LED ASSEMBLY, LED FIXTURE, CONTROL METHOD AND SOFTWARE PROGRAM

• US 20110084615A1
• Filed: 03/12/2009
• Published: 04/14/2011
• Est. Priority Date: 03/17/2008
• Status: Active Grant

• Current Assignee: eldoLAB Holding B.V. (Acuity Brands, Inc.)
• Original Assignee: eldoLAB Holding B.V. (Acuity Brands, Inc.)
• Inventors: Welten, Petrus Johannes Maria
• Granted Patent: US 8,618,737 B2
• Time in Patent Office: Days
• US Class Current: 315/152
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

A plurality of LEDs arranged in groups, each group comprising at least one LED, a control circuit for driving the LEDs, the control circuit comprising a sensing device for sensing an operative parameter of the LEDs. The control circuit is arranged to: a) operate at least one group of the LEDs: b) sense by the sensing device a value of the operative parameter of the at least one group; c) repeat a) and b) for at least a different one of the groups; d) assign to each of the groups of LEDs a value of the operative parameter from the sensed operative parameter values; and e) control the driving of the groups of LEDs from the assigned operative parameter values.

Claims

1. A LED assembly comprising:

a plurality of LEDs arranged in groups, each group comprising at least one LED,

a control circuit for driving the LEDs, the control circuit comprising a sensing device for sensing an operative parameter of the LEDs,

the control circuit being arranged to;

a) operate at least one group of the LEDs;

b) sense by the sensing device a value of the operative parameter of the at least one group;

c) repeat a) and b) for at least a different one of the groups;

d) assign to each of the groups of LEDs a value of the operative parameter from the sensed operative parameter values; and

e) control the driving of the groups of LEDs from the assigned operative parameter values.

2. The LED assembly according to claim 1, wherein the sensing device is arranged to measure a total operative parameter of simultaneously operated LEDs.

3. The LED assembly according to claim 1, wherein at least two groups of LEDs are operated simultaneously in a), a total operative parameter of the simultaneously operated LEDs being sensed in b).

4. The LED assembly according to claim 1, wherein the or each repetition is performed for a respective subset of at least two of the groups.

5. The LED assembly according to claim 1, wherein the control circuit is arranged to operate the groups of LEDs, by

a) activating or de-activating a first one of the groups;

b) waiting during a predetermined wait time period; and

c) repeating a) and b) for a second one of the groups.

6. The LED assembly according to claim 1, wherein the groups of LEDs are connected in series, the assembly comprises a current source to generate an LED operating current and a respective switch parallel to each of the groups, the control circuit being arranged to operate each group by driving the respective switch to a substantially non conductive state so that the operating current flows through the respective group, and to deactivate a respective group by driving the respective switch to a substantially conductive state to bypass the operating current via the respective switch.

7. The LED assembly according to claim 6 wherein the current source comprises at least one of a linear regulator or a Buck, Boost, Buck-Boost, Sepcic, Cuk or resonant converter.

8. The LED assembly according to claim 1, wherein the operative parameter comprises an LED forward voltage, the sensing device comprising a forward voltage sensing circuit.

9. The LED assembly according to claim 1, wherein the operative parameter comprises an illumination, the sensing device comprises a light sensor.

10. The LED assembly according to claim 9 wherein the light sensor is a monochrome light sensor.

11. The LED assembly according to claim 9 wherein the illumination is applied by the control circuit to derive a current feedback signal.

12. The LED assembly according to claim 1, wherein the operative parameter comprises an LED operating current, the sensing device comprising a current sensing circuit.

13. The LED assembly according to claim 1, wherein the control circuit is arranged to assign to the groups of LEDs operating cycle parts of an operating cycle of the LEDs, the operating cycle parts during each of which at least one group of the LEDs is operated, the total value of the operative parameter being sensed in each of the cycle parts, the operating cycle parts being assigned to the groups such that values of the operative parameter of each of the groups can be calculated from the measurements of the total values of the operative parameter of the groups activated in the cycle parts.

14. A LED fixture comprising:

a plurality of LEDs, in use having a substantially monochrome light output,

a cover being provided with a coating or coatings of phosphor or phosphorous materials arranged to receive at least part of the monochrome light output and;

a light sensor arranged to receive part of the substantially monochrome light output of the plurality of LEDs.

15. The LED fixture according to claim 14 wherein the light sensor is a monochrome sensor susceptible to the monochrome light output of the LEDs.

16. A method for controlling an LED assembly comprising a plurality of LEDs arranged in groups, each group comprising at least one LED, the method comprising:

a) operating at least one group of the LEDs;

b) sensing by the sensing device a value of the operative parameter of the at least one group;

c) repeating a) and b) for at least a different one of the groups;

d) assigning to each of the groups of LEDs a value of the operative parameter from the sensed operative parameter values; and

e) controlling the driving of the groups of LEDs from the assigned operative parameter values.

17. The method according to claim 16 wherein the sensing device is arranged to measure a total operative parameter of simultaneously operated LEDs.

18. The method according to claim 16 wherein at least two groups of LEDs are operated simultaneously in a), a total operative parameter of the simultaneously operated LEDs being sensed in b).

19. A software program stored on a non-transitory computer readable medium, comprising program instructions to, when loaded into a processing device of an LED assembly control circuit, perform the method according to claim 16.