JPS54162540A - Automatic light tuning flash device for photography - Google Patents

Abstract

PURPOSE:To make possible triggering even with a thyristor of large gate trigger current and dull sensitivity by performing triggering at the discharging separetely from a power source for photo detecting circuit and triggering a thyristor for stopping of emission by the discharge current of the charge having been charged in the third capacitor. CONSTITUTION:When the synchronizing contacts 12 of a camera are closed, an SCR 8 for starting emission is turned ON by the voltage application of a triggering capacitor 15. This causes the current of a capacitor 7 to flow in the primary winding of a trigger transformer 6 and a discharge tube 4 is let to emit light by the trigger voltage of the secondary winding. At the same time, the operating voltage for a photo detecting circuit 28 is generated between both terminals of a Zener diode 19 by the discharging of the first capacitor 17. The reflected light of the discharge tube 4 enters a photo transistor 36 to charge the second capacitor 23. A PUT 39 is turned ON by this charging voltage and as it goes ON, a transistor 40 goes ON, then the charge of the third capacitor 35 flows in an SCR 9 for stopping emission, thus turning ON the SCR. As a result, a capacitor 16 for stopping emission discharges through the SCRs 8, 9 and the SCR 8 turns OFF, thus stopping the emission of the discharge tube 4.