20.2 Architectural Overview

The Quadrature Encoder Interface (QEI) module provides the interface to incremental encoders for obtaining mechanical position data. Quadrature encoders, also known as incremental encoders or optical encoders, detect the position and speed of rotating motion systems. Quadrature encoders enable closed-loop control of motor control applications, such as Switched Reluctance (SR) and AC Induction Motors (ACIM).

The Hall sensor interface provides the mechanical position data of the rotor. In order to energize the correct stator winding, the rotor position must be known. Typically, the BLDC motors have three Hall effect sensors mounted to the stator and use six-step commutation to drive the motor. When the rotor passes a sensor, it produces either a high or a low signal to indicate which rotor pole (N or S) has passed. This switching of the three Hall effect sensors (from high to low or from low to high) provides the rotor position.