Circuit Arrangement and Method for Controlling at Least One Light Source

• US 20090302769A1
• Filed: 05/04/2007
• Published: 12/10/2009
• Est. Priority Date: 05/04/2006
• Status: Active Grant

• Current Assignee: Austriamicrosystems AG (Ams-Osram AG)
• Original Assignee: Austriamicrosystems AG (Ams-Osram AG)
• Inventors: Trattler, Peter, Pauritsch, Manfred
• Granted Patent: US 8,344,663 B2
• Time in Patent Office: Days
• US Class Current: 315/152
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

A circuit arrangement for controlling at least one light source comprises a photodetector (2), a sampling circuit (6) for selectively sampling a photodetector signal (lin2) generated by the photodetector (2) as a function of a first and a second light source (10, 12), and a control unit (5), which is coupled on the input side to the sampling circuit (6). The circuit arrangement further comprises a first power-supply source (7), which is coupled to the control unit (5) and is designed for controlling at least one parameter of a first light source (12), and at least one second power-supply source (11), which is coupled to the control unit (5) and is designed for controlling at least one parameter of a second light source (12). The circuit arrangement is suitable, for example, for RGB lighting.

Claims

1. A circuit arrangement for controlling at least one light source, comprising:

a photodetector arranged to detect light from a first and a second light source;

a sampling circuit coupled to the output of the photodetector;

a control unit, which comprises a first filter having an input coupled to the sampling circuit and an output coupled to a first and a second output of the control unit;

a first power-supply source, having a control input coupled to the first output of the control unit and which is adapted for controlling at least one parameter of the first light source; and

a second power-supply source, having a control input coupled to the second output of the control unit and which is adapted for controlling at least one parameter of the second light source.

2. The circuit arrangement according to claim 1, wherein

the output of the first filter is coupled to at least a third output of the control unit, and the circuit arrangement comprises a third power-supply source, having a control input coupled to at least the third output of the control unit and which has an output coupled to a third light source that generates light detected by the photodetector.

3. The circuit arrangement according to claim 1, wherein

the first filter is a low-pass filter.

4. The circuit arrangement according to claim 1, wherein

the first filter comprises an amplifier.

5. The circuit arrangement according to claim 1, wherein

the first filter comprises an integrator.

6. The circuit arrangement according to claim 1, wherein

the first filter comprises a switched capacitor.

7. The circuit arrangement according to

claim 1, comprising a sequence controller, which is coupled to the sampling circuit and at least one of the first and second power-supply sources for outputting at least one control signal.

8. The circuit arrangement according to claim 1, wherein

the photodetector comprises a photodiode, a phototransistor or a photoresistor.

9. The circuit arrangement according to claim 1, wherein

the photodetector is coupled to a power-supply circuit for electrically powering the photodetector.

10. The circuit arrangement according to claim 1, comprising

a preamplifier coupled between the photodetector and the sampling circuit.

11. The circuit arrangement according to claim 1, wherein

the sampling circuit comprises a first sampling circuit, which is coupled to the first power-supply source, and a second sampling circuit, which is coupled to the second power-supply source.

12. The circuit arrangement according to claim 2, wherein

the sampling circuit comprises a first sampling circuit, which is coupled to the first power-supply source, and a second sampling circuit, which is coupled to the second power-supply source, and at least one third sampling circuit, which is coupled to at least one third power-supply source.

13. The circuit arrangement according to claim 11, wherein

at least one of the sampling circuits comprises a sample-and-hold circuit.

14. The circuit arrangement according to claim 11, wherein

at least one of the sampling circuits comprises a field-effect transistor or transmission gate.

15. The circuit arrangement according to claim 11, wherein

at least one of the sampling circuits comprises a field-effect transistor.

16. The circuit arrangement according to claim 1, wherein

the control unit comprises a set-point generator.

17. The circuit arrangement according to claim 1, wherein

the control unit comprises a memory for storing at least one measurement value of the photodetector current or at least one value derived from the one or more measurement values of the photodetector current.

18. The circuit arrangement according to claim 1, wherein

the first power-supply source has an output coupled to the first light source, and

the second power-supply source has an output coupled to the second light source.

19. The circuit arrangement according to claim 18, wherein

the first power-supply source comprises a switch, to which, at a control input, a control signal is fed, and a current source, which is coupled on the input side to the control unit and is connected in series to the switch between the output of the first power-supply source and a reference-potential terminal.

20. A lighting arrangement, comprising a circuit arrangement according to claim 1 and also the first light source, which is connected to the first power-supply source, and the second light source, which is connected to the second power-supply source.

21. A lighting arrangement according to claim 2,

comprising the first light source, which is connected to the first power-supply source, and the second light source, which is connected to the second power-supply source, and the third light source, which is connected to the third power-supply source.

22. (canceled)

23. A method for controlling at least one light source, comprising the steps of:

successive activation of a first and a second light source in an adjustment phase;

measurement, sampling, and filtering of a photodetector current allocated to each light source; and

controlling a first power-supply source, which is connected to the first light source, and a second power-supply source, which is connected to the second light source, in an operating phase as a function of the values of the photodetector current sampled and filtered in the adjustment phase.

24. The method according to claim 23, comprising the steps of:

activating a third light source in the adjustment phase;

measuring, sampling, and filtering a photodetector current allocated to the third light source; and

controlling, as a function of the value of the photodetector current sampled and filtered in the adjustment phase a third power-supply source, which is connected to the third light source, in an operating phase.

25. The method according to claim 23, comprising the steps of:

controlling the brightness of the first light source by influencing a current intensity or by pulse-width modulation or pulse-density modulation of a current, which is output by the first power-supply source to the first light source; and

controlling the brightness of the second light source by influencing a current intensity or by pulse-width modulation or pulse-density modulation of a current, which is output by the second power-supply source to the second light source.

26. The method according to claim 24, comprising

controlling the brightness of the third light source by influencing a current intensity or by pulse-width modulation or pulse-density modulation of a current, which is output by the third power-supply source to the third light source.

27. The method according to claim 23, comprising

measuring and sampling the photodetector current allocated to each light source by detecting the light signal, sampling the photodetector current, filtering and comparing with a default value.

28. The method according to claim 23, comprising

generating the photodetector current with a common photodetector for the light sources.

29. The method according to claim 23. comprising

filtering, in particular, holding and integrating, the photodetector current allocated to each light source with a switched capacitor.