| 摘要 |
PROBLEM TO BE SOLVED: To prevent abnormal overheat of a lighting circuit and prevent destruction of a circuit part by specifying restart count by a startup counter in case that half wave lighting due to a one-side emission state at the end of service life of a discharge lamp is laminated. SOLUTION: An element 10 for cutting off a direct current component flowing during half wave lighting is inserted into a path that a discharge current of a discharge lamp 7 flows, an oscillation start circuit of a switch element 6 is provided with a reset circuit, reset for a specified number of times is applied by an oscillation start counter 20, and the switch element 6 is restarted. Since the element 10 cutting off the DC component inputted into a path through which the discharge lamp 7 current flows cuts off the DC component of a half-wave waveform generated when a discharge current makes a transition from a preheat state to a lighting state, current flowing in a current feedback transformer 11 decreases, oscillation of the switch element 6 stops, and maintaining the half-wave lighting can be prevented. The oscillation start counter 20, when oscillation of the switch element 6 stops, counts the number of times of the stops, resets the oscillation start circuit 20, re-oscillates the switch element 6 for a specified number of times, so that, non-lighting in half-wave lighting due to preheat shortage with not occrer. |
