Abstract: In a headlamp assembly, a reflector unit includes a bearing surface for supporting a lighting control circuit. The lighting control circuit is mounted to the backside of the reflector unit across a holder, and directly connected to a discharge bulb. The reflector unit further includes a mounting portion to which a lampshade unit is mounted. In the reflector unit, the backside of the mounting portion is offset from the bearing surface in both of the axial direction and the radial direction. That is, the lampshade unit and the holder are fixed to the reflector unit so as to be distanced from each other. Thus the holder is thermally disconnected from the lampshade unit, and thereby the heat transfer from the lampshade unit to the lighting control circuit is reduced.

Abstract: In a discharge lamp control circuit for a discharge lamp mounted on a vehicle, a capacitor in a starting circuit is charged by a high voltage generated by a transformer used in a direct current power source circuit. A transformer necessary for the starting circuit and the transformer necessary for the direct current power source circuit can commonly be used for cost reduction. Further, a thyristor is used in the starting circuit in place of a gap for activating the discharge lamp.

Abstract: In a headlamp assembly, a reflector unit includes a bearing surface for supporting a lighting control circuit. The lighting control circuit is mounted to the backside of the reflector unit across a holder, and directly connected to a discharge bulb. The reflector unit further includes a mounting portion to which a lampshade unit is mounted. In the reflector unit, the backside of the mounting portion is offset from the bearing surface in both of the axial direction and the radial direction. That is, the lampshade unit and the holder are fixed to the reflector unit so as to be distanced from each other. Thus the holder is thermally disconnected from the lampshade unit, and thereby the heat transfer from the lampshade unit to the lighting control circuit is reduced.

Abstract: A headlamp assembly includes a cover member detachably mounted to a headlamp housing. A lighting control circuit is disposed in the housing opposite to the cover member, and directly connected to a discharge bulb. The cover member is an aluminum die-casting, and therefore has high heat conductance. Further fins are integrally formed on the cover member, and the cover member is entirely painted black. According to this construction, the heat generated by the lighting control circuit is transferred to the inner surface of the cover member by radiation, and further conducted to the outer surface efficiently. Then the heat is radiated from the outer surface so as to be blown off, and thereby rise in the internal temperature of the lighting control circuit is suppressed.

Abstract: A hybrid IC of electronic circuit for a discharge lamp is disposed on the bottom of a metal case. A transformer, an inductor, a transformer, and a capacitor are disposed in a resin case. The resin case is contained in a metal case. In this instance, the transformer, the inductor, the transformer, and the capacitor are located outside the outer periphery of the IC so that the IC does not overlap on the transformer and other components. The transformer for a starter circuit has a secondary winding the inductance of which is 2.5 mH or larger, and a capacitance of a smoothing capacitor of a DC—DC converter is 0.5 &mgr;F or smaller. The switching frequency f of a MOS transistor is selected so that L2×C1 is equal to or larger than 1×10−1×f−1.68.

Abstract: In a discharge lamp control circuit for a discharge lamp mounted on a vehicle, a capacitor in a starting circuit is charged by a high voltage generated by a transformer used in a direct current power source circuit. A transformer necessary for the starting circuit and the transformer necessary for the direct current power source circuit can commonly be used for cost reduction. Further, a thyristor is used in the starting circuit in place of a gap for activating the discharge lamp.

Abstract: A discharge lamp control circuit for a vehicular lamp uses a starting circuit capacitor that is charged by the same high voltage generator used later as the lamp's power source after it is turned on. As a result, no separate dedicted starting transformer is necessary. Further, a thyristor and diode are used in the starting circuit in place of a spark-gap for initially activating the discharge lamp.

Abstract: In a discharge lamp control circuit for a discharge lamp mounted on a vehicle, a capacitor in a starting circuit is charged by a high voltage generated by a transformer used in a direct current power source circuit. A transformer necessary for the starting circuit and the transformer necessary for the direct current power source circuit can commonly be used for cost reduction. Further, a thyristor is used in the starting circuit in place of a gap for activating the discharge lamp.

Abstract: In a discharge lamp device, the electric power supplied to a discharge lamp is controlled in order of first to fourth control regions from the start of lighting of the discharge lamp. In the first control region, the lamp current is held constant until the lamp voltage reaches a first voltage value. In the second control region, the lamp current is reduced so as to have a correlation with a first time constant curve for a constant time after the lamp voltage reaches the first voltage value. In the third control region, the lamp current is reduced so as to have a correlation with a second time constant curve after a lapse of the constant time. The second time constant curve differs from the first time constant curve.

Abstract: A lamp current i.sub.L flows through a first resistor. Electric current I, which is the output current of a voltage-current converter which converts a lamp voltage V.sub.L to a lamp current I, flows through a second resistor. Feedback control is executed to make V.sub.-, which is the voltage of one terminal of the second resistor, equal a reference voltage V.sub.ref. The power applied to the lamp during start-up is controlled to be the same as the power applied to the lamp during its stable lighting for a predetermined lamp voltage range. Using the following two linear equations, the electric current I is set as I=aV.sub.L +b (where a and b are positive constants) when the lamp voltage V.sub.L is lower than a first predetermined voltage V.sub.a which is less than the lamp voltage during the normal stable lighting period of the lamp, and as I=cV.sub.L +d (where c and d are positive constants with c<a and d>b), when the lamp voltage V.sub.L is greater than or equal to the first predetermined value V.sub.

Abstract: A semiconductor switching element is connected to the first winding of a transformer. A smoothing capacitor is connected to the second winding of the transformer through a rectifier diode. The charging voltage Va of this smoothing capacitor serves as the applied voltage of a discharge lamp. When the discharge lamp is lighting, the second winding serves as a power source for supplying power to the discharge lamp. A capacitor is connected to the third winding of the transformer through a rectifier diode. The charging voltage of this capacitor serves as the applied voltage of a discharge tube. When the discharge tube discharges, a high-voltage starting pulse is provided to the secondary winding of a high-voltage coil, thereby rendering the discharge lamp ready for lighting. Therefore, when the discharge lamp is starting, the third winding serves as a power source for supplying starting power to the discharge lamp.