Pulsed flash tube regulator using thyristor gate control

In an electronic timing apparatus wherein the duration of light energy emitted from a flash tube is regulated to produce a predetermined quantity of emitted light energy:

• first means including a normally closed controllable gate serially connected with the main electrodes of the flash tube for applying operating voltage to the main electrodes when the gate is open, the gate having a control electrode responsive to signals of one polarity for opening the gate and responsive to signals of the opposite polarity for closing the gate;
• second means for selectively applying an igniting pulse to the trigger electrode of the flash tube, the tube being operated to emit light by the simultaneous application thereto by operating voltage and of an igniting pulse;
• third means responsive to the application of the igniting pulse to the trigger electrode for applying a signal of the one polarity to the control electrode to open the gate;
• a transformer;
• means for connecting the primary winding of the transformer in series to the output of the flash tube;
• integrating means including a photosensitive element in operative association with the light emitted from the flash tube;
• means for coupling the secondary winding of the transformer to the input of the integrating means for energizing the latter to produce a control voltage that varies in proportion to the light energy emitted from the flash tube;
• fourth means including a control thyristor having a normally disabled transconductive path for reversing the polarity of the signal applied to the gate by the third applying means when the transconductive path of the control thyristor is enabled, the control thyristor having a control electrode triggerable when a voltage applied thereto reaches a predetermined value for enabling the transconductive path of the control thyristor;
• and
• means for coupling the output of the integrating means to the control electrode of the control thyristor.

In an electronic timing apparatus wherein the duration of light energy emitted from a flash tube is regulated to produce a predetermined quantity of emitted light energy:

• a source of operating voltage;
• a normally closed controllable gate serially connected with the voltage source and the main electrodes of the flash tube and operative when opened to supply operating voltage to the main electrodes, the gate having a control electrode responsive to signals of one polarity for opening the gate and responsive to signals of the opposite polarity for closing the gate;
• means for selectively applying an igniting pulse to the trigger electrode of the flash tube;
• a normally disabled switch having an output connected to the control electrode of the gate;
• means for connecting the input of the switch to a predetermined terminal of the operating voltage source for applying a voltage of the one polarity occurring at said terminal to the input of the switch;
• means responsive to the application of the igniting pulse to the trigger electrode for enabling the switch to couple the voltage of the one polarity to the control electrode of the gate to open the gate and to operate the flash tube so that the latter emits light;
• means rendered effective upon the operation of the flash tube for generating a control signal that varies in proportion to the total light energy emitted from the flash tube;
• means including a thyristor having a normally disabled transconductive path for reversing the polarity of the voltage at said predetermined terminal when said transconductive path is enabled and for applying the resulting signal of the opposite polarity to the control electrode of the gate, the thyristor having a control electrode triggerable when a voltage applied thereto is at least a predetermined value for enabling the transconductive path of the thyristor;
• and
• means for coupling the output of the control signal generating means to the control electrode of the thyristor.