Stepping motor control including a high level supply for stepping and a low level supply for holding

Claim 1

A control circuit for a stepping motor having first, second, third, and fourth windings, said control circuit comprising: first, second, third, and fourth switching circuits each having control inputs; first, second, third, and fourth series circuits each including one of said windings and one of said switching circuits as series elements; a parallel circuit formed by connecting said series circuits in parallel with one another; a constant current source connected in series with said parallel circuit to form a fifth series circuit; said constAnt current source having two terminals and comprising a sixth series circuit including a resistor and a controllable current regulating element, a reference potential source, and amplification means for controlling the current regulating element so as to maintain the voltage across the resistor proportional to the reference potential; said reference potential source comprising a zener diode having a first terminal connected to a terminal of the resistor and a second terminal connected to both the amplification means and to a source of current, wherein said source of current is normally shut off and is turned on only during periods when the stepping motor is advanced; a source of electrical energy parallelly connected to said fifth series circuit; and waveform generating means connected to the control inputs of said switching circuits for sequentially energizing said windings so as to advance said stepping motor.