 has a relaxation time t_relax i and the far-zone light buffer 9 has a relaxation time t_relax_f, which differ. The relaxation times are selected such that the condition t_relax_n> max {t_relax_i, t_relax_f} is fulfilled.

When operating with the 50 Hz mains voltage selected here by way of example, the LEDs light up with corresponding frequency. Then, the light energy emitted by the LEDs is first absorbed to a significant extent by the near-zone light buffer 7 and released again with a corresponding relaxation time t_relax_n at the same wavelength with a time delay. By The near-zone light buffer 7 thus "smears" the light flux tips of the LEDs, which reduces the flickering of the lighting device 1. The UV light radiated again by the near-zone light buffer 7 then passes to the intermediate-zone light buffer 8, where it is likewise absorbed and re-emitted. However, the emission now happens with a longer relaxation time t_relax_i. In addition, the inter-zone light buffer 8 has a wavelength conversion material, so that the light emitted by it is shifted in the visible range. Similarly, light emitted by the intermediate-zone light buffer 8 reaches the far-zone light buffer 9. There it is absorbed and re-emitted with a relaxation time t_relax_i, which is also greater than t_relax_n. Also, the far-zone light buffer 8 has at least one wavelength conversion material, so that the light emitted by it has a wavelength which is shifted in a certain visible range, which differs at least partially from the spectral range which emits from the inter-zone light buffer 8 becomes. By suitably choosing the thicknesses of the light buffers 7, 8, 9, their light buffering materials and material thicknesses, as well as their wavelength conversion material, their wavelength conversion material density uvKi. For example, an LED lighting device 1 can be obtained which does not flicker or has very little flickering and also has a defined color emission.

2 shows a lighting device 11 in the form of a retrofit LED lamp to a fluorescent tube. The light buffer 12 in the form of a phosphorescent layer is applied to a glass envelope 13. The light source is also UV LEDs 2, which are arranged on a substrate 14. The base 15 and the contacts 16 are designed so that the lamp 11 can be inserted into a conventional version of a fluorescent lamp. Here, therefore, only one light buffer 12 is present, which absorbs the UV light radiated by the LEDs 2 and wel- lenlangenumgewandeltes light in the visible range with a relaxation time t_relax than again gives off.

Of course, the present invention is not limited to the embodiments shown. For example, other light sources may be used instead of an LED, for example a compact fluorescent tube. Also white or monochrome or clusters of monochrome light sources can be used. The lamps do not have to have a retro fit shape. Also, no wavelength conversion is required. The power source may also have a frequency other than 50 Hz, e.g. B. 60 Hz, and may additionally or alternatively be pulse width modulated. Then the relaxation time of at least one light buffer is preferably matched to a typical distance between 'Em' phases of the PWM.

Reference sign list

1 lighting device

2 LED 3 substrate

4 pistons

5 sockets

6 electrical contact

7 Near-zone light buffer 8 Inter-zone light buffer

9 remote zone light buffer

11 fluorescent tube

12 light buffers

13 glass case 14 substrate

15 sockets

16 Contact t_relax Relaxation time of the light buffer 12 t relax n Relaxation time of the near-zone light buffer 7 t_relax_i Relaxation time of the intermediate-zone light buffer 8 t_relax_f Relaxation time of the remote zone light buffer 9

Claims

claims

1. Lighting device (1, 11) with at least one intended for AC and / or PWM operation light source (2), in particular light emitting diode, comprising at least two light buffer (7,8,9) for absorbing light energy from the light source (2) and time-delayed emission of the stored light energy, wherein the at least two light buffers (7,8,9) have different relaxation times (t_relax_n, t_relax_i, t_relax_f) and are sensitive to different wavelengths.

Second lighting device (1) according to claim 1, comprising a layer-like near-zone light buffer (7) in the immediate vicinity of the at least one light source (2) and a stratified on a piston (4) Fernzonen nen light buffer (9).

3. lighting device (1) according to claim 2, further comprising a diffusely scattering inter-zone light buffer (8), which surrounds the near-zone light buffer (8) and is surrounded by the remote zone light buffer (9).

4. lighting device (1) according to any one of the preceding claims, wherein the light buffer (7), which is sensitive to the shortest wavelength, the longest Relaxa- tion time (t_relax_n) has.

5. Lighting device (1) according to one of the preceding claims, wherein the light buffer (7) which is sensitive to the shortest wavelength, the at least one light source (2) is arranged next.

6. A lighting device (1; 11) according to any one of the preceding claims, wherein the light buffer comprises phosphorus.

7. Lighting device (1; 11) according to one of the preceding claims, wherein at least one of the light buffers

(8, 9; 12) additionally has a wavelength converting property.

8. A lighting device (1) according to claim 1 in combination with claims 4 and 7, wherein the light buffer (7), which is sensitive to the shortest wavelength, has no significant amount of wavelength conversion material.

9. A lighting device (1; 11) according to claim 7 or 8, wherein the wavelength conversion material comprises phosphorus.

A lighting device (1; 11) according to any one of the preceding claims, wherein a half-life decay time of the light buffer (7-9; 12) is at least 1 ms, preferably at least 5 ms, more preferably at least 10 ms.

11. Lighting device (1; 11) according to one of the preceding claims, wherein the light source (2) is adapted for operation with alternating current.

A lighting device (1; 11) according to claim 11, wherein a relaxation time (t_relax_n; t_relax) of at least one light buffer (7; 12) is greater than the period (T) of the AC voltage.

13. Lighting device (1; 11) according to claim 12, wherein the

Relaxation time (t_relax_n; t_relax) of the at least one light buffer greater than five times the period T of the AC voltage.

14. A lighting device (1; 11) according to claim 13, wherein the relaxation time (t relax n; t relax) is ten times longer than the period (T) of the AC voltage, but shorter than fifty times the period (T) of the AC voltage.

15. Lighting device (1; 11) according to one of the preceding claims, wherein the light source is a UV light-emitting diode (2).

16. Lighting device (1; 11) according to one of the preceding claims, which has as a light source a chain of several antiparallel-connected LEDs (2) which can be connected directly to the power source.

17. Lighting device according to one of the preceding claims, which has a driver for driving the at least one light source comprising a rectifier with no or with only small-sized smoothing capacitor.

18. Lighting device (1) according to one of the preceding claims, which has a light bulb socket (5).

19. Lighting device (11) according to one of the preceding claims, which is adapted to be inserted into a fluorescent lamp socket.

20. Method for illuminating, in which a light source, in particular light-emitting diode, is operated with alternating current and / or in PWM mode, light energy emitted by the light source (2) is absorbed by at least one light buffer (7-9; absorbed light energy is re-emitted time delay.