THREE PHASE BRUSHLESS DC MOTOR SENSOR-LESS CONTROL USING SINUSOIDAL DRIVE METHOD AND APPARATUS

摘要

The counter electromotive force (BEMF) of a brushless DC (BLDC) motor can be determined by calculating the voltage for the common portion (ground) of each phase of the BLDC motor when the phase current is substantially zero when using continuous sinusoidal drive. These phase voltages can be calculated from the DC supply voltage and the duty cycle of the pulse width modulation (PWM) drive to each of the motor phases. From each of the three phase voltages calculated at the time of generation of the zero-phase current, each coil voltage can be calculated. The BEMF of the coil is substantially equal to the coil voltage at zero current. The phase voltages calculated at the zero current point can be used to determine the BEMF. Once the BEMF is determined, the determined BEMF can also be used to adjust the motor speed using the K factor of the BLDC motor.