Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

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
Document File: 4 page(s) / 179K

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.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 4

XEROX DISCLOSURE JOURNAL

PULSE-WIDTH MODULATION Proposed Classification CONTROL OF BRUSHLESS U.S. C1.318/599 MOTORS Int. C1. G05B 11/28 Stuart A. Schweid
Robert M. Lofthus
Russell J. Sokac
Charles F. Evans

'4

GO

+ 5v

? f l6

Digital Contro Logic

PWM

+ 5v

t

FIG. I

FIG. 2

XEROX DISCLOSURE JOURNAL - Vol. 16, No. 3 May/June 1991 153

[This page contains 1 picture or other non-text object]

Page 2 of 4

PULSE-WIDTH MODULATION CONTROL OF BRUSHLESS MOT0 RS(Cont'd)

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.

Therefore, the present invention is directed towards enabling a logic PWM input to control the coil voltage of a brushless motor having three coils. The invention is based on the premise that motor commutation and control are separable functions. This is evidenced by the fact that while commutation is position dependent, the applied winding voltage is an independent controllable input. In the case of the DC brush type motor, commutation is accomplished by the brushes. On the other hand, the DC brushless motor is electrically commutated by circuitry external to the chip. With regard to the present invention, the Sprague commutator chip is utilized to function as either a full or half H-bridge type amplifier.

Referring now to the full H-bridge configuration illustrated in Figure 1, the GO output from digital controller 14 provides an active low enable line for the circuit. When the GO output is driven high or floating, the voltage on the brake input, line 5 of driver chip 16, will be low, thereby dynamically braking the motor. Alternatively, when the GO output is low, brake input 5 will be high, enabling the outputs of driver 16 in accordance with the commutation logic contained therein, based upon the states of the hall effect sensors (not shown). More specifically, when the GO output is low, the three hall effect sensor inputs are high, and the PWM output if controller 14 is high, the output state of driver 16 becomes: coil A off, coil B high, and coil C low. This coil output combination results in the supply voltage being applied across coil pair B-C (not shown)...