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In a lighting circuit, a battery voltage is sent via a DC power supply section to a DC-AC converter to be converted to a square-wave AC voltage which is in turn supplied to a discharge lamp. The lighting circuit comprises an auxiliary power supply section for producing a predetermined voltage based

In a lighting circuit, a battery voltage is sent via a DC power supply section to a DC-AC converter to be converted to a square-wave AC voltage which is in turn supplied to a discharge lamp. The lighting circuit comprises an auxiliary power supply section for producing a predetermined voltage based on the input voltage from a battery and supplying this predetermined voltage to the individual sections of the lighting circuit and an abnormality detection circuit for detecting an abnormality in the discharge lamp, the circuit status, the battery voltage and so forth. In accordance with a signal from the abnormality detection circuit, a switch section, which is provided on a current line whose current is smaller than a current flowing on a power supply line to the discharge lamp, is switched on or off to enable or disable the auxiliary power supply section, thereby permitting or inhibiting power supply to the discharge lamp.

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[ What is claimed is:] [1.] A lighting circuit for a discharge lamp, designed to supply an input voltage from a DC power supply to a discharge lamp via a DC power supply section, said lighting circuit comprising:an auxiliary power supply section for producing a predetermined voltage based on said in

[ What is claimed is:] [1.] A lighting circuit for a discharge lamp, designed to supply an input voltage from a DC power supply to a discharge lamp via a DC power supply section, said lighting circuit comprising:an auxiliary power supply section for producing a predetermined voltage based on said input voltage from said DC power supply and supplying said predetermined voltage to individual sections of said lighting circuit;an abnormality detection circuit for detecting an abnormality in said discharge lamp or said lighting circuit; andswitch means for permitting or stopping power supply to said individual sections of said lighting circuit from said auxiliary power supply section in accordance with a detection signal from said abnormality detection circuit, thereby permitting or inhibiting power supply to said discharge lamp, whereina supply voltage stabilized by said auxiliary power supply section is supplied from a first terminal at an output stage thereof to said abnormality detection circuit, and a predetermined supply voltage is supplied to individual sections of said lighting circuit excluding said abnormality detection circuit from a second terminal connected to an output terminal of said switch means provided at a subsequent stage of said first terminal or the other power supply terminal of said auxiliary power supply section.