| 摘要 |
PURPOSE:To prevent a fuse from blowing even when a source voltage is intermitted frequently in power-on operation by actuating a time limiting circuit which sets delay time on every power-on operation before the output voltage of a filter circuit attains to a specific voltage. CONSTITUTION:Transistor TRQ1 compares a power source filter output voltage Vc with the breakdown voltage Vd of a constant voltage diode and when the voltage Vc does not attains to the voltage Vd, an inhibited state is held and a TRQ2 turns on to short-circuit a capacitor C2. When the voltage Vc attains to the voltage Vd, the TRQ1 is turned on and the TRQ2 is turned off. Consequently, the capacitor C2 is charged again to generate a trigger voltage tr and the timer limiting circuit TM starts clocking delay time. Then, the signal tr is never inputted to the circuit TM unless the voltage Vc drops below the voltage Vd. Therefore, the circuit TM outputs a driving circuit dv a specific delay time later to operate a relay RL, short-circuiting a resistance R1 by the fuse F. |
