CONTROL CIRCUIT OF ELECTRONIC FLASH DEVICE

摘要

PURPOSE:To realize size reduction by connecting a GTO in series with a xenon lamp, a turn-on circuit and a turn-off circuit to the gate of the GTO, and a spike voltage absorbing circuit between the anode of the GTO and high-voltage side of a main capacitor. CONSTITUTION:The main capacitor 2 and a capacitor 14 are charged by a converter 1 respectively. When a shutter button is pushed, a trigger pulse is applied to the gate of an SCR5 and the gate of the GTO 31 to turn on the both. At this time, the capacitor 14 is discharged through an SCR5 to turn on the xenon lamp 9, and a current (i) flows from the main capacitor 2 to maintain the light emission. A photodetecting circuit 24 outpus a trigger pulse when its photodetection amount attains to a specific value, and the turn-on circuit 34 leads a turn-off current from the gate of the GTO31, so that the xenon lamp 9 does not emit light any more. Further, a spike voltage VSP generated when the GTO31 turns off has its peak value suppressed by a diode 35. This system is suitable for the size reduction and protects the GTO from the spike voltage.