| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a switching power supply which can prevent a switching element from being driven by a drive signal of a frequency which is different from a desired frequency. Ž<P>SOLUTION: The switching power supply 1 includes a signal output circuit 45 which outputs a drive signal of a frequency corresponding to a cycle of the charging/discharging of a capacitor 47, a transistor 41 which is driven on the basis of the drive signal, and a current variable circuit 58 which makes variable a current flowing to a resistor 46 according to the charging/discharging of a capacitor 59. In the switching power supply, a time for charging the capacitor 59 is set longer than a time for charging the capacitor 47, and when the capacitor 59 is charged so that a voltage applied to the capacitor 59 becomes not lower than a voltage V4, the frequency of the drive signal is brought into a range of the desired frequency. The transistor 41 is turned off until the voltage applied to the capacitor 59 becomes not lower than the voltage V4. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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