The present invention relates to a discharge lamp apparatus that uses a discharge lamp as a light source, and particularly to an apparatus in which an electronic controller unit for applying a voltage to the discharge lamp is directly coupled with the discharge lamp.
A discharge lamp apparatus that uses a discharge lamp as a light source is used as a vehicle headlight. An electronic controller unit that generates and controls a voltage applied to the discharge lamp includes a DC/DC converter for transforming an output voltage by switching an input voltage by a power device, a high voltage generation circuit for generating, from the output voltage of the DC/DC converter, a high voltage applied when lighting of the discharge lamp is initiated, and the like.
When the temperature of electronic circuit components forming the controller unit rises, it is likely that, for instance, the soldered part of the circuit components melt and the circuit components operate erroneously. In the discharge lamp apparatus disclosed in JP-A-2000-235809, a part of a metallic heat radiator thermally coupled with a circuit substrate mounting circuit components thereon is exposed outside a headlight so that the heat generated by the discharge lamp and the circuit components may be radiated to the outside of the headlight through the metallic heat radiator.
In the discharge lamp apparatus disclosed in JP-A-2000-235809, an igniter part and a lighting device need be connected by a harness. This increases the number of component parts, complicates assembling work and adds manufacturing cost.
It is therefore proposed to directly couple and electrically connect the discharge lamp and the controller unit. However, if the discharge lamp and the controller unit are directly coupled and the controller unit is disposed near the discharge lamp, the internal temperature of the controller unit rises due to heat transferred or radiated from the discharge lamp and the heat generated by the controller unit itself. This is likely to cause erroneous operation of the circuit components in the controller unit.
It is therefore an object of the present invention to provide a discharge lamp apparatus that uses no high voltage wire nor high voltage connector and suppress rise of temperature of an electronic controller unit.
In a discharge lamp apparatus according to the present invention, a discharge lamp and an electronic controller unit for applying a voltage to the discharge lamp are directly coupled with and electrically connected to the discharge lamp. Therefore, a high voltage connector and a high voltage wire for connecting the discharge lamp and the controller unit are not necessitated.
Preferably, a second casing mounting a power device of a DC/DC converter has a thermal conductivity higher than that of a first casing coupled with the discharge lamp. As a result, heat generated by the discharge lamp is less likely to be transferred from the first casing to the second casing, and the heat of the discharge lamp is less likely to be transferred circuit components mounted in the second casing.
In addition, heat generated by the power device of the DC/DC converter is more likely to be radiated to the outside of the second casing from the second casing that has the thermal conductivity higher than that of the first casing. Because the power device of the DC/DC converter generate more heat among the controller unit, the heat generated by the power device is readily radiated from the second casing to the outside of the second casing, thus suppressing rise of temperature of the circuit components in the controller unit including the power device. Thus, erroneous operation of the circuit components is prevented.