Brightness adjustment for a white-light lamp

A method for powering a (i) first light-emitting device configured to emit a first white light of a first correlated color temperature (CCT) and (ii) a second light-emitting device configured to emit a second white light of a second CCT with a second brightness, wherein the second CCT is lower than the first CCT, for the first white light to mix with the second white light to yield a combined white light having a combined-light CCT with a combined-light brightness, the method comprising:

• receiving an input voltage Vin;
• and
• distributing the input supply power to the first and second light-emitting devices according to a power-distribution scheme that differentiates between whether Vin is in an upper range or a lower range such that:
• throughout the upper range:
• as Vin decreases, the combined-light CCT decreases and the combined-light brightness remains substantially constant, and
• throughout the lower range:
• as Vin decreases, the combined-light brightness decreases.

A light fixture comprising:

• a first LED device that is configured to emit a first white light of a first correlated color temperature (CCT) in the range 4000K to 7000K;
• a second LED device that is configured to emit a second white light of a second CCT in the range 1500K to 3000K;
• a housing that
• supports the first and second light-emitting devices in positions relative to each other such that the first white light will mix with the second white light to yield combined white light of a combined-light CCT having combined-light brightness, and
• is configured to be installed in a ceiling as a recessed light fixture;
• an input configured to receive a user-adjustable DC input voltage Vin;
• and
• a controller that is configured to:
• distribute the input supply power to the first and second light-emitting devices according to a power-distribution scheme that differentiates between whether Vin is in an upper range or a lower range such that:
• throughout the upper range:
• as Vin decreases, the combined-light CCT decreases and the combined-light brightness remains substantially constant, and
• throughout the lower range:
• as Vin decreases, the combined-light brightness decreases.