Patent ID: 8674671
Filing Date: 2014-03-18
Classification: G05F

Abstract:
1. A constant-voltage power supply circuit comprising: a first transistor of a first conductivity type, connected between a power supply terminal and an output terminal; a voltage divider circuit including a first resistor having a first end connected to the output terminal and a second resistor having a first end connected to a second end of the first resistor and a second end connected to ground, the voltage divider circuit outputting a divided voltage between the first resistor and the second resistor; an output voltage control amplifier comparing the divided voltage and a reference voltage and controlling a voltage of a control terminal of the first transistor so as to equalize the divided voltage and the reference voltage; and a current-limiting characteristic control circuit controlling the voltage of the control terminal of the first transistor according to the divided voltage and an output current, the current-limiting characteristic control circuit comprising: a first constant current source having a first end connected to the power supply terminal and outputting a constant current; a second transistor of a second conductivity type, the second transistor being diode-connected, having a first end connected to a second end of the first constant current source, and having a second end supplied with a control voltage based on the divided voltage; a third transistor of the second conductivity type, having a control terminal connected to a control terminal of the second transistor; a fourth transistor of the first conductivity type, connected between the power supply terminal and a first end of the third transistor and having a control terminal connected to the control terminal of the first transistor; a third resistor connected between a second end of the third transistor and the ground; a fourth resistor connected between the first end of the third transistor and the ground; a fifth transistor of the first conductivity type, having a first end connected to the power supply terminal and a second end connected to the control terminal of the first transistor and the control terminal of the fourth transistor; a fifth resistor connected between the power supply terminal and a control terminal of the fifth transistor; and a sixth transistor of the second conductivity type, connected between the control terminal of the fifth transistor and the ground and having a control terminal connected to the first end of the third transistor.