DC/DC converter and electronic apparatus
View Patent ↗To provide a DC/DC converter equipped with a clamp circuit having low power consumption, and reducible in chip area. A clamp circuit which clamps an output terminal of an error amplifier circuit equipped with an amplifier and a first transistor connected to an output terminal of the amplifier is configured to include a second transistor having a source connected to a source of the first transistor, a gate connected to a constant voltage circuit, and a drain connected to a constant current circuit, and a third transistor having a gate connected to the drain of the second transistor and a drain connected to the output of the amplifier.
1. A DC/DC converter comprising:
an error amplifier circuit including an amplifier which amplifies and outputs a difference between a divided voltage obtained by dividing a voltage outputted from an output transistor and a reference voltage, and a first transistor having a gate connected to an output terminal of the amplifier;
a clamp circuit which clamps an output voltage of the error amplifier circuit;
a ramp wave generating circuit which generates a ramp wave; and
a PWM comparator which compares the output voltage of the error amplifier circuit and the ramp wave,
said clamp circuit including:
a constant voltage circuit,
a constant current circuit,
a second transistor having a source connected to a source of the first transistor, a gate connected to the constant voltage circuit, and a drain connected to the constant current circuit, and
a third transistor having a gate connected to the drain of the second transistor and a drain connected to an output of the amplifier.
2. An electronic apparatus comprising the DC/DC converter according to claim 1 .
3. A DC/DC converter comprising:
an error amplifier circuit including an amplifier which amplifies and outputs a difference between a divided voltage obtained by dividing a voltage outputted from an output transistor and a reference voltage, and a first transistor having a gate connected to an output terminal of the amplifier;
a clamp circuit which clamps an output voltage of the error amplifier circuit;
a ramp wave generating circuit which generates a ramp wave; and
a PWM comparator which compares the output voltage of the error amplifier circuit and the ramp wave,
said clamp circuit including:
a constant voltage circuit,
a first constant current circuit,
a second constant current circuit,
a second transistor having a source connected to a source of the first transistor and a drain connected to the first constant current circuit,
a third transistor having a gate connected to the drain of the second transistor and a drain connected to an output of the amplifier, and
a fourth transistor having a source connected to the constant voltage circuit and a gate and drain connected to the second constant current circuit and a gate of the second transistor.
4. An electronic apparatus comprising the DC/DC converter according to claim 3 .