| 摘要 |
PURPOSE:To accurately detect the life of a discharge lamp by stopping the lighting of the discharge lamp when the integrating lighting time of the discharge lamp reaches a given value. CONSTITUTION:The lamp voltage VDL of a discharge lamp DL1 is gradually raised following lamp life performance, and when the value of the lamp life performance reaches some value, the life of the discharge lamp DL1 is expired. Here, a lighting time is used instead of the lamp voltage VDL for detecting the life of the discharge lamp DL1. In concrete, a lighting time integrating circuit SK1 for integrating the lighting time of the discharge lamp DL1 is provided. When an integrated time by this lighting time integrating circuit SK1 reaches a given value (e.g. rated life time), a lighting stop signal is sent to a control circuit CR1 from the circuit SK1 to stop the oscillation action of the circuit CR1, and a switching element Q is kept in an OFF condition to stop the lighting of the discharge lamp DL1. |
