Electronic photoflash with automatic luminance proportioning - has switchable thyristor, to which series circuit of capacitor and second thyristor is parallel coupled

摘要

In order to permit a more rapid series of flashes, the photoflash arrangement has a semiconductor switch in series with the flash tube. The switch is formed by a switchable thyristor whose control electrode can be supplied with a defined potential. The thyristor anode is directly or indirectly connectable to the flash tube cathode, while the thyristor cathode is directly or indirectly connectable to a fixed reference potential. Parallel to the switchable thyristor (8) is connected a series circuit of a capacitor (50) and a thyristor (55). Pref. an input of a trigger circuit (62) is incorporated between the switchable transistor cathode and a current measuring resistor in series to this transistor. The outputs (Q,Q') of the trigger circuit are linked to inputs of two AND-gates (59,60) whose other inputs receive the switch-off signal (A) for the flash tube (6).