Drive circuit for stepper motor

Claim 2

A drive circuit for energizing the winding of a stepper motor in response to an input pulse applied thereto, including in combination: a source of bipolar voltage, first circuit means coupled to said voltage source and the first terminal of said stepper motor winding, and second circuit means coupled to said voltage source and the second terminal of said stepper motor winding, said first and second circuit means receiving simultaneously a stepper motor pulse and in response thereto said first circuit means applying to said first terminal a voltage of a first polarity of a predetermined magnitude and said second circuit means applying to said second terminal for a predetermined time period only, a voltage of opposite polarity but of a magnitude substantially equal to that applied to said first terminal, whereby a double voltage is applied across said winding for rapid torque builup in said stepper motor.

Claim 3

A stepper motor drive circuit as claimed in claim 1 wherein said second circuit means includes voltage detector means for sensing a predetermined characteristic of said input pulse and means responsive thereto for applying to the second terminal of said winding a voltage opposite in polarity but of substantially equal magnitude to that applied at said first terminal of said winding.

Claim 4

A stepper motor drive circuit as claimed in claim 2 further including first and second differentiating networks, and wherein said means responsive to said predetermined characteristic of said input pulse comprises first circuit element means operative to supply a voltage signal of a first polarity to said differentiating networks if the amplitude of said input pulse is greater than a predetermined amplitude and to supply a voltage signal of a second polarity to said differentiating networks if the amplitude of said input pulse is less than a predetermined amplitude, said first differentiating network being responsive to the receipt of one of said positive and negative voltage signals and said second differentiating network being responsive to the receipt of the other of said positive and negative voltage signals, respectively, to supply for said predetermined time period form said bipolar voltage source to said second terminal, a voltage signal of opposite polarity but of substantially equal magnitude to that applied to said first terminal.

Claim 5

A stepper motor drive circuit as claimed in claim 3 wherein each said differentiating network includes capacitor means having a predetermined time constant, said capacitor means controlling the period of time that said voltage signal is applied to the second terminal of said winding.

Claim 6

A stepper motor drive circuit as claimed in claim 1 wherein said first and second circuit means each include voltage detector and switch means, each having an input and an output, the inputs of said first and second voltage detector and switch means coupled for receiving an input pulse simultaneously and in response to a predetermined characteristic thereof, each providing at the output thereof a voltage signal of a predetermined polarity and magnitude, said first circuit means applying said last-mentioned output voltage signal to said first terminal of said winding, said drive circuit further including differentiating circuit means coupled between the output of said second voltage detector and switch means and said second terminal of said stepper motor winding, said differentiating circuit means receiving said voltage signal from said second voltage detector and switch means and in response thereto applying from said bipolar voltage source to the second terminal of said winding for a predetermined period of time only, a voltage signal substantially equal in magnitude to the signal applied to said first terminal, but opposite in polarity.

Claim 7

A stepper motor drive circuit as claimed in claim 5 wherein said differentiating circuit means comprise a circuit arrangement including capacitor means having a predetermined time constant, said capacitor means controlling the period of time of application of said voltage signal by said differentiating means to said second terminal of said stepper motor winding.

Claim 8

A stepper motor drive circuit as claimed in claim 5 wherein each said voltage detector and switch means include first and second solid state means, said first solid state means being operative in response to the receipt of an input pulse having an amplitude above a predetermined level to provide a voltage signal of one of a positive and negative polarity at the output thereof and said second solid state means being operative in response to the receipt of an input pulse having an amplitude below a predetermined level to provide a voltage signal of the other of a positive and negative polarity at the output thereof, the output of said voltage detector and switch means of said first circuit means coupled to said first terminal for application of said output voltage thereto and further said differentiating means having first and second voltage detector circuits, said first and second voltage detector circuits coupled between said first and second solid state means of said second voltage detector and switch means and said second terminal of said stepper motor winding, said first voltage detector circuit of said second voltage detector and switch means sensing the output of said first solid state means and in response thereto providing for said predetermined time period, an opposite polarity voltage signal of a magnitude equal to that applied to said first terminal of said winding, to said second terminal and said second voltage detector circuit of said second voltage detector and switch means sensing the output of said second solid state means and in response thereto providing for said predetermined time period an opposite polarity voltage signal of an amplitude equal to that applied to said first terminal of said winding, to said second terminal of said winding, respectively.

Claim 9

A stepper motor drive circuit as claimed in claim 7 wherein each said first and second voltage detector circuits of said differentiating means comprises a network including a capacitor having a predetermined time constant and a transistor switch having an input and an output, the input of said transistor switch being coupled to said network and the output thereof coupled to the second terminal of said stepper motor winding, said transistor switch also being coupled to said source of bipolar voltage, whereby upon the detection of an output from a corresponding one of said first and second solid state means, a corresponding one of said transistor switches is operated to apply at the second terminal of said winding the voltage signal of a magnitude equal to that applied at the first terminal of said winding, but of opposite polarity, said capacitor controlling the period of time said last-mentioned voltage signal is applied to said terminal.