LIGHT SYSTEM WITH ANTI-PARALLEL LEDS

Abstract

Example embodiments relate to light system with anti-parallel LEDs. One example light system includes a driver configured to generate a DC current. The light system also includes at least one first group, a first group thereof including a first and a second LED connected in anti-parallel. The light system also includes at least one second group, a second group thereof including a first and a second LED connected in anti-parallel. The at least one second group is connected in series with the at least one first group. Additionally, the light system includes control circuitry configured for selectively operating the first and second group in at least one first one and at least one second mode.

Claims

1. A light system, comprising: a driver configured to generate a DC current, at least one first group, a first group thereof comprising a first and a second LED connected in anti-parallel, at least one second group, a second group thereof comprising a first and a second LED connected in anti-parallel; said at least one second group being connected in series with said at least one first group, and control circuitry configured for selectively operating the first and second group in at least one first mode and at least one second mode, wherein in the at least one first mode, the DC current is used to activate the first LED(s) of at least one of: the at least one first group or the at least one second group; and in the at least one second mode, the DC current is used to activate the second LED(s) of at least one of: the at least one first group or the at least one second group.

2. The light system according to claim 1, further comprising: a first optical element associated with the first and second LED of the first group; and/or a second optical element associated with the first and second LED of the second group.

3. The light system according to claim 1, further comprising a single optical element associated with the first and second LEDs of the first group and the second group.

4. The light system according to claim 2, wherein each optical element is a lens element.

5. The light system according to claim 1, wherein the at least one first group comprises at least two first groups connected in series, preferably at least three first groups, and/or wherein the at least one second group comprises at least two second groups connected in series, preferably at least three second groups.

6. The light system according to claim 2, further comprising an optical plate with a plurality of optical elements, wherein each first and/or second group is associated with an optical element of said optical plate.

7. The light system according to claim 1, wherein the at least one first mode comprises at least two of the following: a common first mode wherein the first LEDs of the at least one first group and the at least one second group are activated; a first mode wherein the first LED(s) of the at least one first group are activated and the first LED(s) of the at least one second group are not activated; a further first mode wherein the first LED(s) of the at least one second group are activated and the first LED(s) of the at least one first group are not activated; and/or wherein the at least one second mode comprises at least two of the following: a common second mode wherein the second LEDs of the at least one first group and the at least one second group are activated; a second mode wherein the second LED(s) of the at least one first group are activated and the second LED(s) of the at least one second group are not activated; a further second mode wherein the second LED(s) of the at least one second group are activated and the second LED(s) of the at least one first group are not activated.

8. The light system according to claim 1, wherein the first and second LED of the first group each have a first terminal connected to a first common line portion, and wherein the first and second LED of the second group each have a first terminal connected to a second common line portion wherein optionally the first common line portion runs parallel to the second common line portion, and wherein the first common line portion is connected to the second common line portion at an end portion thereof, wherein preferably the first and second LED of the first group each have a second terminal which is connected to a further common line portion in line with the first common line portion, and wherein the first and second LED of the second group each have a second terminal which is connected to a further common line portion in line with the second common line portion.

9. (canceled)

10. (canceled)

11. The light system according to claim 1, wherein the control circuitry is configured for at least one of: switching between a first mode of the at least one first mode and a second mode of the at least one second mode, such that the DC current provided by the driver before, during, and after the switching, is substantially the same; receiving the DC drive current from the driver; and directing the DC current through the at least one first and/or second group, without dimming, in accordance with a first or second mode of the at least one first and second mode.

12. (canceled)

13. The light system according to claim 1, wherein the control circuitry comprises at least a first branch with two switching elements connected in series, and a second branch with two switching elements connected in series, said first branch being connected in parallel with said second branch between a first current line for receiving the DC current from the driver and a second current line wherein a first intermediate node between the two switching elements of the first branch is connected to the first group and a second intermediate node between the two switching elements of the second branch is connected to the second group, wherein optionally the control circuitry is further configured for controlling the switching elements such that in a first common mode, the current from the driver flows from the first intermediate node through the first LEDs of the at least one first and second group to the second intermediate node, and such that in a second common mode, the current from the driver flows from the second intermediate node through the second LEDs of the at least one first and second group to the first intermediate node.

14. (canceled)

15. The light system according to claim 13, wherein the control circuitry further comprises a third branch with two switching elements connected in series, said third branch being arranged in parallel with the first and second branch, wherein a third intermediate node between the two switching elements of the third branch is connected to an intermediate node between the at least one first group and the at least one second group, wherein optionally the control circuitry is further configured such that in a first mode, the current from the driver flows from the first intermediate node through the first LED(s) of the at least one first group to the third intermediate node, and such that in a second mode, the current from the driver flows from the third intermediate node through the second LED(s) of the at least one first group to the first intermediate node; and/or such that in a further first mode, the current from the driver flows from the second intermediate node through the first LED(s) of the at least one second group to the third intermediate node, and such that in a further second mode, the current from the driver flows from the third intermediate node through the second LED(s) of the at least one second group to the second intermediate node.

16. (canceled)

17. The light system according to claim 1, wherein the control circuitry is configured to: receive at least one of: a desired light pattern or a control parameter, as an input, to select a control scheme out of a plurality of different stored control schemes in accordance with the at least one of: the desired light pattern or the control parameter; and control the control circuitry in accordance with the selected control scheme.

18. (canceled)

19. (canceled)

20. The light system according to claim 1, wherein the first LED and the second LED have substantially the same forward biasing voltage.

21. The light system according to claim 1, wherein the first group comprises a plurality of first LEDs connected in anti-parallel with one or more second LED(s); and/or wherein the second group comprises a plurality of first LEDs connected in anti-parallel with one or more second LED(s).

22. (canceled)

23. The light system according to claim 1, wherein the first LED is different from the second LED, wherein optionally the first LED has substantially the same forward biasing voltage as the second LED but a different phosphor coating.

24. (canceled)

25. (canceled)

26. (canceled)

27. A luminaire comprising a light system according to claim 1.

28. A light system, comprising: at least one first group, a first group thereof comprising a first and a second LED connected in anti-parallel, at least one second group, a second group thereof comprising a first and a second LED connected in anti-parallel; said at least one second group being connected in series with said at least one first group, and control circuitry configured for selectively operating the first and second group in at least one first mode and at least one second mode, wherein in the at least one first mode, the first LED(s) of at least one of the at least one first group, the at least one second group, are activated; and in the at least one second mode, the second LED(s) of at least one of the at least one first group, the at least one second group, are activated, at least one of: a first optical element associated with the first and second LED of the first group or a second optical element associated with the first and second LED of the second group.

29. A light system, comprising: at least one first group, a first group thereof consisting of a first and a second LED connected in anti-parallel, at least one second group, a second group thereof consisting of a first and a second LED connected in anti-parallel; said at least one second group being connected in series with said at least one first group, and control circuitry configured for selectively operating the first and second group in at least one first mode and at least one second mode, wherein in the at least one first mode, the first LED(s) of at least one of the at least one first group, the at least one second group, are activated; and in the at least one second mode, the second LED(s) of at least one of the at least one first group, the at least one second group, are activated, wherein the control circuitry comprises at least a first branch with two switching elements connected in series, a second branch with two switching elements connected in series, said first branch being connected in parallel with said second branch between a first current line for receiving a DC current and a second current line, wherein a first intermediate node between the two switching elements of the first branch is connected to the first group and a second intermediate node between the two switching elements of the second branch is connected to the second group and a third branch with two switching elements connected in series, said third branch being arranged in parallel with the first and second branch, wherein a third intermediate node between the two switching elements of the third branch is connected to an intermediate node between the at least one first group and the at least one second group.

30. The light system of claim 29, wherein the control circuitry is further configured such that in a first mode, the current from the driver flows from the first intermediate node through the first LED(s) of the at least one first group to the third intermediate node, and such that in a second mode, the current from the driver flows from the third intermediate node through the second LED(s) of the at least one first group to the first intermediate node; and/or such that in a further first mode, the current from the driver flows from the second intermediate node through the first LED(s) of the at least one second group to the third intermediate node, and such that in a further second mode, the current from the driver flows from the third intermediate node through the second LED(s) of the at least one second group to the second intermediate node.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0072] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of light systems of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0073] FIGS. 1A and 1B are circuit diagrams of two exemplary embodiments of a light system;

[0074] FIG. 2 is a circuit diagram of an exemplary embodiment of an invertor for use in a light system;

[0075] FIG. 3A shows circuit diagrams and a table illustrating the operation of a first exemplary embodiment with a single first and second group, and of a second exemplary embodiment with multiple first and second groups, of a light system which is similar to FIG. 1A;

[0076] FIG. 3B shows circuit diagrams and a table illustrating the operation of a first exemplary embodiment with a single first and second group, and a second exemplary embodiment with multiple first and second groups, of a light system which is similar to FIG. 1B;

[0077] FIGS. 4A, 4B and 4C are circuit diagrams of three exemplary embodiments of a light system illustrating how the groups may be arranged on one or more PCBs;

[0078] FIG. 5A shows a top view of a portion of a PCB with LED circuitry according to the prior art;

[0079] FIG. 5B shows a top view of a portion of a PCB on which two first and two second groups are arranged in accordance with an exemplary embodiment;

[0080] FIGS. 5C and 5D are a circuit diagrams of prior art circuits arranged on a PCB;

[0081] FIG. 6 is a circuit diagram illustrating a variant of the embodiment of FIG. 5B;

[0082] FIG. 7 is a circuit diagram of an exemplary embodiment of a light system with multiple first and second LEDs in a single group;

[0083] FIG. 8A-8C illustrate various exemplary embodiments combining a plurality of sets of four LEDs, with each set comprising a first and a second group connected in series; and FIG. 9 is a circuit diagram of a more complex exemplary embodiment illustrating that many variations of the previously described embodiments are possible.

DESCRIPTION OF EMBODIMENTS

[0084] FIG. 1A illustrates a first exemplary embodiment of a light system. The light system comprises a driver 10 configured to generate a DC current I, a control circuitry 20, a first group G1 of LEDs 1, 2 and a second group G2 of LEDs 1, 2. The first group G1 comprises a first LED 1 and a second LED 2 connected in anti-parallel, and the second group G2 comprises a first LED 1 and a second LED 2 connected in anti-parallel. The second group G2 is connected in series with the first group G1. The control circuitry 20 is inserted between the driver 10 and the LEDs 1, 2 and is configured for selectively operating the LEDs 1, 2 of the first and second group G1, G2 in a first mode M1 and a second mode M2. The control circuitry 20 has two outputs A, B, and the current I is sent either from A to B (first mode M1) or from B to A (second mode M2).

[0085] In the first mode M1, the DC current I is used to activate the first LEDs 1 of the first group G1 and the second group G2, whilst the second LEDs 2 are off. In the second mode M2, the DC current I is used to activate the second LEDs 2 of the first group G1 and the second group G2, whilst the first LEDs 1 are off. In other words, depending on the mode M1, M2, either the first LEDs 1 or the second LEDs 2 are switched on.

[0086] FIG. 1B illustrates a second exemplary embodiment of a light system. The light system comprises a driver 10 configured to generate a DC current I, a control circuitry 20, a first group G1 of LEDs 1, 2 and a second group G2 of LEDs 1, 2. The DC current is a regulated DC current. The first group G1 comprises a first LED 1 and a second LED 2 connected in anti-parallel, and the second group G2 comprises a first LED 1 and a second LED 2 connected in anti-parallel. The second group G2 is connected in series with the first group G1. The control circuitry 20 is inserted between the driver 10 and the LEDs 1, 2 and is configured for selectively operating the first and second group G1, G2 in a plurality of first modes M1′, M1′ and in a plurality of second modes M2′, M2″. The control circuitry 20 has three outputs A, B, C. The first output A is connected to the first group, the second output B is connected to the second group and the third output C is connected to an intermediate node 15 between the first and the second group. The control circuitry 20 is configured such that the current I is sent either from A to C (first mode M1′) or from C to A (second mode M2′), or from C to B (first mode M1″), or from B to C (second mode M2″).

[0087] In the first mode M1′, the DC current I is used to activate the first LED 1 of the first group G1, whilst all other LEDs 1, 2 are off. In the second mode M2′, the DC current I is used to activate the second LED 2 of the first group G1, whilst all other LEDs 1, 2 are off. In the other first mode M1″, the DC current I is used to activate the first LED 1 of the second group G2, whilst all other LEDs 1, 2 are off. In the other second mode M2″, the DC current I is used to activate the second LED 2 of the second group G2, whilst all other LEDs 1, 2 are off. In other words, depending on the mode M1′, M1″, M2′, M2″, any one of the LEDs 1, 2 can be switched on, whilst the other LEDs 1, 2 are switched off. Thus, using three control channels A, B, C, four LEDs 1, 2 can be individually controlled. Thus, in such an embodiment, the load seen by the driver 10 is substantially constant and consists in this example of one LED 1 or 2.

[0088] In the embodiments of FIGS. 1A and 1B there is provided a first optical element L1, preferably a lens element, associated with the first and second LED 1, 2 of the first group G1 and a second optical element L2 associated with the first and second LED 1, 2 of the second group G2. In other embodiments an optical element may be associated with only one LED or with more than two LEDs, see also FIGS. 4A and 4B. Preferably, the optical elements L1, L2 are integrated in a single optical plate. For example, the optical elements L1, L2 may be free-form lens elements integrated in a lens plate.

[0089] FIG. 2 illustrates an exemplary embodiment of control circuitry 20. The control circuitry 20 comprises a first branch 100 with two switching elements Q1, Q2, here MOSFETs, connected in series, a second branch 200 with two switching elements Q3, Q4 connected in series, and a third branch 300 with two switching elements Q5, Q6 connected in series. When the control circuitry 20 of FIG. 2 is used to implement the embodiment of FIG. 1A, the third branch 300 may be omitted. The first branch 100 is connected in parallel with the second branch 200 and with the third branch 300, between a first current line 101 for receiving the DC current from the driver 10 and a second current line 102, see also FIGS. 1A and 1B. Optionally, a further branch 350 may be provided which can be activated during switching of any one of the switches Q1-Q6, in order to reduce or avoid discontinuities of the current provided by the driver 10. In the illustrated example the further branch 350 comprises a resistor and a MOSFET Q7, but many other implementations are possible.

[0090] Preferably, the control circuitry 20 is further configured for switching between a first mode of the at least one first mode and a second mode of the at least one second mode, such that the DC current I provided by the driver before, during, and after the switching, is within 30% of a nominal value, preferably within 20% of a nominal value, more preferably within 10% of a nominal value. This may be achieved by appropriately controlling the switches Q1-Q6 and optionally by adding filter elements and/or cross conduction elements such as the optional branch 350 in order to reduce any current ripple and/or flicker. More generally, any solution known to the skilled person to achieve this goal may be used. The control circuitry 20 is configured for receiving the DC drive current I from the driver, and for directing the DC current through the at least one first and/or second group, without dimming, in accordance with a first or second mode of the at least one first and second mode, by switching the switches Q1-Q6. It is noted that in this embodiment the control circuitry 20 does not perform dimming. However, dimming may be implemented in the driver 10. Embodiments of the invention may be performed with any standard driver 10 and optionally the driver 10 may include dimming functionalities.

[0091] FIG. 3A illustrates the operation of a first exemplary embodiment which is similar to the embodiment of FIG. 1A, using the control circuitry of FIG. 2. A first intermediate node 105 between the two switching elements Q1, Q2 of the first branch 100 is connected (see the indication A in FIG. 2 and in FIG. 3A) to the first group G1 and a second intermediate node 205 between the two switching elements Q3, Q4 of the second branch is connected (see the indication B in FIG. 2 and FIG. 3A) to the second group G2.

[0092] The control circuitry 20 is further configured for controlling the switching elements Q1, Q2, Q3, Q4 such that in a first common mode M1, the current I from the driver 10 flows from the first intermediate node 105 through the first LEDs 1 of the at least one first and second group G1, G2 to the second intermediate node 205, i.e. the current flows from A to B in mode M1. This is achieved by switching on Q1 and Q4 and by switching off Q2 and Q3, as shown in the table of FIG. 3A. The control circuitry 20 is further configured for controlling the switching elements Q1, Q2, Q3, Q4 such that in a second common mode M2, the current I from the driver 10 flows from the second intermediate node 205 through the second LEDs 2 of the at least one first and second group G1, G2 to the first intermediate node 105, i.e. the current flows from B to A in mode M2. This is achieved by switching off Q1 and Q4 and by switching on Q2 and Q3, as shown in the table of FIG. 3A.

[0093] As illustrated in the two circuit diagrams of FIG. 3A, either a single first and second group G1, G2 may be present, or multiple first and/or second groups G1, G2 may be present. It is noted that in the embodiment of FIG. 3A, the groups G1, G2 may be identical and may all be indicated with reference letter G instead of making a distinction between G1 and G2.

[0094] FIG. 3B illustrates the operation of a second exemplary embodiment which is similar to the embodiment of FIG. 1B, using the control circuitry of FIG. 2. A first intermediate node 105 between the two switching elements Q1, Q2 of the first branch 100 is connected (see the indication A in FIG. 2 and in FIG. 3B) to the first group G1 and a third intermediate node 305 between the two switching elements Q5, Q6 of the third branch 300 is connected (see the indication C in FIG. 2 and in FIG. 3B) to the second group G2. The second intermediate node 205 between the two switching elements Q3, Q4 of the second branch 200 is connected (see the indication B in FIG. 2 and in FIG. 3B) to an intermediate node 15 between the at least one first group G1 and the at least one second group G2.

[0095] The control circuitry 20 is further configured for controlling the switching elements Q1, Q2, Q3, Q4, Q5, Q6 such that in a first common mode M1′, the current I from the driver 10 flows from the first intermediate node 105 through the first LEDs 1 of the at least one first group G1 to the second intermediate node 205, i.e. the current flows from A to B in mode M1′. This is achieved by switching on Q1, Q4 and Q6 and by switching off Q2, Q3 and Q5, as shown in the table of FIG. 3B. The control circuitry 20 is further configured for controlling the switching elements Q1, Q2, Q3, Q4, Q5, Q6 such that such that in a second common mode M2′, the current I from the driver 10 flows from the second intermediate node 205 through the second LEDs 2 of the at least one first group G1 to the first intermediate node 105, i.e. the current flows from B to A in mode M2′. This is achieved by switching off Q1, Q4 and Q6 and by switching on Q2, Q3 and Q5, as shown in the table of FIG. 3B. The control circuitry 20 is further configured such that in a further first mode M1″, the current I from the driver 10 flows from the second intermediate node 205 through the first LED(s) 1 of the at least one second group G2 to the third intermediate node 305, i.e. from B to C, and such that in a further second mode M2″, the current I from the driver 10 flows from the third intermediate node 305 through the second LED(s) 2 of the at least one second group G2 to the second intermediate node 205, i.e. from C to B.

[0096] As illustrated in the two circuit diagrams of FIG. 3B, either a single first and second group G1, G2 may be present, or multiple first and/or second groups G1, G2 may be present.

[0097] FIGS. 4A and 4B illustrate two further exemplary embodiments, which operate along the same principles as the embodiment of FIGS. 1B and 3B, and wherein the same components have been indicated with the same reference numerals. In the embodiment of FIG. 4A, a string of eight first groups G1 is connected in series with a string of eight second groups G2. A first end of the string of first groups G1 is connected to an output A of the control circuitry 20, and a second end of the string of first groups G1 is connected to the string of second groups G2. Similarly, a first end of the string of second groups G2 is connected to an output C of the control circuitry 20, and a second end of the string of second groups G2 is connected to the second end of the string of first groups G1. An intermediate node 15 between the first and second string is connected to an output B of the control circuitry. This is similar to the embodiment of FIG. 3B. The groups G1, G2 may be arranged as an array on a support 40, typically a PCB. In the illustrated embodiment the groups G1, G2 are arranged according a 4×4 array. The first row comprises four first groups G1, the second row four second groups G2, etc. Further, there is provided a single optical element L1, L2, L3, L4, L5, L6, L7, L8, e.g. a lens element, for a pair of an adjacent first and second group G1, G2. The optical elements L1, L2, L3, L4, L5, L6, L7, L8 may be part of one integral optical plate. For example, the optical elements L1, L2, L3, L4, L5, L6, L7, L8 may be free-form lens elements integrated in a lens plate. In the embodiment of FIG. 4A, the connection between the rows implements a bridge for connecting the second row of four second groups G2 with the fourth row of four second groups G2. However, as illustrated in FIG. 4B, it is also possible to design the connection lines such that no bridge is needed. Preferred embodiments of the invention can be implemented on a PCB with a single conductive layer either without bridges or with one or more bridges (using e.g. a jumper to implement a bridge) or on a PCB with two conductive layers.

[0098] In the embodiments of FIGS. 4A and 4B the four LEDs which are arranged under a single lens L1, L2, L3, L4, L5, L6, L7, L8 may be four individual LED components or a single LED component including four LEDs.

[0099] FIG. 4C illustrates a variant of the embodiment of FIG. 4B where multiple PCB's 40, 40′ are connected in series to form a string of a plurality of first groups G1 connected in series with a string of a plurality of second groups G2. The PCB's 40, 40′ may be the same, and may be designed in a modular manner as shown, such that the first groups G1 of PCB 40 can be connected in series with first groups G1 of PCB 40′, and the second groups G2 of PCB 40 can be connected in series with the second groups of PCB 40′. A first end of the string of first groups G1 is connected to an output A of the control circuitry 20 Similarly, a first end of the string of second groups G2 is connected to an output C of the control circuitry 20. Instead of providing the intermediate node 15 on the PCB as in the embodiments of FIGS. 4A and 4B, the intermediate node 15 may be provided in or at the inverter 20 by connecting outputs B and B′ as shown in FIG. 4C.

[0100] The control circuitry 20 may control the LEDs 1, 2 according to different modes. The modes may comprise at least one first mode and at least one second mode. The at least one first mode may comprise: [0101] a first mode (M1′) wherein the first LEDs 1 of the first groups G1 is/are activated and the first LEDs 1 of the second groups G2 is/are not activated; [0102] a further first mode (M1″) wherein the first LEDs 1 of the second groups G2 is/are activated and the first LEDs 1 of the first groups G1 is/are not activated.

[0103] Similarly, the at least one second mode may comprise: [0104] a second mode M2′, wherein the second LEDs 2 of the first groups G1 is/are activated and the second LEDs 2 of the second groups G2 are not activated; [0105] a further second mode M2″, wherein the second LEDs 2 of the second groups G2 is/are activated and the second LEDs 2 of the first groups G1 is/are not activated.

[0106] FIG. 5B illustrates that the first and second LED 1, 2 of a first group G1 may be connected with its first terminals 411, 421 to a first common line portion 401 on a PCB 40, and that the first and second LED 1, 2 of the second group G2 may be connected with its first terminals 431, 441 to a second common line portion 402. The first common line portion 401 runs parallel to the second common line portion 402. The first common line portion 401 may be connected to the second common line portion 402 at an end portion thereof (not shown). The first and second LED of the first group G1 each have a second terminal 412, 422 which may be connected to a further common line portion 405 in line with the first common line portion 401. Similarly, the first and second LED of the second group G2 each have a second terminal 432, 442 which may be connected to a further common line portion 406 in line with the second common line portion 402. When multiple first groups G1 are connected in series, as shown, the first groups may be interconnected using the common line portion 405 between two adjacent first groups G1. The common line portion 405 is connected to the second terminals 412, 422 of the first and second LED of one (here the first group on the right) of the two adjacent first groups G1 and to first terminals of the first and second LED of the other one (here the first group on the left) of the two adjacent first groups. The same applies for the second groups G2. At the other end of a row, in a similar manner, common line portions 403, 404 may be connected to terminals of a first and second LED of a first group G1 and to terminals of a first and second LED of a second group G2, respectively, see the groups G1 and G2 on the left of FIG. 5B. In that manner, first and second LEDs 1, 2 of a group can be arranged close to each other.

[0107] The width dc of a common line portion 401, 402, 403, 404, 405, 406 may be e.g. between 0.5 and 20 mm Preferably, the distance di between two parallel common lines portions 401, 402 may be smaller than 20 mm, e.g. between 0.2 and 5 mm Preferably, the distance dl between the centers of adjacent LEDs 1, 2 of a first or second group G1, G2 may be between 0.1 mm and 5 mm, e.g. between 0.1 mm and 1 mm. The line portions 401, 402, 403, 404, 405, 406 may be provided in copper, and may be provided in or on a PCB. The line portions 401, 402, 403, 404, 405, 406 are flat portions extending in a plane of the PCB. The PCB may be a metal core PCB (MCPCB) with only one copper layer.

[0108] A typical prior art implementation is shown in FIG. 5A for comparison. In the illustrated prior art solution four rows of LEDs connected in series are arranged on a PCB. A first series connection of LEDs is provided in a first row comprising first line portions 501, a second series connection of LEDs is provided in a second row comprising second line portions 502, etc. The distance dl between a LED included in the first row with first line portions 501 and an adjacent LED included in the second row with second line portions 502, will have to be bigger than the corresponding distance dl in an embodiment of the invention, as shown in FIG. 5B. This is because a minimum distance di has to be present between line portions 501 and 502. It is noted that FIGS. 5A and 5B are not drawn to scale.

[0109] In order to illustrate the advantages of embodiments of the invention, FIGS. 5C and 5D illustrate two prior art circuits with a plurality of LED strings St1, St2, St3, St4. Each LED strings St1, St2, St3, St4 comprises a plurality of LEDs connected in series. In total 4×8 LEDs are arranged on a PCB 40. Each LED strings St1, St2, St3, St4 comprises eight LEDs, and each LED string can be individually activated. In the embodiment of FIG. 5C four connection lines and six bridges are used for the connecting of the 32 LEDs. Also, in the circuit of FIG. 5D four connection lines are needed. When comparing the prior art circuits of FIGS. 5C and 5D with the embodiment of FIGS. 4A and 4B, it can be seen that, for the same amount of LEDs, the amount of connection lines in embodiments of the invention is significantly reduced as compared with prior art circuits. Further, when comparing the prior art circuit of FIG. 5C with the embodiment of FIG. 4A, it can be seen that embodiments of the invention allow reducing the number of bridges: one bridge in the embodiment of FIG. 4A versus six bridges in the prior art circuit of FIG. 5C. Also, when comparing the prior art circuit of FIG. 5D with the embodiment of FIG. 4B, it can be seen that embodiments of the invention allow reducing the number of connection lines returning from one side to the other side of the PCB 40 (here from right to left): two lines in the embodiment of FIG. 4B versus four lines in the prior art circuit of FIG. 5D.

[0110] In FIG. 5B the LEDs 1, 2 are arranged in a matrix:

TABLE-US-00001 2 2 1 1 2 2 1 1

[0111] However, it is also possible to arrange the LEDs as illustrated in FIG. 6, according to the following pattern:

TABLE-US-00002 1 2 2 1 2 1 1 2

[0112] FIG. 7 illustrates a further exemplary embodiment, wherein the first group G1 comprises a plurality of first LEDs 1 connected in anti-parallel with a plurality of second LEDs 2; and wherein the second group G2 comprises a plurality of first LEDs 1 connected in anti-parallel with a plurality of second LEDs 2. However, in order to avoid breakdown risks it is generally not preferred to include too many first or second LEDs 1, 2 in series within a single group. The groups G1, G2 may be controlled in a similar manner as described above.

[0113] FIG. 8A illustrates an example where two sets S1, S2 each comprising at least one first group G1, G1′ and at least one second group G2, G2′, are combined in a light system. As shown, the connection lines may be arranged without the need for any bridges. The first set S1 with the groups G1, G2 may be controlled via lines A, B, C as described above, e.g. as in FIG. 1B. The second set S2 with the groups G1′, G2′ may be controlled via lines A′, B′, C′ as described above, e.g. as in FIG. 1B. Such an embodiment allows to individually control eight LEDs using six channels A, B, C, A′, B′, C′.

[0114] FIG. 8B illustrates another example where three sets S1, S2, S3 each comprising at least one first group G1, G1′, G1″ and at least one second group G2, G2′, G2″ are combined in a light system. As shown, the connection lines may be arranged without the need for any bridges. The first, second and third set S1; S2; S3 may be controlled via respective lines A, B, C; A′, B′, C′; A″, B″, C″ as described above, e.g. as in FIG. 1B. As illustrated in dotted lines, it is possible to provide intermediate connection lines 15, 15′, 15″ which connect the first groups G1, G1′, G1″ and the second groups G2, G2′, G2″, on the PCB. Alternatively, additional connection lines C2, C2′, C2″ may be provided, and the connection between C, C′, C″ and C2, C2′, C2″, respectively, may be done outside of the PCB, e.g. in the invertor. Such an embodiment allows to individually control twelve LEDs using nine channels A, B, C, A′, B′, C′, A″, B″, C″. FIG. 8C shows the example of FIG. 8B in schematic form to further illustrate the compactness of embodiments of the invention. FIG. 9 illustrates yet another exemplary embodiment in which different first groups G1a, G1b are combined with different second groups G2a, G2b. The multiple first groups G1, G1b are connected in series with each other. Similarly, the multiple second groups G2a, G2b are connected in series with each other. The skilled person understands that many different implementations can be envisaged using those principles. The groups G1a, G1b, G2a, G2b may be controlled in any one of the manners described above.

[0115] In all embodiments of the figures, the first LED 1 and the second LED 2 may be the same or different. Also, the first LED 1 of the first group G1 may be the same as or different from the first LED 1 of the second group G2. Also, the second LED 2 of the second group G2 may be the same as or different from the second LED 2 of the second group G2. In most examples a single first LED 1 is shown to be connected in anti-parallel with a single second LED 2. However, as shown in FIG. 9 for groups G1b and G2b, it is also possible to have a group with multiple first LEDs 1 connected in parallel and/or with multiple second LEDs 2 connected in parallel, wherein the first LED(s) are connected in anti-parallel with the second LED(s). Also, embodiments of the invention may use LED components housing a plurality of LEDs 1 and/or 2 connected in parallel, in anti-parallel, or in series.

[0116] The first and second LEDs 1, 2 may be any one of the following: a red LED, a green LED, a blue LED, a white LED, a warm white LED, a cool white LED, etc. Optionally the LEDs may comprise a phosphor coating.

[0117] The first LED 1 and the second LED 2 may have substantially the same forward biasing voltage. The first LED 1 may have a phosphor coating which is the same as or different from a phosphor coating of the second LED 2. Also, some first and/or second LEDs 1, 2 may have a phosphor coating and other first and/or second LEDs 1, 2 may not have a phosphor coating.

[0118] The skilled person understands that the first and second LEDs 1, 2 of the at least one first and second group G1, G2 may be arranged in any suitable manner on a support, typically a PCB. Optionally, the first and second LEDs 1, 2 of the at least one first and second group G1, G2 may be arranged in an array comprising at least two rows and at least two columns, see for example the embodiments of FIGS. 4A and 4B. Preferably, when multiple first and second groups are provided, also the groups are arranged in an array comprising at least two rows and at least two columns. The distance between a first and a second LED within a same group may be different from the distance between two adjacent first LEDs from different groups.

[0119] By choosing an appropriate position for the LEDs 1, 2 in the array on the PCB a different light output can be achieved with different control schemes as described above. A different light output may refer to a different light pattern on the ground, a different color, a different color temperature, a different intensity, a different flashing pattern, etc.

[0120] In the embodiments of the figures, preferably, the control circuitry 20 is configured to receive a desired light pattern and/or a control parameter as an input, to select a control scheme out of a plurality of different stored control schemes in accordance with the input, and to control the control circuitry 20 in accordance with the selected control scheme. The plurality of different stored control schemes may correspond with two or more of the modes described above. The control circuitry 20 may comprise any one or more of the following: a field programmable gate array, an ASIC, a microcontroller, control switches. Those components are then configured to implement the various control schemes. FIG. 2 illustrates a possible implementation, but the skilled person understands that many other implementations are possible.

[0121] Optionally, the driver 10 may comprise dimming circuitry configured to change the DC current in function of a dimming input. In that manner, the light intensity of the light emitted by the LEDs which are switched on can be regulated. Optionally, the driver 10 is further configured to deliver a supply voltage for the control circuitry 20.

[0122] The invention further relates to a luminaire comprising a light system according to any one of the embodiments described above. The luminaire comprises a luminaire head, and optionally a luminaire pole. The luminaire head may be connected in any manner known to the skilled person to the luminaire pole. In other embodiments, the luminaire head may be connected to a wall or a surface, e.g. for illuminating buildings or tunnels. The luminaire head comprises a luminaire housing in which one or more supports, typically one or more PCBs 40, 40′, with the LEDs 1, 2 are arranged. The driver 10 may be arranged in or on a luminaire head, in or on the luminaire pole, or in any other suitable location of the luminaire system. Preferably, the control circuitry 20 is arranged in the luminaire head.

[0123] Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.