| 摘要 |
<p>A switching power source device comprising: a step-down converter provided to a main current line (41) and having an inductor (L1), an FET (11), and a diode (D1); a drive circuit (30) for driving the FET (11); a drive voltage line (42) for applying and transmitting a drive voltage to be applied to a drive circuit (30); a capacitor (C1) connected between the main current line (41) and the drive voltage line (42); a constant voltage circuit (20) for making an input voltage constant and supplying the voltage to the drive voltage line (42) with the electric potential of the main current line (41) as a reference; and a boot-strap diode (D2) for applying and transmitting to the drive voltage line (42) an externally controlled voltage that is higher than the voltage made constant by the constant voltage circuit (20). A switching power source device is thereby provided, in which switching control of a switching element at operation startup is reliably performed and the desired output voltage is obtained even when the timeframe during which an input power source is off is short.</p> |
