Abstract: Back electromotive force (BEMF) of a brushless DC (BLDC) motor may be determined when using continuous sinusoidal drive by computing the voltage to common (ground) of each phase (3) thereof when a phase current is substantially zero. These phase voltages may be computed from the DC supply voltage and the duty cycle of the pulse width modulation (PWM) drive to each of the motor phases. From the three phase voltages computed at a zero phase current occurrence, each coil voltage may be calculated. The BEMF of that coil is substantially equal to the coil voltage when at zero current. The phase voltages, when computed at a zero current instance, may be used in determining the BEMF. Once the BEMF is determined it may further be used to regulate the motor speed using a K factor of the BLDC motor.

Abstract: Back electromotive force (BEMF) of a brushless DC (BLDC) motor may be determined when using continuous sinusoidal drive by computing the voltage to common (ground) of each phase (3) thereof when a phase current is substantially zero. These phase voltages may be computed from the DC supply voltage and the duty cycle of the pulse width modulation (PWM) drive to each of the motor phases. From the three phase voltages computed at a zero phase current occurrence, each coil voltage may be calculated. The BEMF of that coil is substantially equal to the coil voltage when at zero current. The phase voltages, when computed at a zero current instance, may be used in determining the BEMF. Once the BEMF is determined it may further be used to regulate the motor speed using a K factor of the BLDC motor.