Color-Temperature-Tunable Device

Abstract

A method of operating a color-temperature-tunable device is described. The method drives a first light emitting diode (LED) chip with a first driving current from a first power source. The first LED chip is configured to emit a first light having a first peak wavelength. The method also drives a second LED chip with a second driving current from a second power source. The second LED chip is configured to emit a second light having a second peak wavelength. The method further maintains a total driving current, which includes the first driving current and the second driving current, approximately constant. The second peak wavelength is different from the first peak wavelength.

What is claimed is: 
     
         1 . A method of producing white lights having different color temperatures, comprising:
 increasing a first driving current for at least one first light emitting diode (LED) chip which comprises at least one first blue LED chip that emits a first light having a first peak wavelength; and   decreasing a second driving current for at least one second LED chip which comprises at least one second blue LED chip that emits a second light having a second peak wavelength, the second peak wavelength being different from the first peak wavelength.   
     
     
         2 . The method of  claim 1 , further comprising:
 maintaining a total driving current comprising the first driving current and the second driving current approximately constant.   
     
     
         3 . The method of  claim 1 , wherein the first peak wavelength is within a range from approximately 450 nm to approximately 500 nm, and wherein the second peak wavelength is within a range from approximately 370 nm to approximately 440 nm. 
     
     
         4 . The method of  claim 1 , wherein the first peak wavelength is within a range from approximately 450 nm to approximately 470 nm, and wherein the second peak wavelength is within a range from approximately 400 nm to approximately 440 nm. 
     
     
         5 . The method of  claim 1 , wherein the at least one first LED chip and the at least one second LED chip comprise gallium nitride based LED chips made of gallium nitride based materials. 
     
     
         6 . A method of producing white lights having different color temperatures, comprising:
 driving at least one first light emitting diode (LED) chip and at least one second LED chip with a total driving current so that the at least one first LED chip emits a first light having a first peak wavelength and the at least one second LED chip emits a second light having a second peak wavelength different from the first peak wavelength; and   changing a ratio between a first portion of the total current that drives the at least one first LED chip and a second portion of the total current that drives the at least one second LED chip.   
     
     
         7 . The method of  claim 6 , wherein changing the ratio between the first portion of the total current that drives the at least one first LED chip and the second portion of the total current that drives the at least one second LED chip comprises maintaining the total driving current approximately constant. 
     
     
         8 . The method of  claim 6 , wherein the first peak wavelength is within a range from approximately 450 nm to approximately 500 nm, and wherein the second peak wavelength is within a range from approximately 370 nm to approximately 440 nm. 
     
     
         9 . The method of  claim 6 , wherein the first peak wavelength is within a range from approximately 450 nm to approximately 470 nm, and wherein the second peak wavelength is within a range from approximately 400 nm to approximately 440 nm. 
     
     
         10 . The method of  claim 6 , wherein the at least one first LED chip and the at least one second LED chip comprise gallium nitride based LED chips made of gallium nitride based materials. 
     
     
         11 . The method of  claim 6 , wherein the at least one first LED chip comprises at least one first blue LED chip, and wherein the at least one second LED chip comprises at least one second blue LED chip.