| 摘要 |
According to one embodiment, a switching power-supply device includes a switching element, a constant current element, a rectifying element, first and second inductors, and a constant voltage circuit. The switching element supplies, when the switching element is on, a power-supply voltage of a direct-current power supply to and feeds an electric current to the first inductor. The constant current element is connected to the switching element in series and turns off the switching element when the electric current of the switching element exceeds a predetermined current value. The rectifying element is connected to any one of the switching element and the constant current element in series. The second inductor is magnetically coupled to the first inductor and supplies induced potential to a control terminal of the switching element. The constant voltage circuit applies control potential to a control terminal of the constant current element. |
