| 摘要 |
PURPOSE:To carry on the light emission of a flash tube while holding the quantity of light emission nearly equal by providing a pulse generating circuit for applying a continuous pulse signal which increases in duty ratio gradually to the gate terminal of a non-self-holding type semiconductor switching element connected to the trigger circuit of the flash tube. CONSTITUTION:An oscillating voltage-boosting means B oscillates and boosts the output voltage of a power circuit A to charge a trigger capacitor 13 and a capacitor 21 is charged to a voltage to be supplied to the gate of an IGBT 16 so as to turn it on. Then a drive circuit applies a pulse signal to the gate terminal of the IGBT 16, which is turned on. The trigger capacitor 12, therefore, starts discharging operation to excite a primary current at the primary coil of a trigger transformer 13, thereby inducing a high voltage across the secondary coil. The drive circuit 20 applies the continuous pulse signal which increases in duty ratio to the gate terminal of the IGBT 16 to make its ON time along successively. Consequently, the flash tube is put in continuous light emitting operation while its quantity of the light emission is held nearly equal. |
