Patent ID: 8354804

Claim:
A power supply device comprising: a semiconductor light-emitting element; a voltage detection circuit which detects a voltage applied to the semiconductor light-emitting element, and outputs a first detection signal; a current detection circuit which detects a current supplied to the semiconductor light-emitting element, and outputs a second detection signal; and a dimming controller which receives a dimming signal which is set at one of a deepest first dimming depth, a shallowest second dimming depth, and a certain third dimming depth between the first dimming depth and the second dimming depth, drive-controls the semiconductor light-emitting element according to the first detection signal so that the voltage becomes a first target value when the first dimming depth is set, drive-controls the semiconductor light-emitting element according to the second detection signal so that the current becomes a second target value when the second dimming depth is set, and drive-controls the semiconductor light-emitting element according to the first detection signal and the second detection signal so that the voltage and the current respectively become a third target value and a fourth target value when the third dimming depth is set, wherein the dimming controller drive-controls the semiconductor light-emitting element depending on the first detection signal compared to the second detection signal as the third dimming depth is closer to the first dimming depth, and drive-controls the semiconductor light-emitting element depending on the second detection signal compared to the first detection signal as the third dimming depth is closer to the second dimming depth.