Lighting device and luminaire

摘要

According to one embodiment, a lighting device includes a lighting circuit. The lighting circuit includes a direct-current power supply and a DC-DC converter, and lights an illumination lamp by constant-current control. An output capacitor is connected in parallel to an output end of the DC-DC converter. A capacitance of the output capacitor is set to such a value that a peak value of a pulse-like current flowing when the illumination lamp is instantaneously detached from and attached to the output end of the DC-DC converter is one or more and four or less times a load current of the illumination lamp.