| 摘要 |
PURPOSE:To increase the lifetime of an exciting lamp by operating a power source which drives the lamp as a constant-current power source when the lamp is lit and operating the power source as a constant-voltage power source when the lamp is not lit, thereby eliminating the production of an overvoltage. CONSTITUTION:A gate control circuit is controlled by the output of voltage detecting means for detecting the terminal voltage of an exciting lamp when the lamp is not lit, thereby controlling a thyristor circuit so that the power source is operated substantially as a constant-voltage power source. On the other hand, the circuit is controlled by current detecting means for detecting a current flowing through the lamp when the lamp is lit, thereby controlling the thyristor circuit so that the power source is operated substantially as a constant-current power source. |
