| 摘要 |
PURPOSE:To nullify the necessity of an expensive timer circuit by a method wherein a voltage drop generated in a current limiting element is monitored by a charging current of a smoothing capacitor, and the charging current is confirmed, and then, the current limitting elements are short-circuited. CONSTITUTION:When starting, if an input switch SW is turend ON, the charging current of a smoothing capacitor C flows via a current limiting resistor R. At this time, a transistor Tr and a transistor Tr2 which are installed to monitor the voltage drop across the resistor R caused by this current are placed in a continuity state. And then, when the charging approaches to the completion and the charging current decreases, the voltage drop generated across the resistior R becomes equal to or less than the sum of the voltage across a base and emitter of the transistor Tr1 and the voltage drop generated across the resistor RB caused by the base current of this transistor, thus, the transistor Tr1 and transistor Tr2 are in a nonconginuity state and the transistor Tr3 is in a continuity state. On this account, a starting relay A actuates to short-circuit the resistor R at a contact (a), and thereafter, power supply to an interruption load L and a driving circuit D is performed without running through resistors, from a power source. |
