Patent ID: 8368323

Claim:
A power supply unit, comprising: a semiconductor light emitting module: a power supply part configured to light the semiconductor light emitting module in accordance with one of a plurality of load characteristic curves and one of a plurality of inclination lines extending from a base point, inclinations of each of the plurality of inclination lines depending on one of a plurality of dimmer rates, respectively; a voltage detecting part configured to detect a load voltage applied to the semiconductor light emitting module to generate a voltage detection signal; a current detecting part configured to detect an electric current supplied to the semiconductor light emitting module to generate a current detection signal; and a control part configured to control the power supply part depending on the voltage detection signal, the current detection signal, and a dimmer signal having one of the dimmer rates, to adjust a power supplied to the semiconductor light emitting module from the power supply part and set the power depending on the one of the plurality of load characteristic curves and the one of the plurality of inclination lines which is set in accordance with the one of the plurality of dimmer rates; the control part being configured to control the power supply part depending on a constant current characteristic, a constant voltage characteristic, and/or a combination of a constant current characteristic and a constant voltage characteristic, such that if the one of the plurality of dimmer rates is smaller than a predetermined rate, then the current detection signal is weighted and the control part controls the power supply part depending on the constant current characteristic or a combination of the constant current characteristic and the constant voltage biased towards the constant current characteristic, and if the one of the plurality of the dimmer rates is not smaller than the predetermined rate, then the voltage detection signal is weighted and the control part controls the power supply part depending on the constant voltage characteristic or a combination of the constant voltage characteristic and the constant current characteristic biased towards the constant voltage characteristic.