| 摘要 |
PROBLEM TO BE SOLVED: To safely stop operation without causing erroneous operation and the breakage of a component when an AC voltage of a commercial power supply of a switching power supply device is lowered. SOLUTION: The switching power supply device 10 controls a main switching element Q1 by using a control circuit 12 in order to output a DC voltage obtained by rectifying an input AC voltage by a rectifying circuit as a DC output by stabilizing the DC voltage to a desired voltage. An actuation current of the control circuit 12 is obtained from the DC voltage via a first starting resistor R1 and a second starting resistor R2. The switching power supply device also comprises a voltage detection circuit 14 which detects a voltage of the DC input by using a Zener diode ZD1, and a switch circuit 13 which stops the main switching element Q1 when a voltage value of the DC input reaches a prescribed value or lower. The voltage detection circuit 14 monitors a direct current at a connecting point between a plurality of the starting resistors by using the Zener diode ZD1. COPYRIGHT: (C)2008,JPO&INPIT
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