A controller provides power to (i) a first light-emitting device that emits a first white light of a first correlated color temperature (CCT) and (ii) a second light-emitting device that emits a second white light of a second CCT. The second CCT is lower than the first CCT. The first and second white lights mix to yield a combined white light having a combined CCT with a combined brightness. The controller receives a user-adjustable DC input voltage Vin. The controller distributes 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, as follows: (i) In the upper range: as Vin decreases, combined-light CCT decreases and combined-light brightness remains constant. (ii) In the lower range: as the Vin decreases, combined-light brightness decreases.