Power supply unit having dimmer function and lighting unit

摘要

In a power supply unit, if a dimmer rate is changed within a range of k1, k2, ... k7 by a dimmer signal k of a dimmer signal generator (31), light-emitting diodes (19 to 21) are controlled to be lighted by a constant current characteristic in an area where the dimmer rate is small according to a load characteristic corresponding to the dimmer rates k1, k2, ... k7. As the dimmer rate becomes deeper, a tendency of a constant voltage characteristic is gradually strengthened from a constant current characteristic so that the light-emitting diodes (19 to 21) are lighted at the deeper dimmer rate.