Operating a lighting module with LED elements

Abstract

A lighting system and a method of operating a lighting module are described. The lighting module includes a heat sink a first LED element mounted on the heat sink emits light as a low beam pattern. A second LED element mounted on the heat sink emits light as a high beam pattern. A driver circuit electrically connected to the first and second LED elements to selectively supply electrical power for operation. The driver circuit is disposed to operate in a first and a second mode. In the first mode, to provide a low beam illumination, the first LED element is operated in a high power state while the second LED element is turned off. In the second mode, to provide a high beam illumination, the second LED element is operated in a high power state, while the first LED element is operated in a dimmed state.

Claims

1. A lighting system, comprising: a lighting module including a rigid heat sink; a first LED element direclty mounted on the heat sinkin in a backward facing orientation, the first LED element being disposed and arranged such that light emitted therefrom in operation is emitted from the lighting system as a low beam pattern; a second LED element directly mounted on the heat sink in a backward facing orientation, the second LED element being disposed and arranged such that light emitted therefrom in operation is emitted from the lighting system as a high beam pattern, the heat sink being configured to maintain the first LED element and the second LED element in a symmetrical configuration configured to maintain the backward facing orientation of the first LED element and the second LED element; a driver circuit electrically connected to the first LED element and the second LED element to selectively supply electrical power for operation thereof by: in a first mode, operating the first LED element in a high power state, while the second LED element is turned off, to provide a low beam illumination, and in a second mode, operating the first LED element in a dimmed state, while operating the second LED element in a high power state, to provide a high beam illumination.

2. The lighting system according to claim 1, wherein in the high power state the first LED element is operated at a higher electrical power than in the dimmed state.

3. The lighting system according to claim 1, wherein the driver circuit is configured to operate the first LED element in the dimmed state with pulse width modulation, such that the electrical operating power of the first LED element in the dimmed state is less than the electrical operating power of the first LED element in the high power state.

4. The lighting system according to claim 1, wherein: the first LED element comprises a plurality of LEDs, the driver circuit is configured to operate at least one of a first number of the plurality of LEDs in the first mode and a second number of the plurality of LEDs in the second mode, the first number of the plurality of LEDs is higher than the second number of the plurality of LEDs.

5. The lighting system according to claim 4, wherein: the first LED element comprises a first group of the plurality of LEDs and a second group of the plurality of LEDs, and the driver circuit is configured to operate the first group of the plurality of LEDs in the first mode and in the second mode, and operate the second group of the plurality of LEDs in the first mode and not in the second mode.

6. The lighting system according to claim 5, wherein: the second group of the plurality of LEDs is electrically connected in parallel with the second LED element, and the second group of the plurality of LEDs and the second LED element are electrically connected in series with the first group of the plurality of LEDs.

7. The lighting system according to claim 1, wherein: the heat sink comprises a body portion and a protrusion portion protruding from the body portion, and at least one of the first LED element and the second LED element are mounted on the protrusion portion.

8. The lighting system according to claim 7, wherein the first LED element and second LED element are mounted on opposite sides of the portrusion portion.

9. The lighting system according to claim 8, wherein the first LED element is arranged directly opposite to the second LED element.

10. The lighting system according to claim 7, wherein the protrusion portion of the heat sink is formed in one piece with the body portion.

11. The lighting system according to claim 7, further comprising a headlight assembly including an optical system, the lighting module being exchangeably mounted to the head light assembly.

12. The lighting system according to claim 11, wherein: the optical system includes a concave reflector with an inner reflector space, and the protrusion portion projects into the reflector space.

13. The lighting system according to claim 1, wherein, in the high power state, the driver circuit is configured to supply the first LED element with less than 50% of the electrical power supplied in the high power state.

14. A vehicle headlight, comprising: a lighting system including: a lighting module including a rigid heat sink, a first LED element direclty mounted on the heat sink in a backward facing orientation, the first LED element, being disposed and arranged such that light emitted therefrom in operation is emitted from the lighting system as a low beam pattern, a second LED element directly mounted on the heat sink in a backward facing orientation, the second LED element being disposed and arranged such that light emitted therefrom in operation is emitted from the lighting system as a high beam pattern, the heat sink being configured to maintain the first LED element and the second LED element in a symmetrical configuration configured to maintain the backward facing orientation of the first LED element and the second LED element, a driver circuit electrically connected to the first LED element and the second LED element to selectively supply electrical power for operation thereof by: in a first mode, operating the first LED element in a high power state, while the second LED element is turned off, to provide a low beam illumination, and in a second mode, operating the first LED element in a dimmed state, while operating the second LED element in a high power state, to provide a high beam illumination.

15. The vehicle headlight of claim 14, wherein: the first LED element comprises a plurality of LEDs, the driver circuit is configured to operate at least one of a first number of the plurality of LEDs in the first mode and a second number of the plurality of LEDs in the second mode, and the first number of the plurality of LEDs is higher than the second number of the plurality of LEDs.

16. The vehicle headlight of claim 14, wherein, in the high power state, the driver circuit is configured to supply the first LED element with less than 50% of the electrical power supplied in the high power state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of a first embodiment of a lighting module;

(2) FIG. 2 shows a side view of the lighting module of FIG. 1;

(3) FIGS. 3, 4 show a top and a back view of the lighting module of FIGS. 1, 2;

(4) FIG. 5 shows a sectional view of the lighting module of FIGS. 1-4 with the section taken along line A . . . A in FIG. 4;

(5) FIG. 6 shows a partly sectional side view of a lighting system with the lighting module according to FIGS. 1-5;

(6) FIGS. 7a, 7b schematically show a first and a second LED element of a second embodiment of a lighting module;

(7) FIG. 8 schematically shows a motor vehicle with a lighting system according to FIG. 6 as headlight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) A first embodiment of an LED lighting module 10 is shown in FIGS. 1-6. The lighting module 10 includes a heat sink 12 comprised of a body portion 14 and a protrusion portion 16.

(9) The body portion 14 is comprised of a rectangular plate 18 from which the protrusion portion 16 protrudes into a forward direction F (designated in FIG. 2) and which has heat fins 20 extending in backward direction.

(10) The heat sink 12 is made of a metal heat sink material with good heat conducting properties, in particular of Aluminum. In the preferred embodiment, the body portion 14 and protrusion portion 16 are formed in one piece, although in alternative embodiments the parts forming the heat fins 20, plate 18 and protrusion portion 16 may be separate parts fixed to each other.

(11) The protrusion portion 16 protrudes from a center portion of the plate 18. The forward direction F is perpendicular to the forward surface of the plate 18. In the example shown, the protrusion portion 16 has rectangular cross-section. Further, in the preferred example as shown the central longitudinal axis X of the protrusion portion 16 extends in parallel with the forward direction F.

(12) A recess 22a in the shape of a V-shaped groove is formed in an upper surface 24a of the protrusion portion 16. A further recess 22b is provided in the lower surface 24b of the protrusion portion 16 in mirrored configuration.

(13) A first mounting surface 26a is provided on the upper surface 24a, within the groove 22a, and a second mounting surface 26b is provided on the lower surface 24b within the groove 22b. A first and a second LED element 30a, 30b are attached on the respective first and second mounting surfaces 26a, 26b.

(14) As shown in FIG. 3, each of the LED elements 30a comprises a plurality (in the shown example three) of bare LED dies 32 provided on a flat rectangular ceramic carrier 34.

(15) As visible in particular from FIG. 2, the mounting surfaces 26a, 26b are arranged under angles α.sub.1, α.sub.2 relative to the forward direction F and the longitudinal axis X. In the example shown, the angles α.sub.1, α.sub.2 are both at approximately 25°.

(16) In FIG. 2, vectors d1 and d2 designate the normal vectors of the mounting surfaces 26a, 26b. Since the LED elements 30a, 30b are flat and provided with LED dies 32 without optics, the vectors d1, d2 constitute the central light emission direction (center of the lambertian light emission characteristics).

(17) As shown in FIG. 2, the direction of the vectors d1, d2 is partially backwards, i.e. the vectors d1, d2 have a directional component opposed to the forward direction F.

(18) In alternative embodiments, the mounting surfaces 26a, 26b may be arranged to face into different directions, e.g. facing sideways under a 0° angle to the longitudinal axis X, or facing fully or partially forward.

(19) The heat sink 12 of the lighting module 10 is provided with a plastic overcoat 48. The overcoat 48 is molded over the metal heat sink. The overcoat 48 has windows or cutouts formed at the mounting surfaces 26a, 26b to allow directly mounting the LED elements 30a, 30b onto the metal surface of the heat sink.

(20) The lighting module 10 further has a number of module alignment protrusions: A first set of alignment protrusions 28a, 28b is provided on the body portion 14 of the heat sink 12, a second set of alignment protrusions 36a, 36b is provided on the upper and lower surfaces 24a, 24b of the protrusion portion 16 and a third type of alignment protrusion 38 is provided on a lateral surface of the protrusion portion 16. As will be explained below, the alignment protrusions 28a, 28b, 36a, 36b, 38 serve to achieve exact positioning of the lighting module 10 when installed in a lighting system. The alignment protrusions 28a, 28b, 36a, 36b, 38 are formed as part of the plastic overcoat 48.

(21) The lighting module 10 further comprises an electrical plug connector 40 (see FIG. 4) provided at the back of the body portion 14 of the heat sink 12, integrated within a cut out 42 formed between the heat fins 20. The electrical plug connector 40 comprises electrical contact tabs 44 (two pairs, each pair being connected to two poles of each LED element 30a, 30b) arranged to protrude into a space surrounded by a plug housing 46. As shown in the sectional view of FIG. 5, electrical conductors 50 in the form of lead frame elements embedded within a plastic material 52 extend through openings within the plate 18 and through channels within the protrusion portion 16 from the contact tabs 44 to contact pads 54 (FIG. 3) on the mounting surfaces 26a, 26b.

(22) As further shown in FIG. 3, the LED elements 30a, 30b are electrically contacted to the contact pads 54 by ribbon bonds 56. The electrical contacts may be potted, e.g. in Silicone, for protection.

(23) The lighting module 10 may be operated by connecting a power supply plug 90 as shown in FIG. 6 to the electrical plug connector 40 and supplying electrical power to the LED elements 30a, 30b through the conductors 50, contact pads 54 and ribbon bonds 56. The LED elements 30a, 30b then emit light as lambertian emitters around the central directions d1, d2.

(24) FIG. 6 shows a lighting system 60 including the lighting module 10 described above. In addition to the lighting module 10, the lighting system 60 comprises an optical system (shown here only schematically) including a reflector assembly 62 with a reflector comprising an upper reflector part 64a and lower reflector part 64b and a mounting portion 66 including a mounting opening 68 leading to an inner reflector space 70 partially surrounded by the upper and lower reflector parts 64a, 64b. Further, the optical system comprises a lens 72 arranged in front of the reflector assembly 62.

(25) As further shown schematically in FIG. 6, the lighting system 15 comprises a driver circuit 84 electrically connected via a cable and the power supply plug 90 to the lighting module 10.

(26) As shown in FIG. 6, the lighting module 10 is mounted to the reflector assembly 62 by attaching the lighting module 10 to the mounting portion 66 thereof, thereby inserting the protrusion portion 16 through the mounting opening 68 to protrude into the inner reflector space 70.

(27) The lighting module 10 is accurately positioned relative to the reflector assembly 62 such that the LED modules 30a, 30b are arranged at a specified, known position within the reflector space 70. Exact positioning is achieved by the positioning protrusions 28a, 28b, 36a, 36b and 38, which are received in corresponding reflector assembly alignment indentations (not shown in FIG. 6).

(28) Further, the lighting module 10 is fixed to the reflector assembly 62 by clamping (not shown).

(29) Thus, the lighting module 10 is attached exchangeably at the reflector assembly 62. The lighting module 10 may be exchanged by disconnecting the electrical plug connection 90, 40, loosening the mechanical clamping connecting (not shown) and then withdrawing the lighting module 10 from the reflector assembly 62 by backward movement along the axis X. Likewise, a replacement lighting module 10 may be installed, replacing the previous lighting module 10.

(30) FIG. 6 shows the arrangement of the LED elements 30a, 30b within the reflector space 70. Due to the partially backwards facing orientation of the LED elements 30a, 30b, the inner reflector surfaces of upper and lower reflector parts 64a, 64b are well illuminated and reflect the emitted light to form a first beam 80a and a second beam 80b which are projected by projection lens 72 as emitted beams.

(31) The LED elements 30a, 30b thus illuminate separate portions 64a, 64b of the reflector assembly 62. The shape of the reflector parts 64a, 64b may be chosen to obtain, in conjunction with the projection lens 72, desired light distributions of resulting beams 80a, 80b.

(32) For example, the lighting system 60 may form a headlight of a motor vehicle 82 as schematically shown in FIG. 8. The emitted low beam illumination 80a is generated from light emitted from the first LED element 30a, whereas the high beam illumination 80b is formed from light emitted from the second LED element 30b and from the first LED element 30a. Naturally, different beam patterns and combinations thereof are possible.

(33) The driver circuit 84 comprises, as schematically shown in FIG. 6, power circuitry 86 disposed to generate and switch electrical current/voltage as suited for the operation of the LED elements 30a, 30b, and a control circuit 88 to control the switching patterns of the voltage/current delivered from the power circuitry 86 to the LED elements 30a, 30b of the LED module 10.

(34) The driver 84 has separate electrical connections to the LED elements 30a, 30b via the cable, the power supply plug 90 and electrical plug connector 40, embedded conductors 50, contact surfaces 54 and ribbon bonds 56. Thus, the driver circuit 84 can operate the LED elements 30a, 30b separately and independently of one another, according to the switching patterns provided by the control circuit 88.

(35) The control circuit 88 is configured to operate the LED elements 30a, 30b of the lighting module 10 differently according to different lighting modes. In a first lighting mode, corresponding for example to a low beam mode, the driver 84 operates the lighting module 10 to emit the resulting low beam illumination 80a, i.e. comprising an at least substantially horizontal bright/dark cut off according to automotive regulations. In the low beam mode, the driver 84 supplies electrical operating power only to the first LED element 30a and not to the second LED element 30b, which thus remains turned off. The resulting low beam illumination 80a is generated from the light emitted from the first LED element 30a, reflected at the upper reflector part 64a and projected through projection lens 72 as a low beam pattern.

(36) Since the second LED element 30b is not operated in the low beam mode, only heat generated at the first LED element 30a must be dissipated by the heat sink 12.

(37) In a second mode of operation of the driver circuit 84 and of the lighting system 16 as a whole, which may be e.g. referred to as a high beam mode, the control circuit 88 controls the power circuitry 86 to supply more electrical operating power to the second LED element 30b than to the first LED element 30a. In the high beam mode, the resulting high beam illumination 80b is generated by the light emitted from the second LED element 30b, reflected at the lower reflector part 64b and projected by projection lens 72 as a high beam pattern, i.e. an intensity distribution without a horizontal bright/dark cut off, and by the light emitted from the first LED element 30a, reflected at the upper reflector part 64a and projected through projection lens 72 as a low beam pattern.

(38) In the high beam mode, both LED elements 30a, 30b are operated to emit light. However, the first LED element 30a is operated in the dimmed state, such that the generated heat that needs to be dissipated is less.

(39) Thus, the disjunct mode of operation of the first and second LED elements 30a, 30b in the high power state in the first and second operating mode allows to limit the thermal load to be dissipated by the heat sink 12.

(40) According to a second embodiment, FIG. 7a shows an electrical, logical connection of the LED elements 30a, 30b. A lighting module according to the second embodiment corresponds to the lighting module 10 according to the first embodiment. In the following, only differences between the first and the second embodiments will be elucidated. The same reference signs refer to the same elements.

(41) The first LED element 30a comprises ten equal, bare LED dies 31a, 31c which are allocated into a first group 33 and a second group 35. The first group 33 comprises four LEDs 31a of the ten bare LED dies 32 which are electrically connected in series. The second group 35 comprises the other six LEDs 31c which are analogously connected in series. The second LED element 30b comprises six equal, bare LED dies 31b. The LEDs 31b of the second LED element are also electrically connected in series.

(42) The LEDs 31c of the second group 35 are electrically connected in parallel with the LEDs 31b of the second LED element 30b. The LEDs 31a of the first group 33 are connected in series with the parallel connection comprising the second group 35 and the second LED element 30b. Driver means 84 are electrically connected between the first group 33 and the parallel connection.

(43) FIG. 7b exemplary shows a schematic illustration of an arrangement of the LEDs 31a, 31b, 31c. According to a lighting system of the second embodiment, the first LED element 30a is attached on a first mounting surface 26a and the second LED element 30b is attached on a second mounting surface 26b. The LEDs 31a, 31c of the first LED element 30a are arranged adjacent to each other within two horizontal rows. Six LEDs 31a, 31c are arranged in an upper row and the other four LEDs 31c are arranged in the other row directly subjacent of the upper row. Thereby, the first group 33 is arranged in the upper row while the second group 35 is arranged in the upper and in the subjacent row partially surrounding the first group 33. The LEDs 31b of the second LED element 30b are arranged adjacent to each other within one horizontal row.

(44) In a first mode, to realize a low beam illumination 80a, driver means 84 operate a switch such that the second group 35 and the first group 33 are electrically connected in series. Thus, the first LED element 30a is operated in a high power state because all its LEDs 31a, 31c are provided with electrical power. Therefore, in the first mode, all LEDs 31a, 31c that are attached on the first mounting area 26a emit light, while the LEDs 31b that are attached on the second mounting surface 26b remain turned off.

(45) In a second mode, to realize a high beam illumination 80b, driver means 84 operate a switch, such that the second LED element 30b and the first group 33 are electrically connected in series. All the LEDs 31b of the second LED element 30b and the serially connected LEDs 31a of the first group 33 emit light. Thus, the second LED element 30b is operated in a high power state because all its LEDs 31b are provided with electrical power, and the first LED element 30a is operated in a dimmed state to emit dimmed light because only the LEDs 31 that belong to the first group 33 are provided with electrical power. In the second mode, the LEDs 31b that are attached on the second mounting area 26b and the LEDs 31a of the first group 33 that are on the first mounting surface 26a emit light. The other LEDs 31c that are attached on the first mounting area 26a and that belong to the second group 35 remain turned off.

(46) In this embodiment, to switch between the disjunct first and second mode, the driver means 84 switch between the two paths of the parallel connection.

(47) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

(48) In particular, the specific shape of the lighting module 10 as shown should be considered exemplary; different shapes are possible. The shape of the heat sink 12 with a protrusion portion 16 is preferred, but different shapes are possible. The LED elements 30a, 30b which are shown as facing partially backwards may be arranged to face into different directions.

(49) The driver circuit 84, shown as a separate entity spaced from the LED module 10 may alternatively be integrated either into the LED module 10 or mounted to the reflector assembly 62.

(50) Further, different lighting functions besides high beam and low beam may be implemented, i.e. by providing different reflector shapes other beam types may be generated.

(51) These and other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

(52) In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.

(53) The mere fact that certain measures or features are recited in mutually different dependent claims or disclosed in separate embodiments does not indicate that a combination of these measures and features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.