Patent ID: 8624569

Claim:
A voltage regulator comprising: a reference voltage circuit which outputs a reference voltage; an output transistor; a differential amplifier circuit which amplifies and outputs a difference between the reference voltage and a divided voltage obtained by dividing an output voltage supplied 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 output voltage detection circuit comprises: a first constant-current circuit, an input terminal of which is connected to a power supply terminal and an output terminal of which is connected to an output terminal of the output voltage detection circuit; a capacitor, one end of which is connected to the output terminal of the output voltage detection circuit and the other end of which is connected to a ground terminal; a first transistor, a source of which is connected to the power supply terminal and a gate of which is connected to the output terminal of the output voltage detection circuit; a second constant-current circuit, an input terminal of which is connected to a drain of the first transistor and an output terminal of which is connected to the ground terminal; a second transistor, a source of which is connected to the power supply terminal and a drain of which is connected to the output terminal of the output voltage detection circuit; a third constant-current circuit, an input terminal of which is connected to the power supply terminal; a third transistor, a drain of which is connected to an output terminal of the third constant-current circuit, a gate of which is connected to the drain of the first transistor, and a source of which is connected to the gate of the second transistor; and a fourth transistor, a drain of which is connected to the source of the third transistor, a gate of which receives the divided voltage, and a source of which is connected to the ground terminal, wherein the third transistor maintains the second transistor in an open state until the output voltage of the output terminal of the output voltage detection circuit exceeds a first threshold, wherein after the output voltage of the output terminal of the output voltage detection circuit exceeds the first threshold, the output voltage detection circuit controls the inrush current protection circuit to allow the output transistor to output the output voltage, and the third transistor enters an open state, wherein after the output voltage supplied from the output transistor exceeds a second threshold threshold, the fourth transistor enters a closed state, which causes the second transistor to enter and remain in a closed state to thereby maintain the output voltage of the output terminal of the output voltage detection circuit above the first threshold.