| 摘要 |
PURPOSE:To provide the titled circuit compatible to any instantaneous interruption by controlling a thyristor and connecting a current limiting element when the instantaneous interruption of a commercial AC input exceeds an allowable time. CONSTITUTION:A switching power circuit 6A includes a resistor 7 as a current limiting element and a thyristor 16 as a shortcircuiting circuit. A pulse generating circuit 2A monitors a commercial AC input, and generates a pulse signal synchronizing with commercial AC frequency. A drive circuit 20A containing a power output stabilizing circuit 17 controls a switching transistor 15, the thyristor 16, according to the presence of the pulse signal from the pulse generating circuit 2A, and connects the resistor 7 in series with an input capacitor 8 or short-circuits the resistor 7. When the instantaneous interruption of the commercial AC input exceeds an allowable time, the operation of the thyristor 16 is stopped, and the resistor 7 is connected and rush currents are limited.
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