| 摘要 |
PROBLEM TO BE SOLVED: To surely detect an end of service life of a discharge lamp and a mounting status of a discharge lamp with a simple circuit configuration, and to prevent that secondary voltage is repeatedly applied to the discharge lamp when it is detected that the discharge lamp is not mounted at the end of the service life. SOLUTION: A voltage VC is generated by a direct-current part detection circuit detecting a direct current part flowing in the discharge lamp 14. A resistance 27, a diode 28 and a resistance 29 are connected to a +Vcc power supply in series to generate a voltage VA. A resistance 30, a diode 31 and a resistance 32 are connected in series to generate a voltage VB. It is usually set to satisfy VA>VC>VB. The voltage VA and the voltage VB are input into a first comparator 36 for detecting the end of the service life of the discharge lamp by VA<VB. The voltage VC and a reference voltage Vref are input into a second comparator 38 for detecting that the discharge lamp is not mounted by VC>Vref. Priority is given to mounting detection from the start to before the start of lighting, and the priority is given to detection of the end of the service life after the start of lighting. COPYRIGHT: (C)2007,JPO&INPIT |
