GB1281386A - Circuit for the photo electric ignition of an electronic flash tube - Google Patents

Abstract

1281386 Supply circuits for flash tubes MULTIBLITZ DR ING D A MANNESMANN GmbH & CO KG 21 Nov 1969 [6 Dec 1968] 57018/69 Heading H2H A circuit for igniting a flash tube includes a photo-transistor which feeds a pulse through a transistor amplifier to a thyristor, causing a capacitor to discharge through a transformer whose secondary winding is connected to an ignition electrode of the tube. In the arrangement shown, activation of a photo-transistor 46 causes a signal to pass by way of a capacitor 58 to a first amplifier transistor 60 which is directly coupled to a second amplifier transistor 68. This latter transistor is normally biased off by a voltage divider 70, 72, but is now briefly turned on so that a capacitor 80 can discharge through it and cause a gating signal to be transmitted to a thyristor 32. The ignition capacitor 30 can now discharge through the primary winding of transformer 28, so that a pulse is produced at the ignition electrode 34 of flash tube 36. A storage capacitor 38, charged by a voltage doubler circuit 40, 42, 44, now discharges in a very short time through the tube to produce an intense flash. The photo-transistor 46 has a capacitor 56 in its base circuit to divert any pulses originating from the mains supply. A number of such arrangements may be assembled in a studio and triggered simultaneously by a single flash which actuates the phototransistor in each circuit. Alternatively, the flash may be manually triggered by closing a switch 90. A capacitor 84 can then discharge into a transformer 82 which delivers a pulse to the base of transistor 60. The remainder of the circuit operates as before.