| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device where light control by a PWM control will not be accompanied by accidental extinguishing. SOLUTION: The CPU of a control circuit detects the frequency of a PWM signal supplied from the outside (step S2). The value of a detected frequency is compared with a preset reference value (step S3). If the detected frequency value is equal to the reference value (Y in step S3), a high-voltage discharge lamp is extinguished (step S4). If the detected frequency value is different from the reference value (N in step S3), the duty ratio of the PWM signal is detected (step S5). Dimming is performed, so that the output of a DC power source becomes the electric power value which corresponds to the duty ratio of the PWM signal (step S6). |
