Patent ID: 7170263

Claim:
An apparatus for controlling a generator mounted on a vehicle, the generator being electrically connected to an electric load and being equipped with an exciting winding to which an exciting current is supplied for drive of the generator, the apparatus comprising: a switching element placed to turn on and off the exciting current to the exciting winding of the generator, the switching element being driven in response to a driving signal having an adjustable duty ratio; current detecting means for detecting the exciting current; setting means for setting the duty ratio of the driving signal on the basis of (i) a difference between a voltage value relating to an output voltage of the generator and a target voltage value and (ii) a condition in which the electric load is electrically disconnected from the generator, wherein the duty ratio is allowed to lower than a minimum value of the duty ratio depending on a generated state of the generator, the minimum value of the duty ratio allowing the exciting current to flow at a lower limit detectable by the current detecting means; and driving means for driving the switching element based on the driving signal set by the setting means.