LIGHTNING CIRCUIT AND ILLUMINATING FIXTURE

摘要

PROBLEM TO BE SOLVED: To provide a lightning circuit and an illuminating fixture capable of changing a dithering frequency while taking high harmonic wave reduction measures in a flyback converter circuit.SOLUTION: A lightning circuit 22 comprises: a capacitor 4 connected with a rectification circuit 3; a flyback converter circuit 20 connected with the capacitor 4; and a control integrated circuit 9 controlling a MOSFET 8 that is a switching element in the flyback converter circuit 20. The control integrated circuit 9 supplies a control signal to a gate terminal of the MOSFET 8. The control integrated circuit 9 changes a frequency f of the control signal so that an ON time period tis reduced when the frequency f of the control signal is increased, and so that the ON time period tis increased when the frequency f is reduced. In this embodiment, as a more preferable form, the control integrated circuit 9 changes the control signal so that a value K obtained by multiplying the frequency f of the control signal by a square of the ON time period tbecomes constant.