Patent ID: 7408331

Claim:
A constant-voltage power supply circuit that converts a voltage input to an input terminal to a predetermined constant voltage and outputs the constant voltage, comprising: a first constant-voltage circuit including a first output transistor that outputs a current corresponding to a signal input to a control electrode thereof from the input terminal to an output terminal, and a first output voltage controller that generates a predetermined first reference voltage and generates a first proportional voltage in proportion to a voltage on the output terminal, amplifies a difference between the first reference voltage and the first proportional voltage, and outputs the amplified difference to the control electrode of the first output transistor; and a second constant-voltage circuit including a second output transistor that outputs a current corresponding to a signal input to a control electrode thereof from the input terminal to the output terminal, and a second output voltage controller that generates a predetermined second reference voltage and generates a second proportional voltage in proportion to the voltage on the output terminal, amplifies a difference between the second reference voltage and the second proportional voltage, and outputs the amplified difference to the control electrode of the second output transistor; wherein the first output voltage controller and the second output voltage controller start operations or stop operations according to a first control signal and a second control signal, respectively, input from outside, and when starting operations, a rising edge of the corresponding one of the first reference voltage and the second reference voltage is delayed so as to be later than a rising edge of the corresponding one of the first proportional voltage and the second proportional voltage.