A microcontroller embedded AD converter based low cost sensorless technique for brushless DC motor drives

A simple low cost sensorless control technique for BLDC motor drives is proposed in this paper. The proposed sensorless technique is based on the terminal voltage measurement, which is the most widely used and accepted approach in industry for BLDC motor control. The proposed method utilizes the microcontroller embedded AD converter, which is common in state-of-the-art low cost microcontrollers, for terminal voltage measurements. Therefore, the zero crossing point (ZCP) can be calculated precisely using simple algebraic equations eliminating the need for analog low pass filters or comparators. It will be shown that the advantages of the proposed technique include 1) no delays in ZCP due to low pass filtering, 2) precise ZCP detection independent of the PWM state, and 3) minimum hardware requirements. Experimental results are also given to verify the advantages of the proposed technique. In addition, it will be shown that the back-emf voltage profile of the open phase can be obtained while the motor is operating without additional hardware. The potential benefits of obtaining the back-emf profile will also be summarized.