Control circuit for flash tube apparatus

Claim 1

A control circuit for a flash light apparatus comprising (a) a charge capacitor charged by a high voltage generator; (b) a flash tube coupled in parallel with the charge capacitor; (c) a thyristor whose anode to cathode path being connected between the discharge capacitor and the flash tube for controlling the flash tube in ON-OFF fashion; (d) a trigger circuit coupled with a trigger electrode of the flash tube and gate of the thyristor to trigger the flash tube and thyristor; (e) a commutation capacitor coupled in parallel with the anode and cathode of the thyristor; (f) a precharge circuit for precharging the commutation capacitor; (g) a switch circuit connected between the commutation capacitor and the thyristor, said switch circuit being such that when it is rendered ON it causes a reverse voltage resulting from a charge stored in the commutation capacitor to be connected parallel with the thyristor to permit the thyristor to be turned OFF: (h) a timing circuit for turning the switch circuit ON; (i) a carrier recombination capacitor connected in parallel with the gate and cathode of the thyristor to reduce the turn-OFF time; (j) a trigger blocking circuit connected between the trigger circuit and the gate of the thyristor to prevent a trigger signal supplied to the gate of the thyristor; and (k) a timer circuit connected between the switch circuit and the trigger blocking circuit to prevent a supply of said trigger signal to said gate of the thyristor during a predetermined trigger signal blocking period, said predetermined trigger signal blocking time substantially corresponding to a period from the turning ON of said switch circuit until said commutation capacitor is substantially discharged.