| 摘要 |
PURPOSE:To obtain a power supply fluctuation detecting circuit which is suited for prevention of an abnormal operation of a circuit that produces a transient state of a power supply switch regardless of the power supply voltage, by making use of the charging/discharging of a capacitor. CONSTITUTION:The anode of a diode 13 is connected to a power supply terminal via a resistance 15, and the cathode is earthed via a capacitor 17 respectively. The emitter of a transistor TR11 is connected to the terminal 5 via a resistance 14, and the base is connected to the cathode of the diode 13 respectively. Thus a charged current flows to the capacitor 17 by the current according to the transient voltage when the power supply is closed, and at the same time the similar current is applied via the corrector of a transistor. Then a TR2 which controls the muting of an echo circuit that produces a fault like a click, etc. in the transient mode is turned on. In the same way, the ON of the TR2 is controlled via a PNP TR12 when the power supply is open. As a result, a power supply fluctuation detecting circuit suited for prevention of the abnormal operation of a circuit that produces a transient condition when the power supply is switched is obtained regardless of the power supply voltage. |
