Browse Prior Art Database

STEPPER MOTOR DRIVE

IP.com Disclosure Number: IPCOM000024471D
Original Publication Date: 1980-Oct-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 70K

Publishing Venue

Xerox Disclosure Journal

Abstract

An effective way to control current at different levels in an inductive device is via pulse width modulation (PWM). PWM may also be employed to vary the light output of an LED, to control motor current.

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XEROX DISCLOSURE JOURNAL

STEPPER MOTOR DRIVE Lyle Morris

- STEP MQTORl

    " MOVE (ACTIVE iow GATES HIGH DUTY CYCLE)

Proposed Classification
U.S. Cl. 318/491
Int. Cl. H02p 1/00

+V

4v

1

I

-COIL + ENABLE

An effective way to control current at different levels in an inductive device is via pulse width modulation (PWM). PWM may also be employed to vary the light output of an LED, to control motor current.

There are many occasions where open-loop PWM may be employed. For example, in an electromagnet one often requires more current in the initial "pick" stage when the armature plate is at a maximum distance from the pole pieces. When the armature contacts the pole pieces, a smaller current may be used to Ifhold" the gap closed. Using PWM, a high duty cycle may be used to 'Ipick" while a low duty cycle is used to "hold". Similarly, a stepper motor in the "move" state requires more current than may be necessary to detent.

If a multiplicity of loads, each able to utilize a PWM drive scheme, exists in a single system, then a common clock may be utilized to create two levels of drive current. This is accomplished by the use of a fixed duty cycle clock and by one exclusive-OR gate per device to select the high or low duty cycle. In addition, an AND gate can be utilized to give the OFF condition.

Volume 5 Number 5 September/October 1980 50 1

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STEPPER MOTOR DRIVE (Cont'd)

For example, suppose a clock exists with a...