Automatic switching circuit for ac input


PURPOSE: To stabilize constant-voltage characteristics by bridge-rectifier operating a rectifier circuit when AC input voltage is higher than a reference voltage and operating voltage doubler full-wave rectifier-operating the rectifier circuit when AC input voltage is lower than the reference voltage. CONSTITUTION: A smoothing circuit to which smoothing capacitors 20, 22 are connected in a series is connected at an output terminal for a single-phase bridge rectifier circuit 18a, while a TRIAC 24 is connected between a node across the capacitors and one AC input terminal for a rectifier circuit 18. Said smoothing capacitors 20, 22 are controlled selectively by turning the TRIAC 24 ON (OFF). An automatic switching circuit changeover-controlling the rectifier circuit 18 is constituted of a diode rectifier 26 for AC input voltage, a capacitor 38 for smoothing, a Zener diode 34 for reference voltage, operational amplifiers 48, 84, etc. at that time. Accordingly, when AC input voltage is of a 115V system, an output from the operational amplifier 84 reaches a high level and the TRIAC 24 is brought to an ON state, and the rectifier circuit 18 conducts voltage doubler full-wave rectifier. COPYRIGHT: (C)1988,JPO&Japio




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Patent Citations (2)

    Publication numberPublication dateAssigneeTitle
    JP-S5851774-AMarch 26, 1983Fujitsu LtdPower source circuit
    JP-S6158471-AMarch 25, 1986Sharp CorpPower supply apparatus

NO-Patent Citations (0)


Cited By (2)

    Publication numberPublication dateAssigneeTitle
    JP-H02219465-ASeptember 03, 1990Yahata Denki Seisakusho:KkPower source equipment
    US-4933832-AJune 12, 1990Compaq Computer Corp.Automatic line monitor