| 摘要 |
PROBLEM TO BE SOLVED: To prevent electrodes in an electronic instrument having a discharge lamp from being worn to stably light the discharge lamp. SOLUTION: The electronic instrument is equipped with a DC-DC converter 2A, a drive circuit connected to an output side of the DC-DC converter 2A and a discharge lamp 1 connected to an output side of the drive circuit. The drive circuit has an ignitor trigger voltage generating circuit 2B, a polarity changing-over circuit 4 and an ignitor provided in order from the side of the DC-DC converter 2A toward the discharge lamp 1, a circuit 35 for detecting reduction of the output voltage from the DC-DC converter 2A is provided between the DC-DC converter 2A and the ignitor 15, and changing-over of opening and closing is conducted as to 2 switching elements Q1, Q3 on a front stage side among 4 switching elements Q1-Q4 making up the polarity changing-over circuit 4 by the circuit 35 for detecting reduction of the output voltage. COPYRIGHT: (C)2003,JPO |
