Browse Prior Art Database

Step Motor Chopper Driver

IP.com Disclosure Number: IPCOM000052570D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Cook, PA: AUTHOR [+2]

Abstract

Step motor drive circuits use voltage chopping techniques to improve motor performance at high speeds while minimizing power dissipation. Conventional chopper drives control current during high positive back emf (Vemf) operating regions but are limited in their ability to keep current constant during high negative back emf operating regions.

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Step Motor Chopper Driver

Step motor drive circuits use voltage chopping techniques to improve motor performance at high speeds while minimizing power dissipation. Conventional chopper drives control current during high positive back emf (Vemf) operating regions but are limited in their ability to keep current constant during high negative back emf operating regions.

The present system provides the ability to keep motor current relatively constant during both positive and negative back emf operating regions by providing a switching means to apply a voltage across a motor phase winding during approximately one-half of the chop period and a similar magnitude but opposite polarity voltage across the motor phase winding during the remainder of the chop cycle. The new concept always chops the motor phase steering switches and provides a means of applying a reverse polarity voltage across the motor phase whenever the phase steering switch is turned off during both chopping and phase commutation. In this manner, a relatively constant current can be maintained across the motor phase inductance whether the back emf voltage is positive, negative, or zero. The constant current is obtained by pulse- width modulating the forward and reverse voltages such that average net volt time product over each chop cycle opposes the back emf. At zero back emf in the motor and with equal magnitude forward and reverse drive voltages applied, the chopping duty cycle exceeds 50% only by the ratio of the sum of the circuit losse...