| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching step-up power supply circuit capable of protecting a switching element from inrush current without using a large capacity switching element and of performing a proper start of switching control and its stable control. SOLUTION: The switching step-up power supply circuit 1 includes at least a power supply switch 4, a step-up circuit 5, a switching control unit 6, a voltage detection part 7 and a delay circuit 8. The voltage detection part 7 judges whether the input voltage value at a voltage detection position A exceeds a voltage threshold value 7a or not, and the delay circuit 8, after the input voltage value exceeds the voltage threshold value 7a and after an elapse of a rising delay time T1, transmits an approval signal 8a to the switching control unit 6. Furthermore, the delay circuit 8, when the input voltage value becomes smaller than the voltage threshold value 7a, continues to transmit the approval signal 8a, as long as the noise pulse width is within a noise filter time T2. COPYRIGHT: (C)2008,JPO&INPIT
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