| 摘要 |
PURPOSE:To prevent overexposure automatically by stopping the oscillations of the DC-DC converter of a charging source for a main capacitor on detecting the luminosity of a field exceeding a prescribed value. CONSTITUTION:When the luminosity of a field exceeds a prescribed value, the resistance of a photoconductive element 7 increases to turn off a transistor 3, so that an oscillation transformer 2 forming a DC-DC converter will not oscillate. Therefore, a main capacitor 12 is not charged, and a flash discharge tube 18 never flashes. On the other hand, if the luminosity of the field exceeds the prescribed value while the discharge tube 18 is flashing to stop the oscillations of the transformer 2, capacitors 11 and 14 are discharged via a resistance 17 to turn off a neon lamp 9. Simultaneously, a trigger voltage obtained through a boosting transformer 15 is vanished to stop the flashing of the discharge tube 18, thus preventing over-exposure automatically. |
