VOLTAGE REGULATOR AND IN-VEHICLE BACKUP POWER SUPPLY

A voltage regulator is provided wherein electricity flows through a second transistor in an operating state in which a control unit) applies an operating voltage to a base of the second transistor. A Zener diode sets, in the operating state, a voltage of a second conductive path to a voltage corresponding to a voltage across the Zener diode. A current corresponding to an addition value obtained by adding a value of a current flowing through a second resistor portion in the operating state, a value of a current flowing through a third resistor portion in the operating state, and a value of a current flowing through the Zener diode in the operating state flows through a ground-side resistor portion. A control unit stops the output of the operating voltage when a voltage of the second conductive path is lower than or equal to a threshold value.