| 摘要 |
PURPOSE:To certainly detect a discharge lamp in the life end and reduce the stress of a switch element without sending a simultaneous on current. CONSTITUTION:When a discharge lamp L is in the life end, the on-period of a switch element Q1 is shortened, and the input of an inverter gate G2 is changed from level H to level L while the output Q of D-FFIC2 is in the level L. Then, a pulse is outputted from the output Q of D-FFIC3. Thus, the output Q of R-SFF7 is set to the level H, and a transistor Q3 is laid in on-state. Thus, the collector current of a transistor Q4 is determined depending on the parallel resistance values of resistances R7, R6, and the oscillating period of an astable multivibrator IC1 is shortened. Since the operation frequency of the inverter is thus increased to limit the output, a stress such as overcurrent or heating can be reduced. |
