Method and apparatus for regulating the brightness of light-emitting diodes

• US 8,749,157 B2
• Filed: 10/22/2010
• Issued: 06/10/2014
• Est. Priority Date: 10/26/2009
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Inventors: Ludorf, Werner
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Alaeddini, Borna
• Application Number:
  US12/910,407
• Publication Number:
  US 20110095697A1
• Time in Patent Office: 1,327 Days
• Field of Search: 315/158, 315/209.R, 315/224, 315/279, 315/291, 315/297
• US Class Current: 315/224
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output

Abstract

Embodiments of the present invention relate to methods and circuits for brightness regulation for at least one light-emitting diode in the field of general lighting, more particularly, for incandescent lamp replacement by means of a supply voltage comprising a brightness level signal, wherein the brightness level signal contained in the supply voltage is decoded and converted into a modulation signal with a duty cycle corresponding to the brightness level signal for the purpose of driving a driver circuit for the at least one light-emitting diode.

Claims

1. A method for regulating a brightness of at least one light-emitting diode, the method comprising:

decoding a brightness level signal contained in a supply voltage;

converting the decoded brightness level signal into a first modulation signal with a duty cycle corresponding to the brightness level signal;

gating a second modulation signal with the first modulation signal to produce a superposition signal, wherein the second modulation signal has a higher frequency than the first modulation signal; and

driving a driver circuit for the at least one light-emitting diode by the superposition signal, wherein the first modulation signal comprises ON phases and REDUCED phases, wherein the driver circuit is controlled into a fully switched-on state during the ON phases and into a reduced switched-on operating state during the REDUCED phases.

2. The method as claimed in claim 1, wherein the supply voltage comprises a phase-gated supply voltage.

3. The method as claimed in claim 1, wherein the supply voltage comprises a phase-chopped supply voltage.

4. The method as claimed in claim 1, wherein the first modulation signal comprises ON phases and OFF phases, wherein the driver circuit is controlled into a fully switched-on state during the ON phases and into a fully switched-off operating state during the OFF phases.

5. The method as claimed in claim 4, wherein time intervals of the OFF phases of the first modulation signal are chosen in such a way that a human eye does not perceive any flicker of light emitted by the at least one light-emitting diode.

6. The method as claimed in claim 4, wherein time intervals of the OFF phases of the first modulation signal are less than or equal to 10 ms.

7. The method as claimed in claim 1, wherein time intervals of the REDUCED phases of the first modulation signal are chosen in such a way that a human eye does not perceive any flicker of light emitted by the at least one light-emitting diode.

8. The method as claimed in claim 1 wherein time intervals of the REDUCED phases of the first modulation signal are less than or equal to 10 ms.

9. The method as claimed in claim 1, wherein the second modulation signal is a high-frequency modulation signal for efficient energy transfer from the driver circuit to the at least one light-emitting diode.

10. The method as claimed in claim 9, wherein the second modulation signal has a duty cycle that is regulated such that, during ON phases of the first modulation signal, the at least one light-emitting diode is supplied with a current corresponding to an operating range with predetermined color constancy.

11. The method as claimed in claim 1, wherein driving the driver circuit causes the at least one light-emitting diode to emit light for a general lighting application.

12. A method for color-constant brightness regulation for at least one light-emitting diode, the method comprising:

converting a brightness level signal contained in a supply voltage into a modulation signal, and

operating a driver circuit for the at least one light-emitting diode in at least two predetermined operating states repeatedly with a duty cycle corresponding to the brightness level signal in such a way that the at least one light-emitting diode is operated in an operating range with predetermined color constancy in at least one predetermined operation state of the driver circuit, wherein a first of the at least two predetermined operating states is an ON state in which the driver circuit is fully switched on, and a second of the at least two predetermined operating states is a REDUCED state in which the driver is in a reduced switched-on operating state.

13. A circuit comprising:

a decoding circuit configured to decode a brightness level signal contained in a supply voltage; and

a modulator circuit configured to convert the decoded brightness level signal into a first modulation signal that has a duty cycle corresponding to the brightness level signal, the first modulation signal for repeatedly changing over a driver circuit for at least one light-emitting diode between at least two predetermined operating states, wherein the first modulation signal is superposed on a second modulation signal having a higher frequency to produce a superposition signal, and wherein the superposition signal drives the driver circuit, wherein a first of the at least two predetermined operating states is an ON state in which the driver circuit is fully switched on, and a second of the at least two predetermined operating states is a REDUCED state in which the driver is in a reduced switched-on operating state.

14. The circuit according to claim 13, wherein the at least one light-emitting diode can be operated in an operating range with pre-determined color constancy using the first modulation signal in at least one of the two predetermined operating states of the driver circuit.

15. The circuit according to claim 14, further comprising the driver circuit.

16. The circuit according to claim 15, further comprising the at least one light-emitting diode.

17. The circuit according to claim 16, wherein the at least one light-emitting diode comprises a semiconductor light emitting diode.

18. The circuit according to claim 17, wherein the at least one light-emitting diode comprises an organic light emitting diode.

19. A circuit for color-constant brightness regulation for at least one light-emitting diode, the circuit comprising:

means for decoding a brightness level signal contained in a supply voltage; and

means for converting the decoded brightness level signal into a first modulation signal that has a duty cycle corresponding to the brightness level signal, the first modulation signal for repeatedly changing over a driver circuit for at least one light-emitting diode between at least two predetermined operating states, wherein the first modulation signal is superposed on a second modulation signal having a higher frequency, wherein the first modulation signal gates the second modulation signal to produce a superposition signal, and wherein the superposition signal drives the driver circuit, wherein a first of the at least two predetermined operating states is an ON state in which the driver circuit is fully switched on, and a second of the at least two predetermined operating states is a REDUCED state in which the driver is in a reduced switched-on operating state.