| 摘要 |
PROBLEM TO BE SOLVED: To provide a control device for a discharge lamp having a structure capable of stably operating the lamp when it is lighted, when applying constant power control to the discharge lamp. SOLUTION: The output voltage of a chopper circuit is supplied to a full- bridge inverter circuit. A lamp such as a high-pressure discharge lamp is connected to the full-bridge inverter circuit through a current limiting reactor. A lamp voltage Va and a lamp current Ia are detected to be inputted in an arithmetic circuit 4, the product Pa of them is compared with a reference voltage E by an arithmetic amplifier 7 so as to make it constant, and a target value is outputted from a chopper driving circuit 9 in order to apply the constant power control to the discharge lamp. if the lamp voltage Va suddenly rises when it is lighted, the lamp current Ia is suddenly lowered and maintenance of lighting becomes impossible, and therefore, a switch 3 is opened when it is lighted to suppress the amplitude of the lamp voltage Va by a clip circuit 1. |
