Patent ID: RE39374

Claim:
A constant voltage power supply supplying power to a load having an operation condition and a standby condition switched to one another, comprising: a first constant voltage circuit applying a first reference voltage to a first input terminal of a first operational amplifier and a voltage obtained as a result of an output voltage being divided to a second input terminal of said first operational amplifier, and controlling an output transistor with an output of said first operational amplifier; a second constant voltage circuit applying a second reference voltage to a first input terminal of a second operational amplifier and a voltage obtained as a result of the output voltage being divided to a second input terminal of said second operational amplifier, and controlling said ouptut transistor with an output of said second operational amplifier, a current consumption of said second constant voltage circuit being smaller than a current consumption of said first constant voltage circuit; a switching part provided for said first and second operational amplifiers and switching connection between output terminals of said operational amplifiers and said output transistor; and a switching logic circuit controlling said switching part so that said first operational amplifier is connected to said output transistor when said load is in the operation condition but said second operational amplifier is connected to said output transistor when said load is in the standby condition.