| 摘要 |
PURPOSE:To make it possible to light easily a discharge tube constituted in such a way that a firing voltage is boosted with an increase in a discharge time and moreover, to make it possible to design the capacity of the discharge tube into a smaller capacity by a method wherein, when a voltage to apply to the discharge tube exceeds a voltage capable of firing after a power source has been turned ON, the output of a comparator is interrupted. CONSTITUTION:The output voltage of a converter transformer 1 is boosted by the oscillation operation of an oscillation circuit immediately after a power source has been turned ON. A voltage generated in a winding N3 is rectified by D1 and is smoothed by C1. Accordingly, the charging voltage of the C1 comes to a value proportioned to a voltage to be applied to a laser tube 4. The charging voltage of C2 is boosted according to the time constants of the C2 and R1. When the charging voltage of the C2 exceeds a reference voltage Vr2, the output of a comparator 5 is inverted and Q2 is turned-ON. Thereby, an oscillation output control circuit 2 interrupts the base current of Q1 and the oscillation operation is stopped. Accordingly, a supply voltage to the tube 4 is interrupted. After that, a charge which has been charged in the C1 is further charged a little in the C2 through the R1, but the charge of the C2 is discharged by R2 according to the time constants of the R2 and the C2. When the voltage of the C2 falls below the reference voltage Vr2, the Q2 is again turned-ON. |
