Drive circuit for a stepping motor control device

A drive circuit apparatus for a stepping motor control apparatus, the drive circuit apparatus for cooperating with at least one other drive circuit to drive a plurality excitation coils such that the plurality of excitation coils generate a rotating composite magnetic field to variably control a rotation of a rotor of the stepping motor, the drive circuit apparatus comprising:

• a digital-to-analog converter means for converting a first digital control signal to a corresponding first analog control signal, said first digital control signal specifying a conduction, interruption, and magnitude of an excitation current to be supplied to one of the plurality of excitation coils;
• a comparator circuit having a non-inverted input for receiving said first analog control signal and having an inverted input for receiving a feedback signal indicative of an amplitude of said excitation current;
• an excitation interval setting means, coupled to said comparator circuit, for outputting a logic signal having a changing logic state according to a predetermined time interval and responsive to an output of said comparator circuit, said predetermined time interval specifying an excitation interval of said excitation current;
• a control signal switching means, coupled to said excitation interval setting means, for receiving a second digital control signal specifying a polarity of said excitation current, and for receiving said logic signal output by said excitation interval setting means, and for outputting at least one switching control signal indicative of the conduction, interruption, and polarity of said excitation current;
• a switching means, coupled to said control signal switching means and having means for connection to a power supply and to the one of the plurality of excitation coils, for selectively connecting the power supply to the one of the plurality excitation coils to obtain said excitation current according to said at least one switching control signal output by said control signal switching means;
• and,
• a feedback means, coupled to said switching means and said comparator circuit, for supplying said feedback signal to said comparator circuit.