Circuit arrangement and method for controlling at least one light source

• US 8,344,663 B2
• Filed: 05/04/2007
• Issued: 01/01/2013
• Est. Priority Date: 05/04/2006
• Status: Expired due to Fees

• Current Assignee: ams AG (Ams-Osram AG)
• Original Assignee: ams AG (Ams-Osram AG)
• Inventors: Trattler, Peter, Pauritsch, Manfred
• Primary Examiner(s): A, Minh D
• Application Number:
  US12/227,027
• Publication Number:
  US 20090302769A1
• Time in Patent Office: 2,069 Days
• Field of Search: 315/291, 315/307, 315/308, 315/312, 315/244, 315/246, 315/209.R, 315/160, 315/210, 315/211, 315/185.R, 315/192
• US Class Current: 315/312
• 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;

an amplifier coupled to an output of the photodetector;

a sampling circuit coupled to an output of the amplifier;

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,

wherein the sampling circuit comprises a transmission gate,

wherein the first filter comprises an integrator, wherein the integrator comprises a further amplifier, a capacitor and a switch, wherein the switch and the capacitor are connected in a parallel circuit, wherein an input of the further amplifier is connected to the sampling circuit and to an output of the further amplifier via the parallel circuit, and wherein the output of the further amplifier forms an output of the integrator.

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 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.

4. The circuit arrangement according to claim 2, wherein the first light source is connected to the first power-supply source, and the second light source is connected to the second power-supply source, and the third light source is connected to the third power-supply source.

5. The circuit arrangement according to claim 1, wherein the first filter is a low-pass filter.

6. The circuit arrangement according to claim 1, wherein the first filter comprises an amplifier.

7. The circuit arrangement according to claim 1, wherein the first filter comprises a switched capacitor.

8. 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.

9. The circuit arrangement according to claim 1, wherein the photodetector comprises a photodiode, a phototransistor or a photoresistor.

10. The circuit arrangement according to claim 1, wherein the photodetector is coupled to a power-supply circuit for electrically powering the photodetector.

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

13. The circuit arrangement according claim 1, wherein the control unit comprises a set-point generator.

14. 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.

15. 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.

16. The circuit arrangement according to claim 15, 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.

17. The circuit arrangement according to claim 1, wherein the first light source is connected to the first power-supply source, and the second light source is connected to the second power-supply source.

18. 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;

providing a control signal by a sequence controller to control, in the adjustment phase, a sequence of activation and deactivation of the first and second power-supply sources and the sampling of the photodetector current.

19. The method according to claim 18, 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.

20. The method according to claim 19, 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.

21. The method according to claim 18, 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.

22. The method according to claim 18, comprising measuring and sampling the photodetector current allocated to each light source by the light signal, sampling the photodetector current, filtering and comparing with a default value.

23. The method according to claim 18, comprising generating the photodetector current with a common photodetector for the light sources.

24. The method according to claim 18, comprising filtering, in particular, holding and integrating, the photodetector current allocated to each light source with a switched capacitor.

25. 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;

an amplifier coupled to an output of the photodetector;

a sampling circuit coupled to an output of the amplifier;

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;

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; and

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.

26. 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 first amplifier coupled to an output of the photodetector;

a sampling circuit coupled to an output of the first amplifier;

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,

wherein the first filter comprises an integrator,

wherein the integrator comprises a second amplifier, a first capacitor, a second capacitor, a first change-over switch and a second change-over switch,

wherein an input of the second amplifier is connected to an input of the first filter,

wherein the first change-over switch, the second capacitor and the second change-over switch are connected in a series circuit with each other and in a parallel circuit with the first capacitor,

wherein the parallel circuit connects the input of the second amplifier to the output of the second amplifier, and

wherein the output of the second amplifier is connected to the output of the first filter.