| 摘要 |
PROBLEM TO BE SOLVED: To detect the generation of slow leak and perform the specified control by arranging a switching means, a lighting main circuit for supplying the specified lamp power, a starting circuit, an lamp voltage monitoring means, and a means for comparing lamp voltage with two reference voltage to judge abnormality, and reducing or shutting off the supply power when abnormality arises. SOLUTION: A switching means contained in a main lighting circuit 2 of a lighting device of a high pressure discharge lamp 4 such as a short arc metal halide lamp which is easy to continue discharge when slow leak is generated is controlled by constant power according to lamp current and voltage. When lamp voltage detected with a lamp voltage monitoring means 5 goes up more than a first reference voltage and then goes down less than second reference voltage, an abnormality judging means quickly judges as abnormality, and a control means 7 automatically reduces or shuts off supply power, or displays abnormality. Even if the slow leak is generated and discharge is continued, damage of circuit components, emitting smoke, ignition, and the break of a lamp can be prevented. |
