Patent ID: 8841795

Claim:
An on-vehicle generator electrically connected to a battery and an electrical load mounted on a vehicle, supplying power to the electrical load and charging power to the battery, comprising: a rotor having a field pole; a field winding that magnetizes the field pole of the rotor; a stator having an armature winding that generates an AC voltage by rotating field generated by the field pole, the armature winding including a plurality of windings each generates a phase voltage; a bridge circuit capable of rectifying the AC voltage generated by the armature winding into an output voltage, wherein a switching element being connected between an output end of the armature winding and either positive or negative terminal of the battery is included therein and the switching element is controlled to be ON and OFF thereby rectifying the AC voltage; a rotation detecting circuit that detects a rotational state whether or not the rotor rotates, based on the phase voltage and outputs a detection signal representing the rotational state; a first control circuit that controls a current flowing through the field winding to maintain the output voltage to be a first voltage, when the rotation detecting circuit detects rotation of the rotor; an overvoltage detecting circuit that detects an overvoltage state of the on-vehicle generator when the output voltage of the bridge circuit exceeds a second voltage that is higher than the first voltage; a second control circuit that controls the switching element to be ON and OFF when the overvoltage state is not detected by the overvoltage detecting circuit and controls the switching element to be continuously ON when the overvoltage state is detected by the overvoltage detecting circuit; an output enabling circuit that enables the detection signal of the rotation detecting circuit to be outputted to the first control circuit when the overvoltage state is not detected by the overvoltage detecting circuit; and an output holding circuit that outputs a control signal to the first control circuit when the overvoltage state is detected by the overvoltage detecting circuit, wherein the control signal holds the rotational state which has been inputted to the first circuit, when the overvoltage state is detected by the overvoltage detecting circuit.