Switching regulator
View Patent ↗In a switching regulator circuit having a function of bypassing a power supply and an output terminal, there is provided a switching regulator that obtains a stable output voltage even if the operation of the bypass function is changed over. A reference voltage that is inputted to an error amplifier is set to a higher voltage value in a bypass state, and is gradually decreased to a desired value when the bypass state is canceled.
1. A switching regulator, comprising:
a voltage-dividing resistor for dividing a voltage outputted to an output terminal;
an error amplifier for comparing a voltage outputted by the voltage-dividing resistor with a reference voltage;
a chopping wave generator circuit for generating a chopping wave;
a control circuit for inputting an output of the error amplifier and the chopping wave;
a p-type MOS transistor and an n-type MOS transistor controlled according to an output of the control circuit and connected in series between a power supply and a ground; and
a bypass transistor connected between the power supply and the output terminal,
wherein a circuit for generating the reference voltage comprises:
a first reference voltage circuit;
a first switching means for connecting the first reference voltage circuit to the error amplifier in inversion synchronism with the bypass transistor;
a time constant circuit disposed between the first switch means and the error amplifier;
a second reference voltage circuit; and
a second switch means for connecting the second reference voltage circuit to the error amplifier in synchronism with the bypass transistor.
2. A switching regulator control circuit according to claim 1 , wherein:
a voltage of the first reference voltage circuit is lower than a voltage of the second reference voltage circuit; and
an input voltage of the error amplifier is gradually decreased by the time constant circuit when the first switch means is rendered conductive.
3. A switching regulator control circuit according to claim 1 , wherein a voltage of the second reference voltage circuit is set so that the p-type MOS transistor connected to the power supply is rendered conductive in a state where the bypass transistor is in a conductive condition.
4. A switching regulator, comprising:
the switching regulator control circuit according to claim 1 ; and
an inductor and a capacitor which constitute an output smoothing circuit connected between a node of the p-type MOS transistor and the n-type MOS transistor, and the output terminal.