Patent ID: 7038428

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 action 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 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 specific recurring cycles; and DF signal averaging means for averaging values of a DF signal changing with the switching on/off action of said switching device and outputting an averaged DF signal; wherein said DF signal averaging means includes: a counter; a counter control circuit which causes said counter to perform count-up operation when said switching device is in an ON state; a memory circuit which operates at a specific number 2 n of averaging cycles of the PWM control operation, where n is a positive integer, to calculate a value of the averaged DF signal by shifting bits of each successive digital output of said counter and thereby multiplying a digital output value of said counter by ½ n+1 , store the value of the averaged DF signal thus calculated, overwriting a previously stored averaged DF signal value, and output the newly calculated averaged DF signal value; and a preset control circuit which operates at said specific number 2 n of PWM control operation cycles to calculate a preset value for said counter by shifting bits of the averaged DF signal value output from said memory circuit and thereby multiplying the averaged DF signal value by 2 n , and set the preset value in said counter.