Patent ID: 7102332

Claim:
A control apparatus for controlling an automotive generator, said control apparatus comprising: a field coil to which a DC output voltage of the automotive generator is supplied; a switching device connected in series with said field coil, whereby switching on/off operation of said switching device controls a field current flowing through said field coil; a diode connected in parallel with said field coil for recirculating the field current flowing through said field coil when said switching device is in an OFF state; a field current detector for outputting a voltage generated by a detecting device which is connected in series with said switching device as an analog field current detection value; an A/D conversion device for converting the analog field current detection value detected by said field current detector into a digital value and outputting said digital value to an external control unit; and a voltage control circuit for outputting an ON/OFF drive signal to said switching device such that the DC output voltage of the automotive generator follows a specific reference voltage by PWM control operation performed at recurring cycles; wherein said A/D conversion device includes: a counter; a D/A converter for converting a digital output of said counter into an analog value; a comparator for comparing an output of said D/A converter and the analog field current detection value; a counter control circuit for controlling said counter according to an output of said comparator such that said counter counts up when the output of said D/A converter is less than the analog field current detection value; reset means for resetting the output of said counter at a point in time immediately following a rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles; and transfer means for transferring the output value of said counter to said external control unit at a point in time immediately preceding the rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles.