Voltage regulator for controlling output voltage of automotive alternator

#This application is based upon and claims benefit of priority of Japanese Patent Application No. 2003-32595 filed on Feb. 10, 2003, the content of which is incorporated herein by reference.

#1. Field of the Invention

#The present invention relates to a voltage regulator for controlling output voltage of an alternator for use in an automotive vehicle. The output voltage is controlled by controlling excitation current supplied to a field coil of the alternator.

#FIG. 1 is a block diagram showing an electric circuit including an automotive alternator and a voltage regulator;

#FIG. 2 is a block diagram showing a detector for detecting disconnection in a charging circuit, the detector being included in the voltage regulator shown in FIG. 1;

#FIG. 3 is a timing chart showing excitation voltage applied to a field coil of an alternator and output voltage of the alternator; and

#A preferred embodiment of the present invention will be described with reference to accompanying drawings. First, referring to FIG. 1, an entire circuit of an automotive alternator 2 and a voltage regulator 1 will be described. The voltage regulator 1 controls current supplied to a field coil of the alternator 2, thereby regulating output voltage (voltage VB at a B-terminal) of the alternator 2 to a predetermined level, e.g., 14 volts.

#The alternator 2 is mainly composed of a three-phase stator winding 200, a full wave rectifier 202 for rectifying an alternating current output of the alternator into a direct current output, and a field coil 204 wound on a rotor core. The output voltage of the alternator, i.e., the voltage at a B-terminal, is controlled to a predetermined level by controlling current supplied to the filed coil 204 in an ON-OFF fashion. This ON-OFF control is performed by the voltage regulator 1. The B-terminal is connected to an on-board battery 3 and electric loads 4 of an automotive vehicle through a charging wire 6. The circuit including the B-terminal, the charging wire 6 and terminals of the on-board battery 3 and the electric loads 4 is referred to as a charging circuit. The voltage regulator 1 is also connected to an electronic control unit (ECU) 5 through a communication terminal X.

#The voltage regulator 1 includes a power source circuit 100, a voltage control circuit 110, a detector 120 for detecting disconnection in the charging circuit, a communication circuit 140, a switching transistor 160 (also referred to TR) for controlling excitation current supplied to the field coil 204, and a diode 162. The power source circuit 100 generates a predetermined operating voltage when a signal to turn on a power source is fed from a key-switch of a vehicle through a terminal S. The operating voltage is supplied to each component of the voltage regulator 1.