Position sensorless control of BLDC motor in continuous positive airway pressure device

Brushless DC (BLDC) motors are widely used in medical devices due to their high reliability, high efficiency, low maintenance and many other advantages. One of the most popular applications is in sleep apnea machine. For people who suffer from sleep apnea, the most common treatment is the use of a continuous positive airway pressure (CPAP) device. Most CPAP devices use a BLDC motor to drive the blower fan. In this application, blower fan will increase or decrease the patient´s airway pressure in response to their breathing pattern. It splints the patient´s airway open during sleep by means of a flow of pressurized air into the throat. Sensorless BLDC drives are ideal in sleep apnea equipment because the motor is never required to operate below the minimum threshold speed of the drive. In addition and there is no risk of a sudden change in load. Position sensorless control of BLDC motor in sleep apnea machine is done by back EMF difference estimation method.