Abstract: Provided is an apparatus for controlling the power supplied to a discharge lamp by detecting the voltage and current of the lamp's electric supply line. A microcomputer monitors power consumption of the discharge lamp by multiplying the voltage and current detected in the supple line to determine the input power and produces a representative control signal. The actual input power is compared with a preset input power, based upon the signal, and the power consumption of the discharge lamp is controlled in accordance with the results of the comparison.

Abstract: A metal halide discharge lamp operated from a D.C. power source, which is suitable for an optical light source, has a quartz arc tube. Anode and cathode electrodes are disposed in the arc tube. The gap length between electrodes is so short that the metal halide discharge lamp functions as a point light source. The arc tube contains an inert gas, mercury and metal halide additives including metal bromine. By utilizing the catephoresis effects, the transformation of silica (SiO.sub.2) of the arc tube to cristobalite or the formation of an opaque substance on the arc tube is prevented. Atomic percent of bromine to halogen contained in the arc tube is about 60% to 90% and a wall load developed in the arc tube is substantially greater than 40 W/cm.sup.2.

Abstract: An apparatus for starting and operating a discharge lamp includes an inverter circuit. The inverter circuit comprises a parallel resonance circuit including an oscillation coil and capacitor, and which is connected to the discharge lamp, via a current-limiting coil, a switching transistor for triggering the parallel resonance circuit, and a feedback circuit connected to the switching transistor, for allowing a feedback signal for driving the switching transistor to be supplied to the base of the switching transistor, the feedback circuit being magnetically coupled to the current-limiting coil.