| 摘要 |
<p>PURPOSE:To enhance the safety with a lighting circuit for a discharge lamp for car by performing certain sensing of failure. CONSTITUTION:In a lighting circuit 1 for a metal halide lamp, the battery voltage is raised by a DC booster circuit 7 by putting on a lighting switch 5, converted into AC by a DC/AC converter circuit 8, and impressed on a metal halide lamp 11. A failure sensing circuit 15 is furnished to sense the output voltage of the DC/AC converter circuit 8 and judge from the sensed level the lamp condition whether it is open or shortcircuited. A failure sensing signal is fed to a relay circuitry 6 for breaking the power supply, and thereby a relay contact 6a is opened to shut off power to be supplied to the DC booster circuit 7. The shortcircuited state of the lamp can also be judged by monitoring the voltages impressed on the two terminals of the lamp individually and comparing them with each other.</p> |
