Lighting device and luminaire

A lighting device which supplies a current to a solid light emitting element, the lighting device comprising:

• a DC/DC converter including two switching elements connected in series and a resonant circuit connected to a connection point between the two switching elements;
• and
• a control unit configured to control driving of the two switching elements,
• wherein the control unit is configured to:
• perform intermittent driving in which a switching period and a non-switching period are alternately repeated, the switching period being a period in which the control unit switches ON and OFF the two switching elements respectively and inversely;
• and the non-switching period being a period in which the control unit stops switching ON and OFF the two switching elements;
• and
• provide, in an initial part of the switching period, a frequency gradual decrease period in which a driving frequency for driving the two switching elements is gradually decreased.