Voltage regulator
View Patent ↗A voltage regulator is capable of continuously and smoothly preventing an inrush current independently of a startup characteristic of a reference voltage circuit. The voltage regulator is provided with an inrush current protection circuit composed of a constant-current circuit, a first transistor having the source thereof connected to the constant-current circuit and the gate thereof controlled by an output voltage detection circuit, a capacitor connected between the first transistor and the gate of an output transistor, a second transistor having the gate thereof connected to the drain of the first transistor and the source thereof connected to a power supply terminal, and a third transistor, which is connected between the second transistor and the output transistor and the gate of which is controlled by the output voltage detection circuit.
1. A voltage regulator comprising:
a reference voltage circuit which outputs a reference voltage;
an output transistor;
a first differential amplifier circuit which amplifies and outputs a difference between the reference voltage and a divided voltage obtained by dividing a voltage output from the output transistor and controls a gate of the output transistor;
an inrush current protection circuit which controls a gate voltage of the output transistor to prevent an inrush current;
and an output voltage detection circuit which controls the inrush current protection circuit,
wherein the inrush current protection circuit comprises:
a constant-current circuit having one end thereof connected to a power supply terminal;
a first transistor having a source thereof connected to the other end of the constant-current circuit and a gate thereof controlled by the output voltage detection circuit;
a capacitor having one end thereof connected to a drain of the first transistor and the other end thereof connected to the gate of the output transistor;
a second transistor having a gate thereof connected to the source of the first transistor and a source thereof connected to the power supply terminal;
and a third transistor having a drain thereof connected to the gate of the output transistor, a source thereof connected to a drain of the second transistor and a gate thereof controlled by the output voltage detection circuit.
2. A voltage regulator according to claim 1 , wherein the constant-current circuit is composed of a resistor.