| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve a problem of a flyback switching power circuit which feedback controls an output voltage by tertiary winding and which cannot inhibit decrease in voltage at high speed though the output voltage decreases in a light load condition or in no load condition due to a sudden change of a load and the like. <P>SOLUTION: A switching power supply device comprises a load sudden change detection circuit provided between PN output terminals of DC, and which has no power consumption in a stationary state and only detects excessive fluctuations in a DC output voltage. The switching power supply device starts to switch on a semiconductor switch on the primary side even in a state where the semiconductor switch is turned off in no load condition or in a light load condition thereby to enable detection of the DC output voltage by tertiary winding to inhibit decrease in DC output voltage. <P>COPYRIGHT: (C)2013,JPO&INPIT |
