Power supply unit having dimmer function and lighting unit

A power supply unit, comprising:

• a semiconductor light emitting moudule;
• a power supply part which lights the semiconductor light emitting moudule in accordance with one of load characteristics, wherein the load characteristics have inclination lines extending from a base point, whose inclinations are changed depending on dimmer rates, respectively;
• a voltage detecting part which detects a load voltage applied to the semiconductor light emitting moudule to generate a voltage detection signal;
• a current detecting part which detects an electric current supplied to the semiconductor light emitting moudule to generate a current detection signal;
• and
• a control part which controls 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 moudule from the power supply part and the power is set depending on one of the inclination lines of the load characteristic which is set in accordance with the dimmer rate.