PURPOSE: To reduce noises in the output voltage of a stabilized power circuit and speed up the operation rise by turning-on of a power supply.

CONSTITUTION: A constant voltage circuit 1 and a voltage circuit which outputs a fast rising output voltage are provided. A voltage comparing circuit 50 and a transistor Q55 for switching are provided. The constant voltage circuit 1 has a capacitor C12, removing noises in its output voltage VOUT, connected to a voltage line of high impedance. The voltage comparing circuit 50 compares the output voltage VOUT of the constant voltage circuit 1 with the output voltage of the voltage circuit and supplies the comparison output of the voltage comparison as an ON/OFF control signal to the transistor Q55 for switching. When the constant voltage circuit 1 is started up, the capacitor C12 is charged thorugh the transistor Q55 for switching.