Patent ID: 8169146

Claim:
A metal halide lamp in which an arc tube and a starting circuit are housed, the arc tube emitting light by electric discharge between electrodes by an AC power supplied by way of a lamp power supply circuit, the starting circuit abruptly changing current flowing in a ballast interposed in the lamp power supply circuit to output a starting pulse at a high voltage from the ballast, the arc tube and the starting circuit being connected in parallel with each other in an outer tube, wherein the starting circuit includes: a ferroelectric ceramic capacitor that is charged and discharged when a voltage at a predetermined coersive voltage or higher is applied by way of the lamp power supply circuit and changes the current flowing in the ballast thereby outputting the starting pulse at the high voltage from the ballast, a semiconductor switch that turns to a conduction state when a voltage of a predetermined breakover voltage or higher is applied, and a time constant control resistor that retards the discharge time of electric charges discharged by way of a closed circuit extending from one electrode to the other electrode of the capacitor by way of the arc tube when dielectric breakdown is initiated in the arc tube by the starting pulse, wherein a substantially common current flows through the ferroelectric ceramic capacitor, the semiconductor switch and the time constant control resistor, when the dielectric breakdown is initiated in the arc tube by the starting pulse.