Excitation current device for automotive electromagnetic clutch

A control device for controlling an excitation current of an automotive electromagnetic clutch coupled across a voltage source, comprising:

• a first transistor coupled in series with said electromagnetic clutch for controlling an amount of excitation current through said electromagnetic clutch;
• a second transistor coupled in series with said electromagnetic clutch and said first transistor, for turning on said excitation current in response to a base current applied to a base of said second transistor in order to connect said electromagnetic clutch;
• a current detector resistor connected in series with said electromagnetic clutch and said second transistor, wherein said base current and said excitation current of said second transistor flow through said current detector resistor when said second transistor is turned on;
• current detector amplifier means for detecting current flowing through said current detector resistor, said current detector amplifier means outputting a detection signal corresponding to the detected current;
• calculation means for calculating a target value of said excitation current in accordance with running and engine state information of an automobile, said calculating means adding an offset value to said target value in order to correct for said base current of said second transistor;
• deviation detector means, coupled to said calculation means and said current detector amplifier means, for detecting and outputting a deviation, with respect to said target value, of the current detected by said current detector amplifier means;
• and
• means for controlling said first transistor in response to said deviation detected by said deviation detector means so as to minimize said deviation.