Constant voltage circuit

A constant voltage circuit converting an input voltage input to an input terminal into a predetermined constant voltage and outputting the constant voltage from an output terminal, the constant voltage circuit comprising:

• an output voltage control transistor configured to output a current according to an input control signal to the output terminal from the input terminal;
• an output voltage detector circuit part configured to detect an output voltage from the output terminal and to generate and output a voltage proportional to the detected output voltage;
• a first error amplifier circuit part configured to control an operation of the output voltage control transistor so that the proportional voltage is equal to a predetermined first reference voltage;
• a second error amplifier circuit part configured to cause the output voltage control transistor to increase the output current for a predetermined time when there is a rapid decrease in the output voltage from the output terminal, the second error amplifier circuit part being higher in a speed of response to a change in the output voltage than the first error amplifier circuit part;
• and
• a current limiting circuit part configured to control the operation of the output voltage control transistor so as to prevent the output current from the output voltage control transistor from exceeding a first predetermined value by gradually decreasing the output current and the output voltage from the output terminal alternately when the output current is greater than or equal to the first predetermined value,
• wherein the current limiting circuit part stops an operation of the second error amplifier circuit part when the output voltage from the output terminal is less than or equal to a second predetermined value.