TRI-STATING BRUSHLESS DC MOTOR PHASE FOR DIRECT DETECTION OF BACK EMF ZERO CROSS

摘要

A back electromotive force (BEMF) zero cross may be detected in a brushless direct current (BLDC) motor that is controlled by pulse width modulation (PWM). A phase input of the BLDC motor is tri-stated during PWM periods in which the phase input conducts motor drive current, and the tri-stating of the phase input is used to determine whether a BEMF zero cross has occurred in the BLDC motor.

主权项

1. A circuit for a brushless direct current motor, comprising:
a drive circuit having a voltage input lead, a motor ground lead, a first phase lead, a second phase lead, a third phase lead, a first phase control lead coupled with the first phase lead, and a sense lead coupled with the first phase lead; a sinusoidal controller having a zero crossing input and a sinusoidal control output coupled to the first phase control lead; a zero cross circuit having a sense input coupled to the sense output, a motor ground input coupled to the motor ground lead, and a zero crossing output coupled to the zero crossing input; and a slot circuit having a slot signal input, a slot enable input, and a slot output coupled to the first phase control lead.