| 摘要 |
PURPOSE:To prevent wasteful consumption of an electric power source by providing a timer circuit which operates a DC-DC converter for a prescribed time only during low luminance time cooperatively with release operation. CONSTITUTION:When a release button is held half-pushed, a switch 2 goes on, and a detecting circuit 1 for object luminance operates. In the case of low luminance, transistors (TR) 5, 6 go on and off and the electric charge charged in a capacitor 10 is released and therefore a timer circuit 7 starts operating. Thence, transistors 11, 14 both go on, and a DC-DC converter 15 starts operation, and the operation period thereof is determined by the timer circuit. In the case of high luminance, the TR6 remains off and the timer circuit does not operate. It is possible to complete the charging of the capacitor 10 immediately and to stop the converter 15 by closing a lock switch 27. |
