Describing Two Led Colors as a Single, Lumped Led Color

• US 20080203945A1
• Filed: 05/11/2006
• Published: 08/28/2008
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hoelen, Christoph Gerard August, Deurenberg, Peter Hubertus Franciscus, Ansems, Johannes Petrus Maria
• Granted Patent: US 8,410,723 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H05B 45/28 using temperature feedback

Abstract

A light emitting diode (LED) lighting system for producing white light is disclosed. The system comprises sets of LEDs arranged to emit light with different wavelength ranges and associated with different sets of characteristics, and a driving circuit arranged to drive the LEDs. The driving circuit comprises an input for desired light intensity, color rendering index, and color temperature, an input for signals for LED temperature, a model for determining driving currents for said sets of LEDs from said parameters, signals, and characteristics for each of said sets of LEDs; and a current driver for the LEDs. At least one of the sets of LEDs comprises a first subset of LEDs with a first wavelength sub-range and a first set of characteristics, and a second subset of LEDs with a second wavelength sub-range and a second set of characteristics. A lumped wavelength range of the set of LEDs is a range of said first and second wavelength sub-ranges, and the set of characteristics of the set of LEDs is a function of said first and second sets of characteristics. A method for controlling the sets of LEDs is also disclosed.

Claims

1. A light emitting diode (LED) lighting system (100) for producing white light, the system (100) comprising

a first set of LEDs (102, 304, 404) arranged to emit light with a first wavelength range and a first set of characteristics;

a second set of LEDs (103, 310) arranged to emit light with a second wavelength range and a second set of characteristics;

a third set of LEDs (104) arranged to emit light with a third wavelength range and a third set of characteristics; and

a driving circuit (106) arranged to drive said sets of LEDs (102, 103, 104), comprising

an input (108, 204) for parameters determining desired light intensity and color;

an input for signals for LED temperatures of the sets of LEDs;

a model (200) for determining driving currents for said sets of LEDs from said parameters, signals, and sets of characteristics for each of said sets of LEDs (102, 103, 104); and

a current driver (208) for providing said determined currents to said sets of LEDs (102, 103, 104, 304, 404, 310), characterized in that,

said third set of LEDs (104) comprises a first subset of LEDs (306, 406) with a first wavelength sub-range and a first set of characteristics, and a second subset of LEDs (308, 408) with a second wavelength sub-range and a second set of characteristics, wherein said third wavelength range is a lumped wavelength range of said first and second wavelength sub-ranges, and said third set of characteristics is a function of said first and second sets of characteristics.

2. The lighting system according to claim 1, wherein said sets of characteristics comprise temperature dependency of light output, temperature dependency of wavelength, or current dependency of light output, or any combination thereof.

3. The lighting system according to 1, wherein said first wavelength range is from 450 nm to 490 nm, said second wavelength range is from 520 nm to 550 nm, said third wavelength range is from 580 nm to 645 nm, wherein said third wavelength is a lumped wavelength range of a first sub-range from 580 nm to 600 nm and a second sub-range from 610 nm to 645 nm.

4. The lighting system according to claim 1, wherein said first wavelength range is from 610 nm to 645 nm, said second wavelength range is from 580 nm to 600 nm, said third wavelength is from 450 nm to 550 nm, wherein said third wavelength is a lumped wavelength range of a first sub-range from 450 nm to 490 nm, and a second sub-range from 520 nm to 550 nm.

5. The lighting system according to claim 1, wherein said first and second sub-set of light emitting diodes (306, 308) are electrically connected in series.

6. The lighting system according to 1, further comprising a temperature sensor for providing said signals for LED temperatures of the sets of LEDs, wherein said temperature sensor is arranged in a heat sink arranged at said sets of LEDs.

7. The lighting system according to claim 1, wherein said model for each set of LEDs comprises a wavelength function of LED temperature being dependent on a difference between LED temperature and a reference temperature, and a wavelength dependency on temperature parameter according to the characteristics of each set of LEDs.

8. A method for controlling three sets of LEDs, each arranged to emit light with a wavelength range and with a set of characteristics, to provide white light, comprising the steps of:

determining a desired light intensity and color;

determining LED temperatures of the sets of LEDs;

determining for each set of LEDs a driving current for each of said sets of LEDs from said desired light intensity and color, and said LED temperatures; and

providing said driving currents to said sets of LEDs, characterized in that,

at least one of said sets of LEDs comprises a first subset of LEDs with a first wavelength sub-range and a first set of characteristics, and a second subset of LEDs with a second wavelength sub-range and a second set of characteristics, wherein a wavelength range of said set of LEDs is a lumped wavelength range of said first and second wavelength sub-ranges, and a set of characteristics of said set of LEDs is a function of said first and second sets of characteristics.

9. The method according to claim 8, wherein said step of determining for each set of LEDs a driving current for each of said sets of LEDs uses a model for each set of LEDs comprising a wavelength function of LED temperature being dependent on a difference between LED temperature and a reference temperature, and a wavelength dependency on temperature parameter according to the characteristics of each set of LEDs.