Back EMF stands for Back Electromotive Force.
In simple terms, the Back EMF is an electromotive force which occurs as the brushless motor turns. This acts like a generator creating electromotive resistance within the motor. Critically, motor controllers such as the ZDBL15 sensorless brushless DC motor controller can measure the back-EMF generated. As the back-EMF frequency is proportional to the motor speed this enables us to determine the exact speed of the motor.
An intelligent motor controller such as the ZDBL15 sensorless brushless motor controller can then read this force and use it to measure the actual speed of the motor. The ZDBL15 can then maintain this speed using Back EMF as a reference to measure and adjust the speed. It is this method which enables a sensorless brushless motor controller such as the ZDBL15 to be able to deliver constant speed under a variable load.