SWITCHING POWER SUPPLY CIRCUIT

摘要

A switching power supply circuit according to a first invention wherein a smoothing circuit includes an electromagnetic induction circuit the inductance of which is variable, a control circuit controls the electromagnetic induction circuit so that the inductance of the electromagnetic induction circuit may be a predetermined value when the amount of variation of the current is below a predetermined value and may be below the predetermined value when the amount of variation is a predetermined value or more, whereby the ripple voltage is low and the transient response to a variation of the load current is quick. A switching power supply circuit according to a second invention wherein when the variation of the current is a predetermined value or more because of a load variation and when the current increases or decreases, charge is supplied from a capacitive element to the load or absorbed by the capacitive element from the load by applying a positive or negative voltage to the capacitive element to suppress the vibratory voltage whereby a lower ripple voltage is realized and the transient response to a variation of the load current is quick.