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Stepper Motor Drive

IP.com Disclosure Number: IPCOM000075641D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Barcomb, JG: AUTHOR

Abstract

This circuit arrangement reduces the power dissipation on a stepper motor drive when the motor is in an idle state.

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Stepper Motor Drive

This circuit arrangement reduces the power dissipation on a stepper motor drive when the motor is in an idle state.

When a higher voltage is used to reduce the L/R time constant (thereby giving faster response), resistor R1 has a high dissipation when motor is stopped. Usually the motor does not require a full current to hold the motor armature in place. If such a condition exists, this arrangement greatly reduces the total power dissipated during idle.

The drawing shows one of the stepper motor phase controls (A phase), the other phase (B phase) being identical. The stepper motor comes to rest with one of the A drives on and one of the B drives on. After the motor has stopped for sufficient time for all oscillations to die down, the signal drops and then one of the drive transistors, such as T1 or T2, shown for phase A, or the corresponding transistor for phase B, will be pulsed by the line called "OSC," via the appropriate AND circuit 3 or 5. The frequency and pulse width of this signal are determined by the required torque to hold the motor armature from moving. Values could range from 10 to 80% duty cycle with corresponding reduction in total power.

When only one phase, such as A, is pulsed with A phase off, the collector of the drive transistor must be protected from high-inductive voltage spikes caused by rapid reduction of current in motor coils. This can be done by a number of means, two of which are shown in the drawing. By use of dio...