Lighting circuit for vehicular discharge lamp

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide an improved lighting circuit for a vehicular discharge lamp, which can overcome the above shortcomings.
To achieve the object, according to one aspect of the present invention, there is provided a lighting circuit for a vehicular discharge lamp having a DC voltage booster circuit for boosting an input voltage from a DC voltage input terminal, which comprises a current detector for acquiring a detection signal concerning an output current of the DC voltage booster circuit, a voltage detector for acquiring a detection signal concerning an output voltage of the DC voltage booster circuit, an abnormality judging circuit for comparing levels of the detection signals from the current detector and the voltage detector with each other to determine whether or not the lighting circuit is in an abnormal status, and a power cutoff circuit for inhibiting power supply to the discharge lamp upon reception of a signal from the abnormality judging circuit representing an abnormality in the lighting circuit.
With this arrangement, it is possible to determine whether or not the lighting circuit is normal or abnormal, based on the correlation between the output voltage and output current of the DC voltage booster circuit, and power supply to the discharge lamp will be stopped when it is judged that some abnormality has occurred.
It is therefore possible to protect the lighting circuit and discharge lamp as well as prevent the abnormality-originating damages.
In addition, this can be realized without the need to provide an abnormality detecting circuit for every cause of the abnormality, ensuring the simplified circuit structure.