WO2019137909A1

WO2019137909A1 - A led lamp and a method of controlling a led lamp

Info

Publication number: WO2019137909A1
Application number: PCT/EP2019/050332
Authority: WO
Inventors: Hexi QIN; Jiang Zhang
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2018-01-10
Filing date: 2019-01-08
Publication date: 2019-07-18
Anticipated expiration: 2020-07-10

Abstract

A LED lamp has a central LED group and at least one peripheral, i.e. annular, arrangement of LED groups, with a collimator lens provided over the LED array. The central LED group and the peripheral arrangement of LED groups can be driven independently to implement beam angle control and/or beam steering. This provides electronic control in way which does not impact on the optical efficacy of the lamp.

Description

A LED lamp and a method of controlling a LED lamp

FIELD OF THE INVENTION

This invention relates to LED lamps and in particular for providing a light output with a controllable beam width and/or direction.

BACKGROUND OF THE INVENTION

LED lighting is becoming increasing common in nearly all lighting applications. It offers low power consumption combined with the ability to create dynamic intensity and color lighting effects.

One function which is also desired in some lighting applications is control of the beam angle of an illumination beam, and/or control of a beam output direction.

One known way to implement an adjustable beam angle for an LED lamp is to use a telescopic tube. When the tube is retracted, a large beam angle is achieved, and when the tube is extended, a smaller beam angle is achieved.

A problem with this approach is that the optical efficacy is much lower than a standard LED lamp. It would be desirable to enable adjustable beam angle control and/or beam steering control but with comparable optical efficacy to a normal LED lamp.

Furthermore, it would be desirable for this controllability to be achieved without providing a high level of additional complexity to the driver arrangement.

US9470406 discloses light sources with arrangements of multiple LEDs (or other light-emitting devices) disposed at or near the focus of a reflecting optic having multiple segments facilitate varying the angular distribution of the light beam (e.g., the beam divergence) via the drive currents supplied to the LEDs.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a LED lamp, comprising: a LED array comprising a central LED group wherein the group has a first optical axis, and at least one peripheral arrangement of LED groups around the central group of LEDs;

a collimator lens provided over the LED array; and

a LED driver, which is adapted to drive independently at least the central LED group and the peripheral arrangement of LED groups thereby to implement beam angle control, wherein the LED driver is adapted to drive the central group of LEDs for generating a narrow beam and to drive at least the peripheral arrangement of LED groups for generating a wide beam.

This LED lamp makes use of an array of LEDs at different positions under a collimator lens. By selecting which LED group or LED groups to illuminate, the beam angle may be controlled. In particular, the lamp can switch between a narrow beam and a wide beam output with no moving parts. Note that the terms "narrow beam" and "wide beam" are simply used as relative terms, i.e. there is one drive configuration which generates a wider beam than the other. By way of example only, a narrow beam for example has a beam angle (the full cone angle) of less than 20 degrees whereas a wide beam for example has a beam angle (the full cone angle) of more than 20 degrees.

The peripheral arrangement of LED groups and the central LED group generate an output beam with different beam angles, and one may be selected, or the other, or a combination. The beam angle is selectable independently of output color. In other words, the same color output may be generated but with different beam angles. The LED array may be formed of LEDs all of the same color, but it is equally possible for the LED array to include LEDs of different color. For example, each LED group may itself comprise an array of different color LEDs.

By forming the LEDs into groups, the driving is simplified, in that there is a reduced number of channels.

By "optical axis" of a group of LEDs is meant a general illumination direction, for example a direction about which the light distribution has the greatest rotational symmetry, when all LEDs of the group are illuminated. It is for example a normal direction to the light emitting surface of the individual LEDs within the group and extending from a center of area of the group of LEDs.

The peripheral groups of LEDs surround the central group, thus forming a closed shape i.e. an annulus around the central group. The LED groups in the peripheral arrangement for example lie on a circular path, but they may for example form a square (if there are four LED groups in the peripheral group) or any other polygonal shape.

In one arrangement, the LED driver is adapted to drive independently the central LED group, a first sub-group of the peripheral arrangement of LED groups for creating a first elongate beam shape and a second sub-group of the peripheral arrangement of LED groups for creating an elongate beam shape in an orthogonal direction to the first elongate beam shape.

This requires only three driver channels to enable a wide symmetric beam, a narrow symmetric beam or generally elliptical beams (in two possible orthogonal orientations) to be created.

The collimator lens may comprise:

a solid body having a first cavity extending into the solid body from a first outer surface, with the LED array provided in the vicinity of the first outer surface at an opening of the first cavity and an end of the first cavity defining a collimating lens surface;

a light exit surface having a larger area than the first outer surface of the solid body; and

a side wall extending between the first outer surface of the solid body and the light exit surface.

This defines a collimator in the form of a solid body, for example of the type known as a tulip collimator. This is a low cost and compact collimator design. Light rays emitted near to the normal are refracted by a lens surface, and light rays with a larger angle to the normal are reflected from the side wall.

The side wall may provide reflection by total internal reflection.

The first cavity is for example circular in cross section perpendicular to the first optical axis. This enables a rotationally symmetric design.

The first cavity may be aligned along the first optical axis and is a cylinder or a conical frustum with a slant angle of less than 10 degrees.

The angle of the conical frustum is for example simply sufficient to function as a draft angle for injection molding purposes.

The opening of the first cavity (which is coplanar with the first outer surface) is for example circular with a radius R and the peripheral arrangement of LED groups is arranged around the optical axis with a radius not less than 0.5R.

In this way, the LEDs in the peripheral arrangement have a significant displacement from the optical axis so that they create a differently directed output beam. The light exit surface may comprise a diffusive surface.

This diffusive surface may be provided over the outermost part of the light exit surface, and also over any recess provided in that surface (discussed below). The diffusive surface may be formed as a microlens surface or other kinds of surface texture.

The solid body may have a second cavity extending into the solid body from the light exit surface. The use of this cavity reduces light loss through the solid body as well as reducing weight of the optical component.

The second cavity is preferably also aligned along the first optical axis and is a cylinder or a conical frustum with a slant angle of less than 10 degrees. The angle of the conical frustum is again for example simply sufficient to function as a draft angle for injection molding purposes.

The second cavity for example has a larger maximum radius than the maximum radius of the first cavity. Thus, it provides a significant reduction in weight.

The peripheral arrangement of LED groups for example comprises four groups of LEDs at 90-degree angular separation.

This enables each LED group to direct a beam generally in one of four orthogonal directions (i.e. up, down, left, right) and by selecting a suitable combination, beam steering is possible. The LED groups may be selected in opposing pairs to general an elongate e.g. elliptical beam shape.

The LED driver may instead be adapted to drive independently the central LED group and each LED group of the peripheral arrangement of LED groups thereby to implement beam angle control and beam steering. This requires more channels (one for each LED group) but gives additional control options.

The collimator lens for example comprises a body of glass or a polymer selected from poly (methyl methacrylate) (PMMA), polycarbonate and polyethylene terephthalate or a blend of one of more of these polymers. One option is a lens body of poly (methyl methacrylate.

The invention also provides a method of controlling a LED lamp which comprises a LED array comprising a central LED group wherein the group has a first optical axis and at least one peripheral arrangement of LED groups around the central LED group; and a collimator lens provided over the LED array, wherein the method comprises:

driving independently the central LED group, a first sub-group of the peripheral arrangement of LED groups for creating a first elongate beam shape and a second sub-group of the peripheral arrangement of LED groups for creating an elongate beam shape in an orthogonal direction to the first elongate beam shape.

The method may comprise driving the central LED group for generating a narrow beam; and driving at least the peripheral arrangement of LED groups for a generating a wide beam, thereby to implement beam angle control.

The method may comprise driving independently all of the LED groups thereby to implement beam angle and beam steering control.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 shows a LED lamp;

Figure 2 shows a multi-channel LED driver for driving the lamp;

Figure 3 shows the light output paths from the central group of LEDs and separately the light output paths from one LED group from the peripheral arrangement;

Figure 4 shows a table of possible drive levels to the three channels of the driver of Figure 2; and

Figure 5 shows a method of controlling a LED lamp.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides a LED lamp, having a central LED group of LEDs and at least one peripheral, i.e. annular, surrounding arrangement of LED groups, with a collimator lens provided over the LED array. The central LED group and the peripheral arrangement of LED groups can be driven independently to implement beam angle control and/or beam steering. This provides electronic control in way which does not impact on the optical efficacy of the lamp.

Figure 1 shows a LED lamp 10, comprising a LED array 12 on a substrate 13 such as a PCB and a collimator lens 14 provided over the LED array. The lamp is shown in cross section in the top part and from beneath in the bottom part (to show the LED array design).

As shown in the top part of Figure 1, the collimator lens 14 comprises a solid body 16 having a first cavity 18 extending into the solid body from a first outer surface 20, in particular a base of the solid body, where "base" is used to mean the region where the LED array is located. Thus, the LED array 12 is provided in the vicinity of the first outer surface 20 at an opening of the first cavity 18. The first cavity is generally cylindrical, although it may have a draft angle to assist in injection molding of the solid body, for example from a plastics material such as PMMA. This draft angle is for example less than 10 degrees (on each side, i.e. opposing regions have an angle of less than 20 degrees to each other).

The solid body may be PMMA as mentioned above, but it may instead be a body of glass or a polymer selected from poly (methyl methacrylate), polycarbonate and polyethylene terephthalate or a blend of one of more of these polymers.

A bottom end of the first cavity 18, i.e. opposing the location of the LED array 12, defines a collimating lens surface 22.

The body 16 has a light exit surface 24 opposite the first surface 20. In particular, this light exit surface may be considered to be the top. This has a larger area than the first outer surface 20 of the solid body so that the body forms a tulip shape.

A side wall 26 extends between the first outer surface 20 of the solid body 16 (the base) and the light exit surface 24 (the top).

The solid body has an axis 28 of rotational symmetry and this functions as the general optical axis of the lamp, namely an axis about which the light output from the lamp has the greatest degree of rotational symmetry (when all LEDs are illuminated). This axis is normal (i.e. perpendicular) to a light exit surface of the LEDs of the LED array. The cavity 18 has a central length axis aligned with the optical axis 28.

Light rays emitted near to this normal are refracted by the lens surface 22, and light rays with a larger angle to the normal are reflected from the side wall 26. The side wall 26 provides reflection by total internal reflection.

The opening of the first cavity 18 is circular with a radius R (and hence diameter 2R as shown). As shown in the bottom part of Figure 1, the LED array 12 comprises a central LED group 120 of LEDs wherein the central group has a first optical axis corresponding to the axis 28, and at least one peripheral arrangement of LED groups 122, 124, 126, 128 around the central group 120 of LEDs.

In the example shown, there is one central group 120 centered on the optical axis 28 and four LED groups around the outside, forming an annulus (i.e. any closed shape around the central group 120). The LED groups of the peripheral arrangement are uniformly angularly spaced around the central group so that in the example shown they form a square.

The peripheral arrangement of LED groups 122, 124, 126, 128 is arranged around the optical axis with a radius not less than 0.5R. In this way, the LEDs in the peripheral arrangement have a significant displacement from the optical axis 28 so that they create a differently directed output beam primarily as a result of the different positioning with respect to the lens surface 22.

The solid body 16 also has a second cavity 30 extending into the solid body 16 from the light exit surface 24. This cavity is used to reduce light loss through the solid body as well as reducing weight of the optical component.

The second cavity 30 is also aligned along the optical axis 28 and is also a cylinder or a conical frustum with a slant angle of less than 10 degrees (on each side), again for injection molding purposes.

The second cavity is larger than the first cavity, namely with a larger maximum radius than the maximum radius of the first cavity 18.

Figure 2 shows that the LED lamp is driven by a LED driver 40, which is adapted to drive independently at least the central LED group and the peripheral arrangement of LED groups 122, 124, 126, 128 thereby to implement beam angle control. In the example shown, the LED driver has three channels. Channel 1 is for the central LED group 120. Channel 2 is for the left and right LED groups 124, 128 and channel 3 is for the top and bottom LED groups 122, 126.

This enables a small number of channels to enable various effects. If only the central LED group 120 is actuated, a narrow beam results in a normal direction (along the optical axis 28). If all LED groups are actuated, a wide beam results in a normal direction. The intensity of the central part of the beam can be controlled by using or not using the central group. If only the left and right LED groups are actuated (with or without the central group) a generally elliptical output beam shape is provided with a length axis in the left-right direction.

If only the top and bottom LED groups are actuated (with or without the central group) a generally elliptical output beam shape is provided with a length axis in the up-down direction.

Thus, as a minimum, the LED driver is able to drive the central group of LEDs for generating a narrow beam and to drive at least the peripheral arrangement of LED groups for a generating a wide beam.

For the three-channel arrangement, there is more generally a first channel for a central LED group, a second channel for driving LED groups to create an elongate beam shape in a first direction and a third channel for driving LED groups to create an elongate beam shape with an orthogonal orientation. When the first channel is operated, a generally rotationally symmetric narrow beam is produced. When the second and third channels are operated together a generally rotationally symmetric wide beam is produced.

There may instead be 5 channels, one for each LED group. This gives additional freedom to provide beam steering by actuating individual LED groups, but at the expense of a more complicated driver, with more independent channels.

There may be two annular LED group arrangements around the central LED group, to give a three-level structure. Even with two levels, the central group may itself be formed as a ring of LEDs.

Generally, the LED lamp makes use of an array of LEDs at different positions under a the collimator lens. By selecting which LED group or LED groups to illuminate, the beam angle may be controlled.

The beam angle is selectable independently of output color. In other words, the same color output may be generated but with different beam angles. The LED array may be formed of LEDs all of the same color, but it is equally possible for the LED array to include LEDs of different color. For example, each LED group may itself comprise an array of different color LEDs. By providing more channels, color control may be achieved. For example each channel shown in Figure 2 may be dividing into three sub-channels to enable beam angle/shape control as well as output color control.

Figure 3 shows in the top part the light output paths from the central group 120 of LEDs, to show a narrow beam directed in a normal direction. Figure 3 shows in the bottom part the light output paths from one LED group 128 from the peripheral arrangement, to show a beam directed in an off-axis direction.

The light exit surface 24 may comprise a diffusive surface. This diffusive surface may be provided over the outermost part of the light exit surface shown as 24a in Figure 1 , and also over the base of the second cavity 30 shown as 24b in Figure 1. The diffusive surface may be formed as a microlens surface or other kinds of surface texture.

Figure 4 shows a table of possible drive levels to the three channels (Chl, Ch2 and Ch3) for the example above. It shows various options which create the same overall light output flux.

The columns of the table show the drive levels as in terms of the flux level (in units of candela (cd)) to be output by the central FED group (C), the upward FED group (U), the downward FED group (D), the left FED group (F) and the right FED group (R). The next column is the summation (SUM) of these flux levels. The next column is the beam angle (BA) and the next is the optical efficiency (O.E.).

The beam angle is the full width at half maximum (FWHM) angle.

The final column shows a schematic representation of the light distribution.

The first row of data shows the central FED group as dominant, giving a narrow beam profile. The intensity of the output from the central group is kept to a limit (185) and the other FED groups are used to contribute to the overall light output (385). Of course, if the central group can create sufficient light intensity alone, an even narrower beam may be obtained.

The second row of data shows equal driving of the five FED groups, thereby giving a larger beam angle.

The third row shows increased flux to the peripheral FED groups (and reduced flux to the central group to maintain the same overall flux) giving an even wider beam angle. The fourth row shows yet further increased flux to the peripheral FED groups (and reduced flux to the central group to maintain the same overall flux) giving an even wider beam angle.

The fifth row shows yet further increased flux to the peripheral FED groups (and reduced flux to the central group to maintain the same overall flux) giving an even wider beam angle.

These measures enable control of the beam angle from 11.8 degrees to 40 degrees while maintaining the same overall flux.

The last row shows an asymmetric beam shape by using only the up and down FED groups and the central group (to a small degree). The beam angle is 53 degrees and 27 degrees in two orthogonal directions. Of course, many other control settings are possible, and a five-channel system will enable beam steering as well as beam shaping.

Figure 5 shows a method of controlling a LED lamp which comprises a LED array comprising a central LED group wherein the group has a first optical axis and at least one peripheral arrangement of LED groups around the central LED group; and a collimator lens provided over the LED array, wherein the method comprises:

in step 50, driving the central LED group for generating a narrow beam; and in step 52 driving at least the peripheral arrangement of LED groups for a generating a wide beam, thereby to implement beam angle control.

The center LED group may comprise a single LED although it may also comprise an array of LEDs. Similarly, each LED group may comprise one or more individual LEDs.

The LED lamp of the invention is for example of interest for applications such as retail stores and museums, where changes in layout may take place regularly, and

corresponding changes in lighting characteristics are desired.

Other variations to 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. 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. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A LED lamp (10), comprising:

a LED array (12) comprising a central LED group (120) wherein the group has a first optical axis and at least one peripheral arrangement of LED groups (122, 124, 126, 128) around the central LED group;

a collimator lens (14) provided over the LED array; and

a LED driver (40), which is adapted to drive independently at least the central LED group and the peripheral arrangement of LED groups (122, 124, 126, 128) thereby to implement beam angle control, wherein the LED driver is adapted to drive the central LED group for generating a narrow beam and to drive at least the peripheral arrangement of LED groups for generating a wide beam;

wherein the LED driver (40) is adapted to drive independently the central LED group (120), a first sub-group of the peripheral arrangement of LED groups for creating a first elongate beam shape and a second sub-group of the peripheral arrangement of LED groups for creating an elongate beam shape in an orthogonal direction to the first elongate beam shape.

2. A LED lamp as claimed in claim 1, wherein the collimator lens comprises:

a solid body (16) having a first cavity (18) extending into the solid body from a first outer surface (20), with the LED array (12) provided in the vicinity of the first outer surface at an opening of the first cavity (18) and an end of the first cavity defining a collimating lens surface (22);

a light exit surface (24) having a larger area than the first outer surface (20) of the solid body; and

a side wall (26) extending between the first outer surface (20) of the solid body and the light exit surface (24).

3. A LED lamp as claimed in claim 2, wherein the first cavity (18) is circular in cross section perpendicular to the first optical axis (28).

4. A LED lamp as claimed in claim 3, wherein the first cavity (18) is aligned along the first optical axis (28) and is a cylinder or a conical frustum with a slant angle of less than 10 degrees.

5. A LED lamp as claimed in claim 3 or 4, wherein the opening of the first cavity (18) is circular with a radius R and the peripheral arrangement of LED groups is arranged around the optical axis with a radius not less than 0.5R.

6. A LED lamp as claimed in any one of claims 2 to 5, wherein the light exit surface (24) comprises a diffusive surface.

7. A LED lamp as claimed in any preceding claim, wherein the solid body (16) has a second cavity (30) extending into the solid body (16) from the light exit surface.

8. A LED lamp as claimed in claim 7, wherein the second cavity (30) is aligned along the first optical axis and is a cylinder or a conical frustum with a slant angle of less than 10 degrees.

9. A LED lamp as claimed in claim 8, wherein the second cavity has a larger maximum radius than the maximum radius of the first cavity (18).

10. A LED lamp as claimed in any preceding claim, wherein the peripheral arrangement of LED groups comprises four groups of LEDs at 90-degree angular separation.

11. A LED lamp as claimed in any one of claims 1 to 9, wherein the LED driver (40) is adapted to drive independently the central LED group (120) and each LED group of the peripheral arrangement of LED groups (122, 124, 126, 128) thereby to implement beam angle control and beam steering.

12. A LED lamp as claimed in any preceding claim, wherein the collimator lens comprises a body of glass or a polymer selected from poly (methyl methacrylate), polycarbonate and polyethylene terephthalate, or a blend of these polymers.

13. A method of controlling a LED lamp (10) which comprises a LED array (12) comprising a central LED group (120) wherein the group has a first optical axis and at least one peripheral arrangement of LED groups (122, 124, 126, 128) around the central LED group; and a collimator lens (14) provided over the LED array, wherein the method comprises:

driving independently the central LED group (120), a first sub-group of the peripheral arrangement of LED groups for creating a first elongate beam shape and a second sub-group of the peripheral arrangement of LED groups for creating an elongate beam shape in an orthogonal direction to the first elongate beam shape.

14. A method as claimed in claim 13, comprising driving the central LED group for generating a narrow beam; and

driving at least the peripheral arrangement of LED groups for a generating a wide beam, thereby to implement beam angle control.

15. A method as claimed in claim 13, comprising driving independently all of the LED groups thereby to implement beam angle and beam steering control.