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PULSE-WIDTH MODULATION CONTROL OF BRUSHLESS MOTORS

IP.com Disclosure Number: IPCOM000026330D
Original Publication Date: 1991-Jun-30
Included in the Prior Art Database: 2004-Apr-05

Publishing Venue

Xerox Disclosure Journal

Abstract

Generally, the common H-bridge amplifier makes digital control of DC brush type motors straightforward, and a microcontroller can execute the control algorithm to vary a pulse-width modulated (PWM) output which in turn alters the voltage to the motor coil. Actually, many microcontrollers have the PWM capability incorporated therein, thereby enabling single chip control of one or more motors. However, DC brushless motors require electrical circuitry for the commutation of the motor. The commutation is accomplished with coil switching logic, the inputs of which are hall effect sensors that are aligned with the motor. Currently, an example of such a brushless motor commutator chip is the Sprague 2936W, which incorporates the required switching logic therein. Unfortunately, these commutation chips do not allow voltage control of the motor with a PWM input, for example, from a microcontroller chip.