| 摘要 |
PURPOSE:To rapidly reset after PUT operation by providing an input power source detector, and inverting the PUT for protecting the interruption by the OFF signal of the input power source from ON to OFF. CONSTITUTION:A switching power source having an interruption protecting circuit has a switching transistor (Tr)5, a controller 6, a PUT9 for forming a protecting circuit. In this case, an input voltage detector having a photocoupler of a photodiode 13a through a rectifying diode 10 and a phototransistor 13b, and a circuit of Tr18 for inverting the PUT9 from ON to OFF are provided. Thus, the Tr18 is turned OFF in the state that the PUT9 is ON by the protection of the interruption to charge a capacitor 19. When an input power source 1 is turned OFF from this, the Tr18 is turned ON through the photocoupler 13, the PUT9 can be instantaneously turned OFF to immediately restart oscillating when the input power source is returned ON. |
