| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power-supply circuit that allows precise start-up even in a state that an output voltage is not zero, while suppressing an increase in the circuit area.SOLUTION: A charging circuit 8 generates a charge current Ic by receiving supply of an input voltage Vi. A bootstrap circuit 9 includes a capacitor C2 charged by the charge current Ic. The voltage of each terminal of the capacitor C2 is supplied to a driving circuit 2 as an operating voltage. The driving circuit 2 outputs a driving voltage for driving a transistor T1 to a gate of the transistor T1. A voltage control circuit 5 monitors a voltage Vc between terminals of the capacitor 2. The voltage control circuit 5 outputs a charge control signal Sc that commands the execution of charging when the voltage Vc is less than a set voltage Vth, and outputs the charge control signal Sc that commands the termination of charging when the voltage Vc is larger than or equal to the set voltage Vth. |
