Patent ID: 7400125

Claim:
A power supply circuit comprising: a transistor whose emitter and collector are connected to a power input terminal and a power output terminal, respectively, the transistor being either a PNP-type of transistor or a PMOS-type of transistor; a voltage detection circuit configured to detect an output voltage at the power output terminal; a voltage control circuit connected to a base of the transistor and configured to control a base current of the transistor on the basis of both of the output voltage detected by the voltage detection circuit and a given target voltage; a resistor circuit placed to connect the base and the collector of the transistor; a current bypass circuit placed to connect the emitter and the base of the transistor and configured to bypass the transistor so that a bypass current flows through the current bypass circuit; and a current accepting circuit connected to the power output terminal and configured to accept a given amount of current from an output current passing the power output terminal by performing either absorption or discharge of the given amount of current, wherein the amount of current to be accepted is equal to or larger than an amount of the bypass current and a product of the amount of the bypass current and a resistance value of the resistance circuit is equal to or more than a difference between a voltage at the power input terminal and the target voltage.