Voltage regulator
View Patent ↗Provided is a voltage regulator which includes an inrush current prevention circuit so that no current is consumed after the start-up of the voltage regulator. A start-up circuit of the voltage regulator includes: a constant current circuit; a first transistor connected between the constant current circuit and a constant voltage generation circuit; a second transistor including a drain connected to a gate of the first transistor, and a gate to which a voltage based on an output voltage is input; a first depletion transistor including a gate connected to the drain of the second transistor, and a source connected to a source of the second transistor; and a third transistor including a gate connected to the gate of the second transistor, and a drain connected to the drain of the second transistor.
1. A voltage regulator, comprising:
a constant voltage generation circuit for generating a reference voltage;
an amplifier for amplifying and outputting a difference between the reference voltage and a divided voltage obtained by dividing an output voltage output from an output transistor, and controlling a gate of the output transistor;
an external terminal for inputting a signal for turning ON and OFF a circuit from outside; and
a start-up circuit for starting the constant voltage generation circuit,
the start-up circuit comprising:
a constant current circuit;
a first transistor connected between the constant current circuit and the constant voltage generation circuit;
a second transistor including a drain connected to a gate of the first transistor, and a gate to which a voltage based on the output voltage is input;
a first depletion transistor including a gate connected to the drain of the second transistor, and a source connected to a source of the second transistor; and
a third transistor including a gate connected to the gate of the second transistor, and a drain connected to the drain of the second transistor.
2. A voltage regulator according to claim 1 , wherein the second transistor includes a back gate connected to one of a drain of the first depletion transistor and the source of the second transistor.
3. A voltage regulator according to claim 1 , wherein the constant current circuit further comprises a second depletion transistor including a gate and a source which are connected to each other.
4. A voltage regulator according to claim 2 , wherein the constant current circuit further comprises a second depletion transistor including a gate and a source which are connected to each other.
5. A voltage regulator according to claim 1 , wherein the constant voltage generation circuit comprises:
a third depletion transistor including a gate and a source which are connected to each other;
a fourth depletion transistor including a gate and a source which are connected to each other, and a drain connected to the source of the third depletion transistor; and
a fourth transistor including a gate and a drain which are connected to the gate and the source of the fourth depletion transistor.
6. A voltage regulator according to claim 1 , wherein the constant voltage generation circuit comprises:
a resistor;
a fourth depletion transistor including a gate and a source which are connected to each other, and a drain connected to the resistor; and
a fourth transistor including a gate and a drain which are connected to the gate and the source of the fourth depletion transistor.