| 摘要 |
PURPOSE:To prevent an output signal from being suppressed for a prescribed period after power reapplication by comparing and deciding a power voltage with a preset value and short-circuiting a smoothing capacitor of a rectifier circuit when the power voltage is lower than the prescribed value. CONSTITUTION:When a power terminal voltage is lower than a prescribed voltage, an output of a comparator CP goes to high level and a transistor (TR) Q2 is turned on. Since the power supply terminal voltage has a slow leading and trailing by the operation of a ripple filter R1, C1 just after application and interruption of a power source switch S1, the TR Q2 is turned on for a prescribed time. Thus, the electric charge in a smoothing capacitor C3 is discharged in a short time after the switch S1 is interrupted and the residual electric charge is nearly zero. Since most of the charging current to the capacitor C3 by a shock noise voltage appearing at an output terminal (c) is short- circuited by the TR Q2 at the application of the switch S1, the circuit reaches the steady-state quickly even at reapplication of power.
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