| 摘要 |
PROBLEM TO BE SOLVED: To provide a soft-start circuit and a switching power supply, which takes countermeasures against the overshoot of an output voltage in subsequent soft-start operation, even if a reset signal input from outside has a small pulse width. SOLUTION: With regard to a soft-start circuit 2a including an integration circuit to which a capacitor Cs and a current source 20 are connected in series and which employs as a soft-start signal Vs a potential of the connecting point between the capacitor Cs and current source 20, and a discharging switch element Ms one end of which is connected to the connection point between the capacitor Cs and current source 20, the discharging switch element Ms is turned on through an external reset signal RESET to start discharging of the capacitor Cs and to allow the discharging to continue till the soft-start signal Vs becomes lower than or equal to a discharge decision potential▵V, preventing the overshoot of the output voltage due to the soft-start signal Vs beginning with a large value. COPYRIGHT: (C)2011,JPO&INPIT |
